Abstract
Dynamic frequency tuning of the 40.67 GHz intermode beat frequency of a 1255 nm emitting 1 mm long monolithic self mode-locked single section optical frequency comb InAs/InGaAs quantum dot laser across 70 MHz is experimentally demonstrated by fine-delay dual-cavity controlled all optical self-injection. Fiber-based macroscopic optical delay lengths are 9.4 m (round-trip time of 62.7 ns) and 16.5 m (round-trip time of 110.1 ns), the maximum studied microscopic delay tuning times are 40 ps and the optical self-injection strengths are below 0.02%. For selected delay times, the lowest intermode beat frequency line width amounts to 2 kHz indicating an improvement of carrier phase coherence by a factor of 700 as compared to the free-running laser. We validate these experimental results by a simple and universal stochastic time-domain model which is applied for the first time to model a self mode-locked quantum dot laser subject to optical self-injection. Modeling results are in good quantitative agreement.
Highlights
Optical frequency comb (OFC) self mode-locked (SML) semiconductor lasers are compact monolithic photonic sources providing a large number of mutually locked optical carriers for application as coherent multi-frequency super-channel sources in high data rate optical communication [1]–[4] or dual-comb spectroscopy [5]
The qualitative and quantitative agreement obtained by the simple stochastic model to the experimental data in Fig. 3 suggests that the intermode beat frequency (IBF) of OFC emitted by the quantum dot SML semiconductor laser and the mechanism of Intermode beat line widths (IBLWs) reduction by external time-delay control appears of the same stochastic origin as demonstrated for passively mode-locked (PML) lasers based on quantum dot [43] and quantum well [44] active regions
We find that the OFC stabilization in quantum dot SML lasers relies on the effective interaction of the timing of the intra-cavity laser signal and the time-delayed Optical self-injection (OSI) laser signal in conjunction with a statistical averaging of the independent timing deviations of both
Summary
Optical frequency comb (OFC) self mode-locked (SML) semiconductor lasers are compact monolithic photonic sources providing a large number of mutually locked optical carriers for application as coherent multi-frequency super-channel sources in high data rate optical communication [1]–[4] or dual-comb spectroscopy [5]. The IBF timing phase noise stability, directly correlated to the IBLW of a mode-locked semiconductor laser [23], indicates the degree of phase coherence between the OFC carriers. It can be optimized by laser cavity design or improved by multi-section cavity layout and laser biasing [24]–[27], passive electrical stabilization [28], [29] or by external control including active mode-locking [30]–[33], electrical modulation or hybrid mode-locking [31], [34], single- and dual-mode injection [35], [36] or mutual synchronization [37]. We quantify the improvement in timing stability by IBLW measurements and confirm these experimental results by an universal stochastic model
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