Kiichi Hamamoto

Thermal resistance reduction in high power superluminescent diodes by using active multi-mode interferometer

Low thermal resistance of high power superluminescent diodes (SLEDs) by using active multi-mode interferometer (active-MMI) is presented in this paper. The active layer temperature evaluation demonstrates that the power saturation mechanism in active-MMI SLED is heat for the first time. Low thermal resistance of 4.83 K/W in active-MMI SLEDs leads to a high power of 115 mW. Moreover, the effect of the active area size on the output power is demonstrated both experimentally and theoretically. Good agreement between the theoretical and experimental results indicates that active-MMI configuration is a new design in support of efficient heat dissipation and thermal resistance reduction for SLEDs.

High-Power (

We have designed and fabricated, for the first time to our knowledge, novel superluminescent diodes by using active multimode interferometers that emit at a wavelength of 1.55 ¿ m. An output power as high as 115 mW was obtained with a wide 3-dB bandwidth of 50 nm and low spectral ripple of 0.03 dB. In addition, they showed stable single-transverse-mode outputs up to the maximum output power.

> 110

We developed compact (1.136 mm/sup 2/) eight-channel wavelength-selectable microarray distributed feedback laser diodes (DFB-LDs) with a monolithically integrated 8/spl times/1 multimode-interference (MMI) optical combiner, a semiconductor optical amplifier (SOA), and an electro-absorption (EA) modulator. By using /spl plusmn/10/spl deg/C thermal tuning, an addressable wavelength range of 15.3 nm with uniform device characteristics and 2.5-Gb/s modulation performance were successfully demonstrated.

mW) Superluminescent Diodes by Using Active Multimode Interferometer

Integrated 4*4 GaAs/AlGaAs optical matrix switches constructed from 12 electrooptic directional couplers have been realized. In order to achieve uniform device characteristics, molecular beam epitaxy and reactive ion beam etching were chosen as the crystal growth technique and waveguide fabrication technique, respectively, in addition to the simplified tree structure as a matrix switch architecture. As a result, matrix switches with quite uniform device characteristics, such as small switching voltage deviation and little path dependence in +or-0.5-dB propagation loss, have been realized. >

1.55-μm wavelength-selectable microarray DFB-LD's with monolithically integrated MMI combiner, SOA, and EA-modulator

A transceiver PIC consisting of a DFB-LD, a receiver PD and a Y-shaped branch waveguides is realized by in-plane bandgap energy controlled selective MOVPE. Both active and passive core layers are formed in one step selective growth, and complicated fabrication procedure is no longer required. More than 1 mW fiber coupled power and 7 GHz receiver bandwidth are obtained. The modulation and detection operations at 500 Mb/s are successfully demonstrated.

4*4 GaAs/AlGaAs optical matrix switches with uniform device characteristics using alternating Delta beta electrooptic guided-wave directional couplers

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.

A transceiver PIC for bidirectional optical communication fabricated by bandgap energy controlled selective MOVPE

Here we propose novel active multi-mode-interferometer (MMI) laser diodes (LDs) for 14XXnm fiber amplifier pump applications. The waveguide of the LDs is consisted from 1x1-MMI couplers integrated with 1st order-mode permitted waveguides to enhance the total active area. Although there is no single-mode waveguide region inside the cavity, the novel active MMI-LDs emitted in stable single-transverse-mode output up to maximum output power. Moreover, they achieved high output power of 1.46W, and low driving voltage of only 1.75V at 1W output power.

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

We report the first atmospheric-pressure narrow-stripe (<2 μm) selective MOVPE. The extremely large bandgap wavelength shift of 370 nm for a selectively grown InGaAsP/InGaAsP multiple quantum well (MQW) was obtained with a small mask width variation (0-30 μm). This shift was four times that obtained under growth at 75 Torr. High-quality MQWs with flat interfaces and a photoluminescence full-width-at-half-maximum of less than 40 meV (0.5 kW cm 2 ) were obtained by optimizing growth conditions. We deduced that the essential flattening mechanism under these conditions is the formation of a (100) facet under step-flow growth mode. We fabricated 1.55 μm MQW Fabry-Perot laser diodes with a room temperature threshold current as low as 5 mA.

First demonstration of novel active multi-mode interferometer (MMI) LDs integrated with 1st order-mode permitted waveguides

We developed compact (1.136 mm/sup 2/) eight-channel wavelength selectable microarray DFB-LDs with monolithically integrated 8/spl times/1 MMI combiner, S0A, and EA-modulator. The wavelength tuning range of 15.3 nm with uniform device characteristics and 2.5 Gbit/s modulation performance were successfully demonstrated.

Narrow-stripe selective growth of high-quality MQWs by atmospheric-pressure MOVPE

We demonstrate fast and low energy all optical flip-flop devices based on asymmetric active-multimode interferometer using high-mesa waveguide structure. The implemented devices showed high speed all-optical flip-flop operation with 25 ps long pulses. The rising and falling times of the output signal were 121 ps and 25 ps, respectively. The required set and reset pulse energies were only 7.1 fJ and 3.4 fJ, respectively.