Nano-Optics, Metamaterials, Nanolithography and Academia

Working for Physical Sciences Inc. (PSI)

2010-10-17T09:43:00.000-07:00

I have moved from industry to academia about ~2 months ago, so this is the reason why this blog has not been very active. I am currently working for Physical Sciences Inc.(PSI).

www.psicorp.com

PSI is a company with ~180 people and 4 subsidiaries, which provides contract research and development services in a wide diversity of technical areas to both government and commercial customers. It's a very exciting place to be for applied R&D.

I interviewed at several companies across the U.S., from non-profit organizations to Fortune 100 companies, and also from start-ups to large corporations! It was hectic since every interview typically lasted a whole day. Basically, it was like a marathon! In the end, it was extremely rewarding and I was able to make a much more informed or educated choice about my next career move.

I got several offers but PSI's mission and company culture aligned best with my core competencies and values.

Being now in a more "closed source" environment, this blog will remain as is, until further notice...

How to make awesome powerpoint presentation slides?

2010-06-16T17:00:00.000-07:00

Whether you're in industry or academia, you'll need at some point to give a talk and/or make a powerpoint presentation. This is unavoidable! Even if you go for a job interview, you'll need to make a presentation and impress your future employers. And the audience's confidence in your abilities is generally proportional to how well you deliver your talk.

You need to learn to make neat slides for a start. I've seen lots of people who do good work but make horrible presentations. After the horrendous talk, their credibility goes down exponentially.

I can give a whole lecture regarding powerpoint slides but I'll cut to the chase.

Here are a few pointers:

1. Design your own template or buy them online. People are sick of seeing the same old powerpoint templates.

Use a white background (Colored backgrounds are distracting!). Go for a minimalistic design.

2. Use high quality graphics, logos and make some 3D illustrations.

Avoid making your powerpoint dull with low-resolution graphics and too many 2D images.

3. Cut down on text. Avoid crowded slides and use more graphics to get your message across.

4. Use some powerpoint custom animation (appear/disappear) to help the audience focus on some specific information on the slide.

Make information appear one at a time, if the slide is full of information. But don't go overboard on the custom animation.

5. Always use a powerpoint presenter.

It makes you look more professional! I always carry my Kensington presenter whenever I need to give a talk. It's old school using the page up/down button on a keyboard.

6. Check out Garr Reynolds (presentation guru!) presentation tips.

7. Rehearse...

You have to bear in mind that you have only one shot at it. Just one bullet so to speak, and you cannot afford to miss the target! So rehearse a few times before the actual event. Also, make sure that you're conveying your message.

When delivering the actual presentation, be enthusiastic about your talk and convey your enthusiasm!

Google Analytics and Readers Feedback

2010-05-19T08:20:00.000-07:00

I've tracked the *success* (in terms of traffic) of this blog with Google Analytics. It's a very cool and comprehensive tool to monitor traffic on your website. And, it's FREE! Google Analytics gives you an enormous amount of information about web surfers.

I've had like 60% increase of traffic lately and it appears that my most popular post is about 'coloring SEM images'! So, I'm guessing that people are in dire need of practical tools (or codes) more than anything else. :)

I also received a lot of feedback from readers: People have been emailing me and asking me to give more advice rather than commenting on papers. Also, some readers want more scripts or codes. Some people asked me to comment on certain specific topics. Well, it's all good and I will try as far as possible to accommodate certain requests, but please bear in mind I have limited time (like everybody else!).

A number of people have requested that I allow anonymous commenting, as opposed to registered users. Typically, this opens doors to spammers, but I'll give it a shot anyway as from today. If it looks like the site is being nuked, I'll disable it.

Hack Proof your Network with RSA SecurID®

2010-05-17T14:23:00.001-07:00

People have often asked me if it's possible to add an extra layer of authentication when tunneling (SSH) to a Linux server containing sensitive information. The problem comes from users who adopt weak and/or reusable passwords that hackers can easily retrieve.

Well, there's a very good solution: Purchasing RSA SecurID® authenticator(picture below) and software.

RSA SecurID® two-factor authentication is based on using your usual password when accessing a system, followed by input of some random number generated every 60 secs by an authenticator.

So, basically even if a hacker manages to guess a user's password, he must have the authenticator hardware at hand to get in the system. This makes it much harder for hackers to gain access to your network.

Worth the investment if you have to access classified information remotely!

On why it is important to maintain good relationships with people!

2010-05-14T20:44:00.000-07:00

This post is an extension of the previous one on networking.

In academia or industry, influential people and talented people are all connected to each other. With this said, it is important to maintain very good relationships with everybody.

I always see people burning bridges with their former employees, grad students cursing professors, employees sending angry letters to companies who rejected them, researchers sending unprofessional emails to editors of scientific journals who trashed their articles, etc...

This is not good! You will realize that the top performers will always maintain a professional behavior. For instance, even if professors do not like each other, they would always be very polite and act with decorum. The top performers know very well that influential people are connected to other influential people, and unprofessional behaviors might "come and bite them in the ass later on"(the American expression for it!).

What I mean is that there might be a situation where you step on the toe of Mr X. Two years later you apply for a job and your hiring manager is Mr Z, who's connected to Mr X via Ms Y. And, you find out that they decline you you dream job, following a call from Mr X! I can cite countless examples like this.

Be always courteous! Try to have good working relationships with your colleagues, advisor, boss and everyone around you. Get genuinely interested in people. There will always be people who have difficult personalities, but you should never lose your cool or do something irrational that you might regret later on. Practice empathy and try to understand difficult people. But always smile and maintain a professional behavior!:)

Along the same lines, be a good Mensch, like Guy Kawasaki would put it!

The Art of Networking

2010-05-14T20:00:00.000-07:00

I attended Peter Fiske's seminar at MIT recently. For those who do not know him, he is a well-known columnist for AAAS and he writes on career development for young scientists and engineers. He recently wrote a book entitled "Put Your Science to Work: The Take-Charge Career Guide for Scientists - Practical Advise, Proven Techniques".

One of the things that he talked about is the right way to network and this is exactly what I've been doing for years: He mentioned that many people have the misconception that networking means to contact everyone or influential people that you know when you are looking for a new job and asking if they know of any job openings!

I know people who would introduce themselves briefly to others and immediately flaunt their resumes. This is the wrong way of networking and the most likely outcome is that the other person would trash your CV.

Networking begins long before a job search. In reality, networking means that you have to get out of the lab and attend professional meetings or conferences, and meet people. Most importantly, you must have a genuine interest in the people that you meet (ask about their background, culture, hobbies, etc...). Also, you have to get interested in their work. It is important that you really want to know them personally and without expecting anything in return.

Once you've established a connection, you may keep in touch by sending an email from time to time. Send relevant articles or give a phone call!

Typically, if you have a genuine connection with people, they would help you when you need help. I always have a genuine interest in people and helped others (without expecting anything in return) whenever I could. And, this kind of attitude has always reaped rich rewards!

NPGS Dose Matrix Calculator

2010-05-08T19:47:00.000-07:00

For the folks using Nabity's NPGS and building dose matrices for ebeam lithography, they know that some calculations are needed to figure out the real dose value of each element in the matrix.

I am sharing a small script which will simplify this process of doing these redundant calculations and which will allow users to focus more on the task at hand (i.e. the lithography process!).

Before running the executable file, the text file *array_calc.txt* has to be modified. rows,cols,start(%),end(%),start_dose need to be altered while preserving the "::" spacers.

The output file of the script will yield the dose allocated to different elements of the dose matrix and will reveal the dose variation. This script saved me a lot of time.

Hope you enjoy it!

[dose_matrix_dist_20100508.tar.gz]

The book "Bursts: The Hidden Pattern Behind Everything We Do"

2010-04-30T19:02:00.000-07:00

Today I attended the "Cocktails & Conversation with prof. Albert-László Barabási" event. The purpose of the event was to celebrate Prof. Barabási's new book entitled "Bursts: The Hidden Pattern Behind Everything We Do".

Prof. Albert-László Barabási is a distinguished professor at Northeastern University and one of the world's top researcher in the science of networks. His group routinely publishes in Science/Nature!

There's something to learn here: Part of his appeal to the masses is that he delves in very interesting topics ranging from predicting human mobility, making forecast about mobile phone viruses (which do not exist yet!) to visualizing mood swings of the US population based on data from twitter. Basically, everybody (even a layman!) can relate to this. If only a specialized audience can relate to your obscure work, it's unlikely that you can become popular.

The other part is that it is a relatively new field and he's a pioneer who's making quantum leap progress.

In a nutshell, his research consists of gathering large data sets (e.g. data from anonymous mobile phone users), analyzing the data, generating models and making predictions.

I was able to catch a glimpse of his recent book and I have to admit that it's thought provoking. In short, the book, through some well-crafted stories, reveal the predictability in human behavior. Barabási introduces some seemingly unrelated activities and shows that a virtually identical bursty (this is where the name of the book came from!) pattern emerges. Worth reading!

You may also want to read Linked from the same author!

AAAS Booklet on Building Relationships

2010-04-28T08:41:00.000-07:00

Building relationships with your colleagues and boss is critical to your survival in the lab! I am glad that the American Association for the Advancement of Science, "Triple A-S" (AAAS) has decided to focus on this issue in their latest booklet titled "Career Trends: Building Relationships".

The booklet can be downloaded here:

http://images.sciencecareers.org/pdf/booklets/building_relationships.pdf

As a bonus, the booklet discusses topics like informational interviews and online social networking sites to guide you through your career.

Review on Transformation Optics and Metamaterials

2010-04-28T08:25:00.000-07:00

There's a very good review, by Huanyang Chen (who's also on the Physics advisory board of the Lifeboat Foundation) et al., on transformation optics /metamaterials which was published a few days ago in the journal Nature Materials:

Huanyang Chen, C. T. Chan and Ping Sheng. transformation optics and metamaterials. Nature Materials 9, 387 - 396 (2010) [...]

This review brings the reader up to speed on cloaking.

Protecting your Intellectual Property (IP) a.k.a No FREE Consulting

2010-04-24T21:01:00.000-07:00

Q: What is the ultimate goal of companies?
A: Companies want to make money! Plain and simple.

And, in the economic downturn, they need to innovate to remain competitive. In other words, they need fresh ideas. Most of them don't need super qualified labor at this point in time since it would cost them too much. But, they are in dire need of ideas. Once they have a brilliant idea, they have or will find some engineer with a recent PhD (and those are a dime a dozen nowadays!) to execute the idea.

Some companies contacted me recently and introduced themselves in the following way (adapted):

"Good Morning Dr. Casse. We know that you're a renown expert in the field X. We would like to go in the direction X+DX and would like to have your opinion on it. How would you go about it? BTW, we had some problem with X+D3X for the past 6 months. Maybe you could offer us some insights into solving those problems? Since you have expertise in Y also, we'd like to know the challenges in doing Y+DX? etc...

We may have some openings coming up for somebody who's very talented and qualified as you. But for now, we would appreciate if you could share your expertise with us!"

Do they think that I'm dumb?:)

I was talking with my friend Dr. M. Azize from MIT and colleague R. Tavlykaev (independent consultant) who also shared how some companies have become very aggressive, shameless and unethical to gain a competitive edge.

Let's face it, this is a form of *FREE* consulting. Providing companies some form of clues will make them earn a lot of money and pointing them in the right direction will also enable them to save millions of dollars in doing some redundant trial and error. What's in for the *free* consultant? Nothing. These companies will patent ideas, make million dollars of profit and that's the end of it.

I will advise *freely* universities, opensource communities and non-profit organizations on a limited scope. But I'm not into free consulting for greedy companies who will give nothing in return. And neither should YOU because you have nothing to gain. There is no job prospect either: The companies use it as a bait to lure you. So, these companies, in general, will not contact professors directly (since professors are not that dumb!), but will instead target postdocs and research scientists to do the dirty work for them.

The moral of the story is to protect your intellectual property (IP) and be aware of the dirty game that some companies are playing.

Single-photon source from Diamond Nanowires

2010-04-23T07:47:00.000-07:00

Nature Photonics recently covered the work of Lončar group's where the group together with colleagues in Germany reported efficient diamond nanowire single-photon source based on an array of nanopillars in diamond (~200 nm in diameter and 2 μm high).

This is a very good piece of work which will allow new technologies such as secure communication through quantum cryptography. The work has been featured on the cover of Nature nanotechnology.

More info can be found here:

Thomas M. Babinec et al. A diamond nanowire single-photon source. Nature Nanotechnology 5, 195 - 199 (2010)[...]

The marriage of carbon nanotubes and metamaterial

2010-04-19T11:26:00.000-07:00

Zheludev's group combined carbon nanotubes (CNTs) with metamaterials to engage the resonant local fields in the vicinity of the metamaterial, leading to enhanced nonlinearity. This is a smart idea! Redshift of the plasmon absorption resonance was observed in the CNT-functionalized metamaterial.

More details can be found in this paper:

A. E. Nikolaenko et al. Carbon nanotubes in a photonic metamaterial. Phys. Rev. Lett. 104, 153902 (2010) [...]

Resonance Guided Wave Networks (RGWN) concepts

2010-04-19T08:26:00.000-07:00

Harry Atwater's group is constantly innovating and recently came up with an interesting concept termed as "Resonance Guided Wave Networks (RGWN)". A RGWN is an optical materials design consisting of power-slitting elements arranged at the nodes of a waveguide network. A typical 2D waveguide network is composed of intersecting metal-insulator-metal waveguides. This type of structure exhibits photonic bands and band gaps at IR wavelengths, as well as localized resonances of Q~80 at telecommunications wavelength.

The full story can be found in the Phys. Rev. Lett paper by Feigenbaum and Atwater:

Eyal Feigenbaum and Harry A. Atwater. Resonant Guided Wave Networks. Phys. Rev. Lett 104(14), 147402 (2010) [...]

How to obtain a faculty position in an economic downturn?

2010-03-27T16:24:00.000-07:00

This question comes up very often in academic circles. Because of the economic downturn, it has become non-trivial to obtain any kind of position, whether it is in academia or industry. It is a good time for employers but not a good one for prospective employees. The applicant pool is gargantuan nowadays and there are a lot of talents out there seeking jobs: With laid-offs all over the U.S., experienced hard-working Americans as well as foreign talents and fresh university grads are now all competing for the few jobs out there.

Just to give you a sense of reality, we placed an ad for a postdoc and we got around 400 applicants, ranging from experience industry laid-offs, university professors, mature postdocs and fresh PhD graduates all-together.

To come back to the question, there are a few basic requirements that an applicant has to meet:

(1) Good publications, preferably in high impact factor journals
(2) Postdoctoral research experience ranging from 3-5 years (or more?!)
(3) Teaching experience(desired)
(4) h-index > 5

These days, as mentioned above, there'll be a lot of people who will satisfy requirements (1)-(4). But the decisive factor to get hired is:

FUNDING. Schools prefer postdocs who wrote or co-wrote grant proposals and managed to obtain funding. If an applicant can bring his/her own research funding, they have statistically much higher chances of becoming a faculty member.

The most effective people have excellent time management skills

2010-03-23T17:02:00.000-07:00

Nowadays, especially in the US, people are overburdened with work. Typically, most people are buried underneath paperwork and email. But my boss recently made a good observation: He mentioned that top performers can answer you almost immediately. The most effective people would usually be on top of things and possess excellent time management skills.

We noticed that the very top directors, professors, managers and other top executives would reply to any emails within a few minutes to at most a few hours. While those with poor time management skills have to be literally harassed over a few days to months before responding. Unfortunately, I have often encountered the latter!

But I have also had the chance to interact with top performers, at the top of their field, who managed to respond to my emails and also who gave me their cell number in case I didn't succeed in reaching them fast enough!

These are the kind of people whom you should consider working for and whom you should hire.

Also, this is the kind of professional behavior one should strive to cultivate.

Lecture on lithography

2010-03-09T13:26:00.000-08:00

I just gave a 1 hour lecture on "lithography" for the INT G370 course: Nanosystems Design for Biology and Medicine.

As the old saying goes, it turns out that we learn much more by teaching a course. It's kind of refreshing as you have to dig up some of the old concepts locked inside your memory.

The moral of the story is to try to teach something once in a while!

Facebook for researchers: ResearchGATE

2010-02-19T13:00:00.000-08:00

Dr. Ijad madisch created ResearchGATE which is a 'Facebook for scientists'. So far, ResearchGate has built a social network of more than 250,000 researchers from 196 countries.

One of the benefits of ResearchGate is that it is a centralized forum where people can ask questions or pose problems, and other scientists can answer them.

It's similar to starmind but for free!

Converting bitmap images to vector graphics for lithography

2010-02-08T08:52:00.000-08:00

For presentations, I often show lithographically-made nanoscale images of logos, map of the USA, flowers, Mona Lisa, Obama pictures and other hard-to-make/creative designs!

While, in general, anybody doing lithography would show the usual lines or holes patterns and variations of it. So, I often get the question: "How did you make it? This is hard to draw in DXF (CAD) format!".

It's correct to say that it's hard to draw in DXF. But I don't draw them! I simply use high-resolution pictures on the web (raster graphics or bitmap) and convert the pictures to vector graphics.

To easily convert bitmap images to clean vector art, I use vector magic:

http://vectormagic.com/home

And voilà!

Na Liu won the best female young physicist in Germany (Hertha-Sponer Prize 2010)

2010-02-07T14:54:00.000-08:00

In Germany, one of the groups that have been very successful in advancing metamaterials research, besides Wegener's group, is Harald Giessen's group in Stuttgart. I had the opportunity of meeting Harald Giessen in San Diego in 2008.

The best known works, of Giessen's group, are on Stereometamaterials and the Plasmonic analogue of electromagnetically induced transparency at the Drude damping limit.

And, the work contribution is largely attributed to Na Liu's effort. As a reward, the Hertha Sponer Prize 2010 of the German Physical Society for the best female young physicist in Germany has been awarded to her for her research into metamaterials.

Na Liu is now in Alivisatos group in UC Berkeley.

And of course, Europe has once again been brain-drained!:)

Want visibility: Create professional websites!

2010-02-07T14:25:00.000-08:00

Nowadays, there is such fierce competition that lab PIs want more visibility. One of the ways to achieve more visibility for your lab and to display a high level of professionalism is to create a professional website.

All the bosses that I have worked for so far have stressed this fact and all hired professionals to design their websites:

Prof Frank Watt's center for ion beam application website:
http://www.ciba.nus.edu.sg/

Prof. Herbert Moser's Singapore synchrotron light source website:
http://ssls.nus.edu.sg/

Prof. Sri Sridhar's websites:
http://sagar.physics.neu.edu/
http://www.igert.neu.edu/

A website is a window to the world and making it look outstanding will also reflect on members of the lab.

David R. Smith who is the pioneer for metamaterials or microwave metamaterials (to be more precise!) is the guy who understands this and makes sure that his website always shine! He takes the habit of constantly revamping his website:

http://people.ee.duke.edu/~drsmith/

and making sure that web surfers get the message.

He has also a new website for his center for metamaterials and integrated plasmonics at Duke:

http://metamaterials.duke.edu/

The website has a nice feed aggregator, which captures the latest breakthroughs of the photonics community.

3D Magnetic EZ Antenna

2010-02-07T13:49:00.000-08:00

After our breakthrough in super-resolution imaging, the other news which dominated the national scene is the electrically small and low-profile magnetic EZ Antenna by Richard Ziolkowski et al. [...] This work is a collaboration between the University of Arizona, Boeing Research and Technology, and NIST. To avoid being technical, this metamaterial-inspired, near-field resonant parasitic antenna has a much higher performance that other antennas with similar sizes.

And, quoting Christopher Holloway (NIST):

“The purpose of an antenna is to launch energy into free space. But the problem with antennas that are very small compared to the wavelength is that most of the signal just gets reflected back to the source. The metamaterial makes the antenna behave as if it were much larger than it really is, because the antenna structure stores energy and re-radiates it,”

The antennas developed by the group are printed on copper squares with sizes of only 65 millimeters. A Z-shaped element on their backs acts like a metamaterial, storing energy magnetically.

Image comment: This is the new. metamaterial-based antenna created by experts at NIST
Image credits: C. Holloway / NIST

Richard Ziolkowski is best known for his pioneering work, together with Ehud Heyman on wave propagation in media having negative permittivity and permeability [...]. While Minas Tanielian from Boeing is known for his 3D cubic arrangement of split ring resonators. On a personal note, besides being great researchers, Ziolkowski and Tanielian are very approachable and extremely efficient people.

3D Metamaterials Nanolens: The best superlens realized so far!

2010-01-16T09:44:00.000-08:00

My paper was published online 2 days ago, in Applied Physics Letters:

B. D. F. Casse, W. T. Lu, Y. J. Huang, E. Gultepe, L. Menon, and S. Sridhar. Super-resolution imaging using a three-dimensional metamaterials nanolens. Appl. Phys. Lett. 96, 023114 (2010), DOI:10.1063/1.3291677 [...]

We have manufactured a three-dimensional (3D) metamaterials nanolens, consisting of bulk nanowires embedded in a dielectric matrix, which boasts significant advantages such as low-loss, broad bandwidth operation, and support for both propagating and evanescent waves required for full imaging, over currently available metamaterials prototypes. Additionally, It has a figure of merit which is 4 times higher than the best fabricated metallic-based metamaterial.

“This is probably the best superlens realized so far—In contrast to a grating far-field superlens, it needs only a single measurement to obtain a very large bandwidth in Fourier space to reconstruct superresolution details of an object. And, unlike the hyperlens, the metamaterial nanolens has theoretically no limitations on the imaging area.” says Sri Sridhar.

With this 3D nanolens, we have demonstrated superresolution imaging over a record distance of 6 times the wavelength (λ), in the far-field, with a resolution of at least λ/4. The superior optical properties of the lens and the ability to manufacture the bulk nanowires in large scale, offers the potential for numerous applications in biomedical imaging, transformation optics, optical storage devices and nanolithography.

The press release can be found here:
Northeastern University physicists develop nanolens that improves imaging of nanoscale objects

http://www.nanotech-now.com/news.cgi?story_id=36280

This work is profiled in several online journals.

The tragedy that hit Haiti

2010-01-15T06:56:00.000-08:00

I believe none of us can be deaf to Haiti's worst earthquake in over 200 years, where thousands of people lost their lives and a countless number of others lost their homes.

It is important that we reach out to those in distress. In times like this, direct donations to legitimate organizations are the most helpful.

Debugging a segmentation fault on Linux

2010-01-14T10:37:00.000-08:00

Several of our key softwares run on the opportunity Linux cluster at Northeastern. We have built a state-of-the-art facility for electromagnetic computation. One software that we recently installed gave us a segmentation fault.

It's been a while since I haven't done any troubleshooting in Linux. Well, I used to be the maintainer of the fedora YUM repository for Enlightenment E17 desktop shell, before passing it on to Prof. Gregory Kriehn.

I asked the administrator to install gdb and ran a backtrace. That gave me some useful debugging information to feedback to the software company.

Moral of the story: Use the force, use Linux!

Silveirinha and Alù: Rising stars of the metamaterials community

2010-01-11T16:48:00.000-08:00

Talented individuals are easy to spot. And, we have to appreciate the talent and learn from them. Whenever I am searching for published theoretical papers, I stumble of course on the usual in-depth articles by experienced/mature professors but I also come across very good articles written by young talented professors.

Two such recent articles are:

[1] M. G. Silveirinha et al.
Experimental verification of broadband superlensing using a metamaterial with an extreme index of refraction. Phys. Rev. B 81, 033101 (2010) [...]

and
[2] A. Alù. Mantle cloak. Phys. Rev. B 80, 245115 (2009) [...]

Mário G. Silveirinha and Andrea Alù are both very talented young faculty members who have been extremely productive and publishing several papers a year for the past few years. Specifically, they have published a record number of theoretical papers.

Now, one may wonder how they managed to publish so many papers. Well, they first have a deep understanding of the underlying physics of metamaterials and see a mile ahead of everybody else. Second, they have developed robust simulation tools and in-house templates to chunk out papers rapidly as soon as they have a storyline. Basically, they are able to see the whole picture, but they don't publish it right away. They don't give you all the pieces of the puzzle in one shot! Rather, they break it down to small sub pictures, and publish each one at a time. As a result, they publish more than the average theoretical physicist.

Reading PDFs on the go with a kindle!

2009-12-31T00:39:00.000-08:00

Postings have been a bit slow due to the holidays kicking in! Anyway, I often carry a couple of research papers or books in my backpack and read them on the train and/or buses. My wife found that I carry too much stuff everyday, on my way to work, and decided to offer me an amazon kindle. I must say that it's not only a great gift but also a sound investment. I got rid of my research papers and started uploading the PDFs on my kindle and reading them on the go. As a bonus, I have my time magazines delivered to the device for only $1.49 a month!

Encrypt your data in a shared facility

2009-12-09T12:53:00.000-08:00

Whenever you're using a shared facility, you have to realize that everybody has access to your data, including your competitors. It's your duty to protect your data. I often hear students complaining that people viewed their SEM images on a shared PC or that their macro code was *stolen*.

If you have proprietary code that you must use on shared machines or if you have data images which you wouldn't want to see ending up on some other research group's PC, then my advice is to encrypt your data.

A nice encryption software that I use is AxCrypt. I even requested some systems administrators/ dedicated staff to install it on PCs where I've written a lot of proprietary code for running tools or where I have a lot of confidential data.

This advice is relevant especially if you are funded by the Air Force Research Labs, ARO, DARPA or any other defense funding agencies. You do not want your data to be floating around!

Article Highlight: Subwavelength nanoimaging in 3-D

2009-12-06T09:18:00.000-08:00

I just stumbled upon an interesting article published in Phys. Rev. Lett. by A. Govyadinov et al., entitled "Phaseless three-dimensional optical nanoimaging". Actually, the preprint is on arxiv.

The authors proposed a method in which the subwavelength details of a 3D structure can be recovered in the far-field. It is a very well-thought method which is based on the solution to the inverse scattering problem for a system consisting of a weakly-scattering dielectric sample and a strongly-scattering nano-particle tip. Interestingly, their nano-scale optical tomography technique relies neither on phase-measurements of the scattered field nor on phase-control of the illuminating field.

On the fundamental flaws of cloaking by metamaterials

2009-12-02T18:11:00.000-08:00

Invisibility cloaking, using metamaterials, excites the scientific community, the general public, amateurs of sci-fi and most importantly the funding agencies. If you think about it, it is indeed mind-boggling to be able to realize a Harry Potter type cloak!

The metamaterials community, in particular John Pendry and Ulf Leonhardt have thought and pioneered the first invisibility schemes by using metamaterials. The first demonstration of the invisibility cloak was demonstrated by David Smith's group. And subsequently, several researchers have been actively working (both theoretically and experimentally) on cloaking.

Funding agencies and the general public assume that we're close to cloaking military tanks, fighter airplanes, etc... And accordingly, with this type of technology, we could effortlessly win the war in Afghanistan or any war for that matter!

Well the reality is far from our wild imagination! Cloaking by using metamaterials suffer from two fundamental flaws:

1. We can only cloak objects which are of the same size as the wavelength of light.

For instance a typical human eye will respond to wavelengths from 400nm to 600 nm or so (+/- a few nm of course). It means that if you want to cloak an actual object from humans, it cannot be larger than 600 nm!!! This implies that using metamaterials, we can only cloak nanometer size objects, and if you think about it, these objects are so tiny that they are already cloaked!

2. Metamaterials cloaks are extremely sensitive to loss.

In theory, we can design lossless materials where the cloak works out of the box. But in the real world, we have to use materials which are lossy (suffer from energy dissipation). Thus, realistic materials will kill the cloak! However, in the future, we will be in a position to develop robust gain compensation schemes to compensate for losses.

2009 MRS Fall Meeting (Metamaterials Session)

2009-12-01T14:22:00.000-08:00

The Metamaterials session of the 2009 MRS Fall Meeting started today, at the Hynes Convention center, in Boston.

Good opening talk by Martin Wegener, who talked about his Gold Helix Metamaterial, and showed impressive ray tracing images of the carpet cloak. Like me, he's a fan of 3D ray tracing.

Overall, it was a very productive day. I also gave a talk entitled "Superresolution Imaging Using Bulk Nanowires Metamaterials at Optical Frequencies" in lieu of my colleague who couldn't present his own talk on transformation optics since he was sick.

I presented the first demonstration of the reconstruction of subwavelength features of an object, over a record distance of more than 6 times the wavelength by a nanolens made up of bulk metamaterials of nanowires, and with a resolution of at least wavelength/4. This is considered a significant breakthrough and was well received by the metamaterials community. We recently submitted the paper and are impatiently awaiting its publication. We strongly believe that this piece of work will get extensive media coverage.

Kudos to the session organizers/chairs Nader Engheta and Minas Tanielian.

Video of Zheludev's group at the University of Southampton

2009-11-28T18:42:00.000-08:00

Propaganda for the metamaterials research, led by Nicolay Zheludev, at the Optoelectronics Research Centre ORC (University of Southampton):

Showcasing your research on arXiv

2009-11-28T18:05:00.000-08:00

arXiv is an e-print service in the fields of physics, mathematics, non-linear science, computer science, quantitative biology and statistics. arXiv is owned, operated and funded by Cornell University and also partially funded by the National Science Foundation.

It is NOT peer-reviewed and researchers often use it to *temporarily* showcase their work (in the form of an online published article) to the world, after having formally submitted the manuscript to a journal and awaiting publication. The peer review process in some journals usually take time (it can take several months to years in some cases!), and researchers want their work to be known as soon as possible. They want to let the community know that they were the first to come up with the idea! And, arXiv allows them to do just that.

Please note that it is not advisable to submit your manuscript to arXiv without having first submitted it to a journal, as somebody else can reproduce your work and submit it, before you, for publication in an official journal.

Also, bear in mind that some high impact factor journals will prematurely reject your paper if you have published it online on arXiv.

Is your name too common? Consider getting a Researcher ID.

2009-11-28T16:12:00.000-08:00

It might happen that you have the same exact name as some other researcher(s). And, when fellow scientists try to look up your publications, they are often swamped by other irrelevant papers (from the other researchers) popping up on their screen. Thomson Reuters created the ResearcherID, which is a unique identifier that expressly associates each participating researcher with his or her published work, thereby standardizing and clarifying author names and citations.

With the ResearcherID system, publications can be added from diverse platforms ranging from ISI Web of Knowledge to EndNote Web and RIS files. Additionally, citation metrics can be created and your h-index is computed automatically.

As a bonus, your unique ResearcherID can be used as a ResearcherID Link on your website to direct others to your publication list.

It'd probably worth it if your name is too common!

Thanksgiving in th U.S.!

2009-11-26T14:13:00.001-08:00

Happy Thanksgiving!

(Sent from my mobile device)

Keeping track of patents using RSS feeds

2009-11-24T19:09:00.000-08:00

The hard way of keeping tracks of patents is to physically check it from time to time. The smart way of staying up to date is to use RSS feeds. A good RSS feed reader is the Google RSS reader. There are others.

Let's say you want to keep up to date on "metamaterials" patents. First, you go on Google patents search and then query google with the word 'metamaterials'. This will lead you to here. If you now scroll to the bottom, you'll discover the feed URL, which is this.

Simply add the link to your RSS feed reader and you'll be among the first ones to know when patents are popping up!

The latest metamaterials patent which appeared 6 days ago is on "ACTIVE TERAHERTZ METAMATERIAL DEVICES" and belongs to H. T. Chen et al., best known for their paper in Nature.

Dual screen: The way to boost productivity!

2009-11-24T06:44:00.000-08:00

Screenshot of my office desk:

Taking advantage of technology can help boost productivity!

Making cheap photolithography masks!

2009-11-23T19:11:00.000-08:00

To produce high-quality microstructures in photolithography, we often buy expensive (3 inch mask for 675 USD) chromium masks on quartz / soda lime glass. In academic research, it may happen that we are not really sure if something would work out and might not want to spend that kind of money for a mask in the first place.

I often come across grad students who purchased expensive masks to find out that their final device do not work as expected. It turns out that many people are not aware that we can make or buy cheap masks.

A fast turnaround alternative to chromium masks are mylar transparency masks. First draw your design in a CAD program and then simply print it to scale on a transparency with a high resolution printer. Bear in mind that the dark field will block the light, so watch out for the polarity!

Alternatively, if you don't have a good printer, you can place an order for a transparency mask from the following vendors for ~30 USD or so:

1. Advance reproduction
2. Artnet Pro
3. CAD/Art Services, Inc
4. Infinite Graphics (boasts 50,000 DPI printing!)

Blogging test from my mobile!

2009-11-23T18:59:00.001-08:00

Mobile blogging test. This post was created with my blackberry on the go.

Pretty cool!

Cleaning your shoes before stepping into the cleanroom at CFN, BNL

2009-11-23T13:47:00.000-08:00

The Center for Functional Nanomaterials (CFN) at Brookhaven National Labs (BNL) has an interesting apparatus for cleaning cleanroom users' shoes (see photo below). I have worked at 5 different national labs and it's the only one which actually catered for the dirty shoes of users!

The other labs in the USA had the traditional blue shoe cover only, while in Asia, users were required to remove their shoes completely and wear cleanroom boots.

Loss compensation schemes to compensate for losses in metal-dieletric structures

2009-11-22T19:20:00.000-08:00

An interesting paper appeared 2 weeks ago in Phys. Rev. A :

M. A. Vincenti et al. Loss compensation in metal-dielectric structures in negative-refraction and super-resolving regimes, Phys. Rev. A 80, 053807 (2009). [...]

The authors show that the introduction of gain improves the resolving characteristics of the lens and leads to gain-tunable super-resolution.

The metamaterials which are made up of metallic elements are extremely sensitive to loss. Studies such as those are crucial, before even thinking about practical applications.

We also submitted a related study entitled "Storing light in active optical waveguides with single-negative metamaterials" and eagerly awaiting its publication!

Getting on top of things

2009-11-21T21:16:00.000-08:00

In a more senior position in an academic or industry environment, people are overburdened by so many responsibilities that it becomes nontrivial to respond to all emails, remember appointments, and so on without the use of a blackberry or other corporate tools. After being hired in a more senior role at Northeastern, my responsibilities increased and I had to keep up with the latest technology. Nowadays, in order to get on top of things, I have a blackberry curve 8900 which I optimize to the fullest. And, I also use a myriad of online tools, which I'll discuss later, to boost productivity.

My blackberry is wired for my corporate emails, calendar, Google Maps, Gmail, Google Search, Google voice/Skype, Mobile banking application, weather app (need this when you're in Boston!), among others.

My boss prof. Sridhar is also an advocate of modern technology, and a few months ago, started to use Skype combined with the desktop sharing tool yuuguu to disseminate scientific information.

On reviewing scientific manuscripts for scholarly journals

2009-11-21T11:14:00.000-08:00

When somebody submits a manuscript to a journal, it will be sent to referees for peer review (of course, provided that the editor likes it in the first place!). The editor would normally ensure that your manuscript is being routed to some expert who's in the same field as yours, although sometimes it might not be necessarily the case.

I review papers for like 7 journals and the list is growing. At some point, 1 or 2 journals did send me some manuscripts which were outside my area of expertise. I had to decline because it would take me too long to keep abreast of the literature in other fields. But I find it sad that (1) journals do make that mistake of sending manuscripts to the wrong person, and worst that (2) some researchers rarely decline to review them. Often, the result, in this case, is that you get poorly reviewed manuscripts. I did encounter in the past reviewers who didn't really understand what was going on.

On the bright side, as I mentioned in an earlier posting, ad hoc referees are subjected to statistics. If a reviewer declines 3-4 papers without sending a genuine report, he'll be rejected by the system and his name won't appear on the referee database. Similarly, if a reviewer accepts blindly 4-5 papers, he's most likely to disappear from the referee database. In brief, there must be some balance and genuine review of a manuscript.

As a referee, if you genuinely review manuscripts and demonstrate that you really know your field, you get high scores from the system. And, you'll be invited to review other journals, in which you may have never published in.

A good guideline to review manuscripts can be found on the Small journal website. And, there's also lots of good advice on Google. The bottom line is that if you accept to review a paper, make sure that it's within your area of expertise and remember that you have a duty to do a good job!

The best lithography software for ion beam systems

2009-11-20T18:12:00.000-08:00

Having been affiliated and/or worked in 5 national facilities in Singapore and the United states, I came across a number of lithography software for ion beam systems (SEM, FIB, etc...). The best lithography software that I ever came across, in my opinion, is Joe Nabity's Nanometer Pattern Generation System [NPGS].

NPGS is user-friendly and simply works out of the box! Joe Nabity is a one man company. He's known to answer all his emails and provides very good support. I had the chance to interact with him and he does genuinely listen to user's concerns, and makes every effort to address them.

The other major competing software (Raith150, Elphy, etc...) on the market is from Raith. Although some researchers have successfully mastered it, the control system has bugs and a superfluous alignment of the writefield is necessary before patterning. Also, there's poor software support. I talked to the engineers at Raith concerning improving some of the features of the elphy for Harvard's FIB and they were pretty reluctant to change anything. Personally, the software is bloated and needs a complete rewrite. It has also become too esoteric and needs a lite version.

It's analogous to facebook which has way too many things that a facebook lite was needed. Fortunately they realized it. Along the same line, this is the reason why Google created Chrome instead of trying to fix firefox!

The internal scoring system of high impact factor journals like Science and Nature

2009-11-20T10:44:00.001-08:00

Many people do not realize that high impact factor journals like Science/Nature and others have an internal scoring system where they rate both authors (as well as reviewers!). The huge number of papers being sent to these journals force the editors to use some statistical methods to rapidly eliminate a big chunk of manuscripts.

I often hear people complaining that they send lots of manuscripts to these journals and got turned down even when their work was considered a breakthrough. The thing is that if an author has sent manuscripts 3-4 times and got rejected, the next set of papers being sent, by the same author, will automatically get rejected without even being read. Of course, the editor of the journal will always respond with a standard reply saying that you're unlikely to succeed in the competition for limited space and they have to make harsh choices, and so on. But the truth is that you have been statistically eliminated.

So the advice is that if you sent 2 manuscripts and got rejected, STOP SENDING! Wait for 2 years before sending them another one.

Similarly if you have 2-3 papers already published in prestigious journals, the likelihood that your subsequent ones are going to be sent blindly to referrees is pretty high.

The hierarchical structure of academia

2009-11-19T19:09:00.000-08:00

Comic taken from PhD Comics says it alls.

[original link]

When it comes to describing academia in humor, nobody can beat Jorge Cham!

Dose matrix in electron beam lithography

2009-11-19T17:56:00.000-08:00

In academia, PIs wants results and their grad students want lithography recipes! The newbies often want to know the exact dose which would preserve the geometrical dimensions of their CAD drawing. Telling newbies that the area dose for a particular resist thickness on some substrate fall between 80-200 µC/cm^2 generally irritates them.

They do not appreciate the dynamics of developing processes. The best way to obtain the correct dose in electron beam lithography is to start with a ballpark range and then do a dose calibration to determine the most appropriate dose.

The way to do that is to program the electron beam write to write an array of patterns, starting with an low dose and ending with a very high dose, with judicious increments, as shown below.

In the schematic, we see that the electron beam writer moved in a serpentine manner (e.g. Joe Nabity's NPGS lithography software) with underexposed patterns to overexposed patterns. By carrying some SEM imaging on these patterns, it is possible to determine the exact dose!

Metamaterials for biosensing applications

2009-11-18T18:25:00.000-08:00

An interesting paper by Anatoly Zayats group. I had the opportunity to meet A. Zayats at the APS meeting in 2008, in New Orleans.

A. V. Kabashin et al. Plasmonic nanorod metamaterials for biosensing. Nature Materials 8, 867 - 871 (2009).

The authors demonstrate an improvement in biosensing technology using a plasmonic metamaterial that is capable of supporting a guided mode in a porous nanorod layer. [...]

Here, we notice that there's not much innovation as far as design is concerned, but the concept is new. We have entered in an era where we have complete understanding how to design metamaterials. Our limitation resides in the ability to manufacture (micro-/nanofabricate) them. And, the future of metamaterials lies in applications, in particular life sciences applications .

Compilation of Metamaterials theses and research groups working in photonics

2009-11-18T17:46:00.000-08:00

I applaud Ki Young Kim's effort in having compiled a comprehensive list of metamaterials theses, as well as a list of all the research groups working in electromagnetics and photonics.

Hossein Mosallaei, now assistant professor at Northeastern University was among the first (together with R. A. Shelby) to specialize in metamaterials and completed his dissertation in 2001.

Materials Discovery: Finding the optical properties of materials

2009-11-17T15:24:00.000-08:00

In my job, we're always searching for new materials to engineer, in order to manufacture better metamaterials.

Often, we need to rapidly look up the optical properties of existing materials. There's always Edward Palik's handbook of optical constants in the library but resources on the internet can be faster.

My favorite resources are:

1. Luxpop

2. RefractiveIndex.INFO

3. Photonics Lab at BYU

Bilayer design: The secret to a good lift-off process

2009-11-17T07:49:00.000-08:00

I often come across researchers who struggle with a lift-off process: They usually write decent patterns with electron beam lithography, do a good metal evaporation, but when it comes to lifting off the polymer, everything gets ripped apart including their metallic structures.

Most of the time, it's because the evaporated metal coats the polymer sidewalls. To do a better lift-off, it's best using a bilayer design where you have a higher molecular weight polymer on top of a lower molecular weight polymer, as shown in the figure below.

When you expose the bilayer with ebeam, an undercut is formed. Due to the undercut, you avoid coating the sidewall of the resist when you evaporate metal. Lift-off then becomes a breeze!

Probing the magnetic field of light and Acoustic hyperlens

2009-11-16T17:46:00.000-08:00

There are two papers on metamaterials worth highlighting this week:

(1) M. Burresi, et al. Probing the Magnetic Field of Light at Optical Frequencies. Science 326, 550 (2009).

The authors used concepts from the field of metamaterials to probe the magnetic field of light with an engineered near-field aperture probe. [...]

There's also a complimentary perspective article titled "Glimpsing the Weak Magnetic Field of Light" by Harald Giessen and Ralf Vogelgesang with some insights on Heinrich Hertz mind.

(2) And, another paper from Xiang Zhang's group:

Jensen Li et al. Experimental demonstration of an acoustic magnifying hyperlens. Nature (Advance publication online) DOI: 10.1038/NMAT2561.

The authors report the experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves. [...]

Nanoskiving: A slight variant of it!

2009-11-16T15:05:00.000-08:00

Nanoskiving is a new technique pioneered by George M. Whitesides group that combines thin-film deposition of metal on a topographically contoured substrate with sectioning using an ultramicrotome. G. M. Whitesides is best known to have pioneered soft lithography.

Microtomes have been used since 1800 by biologists to cut thin slices of specimen. The ultramicrotome cuts routinely 200 nm slices.

And, it was very clever to use it for nanofabricating structures! I used a variant of the Nanoskiving technique to manufacture extreme high aspect ratio nanowires.

The moral of the story is to learn from the masters who are inspired in devising lithographic techniques to produce awesome nanostructures, which would otherwise be challenging with conventional lithographic techniques. One of my favorite lithographic masters is Teri W. Odom. Very creative!

How to add color or false color SEM images?

2009-11-15T19:41:00.000-08:00

Nowadays, for publishing manuscripts in high impact factor journals like Science and Nature, Scanning Electron Microscope (SEM) images need to be false colored for enhancing visual illustration. There are several hypothetical ways of adding color to the SEM images.

Among the myriad of solutions, one could either buy expensive software to do the trick or use MATLAB codes.

I coded a matlab script here that you could use.

To use it, simply convert your SEM image file (.jpg/.png/.gif/.tiff) to a text file (.txt) using a program like ImageJ and then use the script to add color your SEM image. You can play with the MATLAB's colormap GUI to add various colors to the SEM image.

The scientific impact of a scientist: the h-index

2009-11-15T17:26:00.000-08:00

In academia, we often want to know the scientific impact of a researcher. Basically, the academic community wants to know if anybody cares about what you have published. In brief, your scientific impact depends on the number of citations you have received for your work. The higher the citations, the more significant your work is.

However, there is a useful metric known as the Hirsch index or h-number which is used nowadays to gauge this scientific impact. And often, universities use this metric to assess potential faculty candidates or use it as a guideline for tenure decisions. Typically, for top universities, assistant professors would have an h-index of around 5+, tenured professors would have it around 10-12 and a full professor would have a value of 20 or more. An average recent PhD graduate would have an h-index of 1-2. But of course, there are always exceptions! There are faculty members with h-index lower than 5!

Michael Nielsen correctly pointed out that it is possible to estimate one's h-index without all the math simply by computing the following:

h ~ √(T)/2, where T is the total number of citations.

To have a more accurate value, you can use prof. Harzing's "Publish or Perish" software.

Just for curiosity, I have an h-index of 6!

Well, h-index, like most things, is not foolproof. It has it's flaws. It can also be tweaked by writing a review article. But nevertheless, it is a good approximation of a researcher's scientific impact on the community.

Welcome To My Blog!

2009-11-15T11:21:00.000-08:00

I have been delving (Designing/Simulating, Micro-/Nanofabricating and Characterizing) in micro-/nanophotonics R&D for the past 8 years and made significant breakthroughs. I have lived in Singapore and the United States and thus possess a broad perspective (both academically and socially) of the East and West. Also, I have acquired a unique skill set and experience by working at national facilities in both countries. Additionally, I have been heavily involved in the past in open source software coding.

I am often giving advice to undergrads, grad students and postdocs from schools that are striving to make a name for themselves, to top Ivy league schools like Harvard and MIT. And, I have always been urged to write my thoughts down somewhere.

This blog is about sharing my thoughts and my personal experience to the world. :)