| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 98 === The main purpose of this thesis is to develop a heterodyne interferometry-based detection system with in-lab developed algorithm to measure the optical rotatory dispersion (ORD) and the circular dichroism (CD) of the ellipticity information of chiral materials simultaneously. According to the phase difference and the magnitude ratio between the two channel signals of the heterodyne interferometry detection system, the ORD and CD can be obtained, respectively. Hence, the stabilities of the phase and intensity of the light source will affect the detection resolution.
Regarding the phase stability issue, the measurement framework based on the phase difference of the two-channel signals will eliminate the laser’s phase instability; hence, the measurement environment will dominate the stability of the phase measurement. To resolve the problem, the temperature of the sample is controlled and the heating sources are isolated from the detection system. The experimental results demonstrate that the phase stability is improved from 0.47 rad down to 0.01 rad in root mean square error. The corresponding detection resolution at the rotation angle of glucose solution is about 8.3×10^-5 rad and the corresponding concentration is 1.8×10^-5 (g/ml) . About the intensity stability, the measurement intensity signal is normalized with a reference beam signal to achieve the intensity signal stability better than 1 %, so the signal-to-noise ratio (SNR) of the amplitude ratio measurement is improved. Currently, the detection resolution of the CD ellipticity is about 2.4×10^-4 rad.
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