All‐Dielectric Programmable Huygens' Metasurfaces

Low‐loss nanostructured dielectric metasurfaces have emerged as a breakthrough platform for ultrathin optics and cutting‐edge photonic applications, including beam shaping, focusing, and holography. However, the static nature of their constituent materials has traditionally limited them to fixed functionalities. Tunable all‐dielectric infrared Huygens' metasurfaces consisting of multi‐layer Ge disk meta‐units with strategically incorporated non‐volatile phase change material Ge3Sb2Te6 are introduced. Switching the phase‐change material between its amorphous and crystalline structural state enables nearly full dynamic light phase control with high transmittance in the mid‐IR spectrum. The metasurface is realized experimentally, showing post‐fabrication tuning of the light phase within a range of 81% of the full 2π phase shift. Additionally, the versatility of the tunable Huygen's metasurfaces is demonstrated by optically programming the spatial light phase distribution of the metasurface with single meta‐unit precision and retrieving high‐resolution phase‐encoded images using hyperspectral measurements. The programmable metasurface concept overcomes the static limitations of previous dielectric metasurfaces, paving the way for “universal” metasurfaces and highly efficient, ultracompact active optical elements like tunable lenses, dynamic holograms, and spatial light modulators

Imaging-based molecular barcoding with pixelated dielectric metasurfaces

Metasurfaces provide opportunities for wavefront control, flat optics, and subwavelength light focusing. We developed an imaging-based nanophotonic method for detecting mid-infrared molecular fingerprints and implemented it for the chemical identification and compositional analysis of surface-bound analytes. Our technique features a two-dimensional pixelated dielectric metasurface with a range of ultrasharp resonances, each tuned to a discrete frequency; this enables molecular absorption signatures to be read out at multiple spectral points, and the resulting information is then translated into a barcode-like spatial absorption map for imaging. The signatures of biological, polymer, and pesticide molecules can be detected with high sensitivity, covering applications such as biosensing and environmental monitoring. Our chemically specific technique can resolve absorption fingerprints without the need for spectrometry, frequency scanning, or moving mechanical parts, thereby paving the way toward sensitive and versatile miniaturized mid-infrared spectroscopy devices

Research of optical pumping effects in a semi-open quantum systems and desing of frequency stabilization system for titanium-sapphire laser

Bakalaura darba ietvaros ir veikta optiskās pumpēšanas efektu daļēji atvērtās kvantu sistēmās skaitliska modelēšana, kā arī izstrādāts situācijas vienkāršots analītisks modelis. Paredzēts izveidot titāna-safīra lāzera frekvences stabilizācijas sistēmu, kas ļaus lāzera frekvenci stabilizēt uz Rb atomu D līnijas supersīkstruktūras komponentēm. Stabilizācijas sistēmas izveidē tiks izmantota bezdoplera piesātinājuma absorbcijas spektroskopijas metode. Atslēgas vārdi: Optiskā pumpēšana, daļēji atvērtas kvantu sistēmas,optiskie Bloha vienādojumi, lāzera frekvences stabilizācijas sistēma,piesātinātās absorbcijas spektroskopija.This work presents numerical solution of optical pumping effects in semi open quantum systems, and also gives simplified analytical solution. This BSc thesis shows the design of laser frequency stabilization system for the titan-sapphire laser. This system allows to stabilize the laser to Rb atom D line hyperferfine lines. The saturated absorbtion spectroscopy is used to make the frequency stabilization system. Keywords: Optical pumping, semi open quantum systems, optical Bloch equations, laser frequency stabilization system, saturated absorbtion spectroscopy

Selective Plane Illumination Microscopy Using Non-spreading Airy Beams

Recently a new field of microscopy has emerged, known as selective plane illumination microscopy (SPIM). Using a SPIM setup the sample is illuminated with a thin light sheet from the side. The selective plane illumination overcomes many problems that conventional microscopes have. Conventional microscopes illuminate the sample axially and collects the light only from the focal plane of the microscope objective. Therefore parts of the sample which are out of focus are illuminated unnecessarily, leading to rapid fluorophore photobleaching and decrease of signal to noise ratio due to out of focus light. The $SPIM$ method overcomes these problems, because only the fluorophores in the focal plane of the objective are excited. Another problem with conventional microscopes is that they are capable of only two-dimensional imaging. The exception are confocal microscopes, but these microscopes are slow and the field of view is restricted to few hundred micrometers. The SPIM method significantly improves the three-dimensional imaging speed and can reach up to few hundred frames per second. This imaging speed enhancement is achieved, because the whole plane is captured with a single snapshot, instead of point by point scanning as in confocal microscopes. To take all the advantages of the SPIM method it is crucial to form a thin light sheet that extends for the whole field of view. Commercially available lasers have Gaussian beam. It is well known that tightly focused Gaussian beams spread out quickly, therefore there will be good axial resolution only in the central part of the image. Because of that the field of view will be restricted to the Rayleigh range of the Gaussian beam. In this work we present how to create non-spreading Airy beams using only two additional lens elements and how they can be implemented in the SPIM setup to significantly extend the field of view keeping high axial resolution. This is an important advancement since Airy beams would allow larger sized objects, e.g. optically cleared tissue specimens, to be imaged with high resolution. This thesis shows a novel design of a light sheet microscope that opens up new possibilities for biological and medical research.The field of optical microscopy emerged in late 17th century, when famous Dutch draper and scientist Anton van Leeuwenhoek pioneered the techniques of microscopy. Since then the field has expanded and has greatly influenced the development of biology, chemistry, physics and medical research areas. Recently optical microscopy reached the realms of super resolution and nano scale, therefore allowing to see even single molecules. For this invention in 2014 three scientists were awarded with Nobel prize in chemistry. Overall, four Nobel prizes have been awarded for discoveries and inventions in microscopy. Most of the research in optical microscopy is done to increase the spatial resolution, neglecting the resolution in time. But obviously there are fast biological processes and understanding them would give significant contribution to medicine and biology. In the last decade a new field of microscopy emerged, called selective plane illumination microscopy (SPIM). What distinguishes SPIM from conventional microscopes is that the sample is illuminated with a thin laser sheet. Therefore fluorescent light will be emitted only from the plane where the light sheet lies. And the light sheet can be made as thin as one hundredth of a human hair width. Therefore the SPIM method allows to image large samples with high temporal resolution and high spatial resolution in all 3 dimensions. With this new technique it is possible to reach up to few thousand frames per second, and it is possible to follow neuron signal propagation in real time. It is a great step forwards for research in neurology. Not only for studying cellular interactions, but also neuronal network interactions throughout the body of small animals. Furthermore bigger and older sample imaging could give better understanding of the neurological diseases that come with age, for instance Alzheimer's disease. Besides significant increase in temporal resolution, with the SPIM technique it is possible to follow biological processes for much longer time periods compared to conventional microscopes. One can follow the evolution from larvae to fully grown organisms with single cell resolution or biological processes in cells for several days. Therefore it is now possible to follow how diseases evolve in tissue and how well the drugs can affect a disease. Thus it is possible to monitor the disease and the treatment in all stages. This is a significant improvement compared to conventional microscopes: now it is possible to study diseases and drug efficacy like never before

Dielectric Metasurfaces Enabling Advanced Optical Biosensors

Dielectric metasurfaces have emerged as a powerful platform for novel optical biosensors. Due to their low optical loss and strong light-matter interaction, they demonstrate several exotic optical properties, including sharp resonances, strong nearfield enhancements, and the compelling capability to support magnetic modes. They also show advantages such as CMOS-compatible fabrication processes and lower resonance-induced heating compared to their plasmonic counterparts. These unique characteristics are enabling the advancement of cutting-edge sensing techniques for new applications. In this Perspective, we review the recent progress of dielectric metasurface sensors. First, the working mechanisms and properties of dielectric metasurfaces are briefly introduced by highlighting several state-of-the-art examples. Next, we describe the application of dielectric metasurfaces for label-free sensing in three different detection schemes, namely, refractometric sensing, surface-enhanced spectroscopy through Raman scattering and infrared absorption, and chiral sensing. Finally, we provide a perspective for the future directions of this exciting research field

Metasurface-Based Molecular Biosensing Aided by Artificial Intelligence

Molecular spectroscopy provides unique information on the internal structure of biological materials by detecting the characteristic vibrational signatures of their constituent chemical bonds at infrared frequencies. Nanophotonic antennas and metasurfaces have driven this concept towards few-molecule sensitivity by confining incident light into intense hot spots of the electromagnetic fields, providing strongly enhanced light-matter interaction. In this Minireview, recently developed molecular biosensing approaches based on the combination of dielectric metasurfaces and imaging detection are highlighted in comparison to traditional plasmonic geometries, and the unique potential of artificial intelligence techniques for nanophotonic sensor design and data analysis is emphasized. Because of their spectrometer-less operation principle, such imaging-based approaches hold great promise for miniaturized biosensors in practical point-of-care or field-deployable applications

Comparison and Verification of Simulation Results of DeST Based on ASHRAE-140 Standard

Based on the ASHRAE Standard 140-2014, this study takes the simulation results of DeST and other simulation software to comprehensively test the accuracy and validity of DeST in calculating building thermal loads and space cooling and heating equipment performance. Special cases were also designed to find out the influencing factors that led to results' differences. It was found that the solar lost through the window, the setting of shading geometry and the mode of inputting surface coefficients can make a big difference to the simulation results. The calculation deviations in most ASHRAE-140 cases are within 10%, which indicate the accuracy of DeST in building energy simulation.BIO

All-dielectric Metasurfaces for Infrared Absorption Spectroscopy Applications

We present a nanophotonic method capable of detecting mid-infrared molecular fingerprints without the need for spectrometry, frequency scanning, or moving mechanical parts. We leverage dielectric metasurfaces featuring ultra-sharp resonances each tuned to discrete frequencies, enabling us to sample molecular absorption signatures over the mid-IR spectral range

Angle-multiplexed all-dielectric metasurfaces for broadband molecular fingerprint retrieval

Infrared spectroscopy resolves the structure of molecules by detecting their characteristic vibrational fingerprints. Subwavelength light confinement and nanophotonic enhancement have extended the scope of this technique for monolayer studies. However, current approaches still require complex spectroscopic equipment or tunable light sources. Here, we introduce a novel metasurface-based method for detecting molecular absorption fingerprints over a broad spectrum, which combines the device-level simplicity of state-of-the-art angle-scanning refractometric sensors with the chemical specificity of infrared spectroscopy. Specifically, we develop germanium-based high-Q metasurfaces capable of delivering a multitude of spectrally selective and surface-sensitive resonances between 1100 and 1800 cm−1. We use this approach to detect distinct absorption signatures of different interacting analytes including proteins, aptamers, and polylysine. In combination with broadband incoherent illumination and detection, our method correlates the total reflectance signal at each incidence angle with the strength of the molecular absorption, enabling spectrometer-less operation in a compact angle-scanning configuration ideally suited for field-deployable applications