Electrical Waveform Shaping for Flat Band Tunable Brillouin Filters

Stimulated Brillouin Scattering (SBS) is widely acclaimed to achieve continuously tunable and high-resolution filtering [1]–[2]. However, having flat gain SBS-based filters is challenging to implement, requiring specific Radio Frequency (RF) waveforms for pump shaping such as linear frequency modulation (LFM) waveforms or multiple frequency tones. In this work, various RF waveforms for shaping the pump required to generate SBS have been explored. Along with this, modifications in the amplitude of the generated waveforms have been done without the use of a feedback loop in order to obtain a flat gain response of the bandpass filter. With our amplitude optimization technique, we have achieved the gain flatness within 2.0 dB for 500 MHz bandwidth and 0.5 dB for 200 MHz bandwidth with gain of around 20 dB at pump power of 21.5 dBm and 17.5 dBm, respectively. The transition rate from passband to stopband is 0.2 dB/MHz with shape factor of 1.3 (ratio between 20 dB to 3 dB bandwidth).