Self-Wavelength Sweeping Laser With Narrow Linewidth Induced by Thermal Effect of Asymmetric Bandpass Filter in Whispering Gallery Mode Resonator

This paper presents a narrow-linewidth, self-wavelength sweeping laser that utilizes the thermal effect within a silica microbubble resonator. By utilizing the Fano lineshape spectrum (FLSS) of the resonator as an intracavity bandpass filter and a thermal (Formula presented.) -switch, the laser attained a linewidth of 8.03 kHz and an average sweeping frequency of 833 Hz using the FLSS filter with a positive slope ratio, while it obtained a linewidth of 13.87 kHz and an average sweeping frequency of 588 Hz using the filter with a negative slope ratio. The average sweeping frequency can be adjusted by tuning the coupling gap between the resonator and the tapered fiber, with a wavelength sweeping range up to 1.1 GHz. As an application example, the proposed laser was utilized to obtain a whispering gallery mode (WGM) spectrum of a microsphere. This work provides a new paradigm for leveraging the thermal effect in WGM resonators, resulting in a laser that uniquely combines narrow linewidth with self-sweeping capability, which is extremely suitable for high-resolution, high-speed optical sensing applications and paving the way for dynamic photonic systems.