Displacement Sensing Based On The Goos-H?nchen Shift In The Double Metal Cladding Waveguide

Goos-H?nchen effect was first discovered in 1947. It describes a phenomenon that the reflected beam in total reflection experiences a lateral shift from the incident point. Since it was discovered, the researches regarding the intrinsic reason of GH shift and its property have being reported continuously. Meanwhile, researchers have found the enhancement effect of GH shift under various conditions.We present the displacement sensing using GH shift in the Double Metal Cladding Waveguide (DMCW) based on the following factors: Firstly, the GH shift of reflected beam is sensitive to the thickness change of guiding layer. Then, the enhancement effect of GH shift in DMCW is significant, which research a scale of several hundred microns. If a one dimensional Position Sensitive Detector (PSD) is used to monitoring the GH shift, a very high degree of accuracy can be obtained. At the same time, the ultra-high modes in the sub-millimeter scale DMCW are highly sensitive to the thickness change of guiding layer. Finally, the energy fluctuation of incident light will not affect the proposed sensor since the GH shift is irrelevant to the incident energy. In this thesis, we begin the electromagnetic field model of DMCW to analyze the guided modes. Further, Stationary Phase method and Gauss Beam model are applied in the theoretical calculation to evaluate the enhancement effect of GH shift. The sensitivity of proposed sensor is derived from the previous analysis, and numerical simulation is performed to get the quantitative result. After that, we carry out the experiment based on the parameters in the simulation. The experimental result shows good accordance to the theoretical prediction.As the enhancement effect of GH shift in DMCW is applied to optical device design more frequently, it is necessary to further understand the beam behavior during the GH shift. Therefore, we use the Gauss Beam model to simulate the practical energy distribution inside the reflected beam spot. We find from the simulation that when the GH shift is enhanced to the scale of beam waist width, obvious beam distortion appears, the reflected spot changes into a double-peak shape. This is very similar to previous researches about the GH shift on multilayered structures. In order to observe the evolution of the reflected beam spot, we use CCD to monitor the reflected beam during wavelength tuning. Experimental result turns out to be good verification to our theoretical analysis. The research regarding beam distortion is a contribution to the understanding of GH shift and the related optical device designs.