Use of PrCl3 in a Solid State Infrared Quantum Counter

A survey of the salts of the rare-earth series shows that anhydrous PrCl3 has energy levels and selection rules suitable for use in a solid state infrared quantum counter as proposed by Bloembergen [N. Bloembergen, Phys. Rev. Letters 2, 84 (1959)]. Two suitable schemes are proposed, one for detection at 2.33 μ and a second for detection at 104 μ. Consideration is given to isolation of the final detector from the pumping signal and a suitable experimental arrangement for unambiguously determining proper operation is shown.