Method for adjusting out-of-band cut-off width of bandpass filter with multicavity structure

Abstract

The invention discloses a method for adjusting the out-of-band cut-off width of a bandpass filter with a multicavity structure. According to the method, the cut-off width of the filter is adjusted by changing the thickness of a membrane layer M made of a material which is the same as that of a spacer layer by adjusting reflection layers in a plurality of Fabry-Boron bandpass membrane systems forming the bandpass filter with the multicavity structure. During actual application, the filter generally needs a relatively big cut-off width; the cut-off width of the bandpass filter in a long wave direction can be increased by increasing the thickness of the M; the increased value of the thickness of the M is required to be less than 0.5 time of the thickness of the original membrane layer; and through adjustment, the cut-off width of the bandpass filter with the multicavity structure in the long wave direction can be increased by over 9 percent. The method has the advantages that the membrane systems of the filter are relatively simple, and a spectral characteristic curve is good, the structure of the whole membrane system is not required to be changed because of slight error of the cut-off width, and the number of membrane layers is not required to be additionally increased.

Description

technical field [0001] The invention relates to optical thin film technology, in particular to a method for adjusting the out-of-band cut-off width of a band-pass filter with a multi-cavity structure. Background technique [0002] Bandpass filters are widely used in the fields of remote sensing, spectroscopy and optoelectronics. There are usually two methods to form a bandpass filter: the first is to coat both sides of the substrate with long-pass and short-pass cut-off films; the second is to coat both sides of the substrate with multiple Fabry-Perot films. Band-pass film system and cut-off film system of the resonator. The second method is easier to produce a band-pass filter with a better waveform, but there are some problems with this method, such as the problem of insufficient cut-off width. Plating the front cut-off film on one side of the substrate can usually meet the cut-off width requirements of the user in the short-wave direction; while on the other side of the...

AI Technical Summary

Problems solved by technology

The second method is easier to produce a bandpass filter with a better waveform, but there are some problems with this method, such as the problem of insufficient cut-off width

Plating the front cut-off film on one side of the substrate can usually meet the cut-off width requirements of the user in the short-wave direction; while on the other side of the substrate, relying on the band-pass film system to meet the cut-off width requirements of the long-wave direction, sometimes encounter to difficulty

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