Development of compact spectrometers based on photonic crystal devices

• Main Authors: Lin, Hsin-An, 林信安
• Other Authors: Huang, Cheng-Sheng
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/s48yzx

碩士 === 國立交通大學 === 機械工程系所 === 104 === In this thesis, new compact, sensitive and inexpensive spectrometers based on guided-mode resonance (GMR) and photodetector are developed and characterized. Two different designs of GMR are proposed, a gradient waveguide thickness and a gradient grating period GMR. GMR functions as an optical filter. When a broadband light source is illuminated normally at a GMR, a specific wavelength of light will be reflected back and the rest of light will be transmitted through. With either gradient waveguide thickness or gradient grating period GMR, both gradient RWGs function as a linear filter where the wavelength of the reflected light depends on the position of the GMRs. Hence, when a gradient GMR is attached to a photodetector, the reflected wavelength at a specific position at a gradient GMR results in a minimum intensity at a specific pixel of the underneath photodetector. By correlating a specific wavelength and its transmission efficiency to a specific pixel, the whole spectrum of an unknown incident light can be determined. Different light sources including monochromatic light, red and yellow LED, and HG-1, were used to test the developed compact spectrometer. Comparing to Ocean Optics spectrometer, the compact spectrometer shows about 2 nm deviation in terms of the peak wavelength and approximately 5-12 nm deviation in FWHM. Overall, the developed compact spectrometer with 2.23 mm long is capable of measuring spectral range from 506-700 nm with 1 nm resolution.