Illumination of Linear Variable Filters with a laser beam

When using Continuously Variable Filters in your optical system it is important to take into consideration how the filter is illuminated.

This white paper examines the illumination effects on linear variable filters when exposed to a laser beam from a super-continuum broadband light source assumed to have a Gaussian intensity distribution.

One of the key characteristics of the laser beam is that the divergence is very small.

We have evaluated how various beam diameters (1mm, 2mm, 3mm) impact the spectral curves of the filters. The filter system consists of a linear variable SWP filter and a linear variable LWP filter in series that forms a tunable bandpass filter.

We show that – in order to obtain the best filter performance –  is is preferable to reduce the laser beam diameter with a lens system rather than using a longer filter.