Masayuki Suehiro

Fabrication and characteristics of GaAs-AlGaAs tunable laser diodes with DBR and phase-control sections integrated by compositional disordering of a quantum well

GaAs-AlGaAs rib-waveguide graded-index separate-confinement heterostructure (GRINSCH) single-quantum-well (SQW) tunable distributed Bragg reflector (DBR) laser diodes were fabricated by EB lithography, ion implantation, and two-step metalorganic vapor phase epitaxy (MOVPE) growth. Active and passive waveguides were monolithically integrated by the compositional disordering of quantum-well heterostructures using silicon ion implantation. First-order gratings and rib waveguides were adopted with EB lithography to improve lasing characteristics, and they have wide application to photonic integrated circuits (PICs). Waveguide losses of partially disordered GRINSCH-SQW passive waveguides were as low as 4.4 cm/sup -1/ at the lasing wavelength. A narrow linewidth as low as 560 kHz and a frequency tuning of more than 2.9 THz were obtained. The results show that this fabrication process is useful for PICs. >

Photonic Integrated Circuit Combining Two GaAs Distributed Bragg Reflector Laser Diodes for Generation of the Beat Signal

We have fabricated a photonic integrated circuit (PIC) that had two GaAs distributed Bragg reflector (DBR) laser diodes (LD) and a Y-branch coupler integrated by means of the compositional disordering of a quantum well. Using this PIC as an optical heterodyne sweeper, frequency characteristics of a GaAs Schottky photodiode were measured.

GaAs/AlGaAs first-order gratings fabricated with electron beam lithography and very-narrow-linewidth long-cavity DBR laser diodes

A technique for fabricating GaAs/AlGaAs first-order gratings using electron beam (EB) lithography and its application to long-cavity distributed-Bragg-reflector (DBR) laser diodes are presented. The field stitching error, which limits the application of EB lithography to optical devices, was reduced to 5 nm by deflection amplitude calibration using marks on the samples. A technique for controlling the coupling coefficient using partially corrugated gratings is also proposed. These techniques were applied to fabrication of GaAs/AlGaAs first-order gratings of graded-index, separate-confinement-heterostructure, single-quantum-well (GRIN-SCH-SQW) distributed-Bragg-reflector (DBR) laser diodes. The resulting stitching error did not influence the single-mode lasing characteristics, and a very narrow linewidth of 237 kHz was achieved. The results show that EB lithography using the above techniques is useful in the fabrication of various optical devices with gratings. >

Monolithic integration of waveguide gratings and quantum-well distributed-feedback laser for implementation of subminiature optical-disc pickup head

We propose a subminiature optical-disc pickup head implementation by monolithic integration of wave- guide grating components, a graded-index separate-confinement heterostructure single-quantum-well distributed-feedback laser and photodiodes. Fabrication of a prototype device and the results of a preliminary experiment are presented.

Fabrication of First-Order Gratings for GaAs/AlGaAs LD's by EB Lithography

High-precision first-order gratings, 110 nm pitch, for GaAs/AlGaAs LDs were successfully fabricated using EB lithography. The field stitching error of EB lithography caused by height difference between reference marks for calibration and the samples, was reduced to 5 nm by controlling the EB deflection voltage calibrated by the detection of the position of the marks on the samples. We also investigated the effect of field stitching error on lasing characteristics using measurement and calculation. We found that a 20 nm stitching error is sufficiently small for single-mode LD operation.

Demonstration of Modulation Format Free and Bit Rate Free Characteristics of 2 ns Optical Switch for Optical Routers

We demonstrated modulation format free and bit rate free characteristics of our high-speed optical switches with 43 Gbps DQPSK, DPSK and 160 Gbps RZ signals. BERs versus OSNR were achieved without penalty for the DQPSK and DPSK.

GaAs/AlGaAs GRIN-SCH-SQW DBR Laser Diodes with Passive Waveguides Integrated by Compositional Disordering of the Quantum Well Using Ion Implantation

GaAs/AlGaAs GRIN-SCH-SQW DBR laser diodes are fabricated by ion implantation and two-step MOVPE growth. Passive waveguides are monolithically integrated by compositional disordering of quantum well heterostructures using silicon ion implantation. Waveguide losses of partially disordered GRIN-SCH-SQW passive waveguides are measured, and propagation losses as low as 4.4 cm-1 are observed at the lasing wavelength. Stable single mode operation is obtained, and the narrowest linewidth achieved is 840 kHz. The results show that this fabrication process is useful for photonic integrated circuits.

Sub-MHz Linewidth GaAs/AlGaAs GRIN-SCH-SQW DFB Laser Diodes with First-Order Gratings Fabricated by Electron Beam Lithography

Narrow-linewidth GaAs/AlGaAs GRIN-SCH-SQW DFB laser diodes with first-order gratings are reported. The first-order gratings and the GRIN-SCH-SQW structures were fabricated using electron beam lithography and MOVPE. The narrowest linewidth achieved is 730 kHz for a 1 mm cavity length. We also report on problems with gratings fabricated by electron beam lithography.

Integration of Laser Diodes and Photodiodes in Photonic Integrated Circuit for Measurement

Fully integrated PICs for measurement have been successfully fabricated for the first time. The device is implemented with waveguide grating components, a GRIN-SCH-SQW-DFB LD and PDs. Special care is taken to prevent direct optical coupling between integrated LDs and PDs in order to detect feeble sensing light. An interference signal is actually detected as photocurrent modulation of ?1-nA amplitude by this integrated structure.

Fabrication of 780-nm AlGaAs Tunable Distributed Bragg Reflector Laser Diodes by Using Compositional Disordering of a Quantum Well

AlGaAs tunable distributed Bragg reflector (DBR) laser diodes (LDs) with a lasing wavelength of 780 nm were fabricated by means of electron beam (EB) lithography, ion implantation, and two-step metalorganic vapor phase epitaxy (MOVPE). Active and passive waveguides were monolithically integrated by using silicon ion implantation for compositional disordering of quantum-well heterostructures. The optimum single-quantum-well (SQW) structure, with low threshold current and low internal loss, is about 5 nm thick and has an Al mole fraction of 0.06. The graded-index separate-confinement heterostructure (GRIN-SCH) with a carrier-blocking layer was also used to improve the characteristic temperature of a two-step-growth LD. A Iinewidth as narrow as 690 kHz and a frequency tuning of more than 1.7 THz were obtained.