EMCCD Tutorial
Q9 Where else may signal be lost?
Every surface through which incoming photons must pass through creates light loss
through reflection and absorption. In fact up to 4% of incident light is lost at
each surface. Some detectors are designed with two, even three windows resulting
in up to 8-12% of precious photons being lost before they strike the sensor. A high-end
EMCCD, ultra-sensitivity being it’s raison d’etre, should be offered with minimal
disruption to the passage of photons. This requires the design to include only a
single entrance window, which should be anti-reflection coated on each side. Only
vacuum protected sensors can offer a single window design, otherwise the sensor
will be critically exposed to damage. As such, non-vacuum cameras must have an extra
non-coated protective window on the sensor. This must be factored in when trying
to determine the actual QE response of the camera.