Abstract
Minimum achievable temperature of ~110 K is measured in a 5% doped Yb:YLF crystal at λ = 1020 nm, corresponding to E4-E5 resonance of Stark manifold. This measurement is in excellent agreement with the laser cooling model and was made possible by employing a novel and sensitive implementation of differential luminescence thermometry using balanced photo-detectors.
Highlights
Optical refrigeration or laser cooling of solids is based on anti-Stokes fluorescence [1]
Minimum achievable temperature of ~110 K is measured in a 5% doped Yb3+-doped LiYF4 (Yb):YLF crystal at λ = 1020 nm, corresponding to E4-E5 resonance of Stark manifold
Our laser cooling model predicted that the minimum achievable temperature (MAT) of ~115 K should be possible if the excitation is tuned exactly to the E4-E5 Stark resonance of Yb3+ at ~1020 nm [11]
Summary
Optical refrigeration or laser cooling of solids is based on anti-Stokes fluorescence [1]. Excitation near the Stark-manifold E4-E5 resonance of a Yb3+-doped LiYF4 (Yb:YLF) crystal has recently led to bulk cooling from room temperature to 155 K [11]. The verification of local cooling to 110 ± 5 K, as reported in Section 4 of this paper, represents a major milestone in optical refrigeration as it demonstrates cooling below 123K (−150 C), designated by NIST as the onset of cryogenics. These measurements were made possible utilizing a novel and sensitive pump-probe technique of two-band differential spectral metrology (2B-DSM), which probes local temperature change directly. This is in contrast to a more popular photo-thermal deflection method where various competing contributions complicate signal interpretation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
