Description
Optical microresonators have been successfully employed in self-referenced laser frequency stabilization, narrow-linewidth laser development, and nonlinear optical conversion. To simultaneously carry out these applications with a single microresonator would be highly useful to the development of advanced laser sources with enhanced performances and functionalities.
In this work, we present an external-cavity laser based on a lithium niobate microresonator. With ferroelectric domain engineering and direct modulation spectroscopy technique, the microresonator allows for strong resonant feedback for narrow-linewidth lasing, gives rise to efficient spectral translation based on second-harmonic generation (SHG), and enables self-referenced frequency stabilization of the external-cavity laser. The domain-inversion-engineered structure in the microresonator introduces strong coupling between counter-propagating modes, which causes efficient resonant feedback that closes the gain-included fibre loop with a circulator. While narrow-linewidth single-mode lasing is enabled across nearly 40 nm, the microresonator also produces quasi-phase-matched SHG with various fundamental and second-harmonic mode pairs. By applying electro-optic modulation on the microresonator, we generate error signals that can be used to lock the laser frequency to the centre of the microresonator resonance and to stabilize the resonance frequency of the microresonator, respectively. With a dual-feedback-control approach, the frequency stability of the external cavity laser is significantly improved.
We develop a coupled-equation-based model to analyse the laser behaviour, showing excellent agreement with the experimental observations. The developed laser prototype showcases the versatility of ferroelectric microresonators in advanced optical and photonic applications and provides a compact scheme for high-performance laser sources in optical clock and quantum applications.
| I am the presenting author | Yes |
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