Silicon-microring into a fiber laser cavity for high-repetition-rate pulse train generation

In 1997, Yoshida et al. inserted a Fabry-Perot filter in a modulation instability fiber laser cavity [1], the free spectral range (FSR) of the Fabry-Perot fixed the RF to 115 GHz; however the pulsed laser was poorly stable. Since then, lasers of increasing performance have been demonstrated using variants of this method. In 2012, Peccianti et al. demonstrated the first fiber laser harmonically mode-locked by integrated high-finesse microresonator [2]. The doped silica, on-chip microresonator provided both high spectral selectivity and nonlinearity, thus promoting the dynamics pulsed at 200 GHz. By using a silicon microring resonator (SMRR), this approach lead to the recent realization of 110 GHz-RF mode-locked fiber laser [3]. Working with silicon takes advantage of the huge investment and experience from the microelectronics industry, and contributes to the development of a monolithic platform for optoelectronics [4]. The high Kerr nonlinearity of silicon is instrumental to induce mode locking with low pumping threshold. However, at the main telecom wavelength (1.55 μm), two photo absorption, free-carriers dispersion and their thermalization have to be considered [5], and can be detrimental to formation of the ultrafast dynamics.