Optical Gain Control Device.

摘要

An optical gain control device limits the light intensity incident on a photodetector or photomultiplier. A fluorescent medium is interposed between a monitored source of electromagnetic energy and the detector and is irradiated by a local oscillator. The irradiation is absorbed by the fluorescent material which undergoes an electronic transition from the ground state to a first excited state. Photons impinging on the fluorescent material from the monitored electromagnetic source cause another transition to a second, more excited state. When the relaxation occurs from the higher state back to the ground the material fluoresces. Because the magnitude of the local oscillator irradiation is kept within prescribed limits, the number of ions in the fluorescing material which are brought to the first excited state stay within certain limits. Consequently, the impinging monitored electromagentic energy cannot excite more ions to the second higher state than were irradiated to the first excited state. Thus, high energy bursts of the monitored electromagnetic energy will not be transmitted to the detection device.