| The whispering gallery mode(WGM)optical microcavity has a very high-quality factor and a very small mode volume.It has great application potential in the application of lasers,high-sensitivity sensors,narrow linewidth filters and other optoelectronic devices.With the trend of miniaturization and portability,optoelectronic devices based on the WGM resonators have attracted wide attention because of the requirements for both ensuring the performance and small size.This article first introduced the theoretical analysis and application development of the WGM microcavity.Secondly,two laboratory preparation methods and two quality factor Q measurement methods for the WGM microcavity were proposed:the commonly used tunable laser wavelength scanning to the time domain transmission spectrum analysis method and high-resolution optical vector analysis method based on single-sideband modulation,showed that the quality factor Q of the microspheres with diameters from 200?m to 400?m used in the laboratory was on the order of10~7,and then used FDTD Solutions to simulate and analyze the coupling effect of the microsphere and the tapered fiber.Two experimental systems are proposed:1.Single-mode narrow linewidth laser based on WGM microcavity.A high-Q silica microsphere was added to the fiber ring laser as a narrow-band mode selector,and a single-mode laser output with a pump threshold of 24.8m W was obtained,and the output laser power varied linearly with the pump power,with a slope efficiency of 4.72%while the center wavelength changed within 1nm.Maintaining single-mode output state,the maximum output power of 1.69m W was obtained.Its stability was measured,and the results showed that the single-mode laser had good stability.The delayed self-heterodyne method was used for the measurement of the single-mode linewidth,and the Voigt line type was introduced to fit and optimize the results of the delayed self-heterodyne measurement method to obtain a more accurate linewidth,which is 910Hz.2.Single frequency Q-switched laser based on nonlinear polarization rotation(NPR)with WGM microcavity.First,the Erbium-doped fiber laser based on NPR was built,and a stable 3d B bandwidth of 7.18nm and a pulse width of 0.7ps of the mode-locked laser was obtained.Then,the microsphere and the tapered fiber were coupled into the system,and the single-frequency Q-switched laser pulse output with an average output power of0.219m W and a single pulse energy of 104n J was obtained at a pump power of 44.16m W,its linewidth is only on the order of k Hz.The Q-switched laser threshold is 41.52m W,and the repetition rate can be adjusted from 0.71k Hz to 3.26k Hz within the 14m W range of the pump power change while the average output power varied linearly with the pump power with a slope efficiency of 3.01%.In addition,the Q-switched mode-locking effect was observed by changing the pump power.According to the characteristics of the NPR effect,the single-frequency Q-switched laser with different repetition rates is obtained by only changing the polarization direction without changing the pump power,which can be used to realize the small adjustment of the repetition rate of the Q-switched laser. |
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