RESUMEN
We experimentally demonstrate an ultralow-threshold cascaded Brillouin microlaser for tunable microwave generation in a high-Q silica microsphere resonator. The threshold of the Brillouin microlaser is as low as 8 µW, which is close to the theoretical prediction. Moreover, the fifth-order Stokes line with a frequency shift up to 55 GHz is achieved with a coupled pump power of less than 0.6 mW. Benefiting from resonant wavelength shifts driven by thermal dynamics in the microsphere, we further realized tunable microwave signals with tuning ranges of 40 MHz at an 11 GHz band and 20 MHz at a 22 GHz band. To the best of our knowledge, it was the first attempt for tunable microwave source based on the whispering-gallery-mode Brillouin microlaser. Such a tunable microwave source from a cascaded Brillouin microlaser could find significant applications in aerospace, communication engineering, and metrology.
RESUMEN
The double transfer matrix method (DTMM) is proposed for calculating the eigenvalues of the resonant mode of a metallically coated dielectric rectangle resonator. Two-dimensional electromagnetic analyses are performed to investigate the optical influences induced by planar structure parameters. The results show that there theoretically exists a highest Q-factor resonance for both TE and TM modes at a certain length-width ratio with fixed resonant wavelength and resonator area. Due to the influence of surface plasma polaritons (SPPs) trapped at the corners of the resonator which is not considered in DTMM, the TM mode resonances are deformed and deviate severely from that of the analytical model. The geometric deformation on the resonator is introduced by replacing the four right angles with circular boundaries, and the SPP accompanied mode behaviors are corrected to the standing waves.
