CC BY
37LS-PS-14
Generation and properties of dissipative Kerr solitons in optical microresonators with backscattering
V. Lobanov1, N. Kondratiev1, D. Skryabin1,2
1Russian Quantum Center, Group of Coherent Microoptics and Radiophotonics, Skolkovo, Russian Federation
2University of Bath, Department of Physics, Bath, United Kingdom
During the last decade generation of optical frequency combs in optical microresonators has been studied extensively and has been demonstrated in different settings [1,2]. Great attention has been paid to the coherent frequency combs associated with the dissipative Kerr solitons (DKS). Conventionally, narrow-linewidth laser sources have been used for microresonator pumping and frequency comb generation. Recently, it was shown that one may use laser diode, single-frequency or even multi-mode, for this purpose [3,4]. Such approach becomes feasible due to the effect of the self-injection locking of a laser diode to a high-Q microresonator [5,6]. Self-injection locking uses resonant Rayleigh scattering on internal and surface inhomogeneities when a fraction of incoming radiation in resonance with the frequency of selected microresonator mode reflects back to the laser providing fast optical feedback. It may result in a significant reduction of laser linewidth. Besides that, such narrow-linewidth laser source may be used as a pump for the generation of DKS that was demonstrated experimentally. However, to date there is no adequate theory describing nonlinear effects in optical microresonators in the self-injection locking regime. As a first step to uncover the physics of soliton generation in this regime it is necessary to describe the backward wave influence on it.
In our work, we derive a model from the first principles taking linear forward to backward wave coupling and nonlinear cross-action into account and got the system of two coupled LLE-like equations. Further it was shown that if microresonator finesse is large enough such equations may be simplified and rewritten in a coordinate system rotating with the angular frequency equal to microresonator FSR. Due to the opposite directions of rotation cross-action terms depend not on the local but on the averaged intensity. Using derived equations, we studied the process of soliton generation by means of conventional frequency scan approach. It was found that soliton generation is possible if linear coupling coefficient is less than some critical value. In that case on may observe the sequence of sech-shaped pulses in the forward and backward waves. If coupling coefficient exceeds this critical value the transition from a chaotic regime to cw state was observed. However, it was found that solitons may exist at high values of the coupling coefficient. It was revealed that soliton existence domain is defined by both coupling coefficient and pump detuning value. Higher values of coupling coefficient require higher values of detuning for soliton existence. Interestingly, since nonlinear cross-coupling is defined by the averaged intensity existence domains for states with different number of solitons are not the same. It was revealed that decreasing the detuning leads to the transition from multi-soliton to single-soliton regime.
This work was supported by Russian Science Foundation (Project 17-12-01413).
References
[1] T.J. Kippenberg, et al., "Dissipative Kerr solitons in optical microresonators," Science. 361(6402), eaan8083 (2018).
[2] A.L. Gaeta, M. Lipson, T.J. Kippenberg, "Photonic-chip-based frequency combs," Nat. Photon. 13, 158-169 (2019).
[3] N.G. Pavlov, et al., "Narrow-linewidth lasing and soliton Kerr microcombs with ordinary laser diodes,". Nat. Photon. 12, 694-698 (2018).
[4] A.S. Raja, et al., "Electrically pumped photonic integrated soliton microcomb,". Nat. Comm. 10, 680 (2019).
[5] N.M. Kondratiev, et al., "Self-injection locking of a laser diode to a high-Q WGM microresonator," Opt. Express 25, 28167-28178 (2017).
[6] R.R. Galiev, et al., "Spectrum collapse, narrow linewidth, and Bogatov effect in diode lasers locked to high-Q optical microresonators," Opt. Express 26, 30509-30522 (2018).
