Naoyuki Shimada

Monolithic integration of laser and passive elements using selective QW disordering by RTA with SiO/sub 2/ caps of different thicknesses

Area-selective disordering of an InGaAs strained quantum wells (QWs) was performed by rapid thermal annealing with thick and thin SiO/sub 2/ caps. Fabry-Perot lasers were fabricated on a selectively-disordered wafers, and a lasing wavelength difference as large as 23 nm was obtained between the lasers in 300-nm and 30-nm capped areas. We present fabrication of lasers integrated with disordered passive waveguides and demonstrate significant reduction of the passive waveguide loss from roughly 40 cm/sup -1/ to 3 cm/sup -1/. A distributed Bragg reflector laser with QW disordering in the grating area was demonstrated, and remarkable improvement of laser characteristics was achieved compared to a laser without disordering.

Monolithically Integrated Master Oscillator Power Amplifier with Grating Coupler for Collimated Output Beam

A monolithically integrated master oscillator power amplifier with a grating outcoupler for emitting a collimated beam is demonstrated. In order to improve the device performance, theoretical simulation is performed based on the beam propagation method, and both compensation for wavefront distortion produced in the amplifier and optimization of the radiation decay factor are incorporated in a new design of the grating outcoupler. The device was fabricated by a simple process without regrowth. Stable single-mode lasing up to 183 mW output power at a wavelength of 985 nm was obtained under CW operation. As a result of optimization to minimize the divergence angle of the output beam, a well-collimated beam, with a nearly circular profile and divergence angles smaller than 0.28°×0.38°, was maintained in high-power operation.

Selective Disordering of InGaAs Strained Quantum Well by Rapid Thermal Annealing with SiO2 Caps of Different Thicknesses for Photonic Integration

Area-selective disordering of an InGaAs strained quantum well was performed by rapid thermal annealing with thick and thin SiO2 caps. The lasing wavelength difference as large as 23 nm was obtained between Fabry-Perot lasers in 300 nm and 30 nm capped areas. We present fabrication of lasers integrated with disordered passive waveguides and demonstrate significant reduction of the passive waveguide loss from roughly 40 cm-1 to 3 cm-1.

Tunable external-cavity semiconductor laser using monolithically integrated tapered amplifier and grating coupler for collimation

A novel lensless tunable external-cavity laser using monolithically integrated tapered amplifier, grating coupler (GC) and an external half mirror is proposed and demonstrated. It can be fabricated by a simple process and emits a collimated output beam. By making use of wavelength dispersion of the GC, the lasing wavelength can be angle tuned. Wavelength tuning over a wide range of 21.5 nm by 4.5/spl deg/ device rotation and an 84-mW output power were achieved under continuous-wave operation. A well-collimated output beam with a divergence angle as small as 0.3/spl deg/ was maintained over the entire tuning range.

High-efficiency InGaAs/AlGaAs quantum well distributed bragg reflector laser with curved grating

An InGaAs quantum well curved distributed Bragg reflector (DBR) laser designed for high efficiency and high wavelength purity operation is demonstrated. The laser was fabricated by a simple process without regrowth. In order to improve the performance, the quantum well was selectively disordered in the DBR grating region to accomplish low absorption loss. As a result of optimization of the curved DBR grating and low-reflection coating on the facet mirror, single-mode lasing with an external differential quantum efficiency as high as 0.74 and a side mode suppression ratio of 52 dB was achieved. Low noise characteristic of only 0.7 dB above the standard quantum limit was obtained.

GaInP/AlGaInP quantum well distributed Bragg reflector laser using surface curved grating

A novel GaInP/AlGaInP quantum well (QW) distributed Bragg reflector (DBR) laser having a surface curved grating was designed and fabricated. QW disordering in the DBR region was performed to reduce the light absorption loss. Single-mode lasing at wavelength of 656.1 nm and peak power of 44 mW were obtained under pulse operation.

InGaAs angled-grating distributed Bragg reflector lasers integrated with grating outcoupler for collimation

An angled-grating distributed Bragg reflector (DBR) laser integrated with a grating outcoupler (GO) is proposed and demonstrated. It consists of an angled broad-area gain stripe surrounded by angled DBR (/spl alpha/-DBR) gratings parallel to the gain stripe and two DBR gratings for feedback at the stripe ends, and a GO for emitting a collimated output beam. Due to distributed Bragg reflection in the /spl alpha/-DBR gratings, filamentation can be suppressed. Single-mode lasing up to 69 mW peak power was obtained under pulse condition. A collimated output beam with divergence angles, close to the diffraction limit, was obtained. These results confirm the effectiveness of the /spl alpha/-DBR gratings.

Tunable external-cavity semiconductor laser using monolithically integrated tapered amplifier and grating coupler for collimating

We present a lensless tunable external-cavity laser (TECL) using monolithically integrated tapered InGaAs-AlGaAs SQW amplifier and grating coupler, which can be fabricated without regrowth and emits a collimated output beam. We demonstrate a well-collimated output beam and wide-range tuning of the novel TECL.

Integrated Distributed Bragg Reflector Laser with Grating Coupler for Divergent Spherical Wave Emission.

We propose and demonstrate an InGaAs integrated distributed Bragg reflector laser with a grating coupler for divergent spherical wave emission from a virtual diverging point (VDP). The small grating coupler is located close to the active channel to realize a compact device. An external lens having a large aperture can be used to focus the output into a small spot. Single-mode lasing up to 2.2 mW and a VDP spot size of 4.6×4.5 µm2 (theoretical size 1.0×2.1 µm2) were obtained.

Selective disordering of InGaAs strained quantum well by rapid thermal annealing with SiO/sub 2/ caps of different thicknesses for photonic integration

We report impurity-free selective disordering by RTA with thick and thin SiO/sub 2/ caps for an InGaAs/AlGaAs strained QW structure. We present Fabry-Perot (FP) lasers integrated with selectively-disordered passive waveguides and demonstrate reduction of the passive waveguide loss. In the experiment, an InGaAs/AlGaAs strained single QW graded-index separate confinement heterostructure was used.