Ultrafast spectroscopy of La2 -x Srx CuO4 single crystals
Journal of Low Temperature Physics 131:5-6 (2003) 755-759
Abstract:
We present measurements of the ultrafast optical response of La2-xSrx CuO4 single crystals at two different doping levels (x=0.15, 0.07) as a function of temperature. Owing to the 40-fs time resolution of our experiment, we are also to measure both the build-up and the decay of the ultrafast signal. We show for the first time that the temperature dependence of the transient reflectance amplitude tracks the thermal depletion of the superfluid density. At low temperature we identify a new regime characterized by an extremely long, temperature-dependent rise-time (3 ps). The doping dependence of the relaxation rate suggests that this is sensitive to the scattering of quasiparticles by low-energy spin excitations.Squeezed light generation in semiconductor waveguides
P INT SCH PHYS 150 (2003) 191-217
Dynamics and gain in highly-excited InGaN MQWs
Current Applied Physics 2:4 (2002) 321-326
Abstract:
The Kerr gate technique is used to time-resolve the gain in an In0.02Ga0.98N/In0.16Ga0.84N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze both the time-integrated and time-resolved spectra. We confirm that the stripe length dependence of the gain in the multiple quantum wells under nanosecond excitation is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity. This is found to fit very well with our data, even beyond the saturation region. Furthermore, we have extended the investigation to examine the dynamics of the emission and gain. These measurements suggest that the photoexcited carriers must localize (possibly at indium-rich sites) before strong stimulated emission is seen. © 2002 Elsevier Science B.V. All rights reserved.Dynamics and gain in highly-excited InGaN MQWs
CURR APPL PHYS 2:4 (2002) 321-326
Abstract:
The Kerr gate technique is used to time-resolve the gain in an In0.02Ga0.98N/In0.16Ga0.84N multiple quantum well sample. A new way of analyzing the data in such a variable stripe length method gain experiment is used to analyze both the time-integrated and time-resolved spectra. We confirm that the stripe length dependence of the gain in the multiple quantum wells under nanosecond excitation is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity. This is found to fit very well with our data, even beyond the saturation region. Furthermore, we have extended the investigation to examine the dynamics of the emission and gain. These measurements suggest that the photoexcited carriers must localize (possibly at indium-rich sites) before strong stimulated emission is seen. (C) 2002 Elsevier Science B.V. All rights reserved.Coherent exciton-biexciton dynamics in GaN
Physical Review B - Condensed Matter and Materials Physics 65:19 (2002) 1931021-1931024