• Emission Filters in Fluorescence Applications
• Order Sorting Filters for Photometry
• Stray Light or Trim Filters to Eliminate any Unwanted Near-Band Radiation
• Raman Spectroscopy Filters
• Astronomy Applications

This longpass filter, with 1500 nm cut-on wavelength, is very useful for isolating regions of a spectrum. This edgepass filter features a durable dielectric coating that withstands the normal cleaning and handling necessary when using any high-quality optical component. The film construction is essentially a modified quarter-wave stack, using interference effects rather than absorption, to isolate their spectral bands.

Unlike colored filter glass, the cut-on wavelength of this filter will shift to a shorter wavelength as the angle of incidence is increased. As a rule of thumb, when the angle of incidence foes from 0° to 45°, the central wavelength shifts down by about 10%. This feature can be useful in applications where it is desirable to fine tune the location of the cut-on, or cut-off wavelength. In addition, this edgepass filter is hermetically sealed to provide maximum humidity protection, and can be stacked with another filter to create a custom bandpass filter.

Thorlabs does not recommend removing the filter from its mount, as the filter consists of several layers of glass that are held together with epoxy and the mounting ring. These glass layers are necessary to protect the dielectric coating from the atmosphere; exposure would significantly reduce the filter’s transmission efficiency over time.

• Cut-On Wavelength: 1500 nm
• Transmission Region: Cut-on λ to 2200 nm Minimum
• Transmission at Peak: 70%
• Rejection Region: 200 nm to Cut-on
• Transmission in Rejection Region: 0.01% abs. (OD = 4.0)
• Cut-off Slope: 3%, OD = 0.3 - 4
• Construction: Immersed Dielectric
• Surface Quality (Scratch/Dig): 80/50 per MIL-0-13830A
• Substrate Material: Soda Lime of Equivalent