BDU-FS Free Space Beat Detection Unit
The BDU beat detection unit generates a beat signal between the comb light and the light from an external cw laser to be measured. By overlapping them with the suitable polarization conditions on an avalanche photodetector a RF signal is generated, which can be fed into a frequency counter. As the repetition rate and the offset frequency of the comb is known, simple school mathematics is enough to calculate the laser frequency.
Beat detection units with free space optics are available for the entire operational range of the FC1500 and FC8004. Just define your laser frequencies to be measured, and we select the suitable set of polarization controlling elements, diffraction grating and detector. Typical operational ranges are 600-1100 nm, 1000-2000 nm. When working with several cw lasers over a broad spectral range, a BDU unit with free space optics is the ideal choice.