A comparison of photoelastic constants of disk- and square-shaped glasses using the heterodyne method: An empirical approach

The photoelastic constant (PEC) of a square-shaped glass, such as very tough and fragile glasses of a mechanical nature and a very small stress-induced birefringent glass, can be successfully obtained by a heterodyne method. The merit is that the PECs can be obtained even for difficult compositions to re-form into disk-shaped, instead of the commonly used method of measuring PECs with disk-shaped glass. The PECs of square and disk-shaped glasses with the same composition can be obtained within ±0.2 × 10−12 Pa−1 measurement accuracy. This phenomenon could be developed into a potential glass that can be processed into square shapes with high precision but is difficult to process into disks using glass lenses and filters.