Ultra-narrow linewidth DFB-laser with optical feedback from a monolithic confocal Fabry-Perot cavity

Abstract

We present a compact, ultra-narrow-linewidth semiconductor laser based on a 780 nm distributed feedback diode laser optically self-locked to a mode of an external monolithic confocal Fabry-Perot resonator. We characterize spectral properties of the laser by measuring its frequency noise power spectral density. The white frequency noise levels at 5 Hz(2)/Hz above a Fourier frequency as small as 20 kHz. This noise level is more than five orders of magnitude smaller than the noise level of the same solitary diode laser without resonant optical feedback, and it is three orders of magnitude smaller than the noise level of a narrow linewidth, grating-based, extended-cavity diode laser. The corresponding Lorentzian linewidth of the laser with resonant optical feedback is 15.7 Hz at an output power exceeding 50 mW.

Widely-Tunable Ring-Resonator Semiconductor Lasers

“…This has been typically done with Fabry-Perot cavities that were free-space coupled to semiconductor lasers [36,37]. The use of a separate cavity for feedback breaks the limitation, as one can engineer the cavity to have the FSR larger than ω R , keeping the laser stable with large effective bandwidth, and offering narrow linewidth due to increased photon lifetime inside the cavity.…”

Stabilization and Frequency Control of a DFB Laser With a Tunable Optical Reflector Integrated in a Silicon Photonics PIC

“…Here, the architecture is intended to remain compatible with off-the-shelf laser diodes and relies on a comparatively weak level of resonant optical feedback compared to the aforementioned external cavity laser. While resonant feedback from external narrow linewidth resonators has been shown to provide, by itself, the means to drastically reduce the linewidth of DFB lasers [16], [17], the relatively low quality factor of the ring resonators used in this work did not result in significant improvement of the laser linewidth, as discussed in the following. Thus we are proposing to complement the relatively low quality factor of the resonators by active resonance tuning with feedback provided by an OPLL in order to achieve linewidth reduction.…”

GaAs-based distributed feedback laser at 780 nm for 87Rb cold atom quantum technology

“…That system used coherent population trapping for the clock transitions whilst we are aiming to first produce lasers for cooling and trapping ions inside vacuum chambers before microwave pulses or controlled lasers are used to create superposition states, recombine them and measure the interference from the final state populations. For cooling 87 Rb atoms, 780.24 nm lasers with linewidths below ~5 MHz are required whilst the lasers for controlling and measuring superposition states typically external cavity lasers have been used to achieve linewidths from 20 kHz [3] down to a few Hz [4]. Most single mode diode lasers aimed at laser cooling have used DBR gratings with regrowth [5] but this is challenging when using AlGaAs materials due to oxidation.…”