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12LS-P-3
LASER SYSTEMS AND MATERIALS
Comparison of pulsed generation parameters in dumbbell-shaped and ring
cavities of the Holmium-doped fiber laser
S.A. Filatova1*, V.A. Kamynin1, Y.G. Gladush2, E.M. Khabushev2, D.V. Krasnikov2, A.G. Nasibulin23, V.B.
Tsvetkov1
ALT'22
1 - Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Str., 119991 Moscow, Russia 2 - Skolkovo Institute of Science and Technology, Nobel Str. 3, Moscow, 121205, Russia 3 - Aalto University, P.O. Box 16100, Aalto, FI-00076, Finland *email address: [email protected]
Particular interest is observed in ultrashort pulsed lasers operating in the spectral range of 2 - 3.5 ^m due to their many possible applications in spectroscopy, gas sensing, materials processing, laser surgery, biodiagnostics, and etc [1]. One of the promising active medium for such sources are Holmium-doped (Ho) fibers due to their broad gain spectrum of 2-2.2 ^m. So in recent years, mode-locked Ho-doped fiber lasers have been intensively studied [2,3].
Most cavities of mode-locked fiber lasers contain expensive or complicated elements such as isolators, polarizers, beam splitters, circulators, etc. However for the further use of ultrashort pulsed lasers as a seed source or in complex hybrid systems, the laser scheme should be simplified and free of elements that can affect laser generation. Therefore, it is of interest to study a fiber laser with a simple dumbbell-shaped cavity [4,5]. This work is focused on comparison of the parameters and efficiency of ultrashort pulse generation in different types of cavities (dumbbell-shaped and ring) and on simplifying of Ho-doped fiber laser scheme.
a) b)
Fig. 1. Experimental setup of the mode-locked Ho-doped fiber laser with dumbbell-shaped cavity (a)
and ring cavity (b).
The experimental setups of Ho-doped fiber laser with different cavities types are shown in Fig. 1. The laser cavities consist of a 2 m of Ho-doped fiber with counter-propagating pumping by a continuous-wave Yb-doped fiber laser at 1130 nm through a 1125/2100 nm wavelength division multiplexer (WDM), fiber couplers, polarization controllers (PC), FC/APC connectors with saturable absorber, single mode fiber (SMF), and isolator in the case of ring cavity. We have used single-walled carbon nanotubes (SWCNT) as saturable absorber for mode-locking implementation. The length of the dumbbell-shaped cavity was about 8.6 m what corresponded to the pulse repetition rate of about 12 MHz, and the length of the ring cavity was compensated by SMF to obtain the same repetition rate and was about 17.3 m.
The dumbbell-shaped cavity configuration, proposed in this work, allowed us to decrease the lasing threshold and increase the generation efficiency relative to the ring cavity of Ho-doped fiber laser. Besides simplifying the laser scheme, we achieved stability and repeatability of laser parameters (ta = 2076 nm, Pavg = 7 mW, t = 1.3 ps, E = 0.6 nJ).
This work was carried out with the support of a grant from the President of the Russian Federation for young scientists-candidates of science MK-3465.2022.1.2.
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