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.

First Publication

My first publication related to my internship on Laser Speckle Contrast Analysis is now online, in which I perform the experiments and data analysis. 

Laser speckle analysis of flow in presence of static scatterers

I have introduced part of the project very briefly in a previous post on internship.

Mie Solution to sphere scattering

In the link below, you can find a short summary of J.A. Stratton's treatment on Sphere scattering in his classic book on 'Electromagnetic Theory'.

the notes--Mie solution of sphere scattering.

The very interesting part is the link between natural oscillation mode of the sphere, and the resonance condition upon plane wave incidence(which is the Mie's solution).
Hope you will enjoy it.

Extraordinary Optical Transmission through nano-hole array--- A revisit to the classical problem: dipole radiation near a lossy interface

Extraordinary Optical Transmission(EOT) phenomena of light through a nanohole array like Fig. 1 was rst observed by T. Ebbesen et al. in 1998. Since then, lots of researches try to explain the mechanism behind such phenomena, most of which attribute it to the Surface Plasmon Polariton(SPP).

Fig. 1, Nano-hole array

In a series of researches by H.T. Liu, P. Lalanne, et al[1, 4, 2], they are trying to build up a `microscopic' theory to explain the EOT phenomena, where each nano-hole is considered to be a elementary scatter, like the case in Fig. 2.

According to their analysis, not only SPP but also the so-called `qusi-Cylindrical wave' also plays an important role. Their theory is built on a fundamental problem:the radiation of dipole near an interface, which they named the `line source problem'. However, even the physical picture of the role of quasi-CW contribution has been widely cited, there are some obvious mathematical errors in their deviation of the line-source problem. In this document, I try to figure those 'messes' out and make a revisit to the classical problem: dipole radiation near a lossy interface based the previous work of W. Lucas, et al. and L. Novotny, et al. .

The document is provided in the link: Dipole radiation near interface. I hope the readers would find it useful. Request for the document can also be sent to my contact info. given in my CV.

Vibration Spectroscopy--Study Notes

Recently, I have been studying vibration spectroscopy, i.e. the vibration infrared and Raman spectroscopy, which indicates the vibration 'fingerprint'of molecules. This is a totally new topic to me, so I didn't know anything about it before, thus I started from zero. Now, I have finished the first step and understand the basics about it. My study notes to this topic can be found in the vibration spectroscopy notes.