Optical rotation angle measurement system

• Main Authors: Hsueh,Chia-Wei, 薛嘉暐
• Other Authors: Twu,Ruey-Ching
• Format: Others
• Language: zh-TW
• Published: 101
• Online Access: http://ndltd.ncl.edu.tw/handle/97194100567135291953

碩士 === 南台科技大學 === 光電工程系 === 100 === In this thesis, a Zn-indiffused lithium niobate phase modulator (ZIPM) is proposed for the applications of optical heterodyne interferometry in visible light. A lock-in amplifier is adopted to receive the sinusoidal-like interferometric signals and measure phase difference between them. In the optical parameter measurements, an oblique incident light of with two orthogonal polarizations has the incident angle dependence on the phase delay when it passes through a birefringence plate. This principle is used as an optical rotation angle or a liquid concentration measurement in the ZIPM-based heterodyne interferometer. The results show that the best achieved resolution was about 2.77×10-5 deg by using a 5mm-thick MgO:LN crystal for the rotation angle sensor. On the test of concentration of liquid, we use an 1mm-thick MgO:LN plate. Under the best conditions, the lowest measured concentration of glucose can reach to 0.01%, and the corresponding refractive index resolution can reach to about 9×10-7 RIU. Besides, the concentration of salt water can be measured nearly to 0.1%, and the accuracy of refractive index can reach to 4×10-6 RIU. Furthermore, the Zn-indiffused mode converter (ZIMC) has been successfully demonstrated on the x-cut/z-propagation MgO:LN substrate. The device shows stable operation irradiated at a wavelength of 632.8nm for 60 minutes. In comparison with the similar ZIMC in the non-doped LN substrate, the proposed one has more stable performance because it’s less influenced by optical damage effect.