TY - JOUR

T1 - Actively Mode Locked Raman Fiber Laser with Multimode LD Pumping

AU - Kuznetsov, Alexey G.

AU - Kablukov, Sergey I.

AU - Timirtdinov, Yuri A.

AU - Babin, Sergey A.

N1 - Funding Information: The study is supported by Russian Foundation for Basic Research (21-72-30024). Publisher Copyright: © 2022 by the authors.

PY - 2022/8

Y1 - 2022/8

N2 - We present our recent experimental results on the pulsed regimes of Raman conversion of highly multimode laser diode (LD) pump radiation into the 1st and higher order Stokes radiation in multimode graded-index fibers. Three different linear cavities of Raman fiber laser with the modulation of losses (by acousto-optic modulator, AOM) or gain (by LD current) are explored and compared. An LD with wavelength of 976 nm is used for pumping enabling Raman lasing at wavelength of the 1st (1018 nm) and 2nd (1064 nm) Stokes orders. At ~27.2-kHz repetition rate corresponding to the laser cavity round-trip frequency (i.e., in the mode-locking regime), nanosecond pulses have been observed for both Stokes orders having the highest peak power of ~300 W in the scheme with bulk AOM and the shortest duration of 5–7 ns in the scheme with fiber-pigtailed AOM. At the same time, the beam quality of generated pulses is greatly improved as compared to that for pump diode (M2 > 20) reaching the best value (M2 = 2.05) for the 2nd order Stokes beam in the scheme with the gain modulation and demonstrating also the most stable regime.

AB - We present our recent experimental results on the pulsed regimes of Raman conversion of highly multimode laser diode (LD) pump radiation into the 1st and higher order Stokes radiation in multimode graded-index fibers. Three different linear cavities of Raman fiber laser with the modulation of losses (by acousto-optic modulator, AOM) or gain (by LD current) are explored and compared. An LD with wavelength of 976 nm is used for pumping enabling Raman lasing at wavelength of the 1st (1018 nm) and 2nd (1064 nm) Stokes orders. At ~27.2-kHz repetition rate corresponding to the laser cavity round-trip frequency (i.e., in the mode-locking regime), nanosecond pulses have been observed for both Stokes orders having the highest peak power of ~300 W in the scheme with bulk AOM and the shortest duration of 5–7 ns in the scheme with fiber-pigtailed AOM. At the same time, the beam quality of generated pulses is greatly improved as compared to that for pump diode (M2 > 20) reaching the best value (M2 = 2.05) for the 2nd order Stokes beam in the scheme with the gain modulation and demonstrating also the most stable regime.

KW - beam quality

KW - brightness enhancement

KW - diode pumping

KW - fiber laser

KW - graded-index

KW - mode locking

KW - multimode

KW - Raman laser

UR - http://www.scopus.com/inward/record.url?scp=85137980437&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/4cc9d112-cf21-3f36-a4b7-51f421bd5d66/

U2 - 10.3390/photonics9080539

DO - 10.3390/photonics9080539

M3 - Article

AN - SCOPUS:85137980437

VL - 9

JO - Photonics

JF - Photonics

SN - 2304-6732

IS - 8

M1 - 539

ER -