By Hongbai Lao, Iridian Spectral Technologies
Superior optical filters can improve output of Raman systems, and product developers need to consider filter implementation early in design. Adept filter manufacturers are able to work with their customers to optimize filter designs, leading to better performance at the instrument level. Such manufacturers can achieve similar results by upgrading the filters on existing products, as well.
Consider that different Raman devices have different optical filtration needs. More traditional Raman spectroscopy instruments (i.e., tabletop devices) also have fluorescence detection features. Thus, they require extended transmission and reflection wavelength ranges, with high transmission and deep blocking.
Handheld Raman devices are subject to two additional requirements that complicate their design and implementation. First, handheld devices must block or reflect any strict lines or visible light from polluting light sources entering the device. Therefore, they need optical filters to block or reflect most visible light other than the laser light. Second, handheld Raman devices require a filter part size about 66 percent smaller than the filters applied to traditional Raman instruments (part size depends on the instrument’s beam size, which obviously is smaller in a handheld device).