A simple, low-cost laser interferometry technique for single-crystal growth

Interferometry is an essential field of optical metrology and is adapted in many applications in optics, crystal growth and industry. The crystal growth rate is one of the critical parameters for the growth of optical-quality single crystals. A laser interferometry technique has been developed and applied successfully for crystal growth rate measurement from solution. A He-Ne laser at the wavelength of 633 nm with an output power of 1.5 mW was used in this experiment. The beam was incident on the crystal growing from solution. As the crystal is growing, the path length of the front and back surface reflected beam changes and hence the phase factor of the detector output signal changes continuously. This phase change is directly related to the growth of crystal. The growth rate of the: L-arginine phosphate crystal was found to be 6.5 nm s(-1). The resolution of the laser interferometry was 9 degrees which corresponds to 5.02 nm.