CC BY
7The 30th International Conference on Advanced Laser Technologies LM-O-5
ALT'23
Femtosecond pulses inscription of fiber Bragg gratings with phase shift by motion velocity modulation
A.Shikin1, A. Smirnov1, O. Butov1
1- Kotelnikov Institute of Radioengineering and Electronics, Russian Academy of Sciences, 11-7Mokhovaya St.,
Moscow 125009, Russia
artem.shikin@phystech. edu
Single-frequency fiber lasers are important for modern sensorios and optical telecommunications [1-3]. One of the ways to create such device is to fabricate a Bragg grating, containing a phase shift. When phase shift is equal to integer number of light waves plus one half, it favors to generation single longitudinal mode with. [4-6]. This results in a low level of phase noise and a narrow emission spectrum.
FBG can fabricated either by UV-light or femtosecond laser pulses. To form a phase shift, one needs to modify existing set-up or to do special post-processing. The latter usually demonstrates poor precision and therefore fabrication of phase shift simultaneous with inscription is preferred. Mask-based processes require careful design of the mask and limited to mask parameters [7]. Though some attempts to overcome this problem were made. Femtosecond point-by-point inscription is more flexible. To form a phase shift using additional piezo-positioner was suggested. Alternative way was to control the shutter of acousto-optic modulator [8,9]. Both methods have good precision in single-pass mode, but struggle in multi-pass.
We demonstrate fabrication of phase-shift in controllable manner by modulating nanopositioner velocity. In combination with technology of synchronization with oscillator firing [10] it allows to fabricate FBG with phase shifts in multi-pass mode. We also present FBG with n-shift in erbium-doped fiber. A laser based on this resonator demonstrates linewidth less than 1 kHz.
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