Abstract: Techniques for spatial spectral holography include a doped crystal comprising Thulium doped into a host crystal of Yttrium Lutetium Aluminum Garnet wherein a concentration of Thulium atoms is less than 3 atomic percent. Techniques further include an apparatus with a source for optical electromagnetic radiation and a cryocooler configured to maintain an operating temperature in a range from about 3 Kelvin to about 6 Kelvin. The cryocooler includes a first optical window. The apparatus also includes a doped crystal comprising Thulium doped into a host crystal of Yttrium Lutetium Aluminum Garnet disposed inside the cryocooler in a position to be illuminated by incident optical electromagnetic radiation derived from the source. The apparatus also includes a detector configured to detect optical electromagnetic radiation emitted from the doped crystal. Techniques include a method for using at least one of the above doped crystals.