| Summary: | 博士 === 國立交通大學 === 光電工程系所 === 93 === In this thesis, there are two parts, one describes about a free-space dense wavelength division demultiplexing system（DWDDM） and the other describes a diffractive phase element （DPE）with special function.
In the first part, the design and fabrication of the DPE that synthesizes three-color psudo-nondiffracting beams (PNDBs) is described. This DPE is designed with the amplitude-phase retrieval method and the conjugate gradient method. The designed element is fabricated by using optical contact lithography and reactive-ion etching (RIE). The influences of several errors on the optical properties of the fabricated element are analyzed with the numerical analysis. Measurements demonstrate that the fabricated DPE has the desired function, i.e., forming six-segment PNDB over a finite axial region and monochromatic in each segment.
In the second part, a free-space dense wavelength division-demultiplexing (DWDDM) system in the fiber communication is proposed. The system has sixteen channels with wavelength spacing of 0.8nm in the C band wavelength region. Firstly, the design and fabrication of a low-loss demultiplexer with a KRS-5 grism structure for this system is carried out. This demultiplexer has been successfully fabricated by a precise plunge-cut diamond-turning technology. The influences of the process errors on the optical properties of the device are discussed. Numerical calculations and measurements indicate that this demultiplexer is polarization-independent and has higher optical efficiency and signal to noise ratio (SNR). Secondly, a light pipe array as a coupling system between the demultiplexer and a commercial fiber array has been designed and fabricated on a silicon-on-insulator wafer by using optical contact lithography and inductively coupled plasma-reactive-ion etching. In order to reduce the insertion loss, an anti-reflection coating is formed on the end surfaces of light pipe array with the thermal oxidation method. Finally, the performances of the DWDDM system that consists of the fabricated demultiplexer and light pipe array are measured. The experimental measurements demonstrate that this demultiplexing system shows good optical performance. The insertion loss for each channel is about 2.4 dB, and the next-neighbor cross talk is lower then -17dB.
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