Anti-Stokes luminescence in heavily doped semiconductors as a mechanism of laser cooling

Abstract

The anti-Stokes luminescence is a mechanism of the optical refrigeration in semiconductor light sources. The heavily doped semiconductors are considered as a material for the laser cooling. The limitation of this mechanism appears to be connected with a transition from the non-degenerate to degenerate occupation. This transition occurs at higher pumping rate (along with the transition to the optical gain and lasing) and at lower temperature. Thus, the limit for the laser cooling can be indicated. The minimal obtainable temperature is about 60–120 K depending on the doping level. The laser cooling of a semiconductor is impeded by the difficulty of extracting the spontaneous emission from a radiating body that is characterized by large angle of the total internal reflection.

Cryogenic optical refrigeration

“…This effect limits the possibility of laser cooling of rare-earth-doped solids at temperatures below about 50 K. In principle this limit does not exist for laser cooling of semiconductors whose electrons and holes are indistinguishable and which thus obey Fermi-Dirac statistics. The feasibility of laser cooling in semiconductors has been extensively investigated both theoretically [17,[51][52][53][54][55][56][57][58][59][60][61] and experimentally [61][62][63][64][65][66][67][68][69]; however, no net temperature reduction has been observed yet. This failure is due to stringent purity requirements, complications associated with inefficient light extraction from the high-refractive-index substrate (η e < 0.2 for nearly index-matched dome [17,66]), and many-body effects such as a carrier-density-dependent quantum efficiency.…”

Edge excitation geometry for studying intrinsic emission spectra of bulk n-InP

“…A more likely candidate for a non-equilibrium stationary state of holes at low temperatures is associated with the spatial fluctuations [36,37,13] in doping concentration and the resultant local potential fluctuations. The ionized donors repel the holes thus increasing their potential energy.…”

Laser cooling of solids

“…Rupper and colleagues (Rupper et al 2008) who investigated the influence of impurities on the cooling process found that the additional low-frequency fluorescence and absorption channel (acceptors are also considered) does not significantly deteriorate the cooling process until concentrations exceed 3 × 10 16 cm −3 . Heavily doped semiconductors have been investigated by Eliseev (2008), who showed that the minimum obtainable temperature in such semiconductors is about 60-120 K depending on the doping concentration.…”