Narrow-linewidth Ring Laser Research Articles

Tunable Narrow-Linewidth Ring Laser Based on the Polarization Conversion in a Tapered Fiber-Coupled Whispering Gallery Mode Resonator

Based on the polarization conversion in a tapered fiber-coupled whispering gallery mode (WGM) system, a simple-structured narrow linewidth band-pass filter was fabricated and a narrow linewidth ring laser was demonstrated. With a fiber Bragg grating (FBG) to further select the resonant mode, the ring laser could be in the single-longitudinal-mode with the linewidth about 6 kHz and its wavelength could be tuned from 1540.10 nm to 1570.01 nm. Benefit from the dense modes in the WGM resonator, high conversion efficiency, and better stability of the structure, a tunable dual-wavelength laser could be achieved based on two FBGs with different resonant wavelengths. The configuration of the proposed laser is simple and stable, which will benefit its applications in the future.

Narrow-linewidth diode laser using a fiber-optic ring resonator

Experimental results of linewidth reduction in AlGaAs diode lasers with frequency-selective Rayleigh scattering from a fiber-optic ring resonator are presented. The intermediate-frequency signal produced by two such lasers is shown to have less than a 100-Hz intermediate-frequency linewidth. Self-homodyning measurements indicate an estimated laser linewidth of 0.6 Hz. Observing the intermediate-frequency beat signal and a Fabry-Perot interferometer, we demonstrate frequency mode stability and tuning. This tuning allowed us to lock a heterodyne optical phase-locked loop successfully. The narrow-linewidth ring laser also produced a stimulated Brillouin scattering wave.