Study of Quality of Thermodiffusion Welding of Crystals in Disk Optical Element by Optoacoustic Method

The possibility of evaluating the quality of thermodiffusion welding of two yttrium aluminum garnet crystals in a composite optical disk has been investigated using an optoacoustic method. To obtain acoustic images of thermodiffusion welding. an optoacoustic sensor connected to a pulsed laser (wavelength 532 nm. pulse duration 10 ns) by an optical fiber was scanned over the disk surface. The ultrasonic pulses in the frequency range up to 80 MHz were registered synchronously with the movement of the transducer on the area of 16x16 mm with a step of 0.1 mm. Two modes of ultrasonic location were used: on reflection and on lumen. Diagnostics of two 15 mm diameter composite disks with different quality of thermodiffusion welding was carried out. The possibility of quantifying the quality of the diffusion layer by an optoacoustic method for objective comparison of the disks is discussed. The obtained data are confirmed by the results of measurements by the optical projection method.