Multiwavelength, Stokes-Anti-Stokes, Highly Transient SRS with Combined Frequency Shifts in a New Sr0.86Ba0.14MoO4 Raman Crystal

Abstract

For the first time to our knowledge, a single-phase cationic Sr_0.86Ba_0.14MoO₄ solid solution was used as an active medium for multiwavelength generation via stimulated Raman scattering (SRS) on dual (primary and secondary) Raman modes. When pumped by a subpicosecond laser with controllable chirping of radiation pulses (at a wavelength of 1030 nm), single-pass highly transient SRS generation of a larger number of Stokes radiation components (up to six) was obtained as compared to the original SrMoO₄ crystal. This is explained by the increase in the spectral width and relative intensity of the secondary Raman mode in the solid solution. In addition, simultaneous efficient anti-Stokes SRS generation was obtained, especially with a low-frequency shift on the secondary Raman mode due to the small phase mismatch of the Stokes–anti-Stokes parametric Raman interaction. The total efficiency of the Stokes–anti-Stokes SRS conversion reached 33% with an optimal duration of chirped pumping pulses of 2 ps. This makes the obtained simple a source of multiwavelength radiation attractive for use in multiphoton microscopy and photodynamic therapy not only in the second (1000–1350 nm) but also in the first (650–950 nm) therapeutic window of biological tissue transparency.