Bandpass filter 1.5 µm in C25

This bandpass filter provides one of the simplest and most economical ways to transmit a well-defined wavelength band of light, while rejecting other unwanted radiation. Their design is essentially that of a thin film Fabry-Perot Interferometer formed by vacuum deposition techniques and consists of two reflecting stacks, separated by an even-order spacer layer. Because of the Fabry-Perot design, these filters are designed to be used at a 0° angle of incidence (AOI).
This element is dually used once as feed back laser and secondly as blocking filter for the pump radiation at 980 nm. When it is used as feed back mirror the element is mounted into the adjustment holder. For this purpose the fibre collimator is removed from the holder and the mirror inserted.