Case Study: 4000nm Short Pass Filter

Data Table

Specification

Value

50% T%

4000 +/- 40 nm

Transmission Range

2000 – 3900 nm

Blocking Range

4100 – 6000 nm

Peak Transmission %

T> 90 % ave.

Substrate

Silicon

Dimensions

12 x 12 mm

Thickness

1 mm

Scratch/Dig

60/40

Quantity Per Year

200

Case Study: Short Wave Pass Filter to transmit hydrocarbon signatures

 

This short-wave pass filter was designed for a customer with a gas sensing application, they wanted to look at a range of hydrocarbon absorption peaks but needed to screen out some interference from gases such as CO₂, CO, NO and NO₂, these gases could cause a false positive result within the system. The filter was being used with a lead selenide (PbSe) detector which has a sensitivity range up to roughly 5.5µm, so it was important that the blocking extended beyond this. The filter shown above was produced and found to be more than adequate.