Abstract
Optical frequency comb technologies have received intense attention due to their numerous promising applications ranging from optical communications to optical comb spectroscopy. In this study, we experimentally demonstrate a new approach of broadband comb generation based on the polarization mode competition in single-mode VCSELs. More specifically, we analyze nonlinear dynamics and polarization properties in VCSELs when subject of optical injection from a frequency comb. When varying injection parameters (injection strength and detuning frequency) and comb properties (comb spacing), we unveil several bifurcation sequences enabling the excitation of free-running depressed polarization mode. Interestingly, for some injection parameters, the polarization mode competition induces a single or a two polarization comb with controllable properties (repetition rate and power per line). We also show that the performance of the two polarization combs depends crucially on the injection current and on the injected comb spacing. We explain our experimental findings by utilizing the spin-flip VCSEL model (SFM) supplemented with terms for parallel optical injection of frequency comb. We provide a comparison between parallel and orthogonal optical injection in the VCSEL when varying injection parameters and SFM parameters. We show that orthogonal comb dynamics can be observed in a wide range of parameters, as for example dichroism linear dichroism (γa=−0.1 ns−1 to γa=−0.8 ns−1), injection current (μ=2.29 to μ=5.29) and spin-flip relaxation rate (γs=50 ns−1 to γs=2300 ns−1).
Highlights
The nonlinear dynamics of externally driven semiconductor laser have been extensively studied last decades [1,2,3]
We have shown that the properties of the two polarization combs induced by parallel optical injection are limited by increasing the injected comb spacing for fixed bias current
We have shown experimentally and theoretically that Vertical-Cavity SurfaceEmitting Lasers (VCSELs) can bifurcate to interesting polarization dynamics under optical frequency comb injection
Summary
The nonlinear dynamics of externally driven semiconductor laser have been extensively studied last decades [1,2,3]. A very recent study has shown that VCSEL output can exhibit complex chaotic dynamics even in free-running [11] These rich nonlinear polarization dynamics in VCSELs have found several applications such as optical frequency comb generation [12]. The question of how parallel optical frequency comb injection in VCSELs induces additional nonlinear polarization dynamics is of great interest and has not been addressed so far. We provide an in-depth experimental and theoretical description of the bifurcation scenarios when the polarization of injection comb is parallel to that of the VCSELs. We show that a variation of the injection parameters together with the bias current allows enabling the excitation of the normally depressed polarization mode accompanied by the generation of two combs with orthogonal polarization directions.
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