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
Continuously variable wavelength selection in one filter
Rugged, durable, and easily cleanable filters cannot be knocked out of alignment
Allows instrument design flexibility and versatility
Can be used as order sorter for gratings
Performance can be custom-designed to your particular system requirements
High volume manufacturing