Improved selectivity and decreased spontaneous emission from an AR-HR coated SL-MQW DFB semiconductor laser amplifier

It is shown that the performance of a DFB filter/amplifier can be improved considerably with respect to selectivity and amplified spontaneous emission by applying a high reflective coating to the output facet. To illustrate this a strained-layer multiple quantum well DFB filter/amplifier with an output facet reflectivity of 97% is compared with a conventional, 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 these DFB filter/amplifiers has been measured over a wavelength span of 30 nm. For the AR-HR coated SL-MQW DFB filter/amplifier the selectivity is improved with 11 dB resulting in an extinction ratio for interfering channels of better than 35 dB and the amplified spontaneous emission is reduced by 16 dB down to /spl minus/37 dBm compared to the conventional DFB filter/amplifier.<
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