Thulium fiber lasers emit light of wavelengths spanning as low as 1650nm to 2200nm. This broad emission band is in the “eye-safety” wavelength regime and intersects with the IR atmospheric transmission window with its opacity subsiding past 1900nm wavelength. Consequently, a high power, single frequency, tunable thulium fiber laser with its tuning range from 1900nm to 2000nm has the unique capability of studying high power beam propagation through the atmosphere in regions of both weak and strong transmission. Moreover, such lasers can be made to tune across individual molecular absorption lines due to chemical species present in the atmosphere. This enables a detailed investigation on how individual molecular absorption lines affect the transmission of high power laser beams. In this paper, a 100kHz linewidth, near diffraction limited, 100W class, widely tunable CW thulium fiber laser system is described for atmospheric propagation studies. The fiber laser is of master oscillator power amplifier(MOPA) architecture with one pre-amp and a final power amplifier. The master oscillator is a 5mW class tunable external cavity diode and is tunable from 1900nm to 2000nm. The pre-amp amplifies the seed to 2-3W level, which is then further amplified to 100W by the final amplifier made from thulium doped 25um core 250um cladding 0.09NA fiber from Nufern. All fiber architecture allows efficient lasing at the lossy molecular absorption wavelengths.

Date Published: 13 March 2019
PDF
Proc. SPIE 10897, Fiber Lasers XVI: Technology and Systems, 108970L (13 March 2019); doi: 10.1117/12.2513501

Published in SPIE Proceedings Vol. 10897:
Fiber Lasers XVI: Technology and Systems
Adrian L. Carter; Liang Dong, Editor(s)