A tunable external-cavity InGaAs/AlGaAs quantum-well laser using a grating coupler monolithically integrated in a selectively disordered waveguide is demonstrated. The laser consists of an amplifier with a narrow channel for lateral single-mode guiding and a tapered section, a grating coupler for output beam collimation and wavelength dispersion, and an external half mirror. Selective quantum-well disordering technique using SiO2 caps of different thicknesses and rapid thermal annealing was employed to reduce the passive waveguide loss in the grating coupler region. Loss reduction from 40 cm-1 to 3 cm-1 was accomplished. Resultant increase of the grating coupler efficiency and expansion of the effective aperture length led to significant improvement of the laser performances. The maximum output power of 105 mW and wide tuning range of 21.1 nm centered at 997 nm were obtained. The well collimated output beam of full diffraction angles at half maximum of 0.16 0.18 was obtained.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

A novel temperature insensitive wavelength filter consisting of GaAlAs/GaAs distributed Bragg reflectors (DBRs) has been demonstrated. This micromachined DBR is mechanically tuned by differential thermal expansion. The strain-induced displacement of one mirror can generate wavelength tuning and trimming functions with an adjustable temperature dependence. We succeeded in the control of temperature dependence in this micromachined semiconductor filter by properly designing a vertical cavity structure. The achieved temperature dependence was as small as +0.01 nm/K, which is one-tenth of that of conventional semiconductor based optical filters. Also, a wavelength trimming of over 20 nm was demonstrated after completing the device fabrication. In addition, we demonstrated a 4 4 multiple wavelength micromachined vertical cavity filter array. The multi-wavelength filter array with a wavelength span of 45 nm was fabricated by partially etching off a GaAs wavelength control layer loaded on the top surface of device.

This paper reports on broad-range wavelength tuning characteristics of DBR lasers which make use of a newly proposed multiple-phase-shift super structure grating (SSG). The reflection characteristics of the SSG reflector are analyzed theoretically. We found that the SSG reflector has periodic sharp reflection peaks each with high reflectivities thus making it a suitable wavelength selective reflector for single-mode lasers. The expected characteristics were evident in multiple-phase-shift SSGs fabricated using a new method which involves multiple-phase-shift insertion. DBR lasers with multiple-phase-shift SSGs were fabricated and their wavelength tuning characteristics were studied. The maximum tuning range is 105 nm in the single longitudinal mode under a CW condition. Dynamic single mode operation was also observed throughout the tuning range.