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Shanghai Optical Machine is making progress in research on mode-locked Raman fiber laser
[ Instrument Network Instrument Development ] Recently, Shanghai Optical Machinery Institute's high-power fiber laser technology laboratory has made new progress in the research of mode-locked Raman fiber lasers. The high-precision linear polarization dissipative soliton Raman laser output is obtained by the full-polarization nonlinear optical ring mirror mode-locking, and the time-domain stability of the laser pulse is greatly improved. The pulse peak power clamp is introduced in the mode-locked Raman fiber laser. The effect is achieved by a high energy rectangular pulse output.
Spectral characteristics of linearly polarized Raman dissipative soliton output
The Raman fiber laser uses the stimulated Raman scattering effect in the fiber as a gain mechanism, which has the advantage of wavelength flexibility. The realization of pulsed laser output in Raman fiber laser can effectively expand the application range of pulsed laser.
In many basic scientific research and biomedical fields, ultra-short pulse lasers of special wavelengths are often required for linear polarization. In response to this demand, the research team built a fully polarization-maintaining laser cavity by means of nonlinear optical ring mirror clamping, and added a polarizing element in the cavity to ensure the linear polarization state of the output laser. At the same time, according to the characteristics of Raman scattering response speed in fiber, the researchers use a more stable amplifying spontaneous emission source in the time domain as the pump, and introduce a dissipative mechanism into the cavity to realize the Raman dissipative soliton output. , effectively improve the overall performance of the Raman ultra-fast laser. The obtained Raman ultrafast laser pulse repetition frequency is 1.23 MHz, the maximum pulse energy and the minimum pulse width are 1.23 nJ and 63 ps, respectively, and the spectral SNR is as high as 85 dB. Related research results have been published in [Optics Express 27, 17905 (2019)].
Relationship between time domain shape and pump power of rectangular Raman pulse
In order to improve the output pulse energy of the mode-locked Raman fiber laser, the research group introduced the pulse peak power clamping effect by optimizing the length of the ring mirror under the nonlinear optical ring mirror clamping mechanism, so that the pulse energy and pulse width increase with the pump power. Large and no pulse splitting. Finally, a high-energy linearly polarized rectangular Raman pulse output with a maximum energy of 64.1 nJ and a maximum pulse width of 25.1 ps is obtained. At the same time, it is also observed that the time domain shape of the Raman pulse gradually evolves from a normal rectangular pulse to a stepped rectangular pulse as the pump power increases. Related research results have been published in [Journal of Lightwave Technology 37, 1333 (2019)].
Relevant research has been supported by the National Natural Science Foundation of China and the China Postdoctoral Science Foundation.