Magnified expansion and compression of subpicosecond pulses from a frequency-doubled Nd:YLF laser

Includes bibliographical references.Pulses from a mode-locked frequency-doubled Nd:YLF laser have been spectrally broadened and subsequently expanded to more than 200 ps and recompressed to 750 fs by grating compressors with magnifying telescopes. The new design magnifies the time delay dispersion to a factor 10 times larger than achievable with standard compressors of similar size. The design of the system and its sensitivity to the variations in the position of its optical components is analyzed. The scheme will allow efficient amplification of subpicosecond pulses in dye amplifiers.This work was supported by N.S.F.-CONICET U.S.A./Argentina Cooperative Science Program under Grant INT 8802563, and by the National Science Foundation under Grants ECS 870507 and ECS 8606226. M. C. Marconi was supported by a Fellowship from the Universidad Nacional de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

Strain-induced modifications of the band structure of InxGa1-xP–In0.5Al0.5P multiple quantum wells

Includes bibliographical references.The effect of strain on the band structure of InxGa1-xP-In0.5Al0.5P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements. The biaxial strain in the wells was varied between +0.6% compressive to -0.85% tensile strain by changing the well composition x from 0.57 to 0.37. Strain increases the valence band offsets in either tensile or compressively strained structures. Whereas relatively insensitive to tensile strain, the valence band offsets showed a strong dependence on the magnitude of the compressive strain. Good agreement is found between the measured valence band offsets and those predicted by the model solid theory, except for the largest compressively strained MQW's, for which the model calculations underestimate the measured valence band offset. Strain and the associated variations in composition also modified the separation among the well states associated with Γ1c, L1c, and X1c. From these results, the bandgaps of each conduction band extrema were calculated in InxGa1-xP for 0.37 < x < 0.57 and compared with the predictions of the model solid theory.This work was supported by the National Science Foundation under Grant DMR 9321422 and Grant ECS-9502888, and by the AFOSR under Contract F49620-93-1-0021

Carrier lifetime and recombination in long-wavelength quantum-well lasers

Includes bibliographical references.We present a novel analysis for correcting the measured differential carrier lifetime to account for carrier population in both the barrier and separate confinement heterostructure (SCH) regions of quantum-well (QW) lasers. This analysis uses information obtained from the measured spontaneous emission spectra to correct the measured lifetime and obtain the intrinsic well lifetime. Once the intrinsic well lifetime is obtained, the intrinsic well recombination coefficients can also be obtained. We show that the carrier population in the barrier/SCH layers can significantly affect the measured carrier lifetime and the extracted recombination coefficients. We also show that this analysis yields transparency carrier density and differential gain numbers which are very different from those obtained with the traditional analysis and much closer to what is predicted for highly strained QW lasers. These differences indicate the importance of accounting for barrier/SCH carriers on the measurement of basic QW laser material properties.This work was supported by the National Science Foundation under Grants ECS 9408321 and DMR 9803066