1.7 μm laser with a low frequency shifted Raman mode cascade connection

Raman frequency conversion based on a solid medium is an effective technical scheme to generate new wavelength laser. 1572 nm KTP optical parametric oscillator was used to pump the KGW crystal intracavity, and Raman laser output at 1616 nm (2nd-order), 1638 nm (3rd-order), 1662 nm (4th-order), 1686 nm (5th-order) and 1711 nm (6th-order) was realized, among which 1711 nm is dominant. The maximum total average output power of the laser is 1.13 W, the minimum pulse width is 20 ns. The single-order average Raman frequency shift corresponding to the multiorder cascade Raman frequency conversion is 86 cm⁻¹, which is consistent with the low-frequency Raman mode of the KGW crystal reported in the literature. Using a 1572 nm KTP optical parametric oscillator as the intracavity pump source of the Raman laser has two advantages: On the one hand, it can effectively expand the output wavelength of Raman frequency conversion; on the other hand, it can provide high-intensity pump light for subsequent multiorder Raman conversion based on the pulse narrowing characteristics of the optical parametric oscillator. By introducing the multi-order Raman frequency conversion scheme, a new idea is provided for the effective use of the unconventional low-frequency shift Raman mode of a solid medium.