Reconfigurable linear-phase response spectral shaping filer

The optical filters are studied according to the applications of photonic-assisted radio frequency (RF) signal gereration and all optical coherent signal processing. Firstly, the finite impulse response (FIR) filter is analyzed theoretically. And it points out that the advantages of FIR lies in the reconfiguration, real coefficients and linear-phase impulse response which could guarantee the coherence of the ultrashort pulse. Based on this, the specific filters for free spectral range (FSR) broadening and sinusoidal signal generation are designed and simulated. The results of the simulation showed that the FSR of comb filter is 20 GHz with a sidelobe suppression of 20 dB, the demand of FSR broadening is satisfied. Meanwhile, based on the FSP stacking over several ten nanometre optical spectrum, shaping filter is realized for sinusoidal signal generation. Finally, the potentials of low dimensional materials enhanced integrated filters for wide FSR (> 50 nm) are discussed in the last part.