High resolution high power mid-IR generation by second-order Stokes shift in hydrogen

We describe the construction of a new type of continuously tunable high power laser source for the mid-IR. The source has many highly desirable characteristics, it is high power, high energy, near-diffraction limited, very high resolution, has very high photon conversion efficiency and is broadly tunable. The approach we have taken to realize such a source is by high-order Stokes shifting in hydrogen of a pulsed single frequency tunable optical parametric oscillator (OPO) that is amplified by a Ti:sapphire regenerative amplifier. There are several advantages to this approach. First, high power high quality radiation in the visible and near lR can easily be obtained from reliable solid-state lasers. Second, Stokes shifting uses hydrogen gas which can easily be replenished if necessary. It avoids the use of expensive IR nonlinear optical crystals such as the calcopyrites which are quite easily damaged, And third, by using soft focusing into a multiple-pass cell, the mid-IR output preserves the wavelength resolution and the spatial quality of the near-IR input