Fiber Laser Based on Electronically Controlled Phase Plates

Authors O.S. Hnatenko

Kharkiv National University of Radio Electronics, 14, Nauky Ave., 61166 Kharkiv, Ukraine

Issue Volume 13, Year 2021, Number 5
Dates Received 15 August 2021; revised manuscript received 20 October 2021; published online 25 October 2021
Citation O.S. Hnatenko, J. Nano- Electron. Phys. 13 No 5, 05038 (2021)
PACS Number(s) 42.55.Wd, 42.60.Fc
Keywords Fiber laser, Optical fiber (3) , Femtosecond (2) , Polarization (6) , Pulse duration, Amplitude, Frequency (15) , Phase (44) .

The physical principles of mode locking in fiber lasers for output radiation with a pulse duration of the femtosecond order have been studied. From the analysis performed, it can be concluded that the most effective method for the development of a ring fiber laser with ultrashort pulses is the method of nonlinear polarization evolution, which is characterized by simple settings for reaching the regime and stable mode locking. Short pulse durations were obtained by means of this method. A theoretical and experimental study of an LC cell for controlling laser polarization has been carried out. For nematic planar LC cells, there is cut-off voltage, which is 2.2-2.5 V for the cell described in this work. When studying the interaction of laser radiation with the cell, it was found that the angle of polarization state in space changes from 0 to 90° when a voltage is applied from 2.2 to 10 V. When a voltage of more than 10 V is applied, the cell is “saturated” and the angle of polarization rotation changes very little, and when a voltage of more than 10 V is applied, an electrical breakdown of the LC layer may occur. A theoretical simulation of mode locking in a ring fiber laser has been carried out. Namely, the formation of output laser pulses at different positions of the wave plates or voltage supply to the liquid crystal cell has been studied. Theoretically, the laser has the ability to generate both continuous and quasi-pulse modes. An experimental prototype of a fiber laser with mode locking by liquid crystal cells has been developed, which has the following parameters: pulse duration of the femtosecond order, radiation wavelength of 1550 nm. These parameters give an advantage in the use of a laser for high-speed data transfer over fiber communication lines and quantum cryptography.

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