[OPTICAL REVIEW Vol. 3, No. 6B (1996) 484-486
Laser Diode Integrated with a Low Radiation Loss Thickness-Tapered Beam Expander for Highly Efficient Fiber Coupling
Makoto TAKAHASHI, Masahiro AOKI, Hiroshi SATO, Tsukuru OHTOSHI and Shinji TSUJI
Central Research Laboratory, Hitachi Ltd., 1-280, Higashi-Koigakubo, Kokubunji, Tokyo, 185 Japan
(Received August 1, 1996; Accepted September 3, 1996)
The optimal structure of a laser diode monolithically integrated with a thickness-tapered beam expander waveguide is demonstrated by analyzing the relationship between fiber coupling efficiencies and radiation losses. It is also found that mode conversion loss is lowered in a ridge waveguide structure than in a buried hetero structure under equivalent fiber coupling. A fabricated ridge waveguide device based on this design shows threshold current as low as 16 mA and narrow beam divergences of 13E and 12E.
Key words : beam expander, optical coupling efficiency, radiation loss, ridge waveguide structure, buried hetero structure, beam propagation method, shadow-masked growth, selective area growth