Interaction of high power CO₂ laser radiation with a nonequilibrium carrier system in Ge at low temperatures

Abstract

CO2‐laser produced damping of electron‐hole drop (EHD) luminescence in Ge at laser intensities of 104 to 5 × 106 W/cm2 is reported. The observed effect is explained to be due to heating of the EHD by 10.6 μm radiation and driving of e‐h plasma by phonon wind generated during absorption and relaxation of hot nonequilibrium carriers.

Phonon wind generation in Ge by C02 laser induced heating of electron‐hole drops

“…Luminescence and microwave conductivity of the laser-excited Ge sample were detected to investigate the response of the system to the CO, laser pulse a~t i o n .~) Fig. 1 in [6] shows the luminescence signals of or-EHD in an unstressed Ge sample a t different CO, laser pulse intensities. The luminescence intensity is sharply suppressed under the CO, laser radiation, becoming irreversible a t I 2 0.5 MW/cm2, but partially restoring a t I < 0.1 MW/cm2.…”

“…Pulse energy of YAG:Nd laser corresponds to generation of 2 x lo1* e-h pairs in Ge sample. Initial EHD radius R = 370 pm (after[7]). The arrow shows CO, laser pulse switching on The oscilloscope traces (initial part) of Ge microwave conductivity signals a t various delay times of the CO, laser pulse of fixed int,ensity I = 2 x lo6 W/cm2.…”

“…The arrow shows CO, laser pulse switching on The oscilloscope traces (initial part) of Ge microwave conductivity signals a t various delay times of the CO, laser pulse of fixed int,ensity I = 2 x lo6 W/cm2. The time scale is 50 ys/div, T = 4.2 K (after[7]) 3, For details of the experiments see [5 to 71 and figure captions.…”