2 research outputs found
Optimization of laser stabilization via self-injection locking to a whispering-gallery-mode microresonator: experimental study
Self-injection locking of a diode laser to a high-quality-factor
microresonator is widely used for frequency stabilization and linewidth
narrowing. We constructed several microresonator-based laser sources with
measured instantaneous linewidths of 1 Hz and used them for investigation and
implementation of the self-injection locking effect. We studied analytically
and experimentally the dependence of the stabilization coefficient on tunable
parameters such as locking phase and coupling rate. It was shown that precise
control of the locking phase allows fine tuning of the generated frequency from
the stabilized laser diode. We also showed that it is possible for such laser
sources to realize fast continuous and linear frequency modulation by injection
current tuning inside the self-injection locking regime. We conceptually
demonstrate coherent frequency-modulated continuous wave LIDAR over a distance
of 10 km using such a microresonator-stabilized laser diode in the
frequency-chirping regime and measure velocities as low as sub-micrometer per
second in the unmodulated case. These results could be of interest for
cutting-edge technology applications such as space debris monitoring and
long-range object classification, high resolution spectroscopy and others
Generation of dual and quad-optical frequency combs in the injected radiation free mode-locked frequency-shifted feedback laser
Abstract The results of an optoelectronic system—frequency-shifted feedback (FSF) laser experimental examination are presented. The considered FSF laser is seeded only with optical amplifier spontaneous emission (ASE) and operates in the mode-locked regime, whereby the output radiation is sequence of short pulses with a repetition rate determined by the delay time in its optical feedback circuit. In the frequency domain, the spectrum of such a pulse sequence is an optical frequency comb (OFC). These OFCs we call initial. We consider the possibility of tunable acousto-optic (AO) dual and quad-comb frequency spacing downconversion in the FSF laser seeded with ASE and operating in the mode-locked regime. The examined system applies a single frequency shifting loop with single AO tunable filter as the frequency shifter that is fed with several radio frequency signals simultaneously. The initial OFCs with frequency spacing of about 6.5 MHz may be obtained in the wide spectral range and their width, envelope shape and position in the optical spectrum may be tuned. The dual-combs are obtained with a pair of initial OFCs aroused by two various ultrasound waves in the acousto-optic tunable filter (AOTF). The dual-combs frequency spacing is determined by the frequency difference of the signals applied to the AOTF piezoelectric transducer and can be tuned simply. The quad-combs are obtained with three initial OFCs, forming a pair of dual-combs, appearing when three ultrasound frequencies feed the AOTF transducer. The quad-combs frequency spacing is defined by the difference between the frequency spacing of dual-combs. Quad-combs with more than 5000 spectral lines and tunable frequency spacing are observed. The successive frequency downconversion gives the possibility to reduce the OFC frequency spacing form several MHz for initial OFC to tens of kHz for quad-combs. Graphical abstrac