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Dichroic beam splitters

Dichroic beam splitters are getting more important for state-of-the-art spectro-graphs such as Dark Energy Spectroscopic
Instrument (DESI), Prime Focus Spectrograph (PFS), or multi-channel CCD cameras to take images in different colours simultaneously.

Dichroic beam splitters split the incident beam to two directions, therefore give the influence to the performance of at least
two or more cameras in terms of wavefront error, throughput, and available wavelength range.

Essential requirements for astronomical dichroic beam splitters are as follows.

There are few vendors in the world that can achieve all the requirements, a~e at the same time.
Asahi is one of potential vendors to provide such dichroic beam splitters with these performances.

We were successful in the fabrication of 390 mm x 365 mm, largest ever astronomical dichroic beam splitter for PFS in 2015.
The dichroic met all the hard specifications required by PFS project.

figure Dichroic Mirror
figure Dichroic Mirror coating