Origin of photoluminescence signals obtained by picosecond-excitation correlation measurements

Includes bibliographical references (page 14355).We have developed a theory that explains the spectral distribution and the different time decay behaviors of the signals observed in picosecond excitation-correlation measurements of semiconductor materials. The results display good quantitative agreement with experiments on multiple quantum wells and show that band filling has an important role in determining the characteristics of the correlation signals. Two limit cases are found and mathematically characterized: the nondegenerate regime, where the signals are positive with exponential-like decays, and the degenerate regime, where band filling gives rise to negative signals. It is shown that the technique is a sensitive probe of the carrier dynamics not fully exploited in previous work

Transient response of vertical-cavity surface-emitting lasers of different active-region diameters

Includes bibliographical references (pages 614-615).The multimode dynamics of vertical-cavity surface-emitting lasers with different active-region diameters was measured under subnanosecond electrical excitation (800-ps pulse duration, 100-ps risetime). The dynamics is characterized by the delayed onset of higher order modes which have a turn-on delay that is dependent on the active-region diameter and the excitation parameters. A simple model that can be used to estimate this turn-on delay for large-area devices is presented. Polarization resolved measurements show that, under this fast excitation condition, both orthogonal polarization states are isomorphic. The influence of the observed dynamics on the relative intensity noise of these devices is also discussed

Ultrahigh frequency oscillations and multimode dynamics in vertical cavity surface emitting lasers

Includes bibliographical references (page 187).We report the observation of ultrahigh frequency oscillations of up to 240 GHz in optically gain switched vertical cavity surface emitting lasers. These oscillations are shown to be produced by multimode emission through mode competition (10-30 GHz) or mode beating (above 100 GHz). Although these oscillations are not related to the intrinsic modulation bandwidth, some of them could be mistaken for relaxation oscillations, calling for careful interpretation of the results of this type of experiments. The highest frequencies observed for single mode relaxation oscillations were about 9 GHz in agreement with values of modulation bandwidth reported in the literature

Transverse mode dynamics in vertical cavity surface emitting lasers excited by fast electrical pulses

Includes bibliographical references (page 592).We report measurements of the transient multimode dynamics of vertical cavity surface emittin glasers excited by short (100-200 ps rise times, 1 ns duration) electrical pulses. Fast changes on the spatial distribution of the output power and strong mode competition are observed. Numerical simulations show that the observed dynamics are due to the partial overlap of the different transverse modes through spatial hole burning

Effect of indirect Γ-L and Γ-X transfer on the carrier dynamics of InGaP/InAlP multiple quantum wells

Includes bibliographical references (page 104).Indirect Γ-L scattering within the well, and real space carrier transfer to the barrier X1c states are shown to significantly affect the carrier dynamics in In0.48Ga0.52P/In0.5Al0.5P multiple quantum wells. When carriers transfer to the indirect states occurs, the carrier dynamics is modified by the slow return of the carriers from the low mobility states to the well. As a result, the absorption recovery time increases by almost an order of magnitude. Carrier transfer to the indirect states also increases the carrier lifetime to values characteristic of indirect recombination.This work is supported by the National Science Foundation through Grant Nos. DMR 9321422, ECS-9502888, EEC-9015128, the Colorado Advanced Technology Institute, Grant No. 0594.75.0738, and by AFOSR contract F49620-93-1-0021

Generation of synchronized trains of picosecond laser pulses at two wavelengths in a single-cavity synchronously mode-locked dye laser

Includes bibliographical references.Synchronized trains of 5 ps pulses at two wavelengths were generated in a single-cavity synchronously pumped dye laser containing a mixture of two dyes in a single jet and intracavity spatial masking for frequency selection. The utilization of this dual wavelength dye laser to monitor the relaxation of photoexcited carriers in multiple quantum wells was demonstrated.This work was supported by the NSF Center for Optoelectronic Computer Systems through NSF Grant No. ECD 9015128, and by the Colorado Advance Technology Institute. C. S. Menoni was supported by the Engineering Foundation AFOSR Research Initiation Grant No. RI-B-91-16

Nonresonant tunneling in InGaP/InAlP asymmetric double quantum wells

Includes bibliographical references (page 401).Nonresonant tunneling rates have been measured in InGaP/InAlP asymmetric double quantum-well structures for which optical phonon assisted tunneling is energetically forbidden. For an initial photoexcited carrier density of 2.4 × 1011 cm-2, tunneling times of 220, 60, and less than 9 ps have been measured in samples with barrier thickness 4.5, 3.0, and 1.5 nm, respectively. The tunneling times were found to be strongly dependent on carrier density. The measured tunneling times and their dependence on carrier density are compatible with impurity scattering being the dominant mechanism assisting the tunneling