IMPROVED SELECTIVITY AND DECREASED SPONTANEOUS EMISSION FROM AN AR-HRCOATED SL-MQW DFB SEMICONDUCTOR-LASER AMPLIFIER

It is shown that the performance of a DFB filter/amplifier can be impr oved considerably with respect to selectivity and amplified spontaneou s emission by applying a high reflective coating to the output facet. To illustrate this a strained-layer multiple quantum well DFB filter/a mplifier with an output facet reflectivity of 97% is compared with a c onventional, AR-coated phase adjusted DFB filter/amplifier. Peak fiber -to-fiber gains for these devices are 21 and 18 dB, respectively, when biased at 98% of their threshold current. The transmission gain of th ese DFB filter/amplifiers has been measured over a wavelength span of 30 nm. For the AR-HR coated SL-MQW DFB filter/amplifier the selectivit y is improved with 11 dB resulting in an extinction ratio for interfer ing channels of better than 35 dB and the amplified spontaneous emissi on is reduced by 16 dB down to -37 dBm compared to the conventional DF B filter/amplifier.