Archive | 2019
Anti-Stokes laser refrigeration of a nanoscale semiconductor gain medium
Abstract
Laser radiation has conventionally been used to cool the mechanical amplitude of oscillators with approaches based on electronic feedback and cavity-induced radiation pressure. However, the direct laser refrigeration of an optomechanical oscillator has remained a challenge. Optically refrigerating the lattice of an optical resonator promises to impact several fields including the development of radiation balanced lasers. In this work, we demonstrate laser refrigeration of a hydrothermally synthesized 10 % ytterbium (Yb3+) doped lithium yttrium fluoride (YLF) crystal placed at the free end of a cadmium sulfide nanoribbon (CdSNR). An incident 1020 nm laser is used to cool the crystal and the back-scattered up-converted Yb3+ emission is analyzed using two-band differential luminescence thermometry (DLT) to monitor the temperature of the YLF crystal. A temperature drop of 23.6 K below room temperature is recorded at a focused laser power of 40.1 mW. Lastly, a combination of finite element wave optics and heat transfer calculations were used to estimate the imaginary part of the refractive index of the YLF crystal.