Probing coherence in microcavity frequency combs via optical pulse shaping

Abstract

Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the initial four-wave mixing sidebands are spaced by multiple free spectral ranges (FSRs) from the pump, then fill in to yield a comb with single FSR spacing, resulting in partial coherence. By using a pulse shaper to select and manipulate the phase of various subsets of spectral lines, we are able to probe the structure of the coherence within the partially coherent comb. Our data demonstrate strong variation in the degree of mutual coherence between different groups of lines and provide support for a simple model of partially coherent comb formation.

Self-locked optical parametric oscillation in a CMOS compatible microring resonator: a route to robust optical frequency comb generation on a chip

“…On the contrary the short length laser was able to achieve oscillation in [24] for a variety of reasons -the main one being simply that the higher intensities in a modelocked system tends to make the nonlinear processes driving the oscillation much more efficient.. By increasing the gain of the short-length amplifier we expect that this scheme should lead to stable OPO operation [24,26]. Finally, we note that the overall power output of our OFC is comparable to other results based on microcavity frequency combs [15,16]. We note though that our output power could easily be increased by as much as 20dB by simply using a fiber Bragg grating centered around the pump wavelength, as a filter to extract the frequency comb lines rather than the 1% tap filter used here.…”

“…These sources are generally characterized by a comb teeth spacing ranging from 80GHz to more than a THz, making them particularly appealing for telecom and optical clocks applications [10]. Several routes to comb formation have been demonstrated [15][16][17][18], leading to either chaotic or coherent regimes. The optical pulses generated in the coherent regime have sometimes been classified as optical cavity solitons since the microcavity OPO can be effectively described by the standard nonlinear Schrödinger equation (NLSE) [19][20][21][22].…”

Intracavity characterization of micro-comb generation in the single-soliton regime

“…To obtain the exact pump phase, we studied the visibility curves, defined as V(θ)=(V0-V1)/(V0+V1) [24,25], where V0 and V1 are the values of the intensity autocorrelation peak and the value half way between the peaks, respectively. θ is the applied pump phase on the shaper.…”

Mode-Locked Ultrashort Pulse Generation from On-Chip Normal Dispersion Microresonators

“…Recently continuous-wave (cw) pumped monolithic microresonators emerge as promising platforms for compact optical frequency comb generation [1][2][3][4][5][6][7][8][9][10][11]. With anomalous group-velocity-dispersion (GVD) and self-phase modulation (SPM), optical solitons can be generated [12,13], and remarkably broad bandwidths [6] and RF-optical stability [3] have been demonstrated.…”