Temperature sensing under harsh environments is important to various industrial applications. Among different types of temperature sensors, semiconductor diode sensor has the advantages of high sensitivity and compatibility with integrated circuits. In this work, a temperature sensor based on 4H-SiC pn diode has been designed, fabricated and characterized. The device is capable of stable operation in a temperature range from 20 °C up to 600 °C. In forward biased region, the forward voltage of the 4H-SiC pn diode shows linear dependence on temperature at a constant current. This dependence is utilized to sense temperature variations and the proposed device achieves a sensitivity of 3.5 mV/°C. These results indicate that an integrated circuit compatible temperature sensor based on 4H-SiC pn diode is a promising technology for harsh environment sensing applications.
We demonstrate wavelength-tunable VCSELs using high contrast gratings (HCGs) as the top output mirror on VCSELs, operating at 1550 nm. Tunable HCG VCSELs with a ~25 nm mechanical tuning range as well as VCSELs with 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for WDM communications systems.
We demonstrate wavelength-tunable SFF transceivers operating at 1550 nm using a tunable VCSEL with a high contrast grating (HCG) as the output mirror. Tunable HCG VCSELs with a ~25 nm mechanical tuning range and over 2 mW output power were realized. Error-free operation of an optical link using directly-modulated tunable HCG VCSELs transmitting at 1.25 Gbps over 18 channels spaced by 100 GHz and transmitted over 20 km of single mode fiber is demonstrated, showing the suitability of the HCG tunable VCSEL as a low cost source for next generation DWDM communications systems in access networks and data centers.
We present a single crystalline silicon optical phased array using high-contrast-gratings (HCG) for fast two dimensional
beamforming and beamsteering at 0.5 MHz. Since there are various applications for beamforming and beamsteering
such as 3D imaging, optical communications, and light detection and ranging (LIDAR), it is great interest to develop
ultrafast optical phased arrays. However, the beamsteering speed of optical phased arrays using liquid crystal and
electro-wetting are typically limited to tens of milliseconds. Optical phased arrays using micro-electro-mechanical
systems (MEMS) technologies can operate in the submegahertz range, but generally require metal coatings. The metal
coating unfortunately cause bending of mirrors due to thermally induced stress.
The novel MEMS-based optical phased array presented here consists of electrostatically driven 8 × 8 HCG pixels
fabricated on a silicon-on-insulator (SOI) wafer. The HCG mirror is designed to have 99.9% reflectivity at 1550 nm
wavelength without any reflective coating. The size of the HCG mirror is 20 × 20 μm2 and the mass is only 140 pg,
much lighter than traditional MEMS mirrors. Our 8 × 8 optical phased array has a total field of view of ±10° × 10° and a
beam width of 2°. The maximum phase shift regarding the actuation gap defined by a 2 μm buried oxide layer of a SOI
wafer is 1.7π at 20 V.
A novel 8x8 optical phased array based on high-contrast grating (HCG) all-pass filters (APFs) is experimentally demonstrated with high speed beam steering. Highly efficient phase tuning is achieved by micro-electro-mechanical
actuation of the HCG to tune the cavity length of the APFs. Using APF phase-shifters allows a large phase shift with an
actuation range of only tens of nanometers. The ultrathin HCG further ensures a high tuning speed (0.626 MHz). Both one-dimensional and two-dimensional HCGs are demonstrated as the actuation mirrors of the APF arrays with high beam steering performance.