Abstract
In the present work, we report a path of RF stabilization versus delay subject to self-mode-locked (SML) two-section quantum-dash (QDash) lasers emitting at ∼1.55 μm and operating at ∼21 GHz repetition rate using a feedback ratio controlled and optical delay phase-dependent symmetric dual-loop optical feedback. For symmetric dual-loops (equal arms of external loops), we identify the three key parameters: power-split ratio through each cavity of the external feedback loop, optical delay phase settings, and overall feedback strength back into gain section, yields jitter stabilization on integer resonance as well as on full delay range tuning. Symmetric dual-loop feedback with two optical delay phase settings (weaker cavity set to integer resonance, fine-tuning of the stronger cavity and stronger cavity set to integer resonance, fine-tuning of a weaker cavity) and four chosen combinations of feedback ratios (−19.5:−29.03 dB, −20.6:−24.3 dB, −21:−22.7 dB, −21.3:−23 dB) has been demonstrated. Based on these four chosen combinations of feedback ratios and optical delay phase settings, a path of stabilization has been identified for SML QDash lasers using symmetric dual-loop optical feedback. Our proposed dual-loop feedback schemes provide a viable path towards the stabilization of mode-locked lasers, promising for various practical applications where ultra-stable optical pulses are highly desirable.
Highlights
Semiconductor mode-locked lasers (MLLs) have been evolved as promising photonics sources for the generation of ultra-short optical pulses with high repetition rates
In the present work, we report a path of RF stabilization versus delay subject to self-mode-locked (SML) two-section quantum-dash (QDash) lasers emitting at ∼1.55 μm and operating at ∼21 GHz repetition rate using a feedback ratio controlled and optical delay phase-dependent symmetric dual-loop optical feedback
We reported the influence of four chosen combinations of feedback ratios and different optical delay phase settings to identify the path towards jitter stabilization of our two-section SML
Summary
Semiconductor mode-locked lasers (MLLs) have been evolved as promising photonics sources for the generation of ultra-short optical pulses with high repetition rates. An asymmetric dual-loop has been demonstrated to reduce the RF linewidth on integer resonance as well as on full delay range tuning [27] For this purpose, the 160 m fiber was used in loop-I and 80 m fiber was used in loop-II and robust stabilization was achieved with predictable delay difference between the two external feedback cavities. Symmetric dual-loop feedback configurations seem to be most suitable in terms of product design and packaging, compared to reported asymmetric dual-loop feedback [26], as it does not require a fiber length in each external feedback loop In this contribution, we experimentally demonstrated the symmetric dual-loop optical feedback to suppress timing jitter of SML two-section QDash laser emitting at ∼1.55 μm and operating at ∼21 GHz repetition rate. The path of jitter stabilization as a function of full delay phase tuning and power split ratio was identified
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