Rugate filters used in slit-lamp delivery to improve color rendering of illumination for retinal photocoagulation.

Laser filters and color filters used in slit-lamp delivery have been developed by the rugate approach to improve color rendering of illumination for retinal photocoagulation. The double-notch laser filter is designed according to the required laser lines and incident angle. Based on the transmission spectrum of a double-notch laser filter and the spectral power distribution (SPD) of the light source of a slit lamp, a scanning search algorithm is applied to find the optimal transmission spectrum of a multi-notch color filter for the best color rendering index of illumination. Open-source software is used to design the refractive index profile of the rugate filters, which are deposited by the reactive pulse magnetron sputtering. Both the theoretical analysis of SPD of slitlamp delivery with consideration of the deposited rugate filters and the experimental results demonstrate that the color rendering property of illumination can be improved remarkably, thus making fundus observation and retinal laser photocoagulation more reliable and efficient.

Numerical investigation of one-dimensional nonpolarizing guided-mode resonance gratings with conformal dielectric films.

We present the nonpolarizing resonance properties of two types of one-dimensional (1D) guided-mode resonance (GMR) gratings consisting of the sinusoidal-profile grating substrate and the conformal dielectric thin films. The optimization with respect to the grating height and the phase of the conformal graded-index layer is important for the design of nonpolarizing type-I GMR gratings. The thin films design of the conformal step-index multilayer and the optimization with respect to the grating height are of two critical steps to obtain the nonpolarizing type-II GMR gratings. Both of the two types of nonpolarizing GMR gratings can be designed to support single-mode resonance and multimode resonance under normal incidence.