Dynamic Evolution of Microcavity Raman Laser subjected to Frequency-shifted Feedback and its Application in Laser Spectrum Encoding Thermal Sensing

Dynamic evolution of microcavity Raman laser subjected to frequency-shifted optical feedback is studied. The relaxation peak of the microcavity Raman laser, which matches the oscillation mode of the feedback signal, can be amplified based on the optical feedback effect. Due to the stronger interaction between the optical field and the frequency-shifted feedback signal, narrower relaxation linewidth of microcavity Raman laser is realized, and multi-level resonance sidebands on the laser intensity spectrum will emerge. Taking the advantage of optical feedback technology, a miniature microcavity Raman laser encoding thermal sensor with ultrahigh resolution of 0.00238 C is demonstrated. The tunability of the measurement range can be obtained by adjusting the frequency shift of the feedback signal. Furthermore, temperature variation determines the overall pattern of the microlaser spectrum when subjected to optical feedback. Based on the spectrum patterns, a laser encoding mechanism that involves simultaneous monitoring of multiple information is illustrated, which serves as a fingerprint of the laser mode and shows potential to study transient thermal dynamics in microsystems. Besides thermal sensing, the proposed method is expected to find further promising applications including physical thermodynamics, environmental monitoring, and biomedical thermal research.