In this paper, we investigate the mode sensitivity (S mode) of subwavelength grating slot (SWGS) waveguides. S mode is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of S mode. The measured S mode value of 79% is consistent with the theoretical prediction of 83%.
The need for a high
optical spectrum throughput, high conductivity,
and controlled energy levels of transparent conductive oxide used
in solar cells stresses the development of novel materials that help
reduce the existing dependency on indium-based oxides. ZnO is a promising
material in this context, and in this work, we demonstrate how Hf
doping of ZnO films allows engineering both electrical and optical
properties to fit the requirements of different solar cell architectures
and materials. We focus on the lightly doped domain where Hf substitution
is believed to be the key for band gap tunability without negatively
affecting the carrier transport behavior. We provide experimental
analysis of controlled changes in the optical and electrical properties,
including work function, and a detailed analysis of the structural
behavior resulting from the deposition at elevated temperature. We
finally present first-principles density functional theory simulations
to elucidate the mechanisms responsible for the obtained electronic
and electrical properties that predict a modification in the band
structure of ZnO when Hf is substituted and/or embedded in the ZnO
matrix as HfO2 phases.
The outstanding performance and facile processability turn two-dimensional materials (2DMs) into the most sought-after class of semiconductors for optoelectronics applications. Yet, significant progress has been made toward the hybrid integration of these materials on silicon photonics (SiPh) platforms for a wide range of mid-infrared (MIR) applications. However, realizing 2D materials with a strong optical response in the NIR-MIR and excellent air stability is still a long-term goal. Here, we report a waveguide integrated photodetector based on a novel 2D GeP. This material uniquely combines narrow and wide tunable bandgap energies (0.51–1.68 eV), offering a broadband operation from visible to MIR spectral range. In a significant advantage over graphene devices, hybrid Si/GeP waveguide photodetectors work under bias with a low dark current of few nano-amps and demonstrate excellent stability and reproducibility. Additionally, 65 nm thick GeP devices integrated on silicon waveguides exhibit a remarkable photoresponsivity of 0.54 A/W and attain high external quantum efficiency of ∼ 51.3% under 1310 nm light and at room temperature. Furthermore, a measured absorption coefficient of 1.54 ± 0.3 dB/µm at 1310 nm suggests the potential of 2D GeP as an alternative infrared material with broad optical tunability and dynamic stability suitable for advanced optoelectronic integration.
Recent theoretical studies proposed that two-dimensional (2D) GaGeTe crystals have promising high detection sensitivity at infrared wavelengths and can offer ultra-fast operation. This can be attributed to their small optical bandgap and high carrier mobility. However, experimental studies on GaGeTe in the infrared region are lacking and this exciting property has not been explored yet. In this work, we demonstrate a short-wavelength infrared (SWIR) photodetector based on a multilayer (ML) GaGeTe field-effect transistor (FET). Fabricated devices show a p-type behavior at room temperature with a hole field-effect mobility of 8.6 - 20 cm2 V-1s-1. Notably, under 1310 nm illumination, the photo responsivities and noise equivalent power of the detectors with 65 nm flake thickness can reach up to 57 A/W and 0.1 nW/Hz1/2, respectively, at a drain-source bias (Vds) = 2 V. The frequency responses of the photodetectors were also measured with a 1310 nm intensity-modulated light. Devices exhibit a response up to 100 MHz with a 3dB cut-off frequency of 0.9 MHz. Furthermore, we also tested the dependence of the device frequency response on the applied bias and gate voltages. These early experimental findings stimulate the potential use of multilayer GaGeTe for highly sensitive and ultrafast photodetection applications.
We demonstrate a dual-band two-mode (de)-multiplexer based on tapered asymmetric directional coupler (ADC). The working principle of the device relies on the conversion of the fundamental transverse electric (TE0) mode to the first order (TE1) mode. A phase-matching condition is applied across the O-and C-bands to broaden the operation wavelength of the device. Measurement performed on a mode division multiplexing (MDM) link formed by a back-to-back connected multiplexer and demultiplexer exhibited an insertion loss of less than 1.2 dB with cross talk better than 16 dB. The response is recorded over dual-bands, each with 100-nm bandwidth covering 1260-1360 nm and 1500-1600 nm (extends to the near Lband). The device is compact with an overall length of 75 µm.
We present an experimental analysis of optical Physically Unclonable Functions enhanced using plasmonic metal nanoparticles in a Silicon on Insulator based integrated structure. We experimentally demonstrate the behavior of possible configurations of simple PUF structures defined only by the nanoparticle distribution. The devices show a promising response when tested with transverse magnetic polarized light. This response offers an easy-to-implement methodology to enhance the behavior of previously proposed optical PUFs. We additionally make a comprehensive analysis of the power, thermal, and polarization stability of the devices for possible side-channels attacks to the systems.
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