CC BY
6*
ALT'23
The 30th International Conference on Advanced Laser Technologies
LS-I-8
Dynamics of generation of polarization and longitudinal modes in short cavity fiber lasers based on composite ytterbium fibers
V.V. Vel'miskin1, B.I. Denker2, V.A. Kamynin2*, S.E. Sverchkov2, A.A. Rybaltovskii2,
A.I. Trikshev2, V.B. Tsvetkov2
1 - Prokhorov General Physics Institute of the Russian Academy of Sciences, Dianov Fiber Optics Research Center,
Moscow, Russia
2 - Prokhorov General Physics Institute of Russian Academy of Sciences, Moscow, Russia
*email address: [email protected]
Narrow-bandwidth laser sources are used in many fields of science and technology. The emission bandwidth of less than 10 kHz is required in systems for coherent reflectometry [1], hydrophones [2], gas analysis and high-resolution spectroscopy [3]. For a number of applications, however, there remains a need to implement radiation with a single longitudinal mode, where extreme narrowing of the line is unnecessary. Such quasi-single-frequency sources are in demand for the realization of high-power, kilowatt-level laser systems [4], coherent combining systems [5]. The bandwidth of these sources can be in the range from a few megahertz to a few gigahertz.
In our work, we investigated some lasers with a short Fabry-Perot cavity based on Bragg gratings directly UV-written into the active fiber core (Fig. 1 (a)). To realize a short cavity length (less than 2 cm), we have used a highly Yb-doped composite fiber. Absorption of a weak signal at a wavelength of 976 nm - 12.5 dB / cm. In the region of the generation wavelength, the background did not exceed 0.1 dB/cm.
dBm/nm
(a)
LD 976 hm
(b)
ISO
FBG PR
FC/APC OUT 1
FBG HR
FC/APC OUT 2
Wavelength, nm
Fig. 1. (a) Experimental setup of the F-P Yb-doped fiber laser, (b) spectral power density depending on wavelength and pump power.
The spectral dynamics, linewidth dynamics, and polarization dynamics of lasers are studied as a function of pump power. Fig. 1 (b) shows the spectral power density as a function of wavelength and pump power. We observed spectral shifts and switching from the single-mode to multi-mode operation during pump power variation.
During laser operation, we observed a transition from narrow-bandwidth generation with a linewidth of about 2 MHz to the mode-beating regime. In addition, polarization mode dynamics with orthogonal polarization modes beating at the 300 MHz frequency have been registered.
We have demonstrated the applicability of Yb-doped phosphate core composite fibers in the fabrication of short cavity lasers with generation wavelengths up to 1070 nm based on direct UV FBG recording. It is shown that narrow bandwidth linear polarized laser generation requires accurate cavity design.
[1] D. Uttam and B. Culshaw, Precision Time Domain Reflectometry in Optical Fiber Systems Using a Frequency Modulated Continuous Wave Ranging Technique, J. Light. Technol., 3(5), 971-977, (1985).
[2] X. Zhang et al., Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection, Photonic Sensors, 7(4), 325328, (2017).
[3] S. Persijn, F. Harren, and A. Van Der Veen, Quantitative gas measurements using a versatile OPO-based cavity ringdown spectrometer and the comparison with spectroscopic databases, Appl. Phys. BLasers Opt., 100(2), 383-390, (2010).
[4] W. Li et al., 694 W sub-GHz polarization-maintained tapered fiber amplifier based on spectral and pump wavelength optimization, Opt. Express, 30(15), 26875, (2022).
[5] A.I. Trikshev, Yu.N. Pyrkov and V.B. Tsvetkov, Phasing of two amplifier channels for the coherent combining of laser beams with a total power of 60 W, Quantum Electronics, 47(11), 1045-1048 (2017).
