Bandpass filters

The use of bandpass filters is one of the simplest and most economical ways to transmit a welldefined band of light and to reject all other unwanted radiation. Their design is essentially a thin film FabryPerot interferometer formed by vacuum deposition, and consists of two reflecting stacks separated by an even-order spacer layer.

Because the Fabry-Perot filter is Lorentzian in shape, the cut-on and cut-off slopes are shallow and the rate of attenuation in the out-of-band blocking range is slow. To improve the slopes and increase the attenuation in the blocking band, we introduce more cavities into the construction of our standard dielectric bandpass filters

Andover offers one of the most extensive selections of bandpass filters in the industry, including many of the primary laser, mercury, biomedical, and analytical spectral lines. We use a proprietary method to stabilize our products to prevent drift of peak wavelength with age and hermetically seal each filter for maximum protection against humidity. Each filter is mounted in a black anodized aluminum ring, adding further protection against chipping, scratching, and moisture penetration.

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Andover now offers a high-transmittance variant of its standard bandpass filter selection. By tailoring the blocking range to match the detector, we can provide maximum possible throughput while maintaining good blocking to meet the customer’s needs. Wavelengths include all popular laser, mercury biomedical and analytical spectral lines. All filters are constructed using the same highquality materials and methods as our standard bandpass filters, thus providing a highly stable, long-lasting filter.

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Our first-surface, hard-coat, broadband filters employ magnetron sputtered, hard-oxide coatings deposited on Borosilicate Glass and do not utilize any absorbing filter glasses, making them suitable for high temperature applications. They provide a steep transition from a high, peak transmission to OD4 blocking. Available at standard Raman wavelengths: 488, 514, 532, 633, 785nm. We offer three standard sizes, with custom sizes available on request.

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Thanks to a large inventory of components, Andover Corporation can fabricate and deliver higher performance commercial quality bandpass filters to your specifications as soon as 5-10 days from receipt of order. To specify your semi-custom filter, all you have to do is follow three quick steps:

1. Select the desired bandwidth, filter type, and center wavelength from the range listed.
2. Select the blocking range.
3. Select the size and corresponding part number.

All other features are predetermined by these three choices. The out-of-band blocking of these filters is 1 x 10-4 within the defined spectral range. Optional threaded rings are available, and image quality versions are also available. Please call for pricing and delivery.

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Order sorting filters from 300 nm to 11,5 µm for monochromators.

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