Shotaro Kitamura

3.8-THz wavelength conversion of picosecond pulses using a semiconductor delayed-interference signal-wavelength converter (DISC)

A new all-optical semiconductor-band-filling-based wavelength converter, named delayed-interference signal-wavelength converter (DISC), is proposed. Its speed is not restricted by the carrier lifetime and its structure is very simple: it consists of only two essential components, namely, a semiconductor optical amplifier and a passive split-delay. Using this converter, 3.8-THz-shifted (from 1530 to 1560-nm) 14-ps-long pulses are generated from 1530-nm 140-fJ 0.7-ps pulses with high-conversion efficiency.

Polarization-insensitive semiconductor optical amplifier array grown by selective MOVPE

Polarization-insensitive 1.3 /spl mu/m wavelength semiconductor optical amplifier (SOA) arrays are developed for the first time, by using a new fabrication process with selective MOVPE. In a four-channel array, the SOAs have uniform device characteristics of more than 20 dB signal gain and less than 1 dB polarization sensitivity.<<ETX>>

Multiple-chip precise self-aligned assembly for hybrid integrated optical modules using Au-Sn solder bumps

We have developed a novel three-dimensional high precision self-aligned assembly using stripe-type Au-Sn solder bumps and a micro-press solder bump formation method. This produces a high bonding precision of 1 /spl mu/m for optical device assembly in both lateral and vertical directions without the need for time-consuming optical axes alignment. Furthermore, we tested a hybrid integrated 4/spl times/4 optical matrix switch, in which multiple SSC-SOAG arrays were simultaneously positioned and optical fibers were passively positioned on a silica based PLC platform using this technology. Four optical chips and seven wiring chips are assembled on a planar lightwave circuit (PLC) platform. The insertion loss for each of these paths at an injection current of 40 mA was within a range of 9/spl plusmn/4 dB. The average extinction ratio was 40 dB. This self-aligned assembly technology was shown to be useful for building hybrid-integrated multichannel optical network components.

All-selective MOVPE-grown 1.3-/spl mu/m strained multi-quantum-well buried-heterostructure laser diodes

Strained InGaAsP multi-quantum-well (MQW) double-channel planar-buried-hetero (DC-PBH) laser diodes (LDs) were fabricated by selective metalorganic-vapor-phase epitaxy (MOVPE). In the laser fabrication process, both the strained MQW active layer and current blocking structure were directly formed by selective MOVPE without any semiconductor etching process. The LDs are called all-selective MOVPE-grown BH LDs. The laser fabrication process can achieve both a precisely controlled gain waveguide structure and an excellent current blocking configuration, realizing the optimized DC-PBH structure. These aspects are essential to the high-performance and low-cost LD, which is strongly demanded for optical access network systems or fiber-to-the-home networks. This paper will show the excellent high-temperature characteristics for 1.3-/spl mu/m Fabry-Perot LDs which have a record threshold current of 18 mA with a low-operation current of 56 mA for 10 mW, and 74 mA for 15 mW at 100/spl deg/C with extremely high uniformity. Furthermore, reliable long-term operation at high temperature (85/spl deg/C) and high-output power of 15 mW has been demonstrated for the first time.

Angled-facet S-bend semiconductor optical amplifiers for high-gain and large-extinction ratio

The extinction ratio of an optical gate with a spot-size-converter-integrated semiconductor optical amplifier (SSC-SOA) is deteriorated following the direct coupling of unguided light between the input and output fibers. In this letter, an S-bend waveguide structure is introduced into an active waveguide to suppress such direct coupling. Angled facet structures are also introduced for obtaining low facet reflectivity. The fabricated SSC-SOA operating at 1.55-/spl mu/m wavelength achieves an extinction ratio up to 70 dB and a fiber-to-fiber gain of 20 dB.

Very low power consumption semiconductor optical amplifier array

Very low power consuming and polarization insensitive semiconductor optical amplifier arrays with submicron-wide InGaAsP active layers are realized by selective MOVPE technique. 20-dB signal gain at a low injection current of 25 mA was achieved in four-channel arrays.<<ETX>>

Spot-size converter integrated semiconductor optical amplifiers for optical gate applications

A spot-size converter integrated semiconductor optical amplifier (SSC-SOA) was developed as a gate element in an optical switch matrix for photonic switching applications. By a selective metal-organic vapor phase epitaxy technique, a bulk InGaAsP stripe, including an active region and thickness tapered SSCs, was grown. Wavelength composition of the stripe, strain on the stripe, and electrode coverage above the SSC region were optimized. As a result, gate operation for fiber-to-fiber gain of 0 dB was achieved at a low injection current of 30 mA, and the polarization dependence of the gain was eliminated as well.

Angled facet spot-size-converter integrated SOA with S-shaped waveguide

Angled facet spot size converter integrated semiconductor optical amplifiers (SSC-SOAs) with S-shaped waveguides are developed as gate elements in optical matrix switches on planar lightwave circuits (PLC). A high fiber-to-fiber gain of +20 dB and a high extinction ratio of 70 dB are achieved.

VERY LOW POWER CONSUMPTION SEMICONDUCTOR OPTICAL AMPLIFIER ARRAY

Polarization-insensitive semiconductor optical amplifier (SOA) arrays are desired for optical parallel interconnection systems as optical loss compensators[1]. The authors have, for the first time, realized four-channel polarization-insensitive SOA arrays with uniform device characteristics, by employing a novel fabrication method with selective MOVPE[2,3]. Uniform gain of more than 20dB at 100mA injection current was achieved for the four-channel array. However, for practical application of multi-channel array, much lower power consumption is required. Reduction of injection current is important because it decreases power consumption of not only SOA itself but also other electronic circuits such as thermo-electric cooler. As for low power consumption SOAs, a discrete SOA with 20dB gain at 40mA injection current have been reported[4]. However, fabrication method of this SOA is not array compatible. Therefore, such a polarization-insensitive SOA haven’t been yet reported in an array configuration where low power consumption is actually desired.

High gain and low operation current spot-size-converter integrated semiconductor optical amplifier for switching gate application

Spot-size-converter integrated semiconductor optical amplifiers have been developed as gate elements for optical switch matrices and an S-shape waveguide has been introduced to prevent re-coupling of unguided light to the output fiber. It was found that an angled-facet structure effectively suppressed light reflection at the end facets. Consequently, a high extinction ratio of 70 dB and a high fiber-to-fiber gain of 20 dB with gain saturation of 4.5 dBm were achieved. Sufficient optical coupling characteristics to a flat-ended single-mode fiber with a coupling loss of 3.5 dB were also demonstrated.