Rare Earth infrared quantum counter

An analysis of an ideal five-level ir quantum counter (IRQC) is presented. The importance of the two additional levels is discussed and analyzed. The parameters for achieving optimum performance as an ir detector and/or an image converter are presented. In theory, the IRQC is the only quantum amplifier with photon gain that can approach a noise temperature of absolute zero. In practice, with the constriction of available materials and technology, the most feasible use for the IRQC in the near term would be in an active system. An ir laser would be used to scan the target while another laser would pump the excited state transition. The IRQC action has been observed in this laboratory in the tripositive rare earths of Pr, Nd, Eu, Tb, Dy, Er, and Tm. These ions were incorporated in single crystal lattices of CaF(2), BaF(2), SrF(2), CdF(2), LaF(3), CaWO(4), A1(2)O(3), YAG, LaCl(3), and in solutions of the various trichlorides (dissolved in D(2)O). A total of 165 schemes are reported. The rare earth impurity concentration varied from 0.05% to 20%. In our laboratory, the primary range of interest for detection and/or image conversion is between 1 micro and 2 micro. Therefore, almost all the systems studied involved the detection of an ir photon in this region.