Two-photon absorption in CuCl and CuBr under hydrostatic pressure

Abstract

Two-photon absorption is used to measure the shift of the longitudinal Z3 and Zi, 2 excitons and the 2P exciton in CuCl under hydrostatic pressure. Hydrostatic deformation potentials for excitons and band states are determined with high accuracy. In CuBr the shift of the longitudinal Zi, 2 exciton is measured, showing a pronounced superlinear pressure dependence. In the high-pressure phase (above 4 GPa) the pressure dependence of luminescence is observed up to 9 GPa in both coxIlp ounds.

Effect of pressure on the Raman anomaly of zinc-blende CuBr and Raman spectra of high-pressure phases

“…These pressures are in agreement with room-temperature x-ray-diffraction, 49 neutron-diffraction, 32 and optical studies. 30,31 Our low-temperature results for the phasetransition pressures to CuBr-IV ͓4.0͑1͒ GPa͔ and CuBr-V ͓6.3͑2͒ GPa͔ agree with those reported by Reimann et al, 31 who have measured the pressure dependence of exciton emission spectra in CuBr at 6 K using a DAC with helium as a pressure medium. The coexistence between CuBr-IV and CuBr-V in the pressure range between 6.3 and 7.3 GPa was not observed by these authors, probably because the luminescence decay channel of both phases have very different lifetimes.…”

“…31,32 The Raman spectra of CuBr-IV and CuBr-V exhibit similarities to those of the structurally related phases CuI-V ͑Ref. 29͒ and CuCl-IV.…”

Determination of the Pressure Dependence of Band‐Structure Parameters by Two‐Photon Spectroscopy

“…Peak 2 3 is caused by one-photon excitation of excitons. The pressure coefficient of this peak is considerably lower than in bulk CuCl (7.65 meV/GPa [19]) and in CuCl nanocrystals in a NaCl matrix [39]. Since peak L occurs at one CuCl LO-phonon energy (26 meV) below 2 3 and since the pressure coefficients of L and 2 3 are nearly the same (the pressure dependence of the LO-phonon energy in CuCl [40] is within the experimental error of our results), we identify peak L as the LO-phonon replica of the 2 3 exciton luminescence [41].…”

Méthodes expérimentales de l'optique non linéaire

“…Puisque la structure cristalline ne possède pas de centre d'inversion, les trois états de symétrie r$ peuvent être excités par absorption à deux photons [5,6]. Le dispositif utilisé est décrit en référence [6].…”

“…En conséquence, en utilisant des impulsions nanosecondes de puissance crête de quelques MW/cm 2 , la variation de l'absorption induite par laser est faible. Si l'on veut étudier des films minces, on peut utiliser une autre technique plus sensible où on ne détecte pas la variation d'absorption mais on mesure l'émission des excitons créés auparavant par absorption à deux photons [5] . Cette technique possède un meilleur rapport signal/bruit.…”