A high-power-handling deformable mirror system employing crystalline coatings

We outline the development of a high-power-handling deformable mirror device, based on a modified Thorlabs DMH40, employing a low-loss substrate-transferred crystalline coating as the reflective element. In standard products, this system features a metal coated (Ag or Al) 18 mm diameter × 150 μm thick BK10 glass substrate mounted to a 40-segment piezoelectric actuator, enabling Zernike compensation up to 4th order, with a peak-to-valley stroke up to ±17.6 μm. In the modified variant described here, the metal coating is replaced with a high-reflectivity (~99.998%) and low-stress (compressive, ~130 MPa) monocrystalline GaAs/AlGaAs Bragg stack transferred to the thin glass substrate via direct bonding. While maintaining similar physical performance, this custom system exhibits a substantial enhancement in power handling, with laser-induced damage tests (performed by Spica Technologies, Inc.) yielding a continuous-wave damage threshold of 75 MW/cm2 at 1070 nm with a 1/e2 spot diameter of 32.8 μm.