Thermally-Adaptive Solid State Laser Crystal Mount

NASA’s laser mount technology introduces a unique flexible crystal mount to accommodate the dynamics of thermal expansion to eliminate unsymmetrical thermally induced mechanical stresses on the crystal. In addition, while the mount accommodates thermal expansion, it also offers fixed placement of the crystal to maintain alignment and provides continuous and uniform surface contact between the mount and crystal for rapid dissipation of heat. The mount is compatible with any heat sink reservoir. The mount design allows unrestrained thermal expansion of the crystal in two dimensions (i.e. a- and c- axes) because of the design shown in the figure below. The L-shape blocks also deliver cooling to the crystal by providing a path to the heat sink reservoir. The L-shape blocks are manufactured with a high thermal conductivity material such as copper. A softer material with high thermal conductivity such as indium is used to buffer the interface between the crystal and the L-shape blocks surfaces. A coolant medium acts to transfer the heat from the crystal to the cooled mount. Cooling can be provided in different ways – for example by water or by heat pipes with radiator (for use in space). The springs used to hold the laser crystal also provide the adjustment method to align the beam, and once aligned, the crystal mount is very stable. The related patent is now available to license. Please note that NASA does not manufacture products itself for commercial sale. NASA’s solid-state laser crystal mounting technology was developed for and implemented in high-energy pulsed 2-micron laser transmitters for airborne differential absorption LIDAR used in measuring carbon dioxide concentrations in the atmosphere and Coherent Doppler lidar used for atmospheric winds. The mount is designed for cubic, tetragonal or orthorhombic laser crystals, such as yttrium aluminum garnet (YAG), yttrium lithium fluoride (YLF), and yttrium orthoaluminate (YALO), respectively, operating in high energy pumped laser transmitters. These crystals are prone to fracturing in use due to the heat generated and resulting unsymmetrical properties, such as thermal expansion, of the crystal. Most of the energy pumped into a laser crystal becomes excess heat. The faster and more uniformly this heat is dissipated, the better the laser beam performance and the lower the chance of crystal fracture. NASA’s laser crystal mount has been used in an actual laser transmitter system and has essentially eliminated the risk of thermally-induced damage to the laser crystal. Research indicated that the mount reduced the crystal damage rate from 17 crystals in a single year to no-damaged crystals for 4 years. The design offers unrestrained thermal expansion of the crystal while maintaining alignment position and continuous contact with the heat sink.