Additional Bandpass Filters
340 to 694.3 nm Center Wavelengths
700 to 1650 nm Center Wavelengths
We also offer custom bandpass filters with other central wavelengths or FWHM. To request a quote, contact Tech Support.

Features

Central Wavelengths from 1750 nm to 4750 nm
0.5 µm Bandpass Region (FWHM)
Minimum Peak Transmission: 70%
Ø1" Mounted Filters with Ø21 mm Clear Aperture
Out-of-Band Transmission <1% from 200 nm - 12 µm

The bandpass filters shown on this page feature center wavelengths from 1.75 to 4.75 µm. Transmission curves for individual filters are available by viewing the Transmission Data link for each filter on the Specs tab. Each filter is mounted in a black anodized aluminum ring with an outer diameter of Ø1" and a maximum edge thickness of 6.1 mm.

Thorlabs' bandpass filters provide one of the simplest ways to transmit a well-defined wavelength band of light, while rejecting other unwanted radiation. Their design is essentially that of a thin film Fabry-Perot Interferometer formed by vacuum deposition techniques and consists of two reflecting stacks, separated by an even-order spacer layer. These reflecting stacks are constructed from alternating layers of high and low refractive index materials, which can have a reflectance in excess of 99.99%. By varying the thickness of the spacer layer and/or the number of reflecting layers, the central wavelength and bandwidth of the filter can be altered.

Transmission Direction
An arrow on the metal housing, next to the item number, indicates the direction of transmission through the filter.

Item #	Center Wavelength	Substrate
FB1750-500	1750 ± 50 nm	N-BK7
FB2000-500	2000 ± 50 nm	N-BK7
FB2250-500	2250 ± 50 nm	Sapphire
FB2500-500	2500 ± 50 nm	Sapphire
FB2750-500	2750 ± 50 nm	Sapphire
FB3000-500	3000 ± 50 nm	Sapphire
FB3250-500	3250 ± 50 nm	Sapphire
FB3500-500	3500 ± 50 nm	Sapphire
FB3750-500	3750 ± 50 nm	Sapphire
FB4000-500	4000 ± 50 nm	Sapphire
FB4250-500	4250 ± 50 nm	Sapphire
FB4500-500	4500 ± 50 nm	Sapphire
FB4750-500	4750 ± 50 nm	Sapphire

Common Specifications
Bandwidth (Full Width at Half Maximum)	500 ± 100 nm
Peak Transmission (Min)	70%
Out-of-Band Transmission	<0.1% from 0.2 - 12 µm
Clear Aperture	Ø21 mm
Housing Diameter	1" (25.4 mm)
Housing Diameter Tolerance	+0.0 / -0.2 mm
Thickness	6.1 mm
Thickness Tolerance	+0.00 / -0.10 mm
Surface/Coating Quality	80-50 Scratch-Dig
Edge Treatment	Mounted in Black Anodized Aluminum Ring
Edge Markings	CWL-FWHM ↑; The Arrow Points in the Direction of the Light Transmission
Operating Temperature	-50 to 80 °C (21 °C is Optimal)

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IR Bandpass Filters: 1750 nm - 4750 nm Central Wavelength

Features