S. Kitamura et al., Angled-facet S-bend semiconductor optical amplifiers for high-gain and large-extinction ratio, IEEE PHOTON, 11(7), 1999, pp. 788-790
The extinction ratio of an optical gate with a spot-size-converter-integrat
ed semiconductor optical amplifier (SSC-SOA) is deteriorated following the
direct coupling of unguided light between the input and output fibers, In t
his letter, an S-bend waveguide structure is introduced into an active wave
guide to suppress such direct coupling. Angled facet structures are also in
troduced for obtaining low facet reflectivity. The fabricated SSC-SOA opera
ting at 1.55-mu m wavelength achieves an extinction ratio up to 70 dB and a
fiber-to-fiber gain of 20 dB.