Conditions for Parametric and Free-Carrier Oscillation in Silicon Ring Cavities

Abstract

We model optical parametric oscillation in ring cavities with two-photon absorption, focusing on silicon at 1.55µm. Oscillation is possible if free-carrier absorption can be mitigated; this can be achieved using carrier sweep-out in a reverse-biased p-i-n junction to reduce the carrier lifetime. By varying the pump power, detuning, and reverse-bias voltage, it is possible to generate frequency combs in cavities with both normal and anomalous dispersion at a wide range of wavelengths including 1.55µm. Furthermore, a free-carrier self-pulsing instability leads to rich dynamics when the carrier lifetime is sufficiently long.

Analysis of Kerr comb generation in silicon microresonators under the influence of two-photon absorption and fast free-carrier dynamics

“…We further develop and numerically validate a design for a silicon-photonic Kerr comb source that has a free spectral range (FSR) of 100 GHz and a threshold pump power of 12 mW and that should even be suitable for dissipative Kerr-soliton (DKS) comb formation. It turns out that the incorporation of fast free-carrier dynamics changes the behavior of the optical waveforms in the microresonator to a notable degree, whereas the conditions for MI are essentially unaffected and remain consistent with the findings from simpler models [17][18][19].…”

“…For wavelengths in the midinfrared, Kerr comb formation in silicon microresonators under the influence of three-photon absorption and free-carrier absorption was already experimentally demonstrated [16]. In contrast to that, at NIR telecommunication wavelengths, Kerr generation comb in silicon microresonators is impaired by two-photon absorption (TPA) and subsequent free-carrier absorption (FCA) and has so far only been investigated theoretically [17][18][19]. Interestingly, Ref.…”

“…Interestingly, Ref. [17] predicts that generation of NIR Kerr combs should also be possible in silicon microresonators, provided that TPA-generated free carriers are removed from the Si waveguide core by reverse-biased p-i-n-junctions [20]. Specifically, the effective dwell times of the carriers in the waveguide core should be reduced from 1 to 5 ns [16,[20][21][22][23] to, e.g., 100 ps, which is of the same order as the round-trip time of the soliton pulses in the cavity [2,24].…”

“…This conclusion, however, conflicts with the fact that Ref. [17] builds upon a formalism (see, e.g., in [21]) that ignores fast carrier dynamics and assumes a spatially uniform distribution of the free carriers along the microresonator circumference.…”

Free-carrier-driven Kerr frequency comb in optical microcavities: Steady state, bistability, self-pulsation, and modulation instability

“…It is discussed earlier that in the absence of all nonlinear losses the steady-state solution will be unstable in the range g − < < g + where g ± is given by Eq. (60). From Fig.…”