Generation of broadband and tunable optical frequency comb based on a 1550 nm vertical-cavity surface-emitting laser under pulsed current modulation and optical injection

Optical frequency combs (OFCs) consist of a set of equally spaced discrete frequency components, and they have been widely applied in many fields such as metrology, optical arbitrary waveform generation, spectroscopy, optical communication, THz generation. In this work, we proposed a scheme for generating broadband and tunable OFCs based on a 1550 nm vertical-cavity surface-emitting laser (VCSEL) under pulsed current modulation and optical injection. Firstly, a pulse electrical signal is utilized to drive a 1550 nm-VCSEL into the gain-switching state with a broad noisy spectrum. Next, a continuous optical wave is further introduced for generating broadband and tunable OFC. Under injection light with power of 18.82 µW and wavelength of 1551.8570 nm, and pulse electrical signal with frequency of 0.5 GHz and pulse width of 200 ps, an OFC with the bandwidth of 82.5 GHz and CNR of 35 dB is experimentally acquired, and the single sideband phase noise at the 0.5 GHz reaches -123.3 dBc/Hz @ 10 kHz. Moreover, the influences of injection light wavelength, frequency and width of pulse electrical signal on the performance of generated OFC have been investigated. The experimental results show that OFCs with different comb spacing can be obtained by varying the frequency of pulse electrical signal. For the frequency of pulsed current signal is varied within the range of 0.25 GHz - 3 GHz, the bandwidths of generated OFCs can exceed 60 GHz through selecting optimized injection optical wavelength and width of pulse electrical signal.