See Applied Nanophotonics (ANP)

Dutch Online Optics Colloquium

The Dutch Online Optics Colloquium is an online colloquium of the Dutch optics community. The goal is to continue scientific discussion and education in times of shutdown and social distancing. The colloquium is held Wednedays at 14:00 CET on twitch.tv/nederlandseoptica. The colloquium is 30 + 15 min for questions.

Speakers

The next few speakers are:


25 March

Michiel de Goede

Disease biomarker sensing using RE3+:Al2O3 ring resonators

1 April

Pritam Pai

Speckle intensity statistics of single transmission channels

8 April

Tianran Liu   

Inverse design of an on-chip diffusive spectrometer

15 April

Thomas Bauer           

To be announched

Further volunteers are always welcome (see email below). The aim is for the colloquium to be given by junior scientists in the PhD or postdoc phase.

Practical information

The colloquium is open to anyone interested in the subject. The colloquium is streamed on Twitch, which is a web platform optimized for streaming from one user to many listeners. Questions can be asked in chat. Note that in order to use the chat, you will need to register on Twitch.

Further information can be had by emailing j.j.renema@utwente.nl

Abstracts

25 March: Michiel de Goede - Disease biomaker sensing using RE3+: AI203 ring resonators

Soluble  biomarkers obtained from human bodily fluids can act as a diagnostic  tool for assessing the presence of a disease or monitoring its progression. Optical resonators are well suited for  detecting disease biomarkers since they have both a high sensitivity due  to a large evanescent field and high quality factors that allow  monitoring minute concentrations of analyte. This talk concerns the investigation of biomarker detection using optical  ring resonators on the rare-earth ion doped alumina (RE3+:Al2O3) photonic material platform. First, the development of integrated, undoped Al2O3 waveguides and ring resonators will be discussed, together with their demonstration for optical sensing. Then it will be shown how Yb3+ doped Al2O3 lasers can be used as optical sensors with better performance than their  undoped counterparts due to the narrow linewidth of the lasers.  Finally, it will be shown how mode-splitting in a ring resonator can be  used to obtain self-referenced sensor operation.

1 April: Pritam Pai - Speckle intensity statistics of single transmission channels

The  transmission channels of a multiple scattering medium are the building  blocks for light transport in the medium and lie therefore at the heart of mesoscopic phenomena.  For samples of low dimensionless conductance, only few channels  contribute to light transport. This is reflected in the speckle  intensity statistics, which deviate from a negative exponential law. The deviation is stronger when the incident wave couples to fewer  transmission channels, as has been theoretically predicted [1,2] and  observed in microwave and optical experiments [3-6]. Since every channel  of the transmission operator (TO) of a medium is orthogonal by definition to the other channels, this raises the  research question as to what occurs to the dimensionless conductance  when an incident field couples to a single channel of the medium,  analogous to an Anderson-localized system that supports only one mode [6]. To be able to answer such a question experimentally,  the channels of the measured transmission matrix (TM), which is  necessarily a partial representation of the TO [7], must be an accurate  representation of the channels of the TO. It is therefore crucial that the largest possible fraction of the TM must be measured  precisely and accurately without inducing spurious correlations from the  optical system or the sampling method [8].

 
Here,  we explore the statistics of individual channels by measuring the  transmission matrices of scattering media in the diffusive regime, where the transport mean free path is  comparable to the wavelength of the incident light field. We observe  indications of a deviation from exponential statistics in the speckle  intensity of single channels.
 
[1] Nieuwenhuizen T. M., van Rossum M. C. W., Phys. Rev. Lett. 74 (1995)
[2] Kogan E., et al., Phys. Rev. B 48 (1993)
[3] Strudley T., et al., Nat. Phot. 7 (2013)
[4] Strudley T., et al., Opt. Lett. 39 (2014)
[5] Stoytchev M., Genack A. Z., Opt. Lett. 24 (1999)
[6] Peña A., et al., Nat. Comm. 5 (2014)
[7] Goetschy A., Stone A. D., Phys. Rev. Lett. 111 (2013)
[8] Pai P., et al., arXiv 1912.00933 (2019)

8 April: Tianran Lui - Inverse design of an on-chip diffusive spectrometer

Random scattering media in the diffusive regime provide a long light path and multipath interference in a compact area, resulting in strong dispersive properties which can be used for on-chip compressive spectrometry. However the performance suffers from the low light transmission through the diffusive medium. It has been found that there exist ‘open channels’ such that light with certain wavefronts can pass through the medium with high transmission. Here we show that a scattering structure can be designed so that open channels match target input-output channels, in order to maximize transmission while keeping the dispersive properties typical of random media. Specifically, we use inverse design to generate a scattering structure where the open channels match the output waveguides at desired wavelengths. For a proof of concept, we propose a 1×10 multiplexer covering a band of 500nm in the mid-infrared spectrum, with a footprint of only 9.4μm×14.4μm. We also show that filters with nearly arbitrary spectral response can be designed, enabling a new degree of freedom in on-chip spectrometer design, and we investigate the ultimate resolution limits of these structures. The structures can also be designed based on a simple topology consisting of circular holes with diameters from 200nm to 700nm etched in a dielectric slab, making them highly suited for fabrication.  With the help of compressive sensing, the proposed method represents an important tool in the quest towards integrated lab-on-a-chip spectroscopy.