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Linear Variable Filters (PDF, 0.13 MB)
Linear Variable Filters
A JDSU Linear Variable Filter (LVF) is a bandpass filter coating that has been intentionally wedged in one direction. Since the bandpass’ center wavelength (CWL) is a function of the coating thickness, the peak wavelength transmitted through the filter will vary in a linear fashion in the direction of the wedge. The variation in CWL can be maintained to within ± 0.5% of virtually any monotonic function (e.g. linear or logarithmic).
A specific wavelength may be selected by simply adjusting the filter to the appropriate linear position. Movement of the filter in front of a source, or raster scanning, will provide a continuous rapid scan of the total wavelength range of the filter.
The LVF coating can be manufactured in any wavelength range from ~300 nm in the VIS region of the spectrum up to ~20 μm in the IR. The specified wavelength range for a typical LVF is ~2x the beginning wavelength of the filter. For example, if the required starting wavelength of the LVF is 380 nm, the ending wavelength can be ~760 nm. The LVF design allows multiple filters to be placed together to provide wavelength coverage greater than 2:1 spread.
The resolution of LVFs has typically been specified between 1-2% of CWL. Higher (or lower) resolutions are possible. In a specific instance, we produced an LVF with 0.005% resolution, corresponding to ~1Å in the NIR. Our LVFs can be customized to meet specific resolution requirements for particular applications.
Key Features
Applications
