Jong-In SHIM Shigehisa ARAI Kazuhiro KOMORI Yasuharu SUEMATSU
The basic properties of 1.55µm GaInAsP/InP distributed reflector (DR) laser were analyzed from the view points of active region structure and π/2 phase shift position. By introducing SCH structure with thin active layer, differential quantum efficiency could be improved up to 60-70% without sacrificing threshold current density. Optimum π/2 phase shift position for high power operation was found to be located inside the active region at a distance of 0.3 times of active region length from the joint portion between active and passive regions.
Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU
Current leakage along longitudinal direction, from active region to connected external waveguide or neighboring opto-electronic (O-E) functional region, commonly occurs in integrated type semiconductor lasers. This current leakage degrades not only lasing characteristics but also interrupts operation of neighboring functional devices. In this paper, the longitudinal current leakage is analytically given for an integrated laser by introducing an effective length of leakage current along the longitudinal direction. The minimum lengths of active region and isolation region to minimize the influence of longitudinal current leakage were clarified. As the results, shortening of current injection region with respect to the active region length as well as increasing sheet resistance were found to be effective for reduction of leakage current.
Kazuhiko SHIMOMURA Shigehisa ARAI Yasuharu SUEMATSU
We propose and analyze a new type of intersectional optical switch using positive refractive index variation in quantum well structure. The switch structure has a built-in refractive index difference in the waveguide, due to which the incident light is reflected to cross port at the OFF state. When the electric field applied to the electrode (ON state), the built-in refractive index difference vanishes by the positive refractive index variation in the quantum well, and the light transmits to straight port. Low insertion loss of lesser than 1 dB and high extinction ratio of more than 20 dB can be obtained at both cross and straight port.
Yuichi TOHMORI Kazuhiro KOMORI Shigehisa ARAI Yasuharu SUEMATSU
Bundle-integrated-guide (BIG) structure distributed-Bragg-reflector (DBR) lasers based on 1.5-1.6 µm GaInAsP/InP system are presented. The significance of this structure is the suitability for the planar fabrication process of integrated optical devices, such as DBR lasers, which comprise active and passive waveguide regions. The BIG structure enables easier fabrication of buried hetero-structure (BH) of such an integrated waveguide device. High coupling efficiency between those waveguides of 95-99 percent is theoretically available with sufficiently large tolerance in thickness and composition of waveguide layers. Devices with different lengths of the active region, such as 200 µm, 100 µm and 50 µm, were fabricated and tested both for DC operation and rapid direct modulation. Threshold current as low as 28 mA and output power of 6.5 mW/facet were obtained for BH-BIG-DBR lasers with 100 µm long and 3 µm wide active region. Side-mode suppression ratio (SMSR) of more than 32 dB was obtained at the bias current of 1.2 times the threshold and it was not much degraded by rapid direct modulation.
Yasuyuki CHAKI Tomoaki SAKAGUCHI Masahiro ASADA Yasuharu SUEMATSU
A novel electronic device named Space Charge Limited Insulator Tetroide (SCLIT), which uses space charge limited current in insulator of a metal-insulator structure is proposed. A possibility for high speed response (fγ1.1 THz) is estimated theoretically. The static characteristics are also shown.
Kazuhito FURUYA Shigeta ISHIKAWA Yasuharu SUEMATSU
Ultimate limit of the bandwidth of the multimode optical fiber with the index profile consisting of α-power and the fourth-order terms of radius is derived, rejecting the effects of the cladding and compensating the material dispersion. The 3 dB-bandwidth can be increased up to 1.9 GHz at 10 km length.