Design and Characteristics of an Optical Wave Meter.

A new optical wavemeter using a quartz azimuth rotator for direct reading of wavelength is described. When linearly polarized light having a certain wavelength enters the quartz rotator the plane of polarization rotates, the angle of rotation depending on the thickness of the quartz and the wavelength. Since the thickness of the quartz in the wavemeter is kept constant, the wave- length can be read from the angle of rotation of the polarized input light. This angle is obtained from the ratio of two polarized light beams which are divided from the input light by using an optical analyzer. The quartz thickness at which the error in measurement of wavelength is minimum is found. The relationship between the dividing ratio of the beams and the wavelength is also found. An azimuth quartz rotator with optimum thick- ness is fabricated. It is confirmed that the calculated and measured characteristics of the dividing ratio versus wavelength are in good agreement. The wavemeter has a wave- length range of 0.6–1.6 μm and measurement accuracy better than 1 nm at input power of -35 dBm. To increase the utility of the wavemeter, a device to measure its input power with high sensitivity is added to the apparatus, the resulting accuracy being better than 0.1 dB at an input level of -35 dBm. [ABSTRACT FROM AUTHOR]