Study On The Abnormal Propagation Of Gauss Beam In Two-dimensional Photonic Crystal And Its Applications

This project is supported by the National Key Basic Research(2007C B935300) and development plan and the National Natural Science Foundation of C hina. We present some transmission characteristics of gaussian beam in photonic crystals, such as inverse Doppler Effect, negative Goos-Hanchen shift and self-collimation. The Doppler Effect relates velocity with frequency, playing a very important role in the astronomy, medicine science, metrology, micro-electronics and many other research interests, especially inverse Doppler Effect in the optical frequencies has potential to bring innovations to the industrial application mentioned above. The size of optical devices will be close to the wavelength as the opto-electronics IC develops in the future, so that the GH shift is a great concern due to its magnitude that might be 10 orders of the wavelength. So it is worthy of deeper research to the Goos-Hanchen shift while light beam is reflected on the surface of photonic crysta ls. Photonic crystals provide diverse solutions to the integrated development of optical communication due to its micro-size and light transmission characteristics. In the meantime, photonics crystals also provide a new combined with terahertz technology as it is applied into the communication.Our research is arranged mainly as follows:1. We analyzed experimental error of inverse Dopper Effect while Gaussian beam transmits in the photonic crystals. A theoretical modal is built with Matlab with PC regarded as ideal medium of negative refractive index and laser as ideal Gaussian beam of primary mode. We analyzed how some factors influence our experimental results, such as angles that reference beam and signal beam are relative to the normal, detective area and CO2 laser power. It showed the data precision is very high and the reverse Doppler Effect verification experiment in the optical spectrum is reliable by comparing analysis with experimental results. Our theoretical preparation established a substantia l foundation for the experiment process.2. We designed pc of negative refractive index and researched the negative GH shift while Gaussian beam transmits in the pc. Theoretical negative GH shift is obtained via simulating transmission of Gaussian beams in the pc with FDTD algorithm. We wrote a GUI with VB to call PI program and control its translation, as well as control translation and rotation of other experimental stages. The experience is designed to verify negative GH shift, and research the transmiss ion characteristics of gaussian beam in the pc, providing guide to the next developments.3. We present self-collimation effect of Gaussian beam in the pc and its applications as well as equi- frequency and gap pattern characteristics of the pc. Via introducing several line defects in the pc and filled 5CB liquid crystals in these defects, we designed optical modulator and attenuator based on self-collimation of pc, and simulated transmission of Gaussian in these devices with Rsoft. The designed intensity modulator is an ideal terahertz optical modulator device with a modulation frequency of 10 KHz, insert loss of 0.308, and modulation range from 0.308-34.32 dB.