Modulation performance of semiconductor laser coupled with an ultra-short external cavity

•We model modulation of semiconductor laser coupled with an ultra-short cavity•We correlate modulation response with carrier to noise ratio and frequency chirp•We focus on increasing the modulation bandwidth or inducing resonance modulation.•Along the route to chaos, feedback improves modulation bandwidth from 19 to 28 GHz•Strong feedback induces resonance modulation over frequency passband around 50 GHz

We present modeling on the evaluation of the modulation performance of semiconductor laser coupled with an ultra-short external cavity in terms of the intensity modulation (IM) response, relative intensity noise (RIN), carrier to noise ratio (CNR), and frequency chirp. The modulation is characterized along the period-doubling (PD) route to chaos induced by optical feedback (OFB). We focus on the possibility of increasing the modulation bandwidth by improving the carrier–photon resonance (CPR) frequency or inducing resonant modulation due to photon–photon resonance (PPR). We show that along the route to chaos, OFB could increase the CPR frequency and improve the 3 dB-modulation bandwidth from 19 GHz to 28 GHz. When strong OFB keeps the continuous wave (CW) operation or induces periodic oscillation (PO), PPR becomes significant and reveals resonance modulation over mm-frequency passband exceeding 50 GHz. Both CNR and frequency chirp are also enhanced around the CPR and PPR frequencies. The highest CNR peak is obtained when modulating the CW or PO laser, whereas the maximum peak of chirp corresponds to non-modulated chaotic laser.