Experimental characterization and modeling of the improved low frequency response of a current modulated bulk RSOA slow light based microwave phase shifter

The enhancement of the low frequency gain response of a microwave phase shifter based on slow light in a TO-can packaged bulk reflective semiconductor optical amplifier, by using forced coherent population oscillations achieved by simultaneously modulating the input optical power and bias current, is experimentally demonstrated. The beat-signal gain improvement ranges from 35 to 0 dB over a frequency range of 0.5-3.5 GHz, thereby improving the noise performance of the phase shifter. Tunable phase shifts of up to 55° are possible over this frequency range. Simulations that show good agreement with experiment, based on a wideband dynamic model that includes spontaneous emission and band structure based calculations of the amplifier active region material, are also presented.