Prof. Ted Young on the 'failure of education'

I have moved to King's for a little more than a year now, doing a 'postdoc'. After a long struggle on the choice between 'industry' and 'academia', probably a question every PhD candidate faces, this is the choice I made at the moment.

While research is my main task as a 'research associate', I do respect those who devote to teaching and think about education. what job is more important in the world than to educate and nurture the minds that will shape our society for the next 100, 200 years?
I am reading this speech made by Prof. I. T. Young on the 'failure of education' in the context of Netherlands, but I believe it is quite general to many places.
http://homepage.tudelft.nl/t5g29/manuscripts/Failure%20in%20Education%20-%20IT%20Young.pdf

Positioning fluorescence microscopy approaching 1nm resolution with the help of optical singularity

I enjoyed quite a lot in reading a nice work from S. Hell's group, namely "Nanometer resolution imaging and tracking of fluorescent molecules with minimal photon fluxes",published recently in Science, but a free version available on arxiv;
The core idea of this paper is to use the absolute zero intensity at the singular point of an ideal donut beam to perform positioning microscopy like PALM/STORM. When fluorescence molecule are exactly at this point, it will emit no photon, the nearer the fluorescent molecule is to the singular point, the emitting photon is less. Finding the minimum of minimum photon emission leads to the determination of the position of the fluorescent molecule. It is really clever idea and a marvelous improvement with much less photon required to achieve 1nm resolution.

Some nice early works applying singular optics to metrology can be found in Joseph Shamir's work "Singular beams in metrology and nanotechnology". And Zheng Xi also proposed to use this singularity to perform position sensing: "Accurate Feeding of Nanoantenna by Singular Optics for Nanoscale Translational and Rotational Displacement Sensing" with a free version on arxiv.

All these demonstrates useful applications of optical singularity, I believe many more nice works will pop out in this field.

FOM veldhoven

My work is accepted by FOM veldhoven 2017 as an oral presentation and I will talk about our paper on "Excitation of the radiationless anapole mode";

nice review on the current "meta-lens" researches

"Meta-lens" researches has drawn lots of attentions in recently years. With many contributions from groups with nanotechnology backgrounds, meta-lens are realized by creating a focusing wavefront using structured surfaces like plasmonic structures and high index dielectric structures. However, compared to the overwhelming attentions it got, the drawbacks of such meta-lens from optics perspective are greatly overlooked, similar to the fact that the losses of plasmonic structures are neglected in many publications which produce lots of highly cited papers and create a "closed" subfield of physics but not many real applications comes out.
Finally a nice and critical review is given by diffraction optics experts  P. Lalanne and P. Chavel on the current "Meta-lens" researches.
https://arxiv.org/ftp/arxiv/papers/1610/1610.02507.pdf

New publication on excitation of the radiationless anapole

My paper on the excitation of the radiationless anapole is just published online in OSA's new open access journal Optica:

Excitation of the radiationless anapole mode
I've made a video recently on this topic for our group website:

new publication on stretchable Fresnel zone plate

Xueming's paper on a stretchable Fresnel zone plate composed of CNT grown on PDMS, in which I performed the simulation and optical measurement,  is published on Scientific Reports:
http://www.nature.com/articles/srep25348
Achieving circularly symmetric stretching is rather difficult task, which results in strong astigmatism aberrations after stretching. But it is a very good idea. If we could have found an ideal circular stretching mechanism, it will be much better, #the power of mechanical engineering:).

New publication on focal field shaping of vector vortex beams

Our publication "Shaping the focal field of radially/azimuthally polarized phase vortex with Zernike polynomials" is published recently on Journal of Optics.: 
http://iopscience.iop.org/article/10.1088/2040-8978/18/6/065608

Krylov model-order reduction approach paper online

Joern's paper is online now. This paper is on the calculation of spontaneous decay rate of resonance in open system with a Krylov model-order reduction approach. http://link.springer.com/article/10.1007/s00339-016-9643-4 This paper will be very interesting for those who deals with resonances of open systems, like plasmonic particles. The proposed approach can calculate all the scattering poles at one time and the corresponding modes. The method is different but deals with similar physical problems like previously Philippe Lalanne's quasi-normal mode analysis(PRL paper, reference to be added later). Lei

New publication provide an alternative view about the Kerker's condition for directional scattering

Broadband active tuning of unidirectional scattering from nanoantenna using combined radially and azimuthally polarized beams . Traditional Kerker's condition deals with linearly plane wave illumination, where a single wavelength can fulfill this condition on direction forward/backward scattering, thus very narrow-band. Our proposed scheme is based on separate control over the induced electric dipole and induced magnetic dipole using two coherent focused beams of radial polarization and azimuthal polarization, respectively. By carefully tuning the amplitude and phase relation of the two beams, a broadband unidirectional scattering can be achieved, even at the antenna’s resonant wavelength where the antenna scatters efficiently. By moving the focus of one beam, a drastic switch of the unidirectional scattering can be observed. Such a scheme enables the design of ultra-compact optical switches and directional couplers based on nanoantennas. PS. More detailed discussion will be added when I have more time. Lei

Our new publication on a focal field shaping technique

Point Spread Function (PSF) design to shape the focal field distribution of an optical system is very important to many applications: optical microscopy, lithography, optical tweezers, etc.  However, often this design process includes tedious numerical calculations and complex optimisation procedures.

In this paper, we explain to the readers the benefits of the well-established Extended Nijboer-Zernike theory(a most recent updates of the ENZ theory can be found in https://www.jeos.org/index.php/jeos_rp/article/view/13044/1026 ) :

1. The 3-D focal field distribution of each Zernike mode on the exit pupil can be analytically obtained and the contribution of each mode to the total focal field are solely related by its Zernike coefficient;
2. The Zernike modes(polynomials ) form a complete and orthogonal set on a unit circle.

Based on these merits, we developed an optimisation algorithm to find a focal field with extended depth of focus. Since the focal fields of Zernike modes are analytically obtained, our optimization parameters  are reduced to the number of Zernike modes applied.

We have build up an experimental setup to demonstrate this idea: a Spatial Light Modulator(SLM) is used to shape the pupil field and a scanning stage is used to measure the 3D focal intensity distribution.

And the actual measurements validated our theoretical results:

Ref.:

A. P. Konijnenberg, L. Wei, N. Kumar, L. C. C. P. Filho, and H. P. Urbach. Demonstration of an optimised focal field with long focal depth and high transmission obtained with the extended nijboer-zernike theory. Opt. Express, 22(1):311–324, Jan 2014.

http://dx.doi.org/10.1364/OE.22.000311

不忘初心（以前写的，再同大家分享一下这些思考）

今天读了曾经台湾清大教授彭明辉的blog，他最近主动辞职了，辞职信里写到“主因是不滿於學術風氣的敗壞，而自己無力阻擋”。他的文章“學術自由的本意與淪喪”看的出来是他的严肃思考。彭先生的文章其实有shock到我，就像小和尚念经，正昏昏欲睡，不知其意之时，师傅后脑门一击，醍醐灌顶。他说的是台湾的现实，却也投射这我们同样的问题。

联想到前段时间Nature 专门做了一期特刊有关于PhD的教育的(The future of PhD)，而新科研究人员（PhD candidates）的培育只不过是当代学术或许现实问题的冰山一角罢了。 

当然我不希望如此悲观，（以至于有可能能够改变游戏规则的人（精英）失望离开。）Nature中提到当前制度的一个后果是“研究人员的过度饱和”，我在想，真的过多了吗？ 还是其实远远不够？ 想想我们这个世代所面临的能源问题、粮食问题、土壤和水资源的污染问题，穷人的医疗问题，哪一个问题缺少得了专业人士的研究、分析与解决？ 我们有做足够这方面的研究吗？也难怪整个世界都在抱怨充斥全宇宙的博士生呢...

我想先问你“为什么而研究？”

我记得印象里里小时候和科学家或科技相关联的画面总是“高精尖”、“最先进”、“突破性的”、“诺贝尔奖”等等，长大后老师说影响因子就是学术的全部，science、nature在中国的大学里会是一件很轰动的事。 我感觉很多人心目中的研究大概是“做前人之未作，或在前人的基础上做的更好”，我们称之为“追求卓越”。然而这是一种追逐的过程，向前奔跑，没有止境的路。你想在哪里停止呢？ 

学术的意义是在于追求卓越吗？我们一窝蜂地追逐最新最热的研究，这就是意义本身吗？

宗萨钦哲仁波切说过“我们的社会总是用一个人拥有什么，而不是他是什么样的人来评价一个人”，这不仅是指物质上的拥有，也包括精神上的。 比如北大的柳智宇拒绝了MIT的录取而选择出家，当然在社会上掀起轩然大波。我们会觉得柳智宇先生“理所当然”地应该接受这份顶级的offer，“理所当然”地该去做最顶尖的研究，我们的社会总是这样“理所当然”地运行着...

如果去想象一个很棒的博士选择去用技术改造一整个村庄而不是去顶级的研究所做研究发表顶级刊物，这真的很难。

然而彭明辉先生说：

“學術的本務不是研究成果的競爭，不是「學術卓越」的追求，不是新穎知識的生產，也不需要有「在五年內要成為數一數二的佼佼者」（李遠哲，2001）這樣的抱負。學術不是一種「專長」，而是一種態度：為了社會更好的未來，而嚴肅探究社會既有的價值、信念與制度，找出其中的盲點，秉著學術良知說出自己能信服的價值、信念與制度，從而使社會獲得自我校正與自我改善的力量。羅素對婚姻與宗教的態度，跟他在學術圈內普受讚譽的數理邏輯無關，但是他對婚姻、宗教與學術自由的省思，卻對社會的進步有不能抹滅的貢獻。”

他的文章有引用罗素的「大學教師理應是具有特殊知識和訓練的人，他們能夠從不尋常的角度去探索具有爭議性的問題，並很有機會因而使我們對該問題有新的瞭解。」（Russell, 1975）

盲目地追逐排名与SCI指标正在使我们的研究与我们本地的问题日渐脱离，我始终不能忘当年大连海湾石油泄漏新闻上的那一幕幕，我们的国家依靠着小小的船没有防护的渔民去清理油污，而与此同时我们的大学们个个都正在宣称自己的努力目标是世界一流的研究型大学！当然这些所谓一流的指标里面，论文分子占了不少，可是这又有什么意义？！我宁愿那个学校用科学安全的方法把那油污给清了，我们就承认那个大学是“一流”。

关键还是想想我们为什么要做研究，然后“不忘初心”

Good book by Kurt E. Oughstun

Kurt E. Oughstun() wrote really nice book on "Electromagnetic and Optical pulse propagation", very much recommended. 

First Bachelor thesis student finished

Last Friday, my first bachelor student Sander has successfully defended his bachelor thesis.
I am very happy to work with him, and together with him and other colleagues we are able to demonstrate an idea I proposed.
He is both curious and diligent, reminding me of the famous phrase of Zen: 'Never forget the beginner's mind'(in chinese: 不忘初心).

Nice book by Jean Bladel: Singular electromagnetic fields and sources

Electromagnetic theory is a quite broad research area, and forms the basis in understanding a wide branch of scientific phenomena, and consequently you can find lots of books using EM theory as their theoretical basics, and the main topics can diverges drastically.
Interestingly, this book by Jean Bladel: Singular electromagnetic fields and sources, aims to summarize a group of problems one may encounter in this area, the 'source/geometrical singularities', one common example is the Green's function which no one can escape when jumping into this area.
It is a very nice companion book as it aims, which provides with a nice read, and I would like to share with you.

Prefaces of a researcher

Knowledge is of great importance for our society, Nobody (or at least not so many) would doubt it any more. Techniques have made knowledge easily accessible to more and more people, just as some said before:"The techniques possibly make a fool of this generation more knowledgeable than genius of last generation"

 But knowledge doesn't come from nothing. Here come the researchers, often at the frontiers of knowledge, providing original new data or new perspectives of our world.

 People often forget that behind those 'cold' data/theories, there exist the researchers with beating hearts. There are not so many places where a researcher could post his/her opinion about researches themselves, or unfortunately, not every researcher is necessarily a good writer at the same time.

 Of course, time has left us with some of sparkling masterpieces, a nice written book or research paper or device. J.M. Ziman's book "Principles of the Theory of Solids" is of course of this kind. Even from its preface, you can learn so much about his opinion on writing/acquiring scientific knowledge. He was aiming to write a book full of ideas, instead of a collection of facts or complex formulas, which would distract the readers away from the science's hard core. Isn't it the very lack of many scientific publications?


 Anyway, I invite you with the preface of this true researcher, and hope it is inspiring for you as well. ---Lei, @Delft Link to the Preface of J.M. Ziman's book The link from the publisher is broken, you may search online about this book's preface, it is worth to read.

'Candle light': Manipulating light and matter at the nanoscale for high-resolution imaging and spectroscopy.

NanoMeta

I have finished the NanoMeta Conference in Seefeld, Austria. I am really inspired by many of the talks given there, thus it is really worthwhile to broadcast it a bit.

The conference is held in the beautiful Seefeld in Tirol area.
You can find the program contents on this website> http://www.nanometa.org/.

I have also made a list of some of my favorite talks or posters during last week> NanoMeta_talks.

NanoMeta2013 Day1

From today on, I have been in the conference NanoMeta2013 which is organized of European Physics Society. (it is quite interesting when I see the poster in front of the congress that the EPS is a 'Grass Root' organisation. the 'Grass Root', 草根 in Chinese, simply meaning ordinary people who do not claim superior power, etc. but gathering together can make an important influence on this society.)

The Conference is kicked off by a plenary talk by Uwe Kreibig on extensions of Mie theory due to Mie's incapability to explain many of the experiments in the area of nano-plasmonics. To Uwe, the field of 'plasmonics' is not new at all.  Many of the Mie's problem lie in the fact that Mie has adopted bulk permittivity of the material for the sphere, actually the spherical surface has a strong influence on the electronic response which can not be exactly described by the bulk. 
He is the author of a book:

Optical Properties of Metal Clusters. 

The section 'Quantum Plasmonics' in the morning leads to a strong debate on the methods of modelling sub-nm plasmonic gaps. The 'Quantum' plasmonics is mainly explaining the plasmonic effects by Quantum Mechanics. Classical electromagnetic theory by using bulk properties of materials will predict infinite field enhancement for a infinitesimal metallic tip, but from quantum physics, we can know this can not be true since the Pauli exclusion principle of the electrons. This is effect is need to take into consideration when tip/gap is below 1 nm. 

 Stephen Maier presented the non-locality theory for sub-nm tips. The non-locality theory is quite popular in recent years, and have been used in publications of F. Javier García de Abajo, D.R. Smith, S.A. Maier, et al.. The basic idea behind it is to introduce an 'electronic friction' in describing the collective oscillation of the electrons. 

Javier Aizpurua claims today that we should be cautious in applying the 'hydrodynamic' model of the electrons, since it has a failure history in describing previous surface physics, and will possibly result in the same consequence in describing closed surfaces- the area of plasmonics.  Javier and his collegues has developed an alternative method-- 'Time-dependent density functional theory', which originates from quantum theory.

I have expected more on Stephen Maier's presentation about broadband plasmonic antennas for SEIRS, but unfortunately he didn't go very deep into this part.

The talk of Frank Neubrech is quite nice as well.

Decay of dipole oscillation near planar interface

Details in the file link: Decay of dipole oscillation near planar interface

Mid-infrared Spectroscopy

As mentioned in a previous post on vibrational spectroscopy, one can use the infrared spectrum to determine the molecular structures, which may offer clues about the 'fingerprints' of the molecules. Compared to the weak vibrational overtone transitions which give rise to near infrared radiation, the mid-infrared gives much stronger signals that serves enough S/N ratio and works as the 'fingerprint' region of molecules. As an example, you can have a look at the absorption spectrum of Methane.

Absorption Spectrum of Methane

The biggest problem for laser spectroscopy in the mid-infrared is the lack of good laser sources in this spectrum range.

F.K. Tittel et al. has listed the available mid-infrared laser sources in the mid infrared in a book chapter, which is also given below:

Laser sources and their working range, courtesy[F.K. Tittel et al.]

Based on an excellent laser they developed in 2009, F. Adler et al. from JILA, Colorado has successfully developed a state-of-art mid-infrared laser spectroscopy. The work is excellent and the paper written is a classic to me, that's really worth to share with you in a summary of the paper in one short document: Google Drive--Mid-infrared Frequency comb Fourier Transform spectroscopy.