Planar Designs Produce Compact Devices

A team from the Weizmann Institute of Science in Rehovot, Israel, has created a set of compact optical devices by using diffractive optical elements deposited on a planar glass substrate. It expects the designs, which consist mainly of grating patterns deposited via a photopolymer or photoresist, to be useful in numerous compact display and projection applications.

Among these devices is a beam expander that uses three linear gratings. The first couples an oncoming beam into the substrate and onto the next grating, which expands the beam in one dimension. The next expands the beam in the perpendicular direction and directs it out of the substrate.

A wavelength division demultiplexer design uses a graded-index coupling lens to direct a multiplexed beam from an optical fiber onto a stack of linear gratings. Each grating refracts a specific wavelength to its own secondary grating that directs the light out of the substrate through another coupling lens. The device can be used in reverse to multiplex signals.

The researchers also designed a beam illuminator similar to the demultiplexer using photopolymer diffractive lenses to separate and expand the red, green and blue components of a multiplexed RGB plane wave. They described the devices and their first experimental models in three articles in the March 1 issue of Applied Optics.