VersaChrome Tunable Bandpass Filters

VersaChrome^® tunable bandpass filters unlock virtually unlimited spectral flexibility for fluorescence microscopy, high-throughput screening and hyperspectral imaging applications. Semrock’s proprietary & patented (U.S. Patent No. 8,441,710 and 9,304,237) tunable thin-film filters use advanced design techniques which can’t be found anywhere else in the market. These tunable bandpass filters are insensitive to polarization splitting from 0° to 60° AOI, allowing angle-tuning over a wide range while maintaining edge steepness, high transmission and OD blocking. The popular VersaChrome tunable bandpass filters allow you to shift center wavelength (CWL) with a fixed 20nm FWHM bandwidth by up to 11% to the blue through angle-tuning, and are offered in center wavelengths (CWL) tuning from 449 to 900 nm.

VersaChrome filters combine the highly desirable spectral characteristics and two-dimensional imaging capability of thin-film optical filters with the wavelength tuning flexibility of a diffraction grating. Diffraction gratings are often used when wavelength tuning is required, but gratings exhibit inadequate spectral discrimination, have limited transmission, are polarization dependent, and are not capable of transmitting a beam carrying a two-dimensional image since one spatial dimension carries spectral information. Similarly tunable bandpass filters provide enhanced spectral performance over other tunable filter technologies, including liquid-crystal tunable filters, acousto-optic tunable filters, and linear-variable filters by delivering nearly identical transmission and blocking performance for both s- and p-polarizations of light, very steep spectral edges, and blocking of optical density 6 or higher over wide spectral regions for maximum noise suppression required in fluorescence microscopy.

In contrast to a typical bandpass filter (left) where for angles greater than about 30° transmission for s-polarized light is approximately 0% and the ripple for p-polarized light is intolerably high, the spectrum of a Semrock VersaChrome tunable bandpass filter (right) maintains high transmission, steep edges, and excellent out-of-band blocking over the full range of angles from 0° to 60° through angle-tuning. At the heart of this invention is Semrock’s discovery of a way to make very steep edge filters (both long-wave-pass, or “cut-on,” and short-wave-pass, or “cut-off,” type filters) at very high angles of incidence with essentially no polarization splitting and nearly equal edge steepnesses for both polarizations of light. An equally significant and related property is that the high edge steepness values for both polarizations and the lack of polarization splitting apply at all angles of incidence from normal incidence (0°) to very high angles. As a consequence, it is possible to angle tune the bandpass filter over this full range of angles with little to no change in the properties of the edges regardless of the state of polarization of the light passing through the filter.

Typical Bandpass

VersaChrome Tunable Bandpass

VersaChrome tunable bandpass filters can be incorporated into instruments supporting fluorescence microscopy high-content screening applications which include varying excitation wavelengths of a white light source or in the detection channel to discriminate fluorescence emissions as fine as 1 nm intervals of a range of fluorophores.

Click here to read our white paper on VersaChrome tunable bandpass filters.
Click here to read more on Spectral Imaging with VersaChrome tunable bandpass filters.

For variable bandwidth tuning, the popular VersaChrome Edge™ longpass and shortpass filters allow even greater instrument flexibility to vary both the center wavelength and bandwidth of a bandpass by angle-tuning both edges independently. The edge filters can also be used for tunable Raman spectroscopy applications.

Download Versachrome Data Sheet