193 – 399nm Bandpass Interference Filters

Bandpass Interference Filters are used extensively in a variety of biotech, biomedical, and quantitative chemical applications to selectively transmit a narrow range of wavelengths while blocking all others. Interference filters are widely used in instrumentation for clinical chemistry, environmental testing, colorimetry, elemental and laser line separation, flame photometry, fluorescence, immunoassays, etc. In addition, interference filters are used to select discrete spectral lines from arc or gas discharge lamps (Hg, Xe, Cd, etc.) and to isolate a particular line from Ar, Kr, Nd:YAG, and other lasers. Interference filters are often used in conjunction with laser diodes and LEDs. Our interference filters are available in two types – low-cost "Traditional” Coated Filters, and high-performance "Hard” Coated Filters.

Traditional Coated Filters

Traditional Coated Filters are fabricated in 3 sections, one of which determines the central wavelength (CWL), bandwidth (FWHM), and shape of the transmittance curve while the other two control the degree and range of blocking outside the passband. The bandpass section of the filter is made by repetitive vacuum deposition of thin layers of partially reflecting dielectric compounds on a glass substrate. Rejection of wavelengths resulting from destructive interference is limited to within 15% of the central wavelength, therefore, additional glass or metallic blockers must be added to reduce out-of-band transmittance. Metallic blockers, such as layers of silver, reflect and absorb radiation outside the filter passband and negate higher order passbands from X-ray to the far IR. The blocking capabilities of metallic blockers are augmented by the addition of color transmitting glass and custom dyes that absorb UV or long wavelength radiation. After thin film deposition is complete, the three sections are scribed, laminated, cut and mounted. All of our traditional coated filters are three cavity designs, resulting in filters with steep slopes, improved blocking close to the passband and relatively flat tops.

Note: Interference filters will function with either side facing the source. We recommend, however, orienting the “mirror-like” side toward the source to minimize any thermal effects. If the source overfills the actual filter area, beam vignetting may be necessary.