Features

25 mm Outer Diameter (Ø21.1 mm Clear Aperture)
Large Transmission Region (Cut-On λ to 2150 nm)
Excellent Suppression in Rejection Region (OD > 5)
Transmission Direction Engraved on Edge
Ideal as Raman Spectroscopy Filters or Emission Filters for Fluorescence Applications

Thorlabs' premium longpass filters are high-performance filters that are very useful for isolating regions of a spectrum. These filters provide better transmission, slope, blocking, and durability than our standard line of longpass filters (see the Specs tab for comparison).

These edgepass filters feature durable, hard-coated dielectric coatings on UV-fused silica. These high-performance filters provide better than Optical Density (OD) of 5 suppression in the rejection region and >90% transmission from cut-on out to 2150 nm.

These coatings can withstand the normal cleaning and handling necessary when using any high-quality optical component. Their film construction is essentially a modified quarter-wave stack, using interference effects to isolate spectral bands (see the Specs tab for transmission information).

	Premium Longpass Filters	Standard Longpass Filters (for comparison purposes)
Transmission Region	Cut-on λ to 2150 nm	Cut-on λ to 2200 nm
Transmission	>90% (Absolute)	80% (400 - 700 nm) [Average] 75% (750 - 1000 nm) [Average] 70% (>1000 nm) [Average]
Cut-on Tolerance	±3 nm	±3 nm (400 to 750 nm) ±15 nm (800 to 1500 nm)
Rejection Region	200 nm to Cut-on
Optical Density (OD) in Rejection Region	OD > 5 (Absolute)	OD = 4
Slope Tolerance	<1.0%	3%
Construction	Hard-Coated Dielectric on UVFS Substrate	Immersed Dielectric
Surface Quality	40-20 Scratch-Dig	80-50 Scratch-Dig
Substrate Material	UV-Fused Silica	Soda Lime or Equivalent
Diameter	25 mm	1.0" (25.4 mm)
Clear Aperture	Ø0.83" (Ø21 mm)
Thickness	0.14" (3.5 mm)	0.24" (6.1 mm)

**Premium Longpass Filters**
Item #	Cut-On Wavelength	Transmission Data*	Equivalent Standard Longpass Filter
FELH0500	500 nm
FELH0550	550 nm
FELH0600	600 nm
FELH0650	650 nm
FELH0750	750 nm
FELH0800	800 nm
FELH1000	1000 nm

*Please keep in mind that the data given is typical, and performance may vary from lot to lot, particularly outside of the specified region for each filter.

Optical Density Equation:

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Posted Comments:
Poster: jlow Posted Date: 2013-01-21 16:18:00.0 Response from Jeremy at Thorlabs: We can do this for larger diameters. I will get in contact with you directly to discuss about this. Poster: roumis.d Posted Date: 2013-01-21 12:07:06.12 Is there any chance of these lp filters being available in larger diameters.. 50mm would be quite helpful. Thanks

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