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Narrow Bandpass Fast Infrared Detector

IP.com Disclosure Number: IPCOM000083312D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Hodgson, RT: AUTHOR [+3]

Abstract

A fast, narrow bandpass infrared detector has been devised which is highly sensitive and is relatively free of noise.

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Narrow Bandpass Fast Infrared Detector

A fast, narrow bandpass infrared detector has been devised which is highly sensitive and is relatively free of noise.

By employing a four-photon parametric process, it is possible to convert infrared photons into ultraviolet photons, the detection of the latter being an indication of the presence of the former.

A schematic showing of the system for achieving a four-photon para metric process is shown in Fig. 1. A cell 2, containing a metal vapor 4, is impressed with one photon of visible laser light at a frequency upsilon(L) and another photon of infrared at a frequency upsilon(IR).

As seen in Fig. 2, the visible light converts infrared light of frequency upsilon(L) into ultraviolet light when upsilon(IR) + upsilon(L) = E/h. The visible light upsilon(L) mixes with itself as well as with the infrared to be detected, so that upsilon(UV) = 2 upsilon(L) + upsilon(IR) = E/h + upsilon(L). The generated ultraviolet light is detected by ultraviolet detector 6.

The infrared bandpass is determined by whichever is larger, namely, the frequency spread of the visible laser delta upsilon(L) or the linewidth (delta E)/h of the material used in the cell. When a broader bandpass of infrared frequencies is desirable, such as when upsilon(IR) is not precisely known, then delta upsilon(L) can be made larger to allow wider bands of infrared to reach resonance and to be detected.

Since upsilon(L) can be selected to be very close to E/h, an infrar...