Shanghai University of Technology had peace research group to enhance the optical nonlinear resonance through the active gain of the optical fiber to achieve precise control of the refractive index to achieve full polarization Polarization Lasers locked. Relevant research results recently published in the "Journal of Optics."
With the ultrafast laser to all optical fiber, all Paul partial, small development, making airborne and spaceborne gradually possible. Therefore, the study of a higher locking accuracy, all-fiber frequency locking method is particularly important.
Researchers in the Ytterbium-doped fiber laser cavity by adding a 980 nm / 1064 nm wavelength division multiplexer and a section of the erbium-doped optical fiber used to control the length of the optical cavity to achieve a full polarization-maintaining fiber laser frequency locking. Under the premise of not affecting the mode-locked state, the number of inverted particles of the erbium ions in the optical fiber is changed by modulating the intensity of the pump light loaded on the erbium-doped optical fiber to control the nonlinear refractive index of the optical fiber, Control of the entire laser optical cavity length.
In the meantime, the effects of different erbium-doped fiber length and initial pump power on the repetition frequency control range and locking accuracy of the laser were also measured in experiments. The results show that when the erbium-doped fiber is 1.75 meters, the frequency adjustment range of 180 Hz can be realized. The frequency locking accuracy is only related to the initial power of pumping light, but not to the length of erbium-doped fiber. When the pump light is 18 milliwatts, the peak-to-peak variation range is ± 0.5 milli-Hz with a corresponding standard deviation of 0.16 milli-Hz.
"With the rapid development of the optical frequency comb, the frequency-locked fiber laser will play an increasingly important role in such fields as absolute distance measurement, astronomical observation and spaceborne optical clock." Zeng Heping said that in the future, Internal noise suppression, supercontinuum generation, carrier phase detection and locking and other issues.
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