This study developed a Liquid Crystal (LC) device that incorporated lasers for machining with output power of the order of kW. The use of sapphire as a substrate along with an appropriate cooling system facilitated the LCs in enabling the control of the phase and polarization of high-power laser light, which is not possible in case of conventional LCs. The exposure of LCs to high-power laser light results in heat accumulation, which causes the destruction of the LC cells. As photochemical damage has a lower occurrence probability at longer wavelengths, the promotion of heat radiation is an important strategy for the application of LCs to near infrared laser beams. The phase control of laser beams up to 6 kW was achieved using the proposed LC substrate as a cooling plate and optimizing the cooling system. Moreover, we compensated for the variation in the properties of the LC with temperature via adjustments to the drive voltage of the LC.