860-Femtosecond Synchronously-Pumped GdVO4 Raman Laser at 1228 nm with 36-Picosecond 1063 nm Pumping
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2019-06-01 |
| Authors | Milan Frank, S. N. Smetanin, Michal Jelínek, David Vyhĺıdal, В. Е. Шукшин |
| Institutions | Czech Technical University in Prague, Prokhorov General Physics Institute |
Abstract
Section titled “Abstract”Summary form only given. At present, we can observe progress in physics of crystalline Raman lasers leading to efficient nonlinear frequency conversion at transient regime for generation of ultra-short pulses of stimulated Raman scattering (SRS) radiation with picosecond duration and shorter [1,2]. Recently the problem of a femtosecond crystalline Raman laser with femtosecond pumping has been solved [1] using an efficient SRS in a Raman-active crystal (CVD-diamond) under synchronous pumping by repetitive femtosecond laser pulses in an external cavity with a round-trip time equal to the pump pulse repetition period. However, a challenge of femtosecond SRS pulse generation in crystals under pumping by picosecond lasers which is more simple, inexpensive, and prevalent in comparison with the unique femtosecond laser systems remained unsolved. In [2] a new method of SRS pulse shortening using a Raman -active crystal with two (v1 and v2) vibrational Raman frequencies (stretching and bending Raman modes) has been demonstrated. It is based on a synchronously pumped cascade SRS process of primary extracavity Raman conversion from a pump radiation into a v1-shifted Stokes component and secondary intracavity Raman conversion from the v1-shifted Stokes component into the (vi + v2) -shifted Stokes component with strong pulse shortening down to the inverse width of the widest v2 line. In the synchronously -pumped extracavity SrMo04 [2] Raman laser, extreme 26 -fold SRS -pulse shortening down to 1.4 ps at the (vi + v2) -shifted SRS component has been experimentally achieved that is close to the inverse value of the widest v2 Raman line width of 10 cm 1 . In this work, we demonstrate the fi rst femtosecond crystalline Raman laser pumped by a picosecond laser. The simplest scheme of the extracavity bow -tie synchronously pumped all -solid-state Raman laser for strong SRS pulse self -shortening has been developed using the identical Nd:GdVO4 crystals as the active elements for both the pump and Raman lasers. A choice of GdVO4 as the Raman -active medium is caused by the fact that besides a high Raman gain (g = 4.5 cm/GW under 1.06 -gm pumping) at the most intense anionic group stretching Raman mode (vi = 882 cm ’) it also has the anionic group bending Raman mode at v2 = 382 cm ’ differing by anomalous broadening up to the widest linewidth of Av2 = 24 cm 1 . We report characteristics of the all -solid-state extracavity GdVO4 Raman laser under synchronous pumping by the 1063-nm, 36 -picosecond, 150 -MHz Nd:GdVO4 laser (Fig. 1) . Cascade two -wavelength SRS generation in the external high -Q ring cavity has been obtained not only at the usual wavelength of 1174 nm corresponding to the vi -shifted fi rst Stokes component, but also at the unusual wavelength of 1228 nm corresponding to the (vi + v2) -shifted Stokes component with individual pulse energy up to 10 nJ, slope efficiency of 5 %, and strong pulse self -shortening. At positive detuning of the external cavity length, the strongest 42 -fold self -shortening of the 1228-nm SRS radiation pulses down to 860 fs which is close to an inverse width (Av2=24cm 1 ) of the widest v2 Raman line has been achieved without using any compressor. This extreme pulse shortening is explained by the theory of ultra -short SRS pulse formation at intracavity pumping taking into account that generation of the highly shortened (vi + v2) -shifted SRS pulses in the extracavity pumped Raman laser took place under intracavity pumping by the vi -shifted SRS radiation. The research was supported by the Czech Science Foundation - No 18-11954S, and by the Russian Foundation for Basic Research - Project No 19-02-00723