University of California

The United States of America As Represented by the United States

Melvin I Buchwald

Richard I Epstein

Bradley C Edwards

Leonard Y Nelson

Claude R Jones

Timothy R Gosnell

Optical refrigerator using reflectivity-tuned dielectric mirrors. Selected working materials can be optically pumped using monochromatic radiation such that the resulting fluorescence has an average photon energy higher than that of the pumping radiation; that is, net anti-Stokes fluorescence. If the quantum efficiency is sufficiently high, the working material will cool and optical refrigeration can be achieved. Parallel mirrored faces are employed to increase the optical path of the incident pumping radiation within the working material by multiple reflections. Reflectivity-tuned dielectric mirrors which allow higher-energy fluorescence photons to readily escape from the working material while inhibiting the escape of the lower-energy photons which are consequently partially trapped in the working material and ultimately reabsorbed and refluoresced at higher energies are employed. This increases the optical refrigerator efficiency. An efficient geometry for the cooling material is a disk having a large diameter and a small height, since the fluorescence can predominantly escape through the tuned mirror on one end face of the working material. An alternative cooling element could be approximately cubic with tuned mirrors on the sides as well as on one end. In another embodiment of the invention, photocells are used to convert escaping fluorescence energy into electricity, thereby reducing the power requirements of the optical refrigerator and reducing the amount of waste that must be removed from the vicinity of the working material.

Optical refrigerator using reflectivity tuned dielectric mirrors

Fluorescent refrigeration is based on selective radiative pumping, using substantially monochromatic radiation, of quantum excitations which are then endothermically redistributed to higher energies. Ultimately, the populated energy levels radiatively deexcite emitting, on the average, more radiant energy than was initially absorbed. The material utilized to accomplish the cooling must have dimensions such that the exciting radiation is strongly absorbed, but the fluorescence may exit the material through a significantly smaller optical pathlength. Optical fibers and mirrored glasses and crystals provide this requirement.

Fluorescent refrigeration

An optically pumped isotopic ammonia laser system which is capable of producing a plurality of frequencies in the middle infrared spectral region. Two optical pumping mechanisms are disclosed, i.e., pumping on R(J) and lasing on P(J) in response to enhancement of rotational cascade lasing including stimulated Raman effects, and, pumping on R(J) and lasing on P(J+2). The disclosed apparatus for optical pumping include a hole coupled cavity and a grating coupled cavity.

Growing community of inventors

Santa Fe, NM, United States of America

Melvin I Buchwald