Yuichi Inaba

A Day and Night Vision MOS Imager With Robust Photonic-Crystal-Based RGB-and-IR

This paper demonstrates a day and night vision MOS imager with red, green, blue (RGB) and extra near-infrared filters placed over individual pixels. The on-chip RGB and IR filters are fabricated from an inorganic photonic crystal color filter (PCCF) technology, thereby realizing a robust and reliable camera module for indoor and outdoor use without mounting a mechanical IR-cut filter. These PCCFs allow the IR band as well as the RGB bands to pass through to the RGB photodiodes from which RGB signals, each involving some amount of IR component, are derived. During the daytime, however, chromatically almost pure RGB colors are reproduced by subtracting a weighed IR signal of an extra IR pixel from the raw RGB signals of the surrounding IR pixels. As a result, the IR components in the resultant RGB signals are minimized from 25%, 21%, and 50% to 9%, 4%, and 21%, respectively. During the night, on the other hand, an IR image having a resolution match with a conventional IR imager can be captured by using the IR components of the raw RGB signals with the IR signal.

A 2.0-/spl mu/m pixel pitch MOS image sensor with 1.5 transistor/pixel and an amorphous Si color filter

In this paper, an ultrafine pixel size (2.0/spl times/2.0 /spl mu/m/sup 2/) MOS image sensor with very high sensitivity is developed. The key technologies that realize the MOS image sensor are a newly developed pixel circuit configuration (1.5 transistor/pixel), a fine 0.15-/spl mu/m design rule, and an amorphous Si color filter (Si-CF). In the new pixel circuit configuration, a unit pixel consists of one photodiode, one transfer transistor, and an amplifier circuit with two transistors that are shared by four neighboring pixels. Thus, the unit pixel has only 1.5 transistors. The fine design rule of 0.15 /spl mu/m enables reduction of wiring area by 40%. As a result, a high aperture ratio of 30% is achieved. A newly developed Si-CF realizes the 1/10 thickness of that of the conventional organic-pigment CF, giving rise to high light-collection efficiency. With these three technologies combined, a high sensitivity of 3400 electrons/lx/spl middot/s is achieved even with a pixel size of 2.0/spl times/2.0 /spl mu/m/sup 2/.

Multiquantum-well lasers with tapered active stripe for direct coupling to single-mode fiber

We demonstrate narrow beam divergence in 1.3-/spl mu/m wavelength multiquantum-well (MQW) lasers with an active stripe horizontally tapered over the whole cavity, for direct coupling to single mode-fibers. The lasers have reduced output beam divergence in a simple structure which does not contain an additional spot-size transformer. The fabricated laser shows narrow beam divergence of /spl sim/12/spl deg/, while a low-threshold current of 6.9 mA and a high efficiency of 0.62 mW/mA are realized. Furthermore, a direct-coupling efficiency to a single-mode fiber is -4.0-dB and -3-dB alignment tolerance is /spl plusmn/2.5 /spl mu/m.

High output-power and narrow spectral-linewidth operation of a 1.3-/spl mu/m gain-coupled DFB laser with InAsP buried absorptive grating

High output-power and narrow spectral-linewidth operation of 1.3-/spl mu/m gain-coupled distributed feedback lasers with grating are reported. The fabricated output power of 230 mW and a linewidth of 100 kHz by reducing optical confinement in multiple quantum wells to improve the single-mode stability at high output-power operation.

Low threshold current and high efficiency of 1.3-/spl mu/m MQW lasers with tapered active stripe for butt-coupling to single-mode fiber

In conclusion, we have reported on lasing characteristics of a 1.3-/spl mu/m InGaAsP strained-layer MQW lasers for butt-coupling modules, in which the active stripe horizontally tapered over almost the whole cavity. The fabricated lasers show low threshold current of 6.9 mA and high efficiency of 0.62 mW/mA with narrow beam divergence of 12/spl sim/13/spl deg/. These results indicate that the fabricated laser is effective to realize direct-coupling laser modules with high-coupling efficiency.

DFB lasers with tapered active stripe for narrow beam divergence

Summary form only given. We present a 1.3-/spl mu/m gain-coupled DFB semiconductor laser with a tapered active stripe. The fabricated laser shows narrow beam divergence of 13-14 degrees and high side-mode suppression ratio (SMSR) of >45 dB. The laser has an InAsP absorptive grating, which is buried between the n-InP buffer layer and the corrugated n-InP substrate.