Jang-hoon Yoo

Nondestructive Optical Measurement of Refractive-index Profile of Graded-index Lenses

We propose a simple nondestructive method to obtain refractive-index profiles of a graded-index (GRIN) light-focusing rod by means of a diffraction grating. In our proposed method, a laser beam is illuminated through a diffraction grating perpendicular to the axis of the GRIN lens and the separation between the zeroth and first-order diffraction peaks is measured and analyzed. The results demonstrate that the refractive-index profiles of commercially available GRIN lenses can be successfully reconstructed.

Investigation of certain diffraction effects in a double-layer optical disk

We study, both by computer simulation and experimentally, the diffraction of the incident beam from the grooved structure of the first layer onto the second layer of a double layer optical disk. We also examine the cross-talk between the focused-error signal curve obtained from the two layers. Good qualitative agreement is obtained between simulations and measurement. It is hoped that these and similar studies will enable us to estimate the magnitude of the noise caused by diffraction from one layer on the signal obtained from the other layer.