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| Home > IR & THz Band Pass Filters |
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| IR & THz Band Pass Filters |
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| Band Pass Filter Preliminary Specifications* |
| Center Wavelength (CWL) Range |
From 10 µm to 200 µm |
| CWL Tolerance |
± 1 µm standard, down to ± 0.1 µm possible |
| Pass Range |
Band pass (FWHM > 10%) or narrow band pass (FWHM < 10%) available |
| CWL Transmission |
60—85% |
| Out-Of-Band Transmission |
2% or less, 0.5% or less when two filters are placed in series |
| Temperature Range |
4 K to 308 K (-269 °C - 35 °C) |
| Filter Diameter(s) |
12.5, 19.0, and 25.0 mm clear aperture |
| Packaging |
Mounted on an outer diameter support ring |
| Delivery |
Standard designs available from stock
Custom designs 8-10 weeks pending quantity, size and performance requirements |
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| *These are preliminary specifications reflecting current off-the-shelf standard filter designs. Optimization of the technology and expanding design options continues such that improved performance and custom sizes or designs are available upon request. |
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Stable & repeatable performance down to 4 K |
| The graph below is indicative of the technologies' performance stability over a wide temperature range. Transmission levels are repeatable within ~2% across the complete operating temperature range. Similar stability also occurs with center wavelength tolerance and FWHM levels. |
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Filters in Series |
| Out-of-band transmission (rejection) levels for a single band pass filter are <2%. For those applications requiring lower out-of-band transmission, two filters can be placed in series and will reduce out-of-band transmission to <0.5%. Corresponding peak transmission and FWHM is reduced by approximately 25—30% and 30% respectively. The example below is a comparision of a single 26 µm center wavelength filter and two 26 µm center wavelength filters placed in series. |
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Reflectance vs. Transmission |
| Unlike other filter technologies that primarily absorb out-of-band wavelengths, metal mesh band pass filters are reflective by design. The figure below shows the typical reflectance and transmission of a metal mesh filter with a 72.0 µm center wavelength. This inherent feature combined with the high thermal conductivity of the metal mesh structure enables operation in high density optical power applications. |
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Handling & Use |
| Lake Shore's band pass filters are based on frequency selective surfaces employing a gold mesh film with nickel support rings. They can be cooled to cryogenic temperatures without significantly changing their spectral characteristics. They are vacuum compatible and are resistant to radiation damage. |
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| To maintain filter integrity and optical performance, when handling and installing handle by support rings only. Touching the metal mesh structure will negatively affect performance or permanently damage the filter. |
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| The metal mesh filters are supported by ferromagnetic nickel support rings that closely match the thermal expansion characteristic of the metal mesh. If the filters are intended for use in a magnetic field, or if the nickel support rings will interfere with a magnetic field of interest, please consult Lake Shore. If a magnet is to be used to hold the filter, the magnetic force should be weak enough that the filter can easily be attached and removed without undue force. |
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| When used in a vacuum, apply or break vacuum slowly and equally on both sides. |
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| Cool slowly. Do not immerse suddenly in a liquid, such as liquid nitrogen. |
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| Do not ultrasonically clean or blow with air. |
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