Phonon-Assisted Photoluminescence Up-Conversion of Silicon-Vacancy Centers in Diamond

Abstract

Phonon-assisted anti-Stokes photoluminescence (ASPL) up-conversion lies at the heart of optical refrigeration in solids. The thermal energy contained in the lattice vibrations is taken away by the emitted anti-Stokes photons’ ASPL process, resulting in laser cooling of solids. To date, net laser cooling of solids is limited in rare-earth (RE)-doped crystals, glasses, and direct band gap semiconductors. Searching more solid materials with efficient phonon-assisted photoluminescence up-conversion is important to enrich optical refrigeration research. Here, we demonstrate the phonon-assisted PL up-conversion process from the silicon vacancy (SiV) center in diamond for the first time by studying ASPL spectra for the dependence of temperature, laser power, and excitation energy. Although net cooling has not been observed, our results show that net laser cooling might be eventually achieved in diamond by improving the external quantum efficiency to higher than 95%. Our work provides a promising route to investigate the laser cooling effect in diamond.

Phonon-assisted up-conversion photoluminescence of quantum dots

“…To further confirm the nature of the phonon-assisted absorption, temperature-dependent absorption of QDs is studied. Figure 2a (inset) shows that, as the temperature increases from 300 to 360 K, the first-excitonic absorption band of the QDs shifts towards low energy and the peak absorbance decreases, which should be a mixed result of bandgap narrowing (obeying Varshni’s equation 35 ), decrease of electron–hole envelope-wavefunction overlap, and increase of phonon population 12 , 13 , 28 . To isolate the last effect, Fig.…”

“…Though optical cooling—samples being cooled upon sub-bandgap photon excitation—based on UCPL of organic dyes dissolved in solution was reported about 25 years ago 5 , 6 , it was found to be inconsistent with the working mechanism 7 – 9 . UCPL was also reported in novel materials including carbon nanotube 10 , CsPbBr 3 perovskite 11 , diamond 12 , and monolayer WS 2 13 , but their UCPL efficiencies are insufficient for practical applications. Overcoming most of the hurdles for organic dyes and rare-earth-doped materials, bulk semiconductors 14 – 17 are technically prohibitive for the crystals to reach an extremely low concentration of non-radiative recombination centres to achieve efficient UCPL under common excitation conditions 17 .…”

Quantum Point Defects for Solid‐State Laser Refrigeration

“…[ 174 ] Subsequent work has successfully reproduced the original observations, and also extended the work to new target designs and also pulsed laser systems. [ 129,175–178 ] To date the authors are unaware of reports of doping nanodiamonds grown through pulsed laser methods which remains a promising future research direction.…”

“…[ 120 ] Moreover, the properties of bulk diamond are preserved when the diamond particle size enters the nanoscale regime. Further, diamond itself is a highly biocompatible allotrope of carbon, [ 121,122 ] and the surface of nanodiamonds are readily functionalized with ligands, [ 123 ] antibodies, [ 124 ] and other biomolecules [ 125 ] allowing fluorescent nanodiamonds to act as both convenient carriers of drugs and bio‐fluorescent markers for cellular imaging in biomedical applications [ 126–131 ] including cryotherapy. [ 132 ]…”

“…Hence it is essential to locate and suppress the sources of nonradiative relaxation in order to realize net cooling. [ 117 ] Anti‐Stokes fluorescence has been observed experimentally in several color centers in diamond including the H3 center, [ 150 ] the SiV − center, [ 129 ] and also NV − and GeV − centers [ 151 ] using standard optical spectroscopy techniques. These recent results motivate future experimental efforts toward observing solid‐state laser refrigeration in diamond.…”