Many detectors including front-illuminated CCDs, photodiode linear arrays, and select CMOS devices lack quantum efficiency in the UV spectral region. The application of a thin coating of METACHROME (also known as Lumogen E) to the surface of these devices effectively, reliably and inexpensively achieves a dramatic increase in device sensitivity in the 120 to 430nm range. METACHROME is a composite phosphor coating that improves the sensitivity of detectors in blue-visible and ultraviolet (UV) wavelengths.
For example, front-illuminated CCDs have virtually no response below 350 nm, and less than 5% quantum efficiency is typically observed at 400 nm. An uncoated front-illuminated CCD cannot be used between 120 and 350nm because it does not exhibit response to light below 350nm. However, a front-illuminated CCD with METACHROME coating may be used at a fraction of the cost of a back-illuminated CCD or photomultiplier tube (PMT).Optical Properties
METACHROME emits light at approximately 540 to 580 nm when excited with light below 450 nm. The high conversion efficiency of Lumogen E, combined with the high quantum efficiency of detectors at the emission wavelength, make METACHROME an ideal UV "down converter" for silicon detectors. Front illuminated CCDs having METACHROME coating exhibit vastly improved quantum efficiency below 350nm as shown in the chart below.
The thin layer of METACHROME becomes transparent at wavelengths greater than 450nm and therefore has no detrimental effect on the quantum efficiency of a detector in the visible and near-infrared. Measurements have been performed to determine the effects of METACHROME coatings on spatial resolution. The contrast-transfer functions for a coated and uncoated CCD with a 20-µm square pixel were compared and found to be identical.Acton Optics Range of Detector UV Enhancement Services Include:
Acton Optics METACHROME Coating Advantages:
- Detector Window Removal
- Lumogen E coating application to customer supplied detectors
- Partial detector surface coating
- Coating layer thickness control to customer specifications
- Detector testing service to customer specifications
- Fitting detectors with windows
- Superior coating formulation offers optimum performance characteristics in comparison to other Lumogen-based formulations.
- Precise coating thickness control – Small coating thickness variation can lead to significant device-device performance variations.
- Coated/uncoated detector QA/QC testing capability to customer specifications
- Acton Optics & Coatings’ 47 years of coatings expertise