Sihai Chen

IR microbolometer with self-supporting structure operating at room temperature

Abstract Microbolometers with 128-linear array utilizing VO x thin films as thermal sensitive material were fabricated using micromachining technology. In order to obtain thermosensitive material with high quality and low cost, a new deposition method of VO x thin film was described in this paper. The process of the new method was compatible with Si micromachining and CMOS technology, which was very important for monolithic integration with CMOS readout circuit. The responsivity and the detectivity of microbolometers were tested to be about 5 kV/W and 2xa0×xa010 8 cmxa0Hz 1/2 xa0W −1 at current bias of 100 μA, respectively.

A new fabrication method for vanadium dioxide thin films deposited by ion beam sputtering

Abstract A new method for fabrication of VOx thin film on substrates of silicon (1 0 0) and quartz glass has been described. The metallic vanadium thin films were deposited by ion beam sputtering followed by a post-deposition oxidation. The X-ray diffractometry shows that the main compound is vanadium dioxide and the highest temperature coefficiency of resistance is up to 3%/°C for as-deposited VOx thin films with size of 25×25 mm and thickness of 200 nm. The new growth method by ion beam sputtering provides a reliable control for x value in VOx films.

Monolithic integration technique for microlens arrays with infrared focal plane arrays

Abstract Based on scalar diffraction theory, 8-phase-level 256×290 element diffractive microlens arrays with lenslet dimension of 50×33 μm 2 have been fabricated on the back side of PtSi infrared focal plane arrays. The design and fabrication process are discussed. The measurement results indicate that the imaging quality has been greatly improved and the ratio of the signal-to-noise of the infrared focal plane array integration with microlens array is increased by a factor of 2.5.

A novel method of fabrication of microlens arrays

Abstract A new self-alignment process to fabricate microlens arrays is introduced. By this method, during the fabrication process, the rigorous alignment is avoided which has great effect on diffraction efficiency in the conventional multi-photolithography process. The large arrays of 1500×640 element silica microlens are manufactured by this method. The measurement results show that the eight-phase-level microlens arrays diffraction efficiency is as high as 93%.

Design and optical performance research of multi-phase diffractive microlens arrays

To improve the performance of infrared focal plane arrays, multi-phase-level 256 × 256 element diffractive microlens arrays with a center wavelength of 4 µm are designed using a novel partial etching method based on the scalar diffraction theory and computer aided design. A testing system is established with an optical communication semiconductor laser and detector for measuring the diffraction efficiency and point spread function of the designed multi-phase diffractive microlens arrays. The measurement results indicate that the measured diffraction efficiency of 16-phase Si and quartz diffractive microlens arrays are 83.7% and 87.5%, respectively, and the optical response of the infrared focal plane arrays with integration of the diffractive microlens arrays is increased by a factor of 2.23.

VO2-Based Infrared Microbolometer Array

V02-based thin film materials on silicon substrates are fabricated by ion beam sputtering and a post-annealing which is different from the conventional fabricating method. An infrared linear microbolometer array with 128 pixels is prepared using as-deposited vanadium dioxide thin films. Optical and electrical properties for V02-based microbolometer array are tested.

1.55 µm spot-size converter integrated polarization-insensitive quantum-well semiconductor optical amplifier with tensile-strained barriers

A 1.55 µm polarization-insensitive lateral tapered spot-size converter integrated semiconductor optical amplifier (SSC-SOA) with tensile-strained barriers was investigated. The optical amplifier structure used a conventional ridge guide for the active layers and a second larger ridge for the passive waveguide. Low beam divergence of 12° × 15° results in about 3.1 dB coupling losses with −1 dB positional tolerances of ±2.3 µm and ±1.6 µm in horizontal and vertical directions using an anti-reflection coated flat-ended single-mode fibre. The active layer of SSC-SOA consisted of a tensile-strained barrier multiple-quantum-well structure. The SSC-SOA exhibited a signal gain of 25.5 dB and a saturation output power of 11.2 dB m with excellent polarization insensitivity (less than 0.5 dB) at 200 mA.

Research on hybrid integration technology between charge-coupled devices and diffractive microlens arrays

Optical concentration using a microlens with high diffractive efficiency is an important method to improve the fill factor and performances of visible charge-coupled device (CCD) sensors. In this paper, a 516 × 516 element diffractive microlens array (MLA) on the quartz substrate is designed based on scalar diffraction theory and fabricated by submicrometer photolithography technology and magnetically enhanced reactive ion etching. The integration procedures between the MLA and CCD chip are presented. The fill factor of the visible CCD with the MLA increases by a factor of 2.4 in comparison with that of CCD without the MLA. The measuring results show that the large-scale diffractive MLA is able to improve the detecting sensitivity of CCD sensors.

Phase Transition VO2 Thin Films for Optical Switches

This paper presents a method to make vanadium dioxide (VO2) crystallites on silicon substrates by reactive ion beam sputtering. The thickness of the thin film is about 100nm. The phase transition temperature of VO2 is 65°C. The transmittance of the semiconducting phase VO2 is about 50% and it is reduced to as low as 3% in metal phase at the infrared wavelenghth spectrum. The extinction ratio of the optical switches is 12dB. and the insertion loss is of 1-2dB. The switching time is about 1ms.

1.55 μm AlGaInAs/InP polarization-insensitive optical amplifier with tensile strained wells grown by MOCVD

Polarization-insensitive AlGaInAsInP semiconductor optical amplifier is realized at wavelength of 1.55 μ. The active layer consists of three tensile strained wells with strain of 0.40%. The amplifier is fabricated to ridge waveguide structure. The testing result shows the amplifiers have excellent polarization insensitivity (less than 0.8dB). The 1540 nm wavelength optical gain is 20 dB at the bias current of 200 mA.