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Ultrafast Broadband Beamsplitters with Controlled Dispersion
20:80 Ultrafast Beamsplitter
80:20 Ultrafast Beamsplitter
UFBS5050 50:50 Ultrafast Beamsplitter in a
90:10 Ultrafast Beamsplitter
50:50 Ultrafast Beamsplitter
Thorlabs' Ultrafast Broadband Beamsplitters offer a 20:80, 50:50, 80:20, or 90:10 (R:T) beamsplitting ratio over the 600 - 1500 nm wavelength range, or a 50:50 (R:T) beamsplitting ratio over the 1000 - 2000 nm wavelength range. They are designed to be used with p-polarized light incident at 45° and are not intended to be used for s-polarized light. For s-polarized or circularly polarized light applications, please see our full selection of plate beamsplitters. As shown by the images at the top of the page, each ultrafast beamsplitter is marked with an arrow that points toward the beamsplitting coating; light being split should be incident on this surface to obtain the intended performance. The wide usable wavelength range of these beamsplitters makes them compatible with femtosecond pulsed Ti:Sapphire, Yb, and Er fiber lasers. The beamsplitters have an AR coating on the back surface that provides <0.5% absolute reflectance over the same wavelength range as the beamsplitter coating. The Infrasil substrate is a type of optical quartz that has nearly identical dispersion to fused silica but higher internal transmission around 1380 nm.
Balancing GDD in the Transmitted and Reflected Beam
Recommended Configuration for Balanced Dispersion in Transmitted and Reflected Beams of 50:50 Ultrafast Beamsplitter (Only Necessary for
Balanced Group Delay for 50:50 Ultrafast Beamsplitter
The UFBS5050 Ultrafast Beamsplitter provides a 50:50 beamsplitting ratio for femtosecond laser pulses with well-defined, nearly equal group delay dispersion in the transmitted and reflected beams. For the shortest pulses (<50 fs), additional dispersion compensation is recommended, as detailed in the text below. Please note for the following discussion that Infrasil® and fused silica have nearly identical dispersion.
In order to balance the dispersion of the reflected beam with that of the transmitted beam, either of our Infrasil windows, which are 1.0 mm thick, can be inserted into the reflected beam at a 0° incident angle. This geometry is shown in the figure to the right. The window allows the net dispersion of the reflected beam to be the same as traveling through 1.7 mm of Infrasil. For pulses with narrow spectral bandwidth (i.e., pulses longer than 50 fs), the group delay dispersion varies slowly enough that this additional window is not necessary.
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Group Delay in Transmission
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Group Delay in Reflection
Thorlabs offers a wide selection of optics optimized for use with femtosecond laser pulses. Please see below for more information.
Recommended Configuration for Balanced Dispersion in Transmitted and Reflected Beam of 50:50 Ultrafast Beamsplitter (Only Necessary for