Takashi Shiota

Wide temperature (15°C to 95°C), 80-km SMF transmission of a 1.55-μm, 10-Gbit/s InGaAlAs electroabsorption modulator integrated DFB laser

Uncooled 10-Gbit/s, 80- km SMF transmission was demonstrated for the first time using a 1.55-μm InGaAlAs EA/DFB laser. A power penalty below 2-dB was achieved over a wide temperature range from 15°C to 95°C.

Selective wet-etching of InGaAs on InAlAs using adipic acid and its application to InAlAs/InGaAs HEMTs

Highly selective wet-etching of InGaAs on InAlAs was demonstrated using pH-controlled adipic acid, and solutions. A maximum selectivity of 250 was obtained by controlling the InGaAs and InAlAs etching mechanisms. By identifying the rate-determining steps for the etching of InAlAs and InGaAs, we found that the high selectivity is due to the difference in solubility between the oxide of InAlAs and that of InGaAs in the adipic acid solution. InAlAs/InGaAs HEMTs fabricated in a diameter wafer by using this highly selective etching had a threshold voltage and a transconductance with standard deviations of 38 mV and , respectively.

100°C, 25 Gbit/s direct modulation of 1.3 µm surface emitting laser

The uncooled 25-Gbit/s direct modulation of a 1.3-µm horizontal-cavity surface-emitting laser was demonstrated. A fabricated laser, which is directly mountable on a high-frequency coplanar line, exhibited 25-Gbit/s eye openings up to 100°C.

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High-speed optical switches are essential devices to construct next-generation optical networks. We have studied 22 InAlGaAs/InAlAs hybrid-waveguide-type Mach-Zehnder interferometer-type optical switches and demonstrated low-polarization-dependent switching operation with crosstalks of less than , injection currents of about 5 mA, and response times of about 3 ns. In this letter, our conventional 22 optical switch was extended to a 44 optical-switch fabric by a cascading approach. As a result, fundamental switching operation was confirmed with low power consumption and low polarization dependence.

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In this letter, we demonstrated a Mach-Zehnder interferometer-type photonic switch using multimode interference (MMI) couplers with InAlGaAs-InAlAs compound semiconductor materials. A hybrid-waveguide structure with different etching depths was adopted for MMI couplers and other parts of the waveguides for polarization-independent operation. As a result, low-crosstalk switching operation of less than -20 dB was confirmed regardless of polarizations of an input light. Switching currents were, respectively, 5.25 and 4.75 mA for TE and TM modes of the input light. High-speed switching operation with about 3-ns transition time was also confirmed.

4 InAlGaAs/InAlAs Optical-Switch Fabric by Cascading Mach–Zehnder Interferometer-Type Optical Switches With Low-Power and Low-Polarization-Dependent Operation

Uncooled 10-Gbps, 1.55-μm InGaAlAs EA/DFB laser has been realized. Error free 80-km transmission was demonstrated up to 95 °C. A power penalty below 2-dB with over 9.8-dB dynamic extinction ratio was achieved over wide temperature range.

Polarization-Independent Low-Crosstalk Operation of InAlGaAs–InAlAs Mach–Zehnder Interferometer-Type Photonic Switch With Hybrid Waveguide Structure

A 1.3-mum-range EA/DFB laser demonstrated 43-Gbps 10-km transmission for the first time. The laser achieved clearly opened eye diagrams with dynamic extinction ratio of over 7-dB over wide temperature range.

Uncooled Electroabsorption Modulator Integrated DFB Laser

Circular, narrow beam emission of a lens-integrated surface-emitting laser operated at 1.3-µm wavelength was demonstrated. The laser consists of a distributed feedback laser cavity monolithically integrated with an etched 45° total reflection mirror and an etched InP lens. The profile of the etched InP lens was estimated to be a highly symmetrical parabolic shape that is ideal for the collimation of a Gaussian beam. A fabricated lens-integrated surface-emitting laser exhibited a circular, narrow far-field pattern with full-width at half-maximums of 3.9° × 3.5°. A highly efficient direct coupling to a single-mode fiber with a coupling efficiency of − 2.7 dB was also confirmed.

A first uncooled (25 to 85°C) 43-Gbps lightsource based on InGaAlAs EA/DFB laser technology

High-coupling-efficiency high-reliability hetero-material integration of InGaAlAs-based and InGaAsP-based optical components on a single InP substrate was achieved. A butt-jointing process with in situ cleaning was used to integrate an InGaAlAs-based component and an InGaAsP-based component. Optical-coupling efficiency at the butt-jointed interface of a novel multiple-butt-jointed laser was quantitatively estimated to be more than 97%. An InGaAlAs laser integrated with an InGaAsP-based component and an InGaAsP laser integrated with an InGaAlAs-based component were fabricated by the butt-jointing process. The fabricated 1.3- mum InGaAlAs laser integrated with an InGaAsP distributed Bragg reflector exhibited 100degC, 10-Gbps direct modulation at a low drive current of 14-mA peak-to-peak. Furthermore, the fabricated 1.55-mum InGaAsP distributed feedback laser integrated with an InGaAlAs electroabsorption modulator exhibited the first uncooled 10-Gbps 40-km transmission (with a 1-dB power penalty) from 0 to 85degC. Aging tests on both types of lasers showed no significant degradation in their driving current for more than one thousand hours.

Circular, narrow beam emission of 1.3-µm surface-emitting laser with monolithically-integrated InP lens for direct fiber coupling

We fabricated an InAlGaAs/InAlAs/InP semiconductor photonic switch with a Mach–Zehnder interferometer (MZI) and multi-mode interference (MMI) couplers for low-power consumption operation. As a result, very-low-current switching operation was attained with as low as 3.5 mA experimentally. High-speed switching operation with nano-second-order switching time was also confirmed.