Two-dimensional Photonic Crystal Applied Research In Laser Radar Systems

Photonic crystal is a new optical structure emerges in recent years, which is periodically constructed by materials with different index constant. Photonic crystal has unique photonic band gap of frequency in which light can not propagate through the structure, therefore, it can provide a new novel mechanism to control the light. As a result, photonic crystal will posses widely application. Recently, research on photonic crystal has become a fast-developing field.With the development of the laser radar, the miniaturization of equipments has become increasingly urgent need. Photonic crystal can manufacture highly integrated optical devices because of its ability in controlling the transmission of light at light wave scale. In our study, the photonic crystal devices will be applied in laser radar system to realize its miniaturization.The main work of this paper is summarized as follows.1. The study begins with the concept of crystals in solid physics, and then leads to the theory of photonic crystal, which includes the first Brillouin zone and the Bloch theory. Based on the Maxwell's equations, the master equation of photonic crystal is derived. The commonly analysis method of photonic crystal, including transfer matrix method (TMM), plane wave expansion method (PWE) and finite different time domain (FDTD) are introduced in this part.2. The 2D photonic crystal band gap structures are calculated with PWE. The influence of changing lattice structure, permittivity and filling contrast for photonic crystal band gap have been researched. Point defect or line defect is introduced into photonic crystal, and the properties of defects mode are researched. The coupled mode theory is used to analysis the coupling of point and line defects. A 2D photonic crystal band-pass filter is designed for applying in laser radar system which works atλ= 1550nm, and its full-width at half-maximum (FWHM) is 1.51nm.3. As a sub-wavelength structure, the emitting light of photonic crystal waveguide will scatter into all directions, because of the diffraction limitation, the coupling into and out of the photonic crystal device would be one of key techniques for an integrated optical system. The collimation of output emitting light from photonic crystal waveguide is studied in this article. Two methods based on the surface wave theory are discussed, which introducing coupled cavity and grating structure into the surface of photonic crystal waveguide. At last, a 2D photonic crystal collimation device with cascade structure which compress the half divergence angle from 60°to 5.56°is designed by summing up the above methods, and its application in laser radar system is discussed.