Angular-insensitive optical filtering based on meta-GMR.

In this study, the optical properties of a meta-GMR consisting of a metasurface stacked on a planar dielectric slab waveguide were theoretically investigated. Two different metasurfaces, namely chiral split-ring resonator dimer arrays with/without a rod-shaped antenna, were investigated and compared. Conventional GMR filters utilize gratings to couple the free-space electromagnetic field to the waveguide. The highly dispersive nature of grating leads to low angular tolerance. Here, the grating is replaced by metasurfaces. The metasurface unit cell can be regarded as a polarizable dipole that couples the free-space electromagnetic field to the waveguide and decouples the waveguide mode to the radiation modes. Based on the localized nature of the resonant metasurfaces, the metasurface/GMR hybrid mode exhibits a superior angular tolerance as compared with a conventional GMR filter. This study can open a new avenue to tailor the optical properties of GMR-based devices.

Triple-Junction Optoelectronic Sensor with Nanophotonic Layer Integration for Single-Molecule Level Decoding.

Interest in developing a rapid and robust DNA sequencing platform has surged over the past decade. Various next-/third-generation sequencing mechanisms have been employed to replace the traditional Sanger sequencing method. In sequencing by synthesis, a signal is monitored by a scanning charge-coupled device (CCD) to identify thousands to millions of incorporated dNTPs with distinctive fluorophores on a chip. Because one reaction site usually occupies dozens of pixels on a CCD detector, a bottleneck related to the bandwidth of CCD imaging limits the throughputs of the sequencing performance and causes trade-offs among speed, accuracy, read length, and the numbers of reaction sites in parallel. Thus, current research aims to align one reaction site to a few pixels by directly stacking nanophotonic layers onto a CMOS detector to minimize the size of the sequencing platforms and accelerate the processing procedures. This article reports a custom integrated optoelectronic device based on a triple-junction photodiode (TPD) CMOS sensor in conjunction with NPL integration for real-time illumination and detection of fluorescent molecules.

Amplification of the signal intensity of fluorescence-based fiber-optic biosensors using a Fabry-Perot resonator structure.

Fluorescent biosensors have been widely used in biomedical applications. To amplify the intensity of fluorescence signals, this study developed a novel structure for an evanescent wave fiber-optic biosensor by using a Fabry-Perot resonator structure. An excitation light was coupled into the optical fiber through a laser-drilled hole on the proximal end of the resonator. After entering the resonator, the excitation light was reflected back and forth inside the resonator, thereby amplifying the intensity of the light in the fiber. Subsequently, the light was used to excite the fluorescent molecules in the reactive region of the sensor. The experimental results showed that the biosensor signal was amplified eight-fold when the resonator reflector was formed using a 92% reflective coating. Furthermore, in a simulation, the biosensor signal could be amplified 20-fold by using a 99% reflector.

A polarization control system for intensity-resolved guided mode resonance sensors.

In this study, a polarization-control setup for intensity-resolved guided mode resonance sensors is proposed and demonstrated experimentally. The experimental results are in good agreement with the simulation data based on rigorous coupled wave approach calculations. The proposed intensity-resolved measurement setup transfers polarization ellipses, which are produced from guided mode resonance to a linear polarization state under a buffer solution condition, and then suppresses the signals to dark using a polarization-control set. Hence, any changes in the refractive index results in an increase in the intensity signals. Furthermore, no wavelength-resolved or angular-resolved measurement is needed in this scheme. According to the experimental results, a wide linear detection range of 0.014 refractive index units is achieved and the limit of detection is 1.62E-4 RIU.

Polarization dependent light extraction of a GaN light emitting diode using dark field angle-resolved photoluminescence spectrometry.

In this paper, the polarization dependent optical properties of GaN surface relief grating are investigated using dark field angle-resolved photoluminescence (ARPL) spectrometer. The light extraction efficiency with the transverse electric (TE) and transverse magnetic (TM) pumping source represents a TE polarized dominated property. It is found that the TE and TM waveguide modes cannot be simultaneously coupled out, therefore light extraction is polarization dependent. The ARPL spectrum also reveals that the extraction efficiency is relatively high as the dispersion line of the waveguide mode is coincident with the folded free-photon dispersion of the 1D GaN grating.

Sensitive metal layer assisted guided mode resonance biosensor with a spectrum inversed response and strong asymmetric resonance field distribution.

In this paper, a metal layer assisted guide mode resonance (MaGMR) device with high sensitivity is proposed for bioanalytical applications and its functioning is experimentally proved. We find that the reflection spectra present a unique inversed response. The resonance mechanism is also discussed. Numerical calculation results indicate that the high sensitivity performance of MaGMR comes from the strongly asymmetric resonance modal profile and low propagation angle inside the waveguide. There is a one-fold enhancement of the evanescent wave in the analytes region compared to typical GMR. According to the experimental results, the proposed MaGMR achieved a bulk sensitivity of 376.78 nm/RIU in fundamental TM mode resonating at 0.809 µm with the first diffraction angle. Experiment results show a 264.78% enhancement in the sensitivity compared to that of the typical GMR sensor in the same resonance conditions of TM mode.

A guided mode resonance aptasensor for thrombin detection.

Recent developments in aptamers have led to their widespread use in analytical and diagnostic applications, particularly for biosensing. Previous studies have combined aptamers as ligands with various sensors for numerous applications. However, merging the aptamer developments with guided mode resonance (GMR) devices has not been attempted. This study reports an aptasensor based home built GMR device. The 29-mer thrombin aptamer was immobilized on the surface of a GMR device as a recognizing ligand for thrombin detection. The sensitivity reported in this first trial study is 0.04 nm/µM for thrombin detection in the concentration range from 0.25 to 1 µM and the limit of detection (LOD) is 0.19 µM. Furthermore, the binding affinity constant (Ka) measured is in the range of 10(6) M(-1). The investigation has demonstrated that such a GMR aptasensor has the required sensitivity for the real time, label-free, in situ detection of thrombin and provides kinetic information related to the binding.