Transparent Waveplate (Retarder) of ZnSe for High Power CO2 Lasers

摘要

Laser processing machines are utilized in various industrial applications such as cutting, welding and drilling. To improve their performance and avoid unstable processing caused by reflected laser beam from processed work, a λ/4 waveplate (phase retarder) is required. The phase retardation mirrors (circularly-polarized mirrors) have been used conventionally, but there are severe constraints such as a polarization azimuth angle and an angle of incidence of linearly polarized beam in designing beam delivery systems. We have developed a new transparent ZnSe λ/4 waveplate by adopting prism shaped substrates and optimized optical coating films free from above constraints. The developed waveplate for 9.6-micrometer laser has a transmittance of 98.0% and phase shift of 87.6 degrees, and the practicability of the 400-watt continuous wave CO2 lasers are confirmed. Moreover, it contains no thorium or cadmium, it is exempt from regulations for radioactivity and RoHS. Our newly developed waveplate is expected to be utilized in various fields.