Widely tunable, low linewidth, and high power laser source using an electro-optic comb and injection-locked slave laser array

Phase-locked, pre-amplified optical injection locking at low input powers

Optical injection locking generally occurs when light from a master laser is unidirectionally injected into a slave laser, such that the injected light overcomes spontaneous emission inside the cavity, and forces the slave laser to behave as a frequency copy of the master. Here, we study the limits of stability for optically pre-amplified optical injection locking in the case of large added noise on the input field and in the presence of a phase locked loop which minimizes the frequency offset between master and slave lasers. We present a set of modified rate equations which we use to describe the physics of the system near the limit of stable injection locking, and report on phase slips which occur due to injected noise momentarily destabilizing the system. We then provide experimental evidence to support the behavior seen in simulation, and are able to successfully recover a CW wave at -80 dBm black box input power (-70 dBm for phase slip free operation), providing 20 dBm of output power from the injection locked slave laser.

Thermorefractive noise reduction of photonic molecule frequency combs using an all-optical servo loop

Phase and frequency noise originating from thermal fluctuations is commonly a limiting factor in integrated photonic cavities. To reduce this noise, one may drive a secondary "servo/cooling" laser into the blue side of a cavity resonance. Temperature fluctuations which shift the resonance will then change the amount of servo/cooling laser power absorbed by the device as the laser moves relatively out of or into the resonance, and thereby effectively compensate for the fluctuation. In this paper, we use a low noise laser to demonstrate this principle for the first time in a frequency comb generated from a normal dispersion photonic molecule micro-resonator. Significantly, this configuration can be used with the servo/cooling laser power above the usual nonlinearity threshold since resonances with normal dispersion are available. We report a 50 % reduction in frequency noise of the comb lines in the frequency range of 10 kHz to 1 MHz and investigate the effect of the secondary servo/cooling noise on the comb.

All-fibre heterogeneously-integrated frequency comb generation using silicon core fibre

Originally developed for metrology, optical frequency combs are becoming increasingly pervasive in a wider range of research topics including optical communications, spectroscopy, and radio or microwave signal processing. However, application demands in these fields can be more challenging as they require compact sources with a high tolerance to temperature variations that are capable of delivering flat comb spectra, high power per tone, narrow linewidth and high optical signal-to-noise ratio. This work reports the generation of a flat, high power frequency comb in the telecom band using a 17 mm fully-integrated silicon core fibre as a parametric mixer. Our all-fibre, cavity-free source combines the material benefits of planar waveguide structures with the advantageous properties of fibre platforms to achieve a 30 nm bandwidth comb source containing 143 tones with <3 kHz linewidth, 12 dB flatness, and >30 dB OSNR over the entire spectral region.

Widely tunable narrow linewidth laser source based on photonic molecule microcombs and optical injection locking

We demonstrate a method to generate a widely and arbitrarily tunable laser source with very narrow linewidth. By seeding a coupled-cavity microcomb with a highly coherent single-frequency laser and using injection locking of a Fabry-Perot laser to select a single output comb tone, a high power, high side mode suppression ratio output wave is obtained. The system is demonstrated across 1530 -1585 nm with a linewidth below 8 kHz, having 5 dBm output power and sidemode suppression of at least 60 dB. Prospects of extending the performance are also discussed.