Optically-Pumped Blue Lasing in Zinc Selenium/zinc Sulfur
Abstract
In the first part of the thesis, stimulated emissions were studied on the wide band gap material ZnSe based heterostructures grown on GaAs substrates by molecular-beam epitaxy. The ZnSe/ZnSSe double heterostructures (DH's) were extensively examined because such structures have the potential to be developed into future laser diodes. Lasing operations were evidenced by the superlinear behavior of light emission versus pump intensity and the spectral narrowing of the emission at threshold. The lasing process was proved to be an inelastic exciton-exciton collision at low temperature. The reduced threshold pump intensities due to the confinement of the double heterostructures have been demonstrated as compared to those of thick ZnSe epilayer and ZnSe/ZnSSe superlattices. The effect of structural defects on lasing threshold has also been investigated. Room temperature lasing with relatively low threshold has been achieved on ZnSe/ZnSSe double heterostructures. In the second part of the thesis, the feasibility of an optically-pumped far-infrared laser based on the intersubband transitions in GaAs/AlGaAs multiple quantum wells is studied theoretically. The criteria for population inversion and efficient lasing operation are established. A system consisting of a superlattice with four quantum wells per period is proposed and shown to satisfy the above criteria. The relaxation processes are investigated with electron-phonon interaction being given a rigorous theoretical treatment. It is shown that in the proposed structure, optical gain in excess of 300cm^{-1} can be realized under practical pumping conditions. Optimization of the proposed laser is discussed. Future work involving improvement of the present theoretical treatment together with utilization of quantum wire and box structures to construct infrared lasers is addressed.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1993
- Bibcode:
- 1993PhDT.......179S
- Keywords:
-
- X) SELENIUM(1-X) DOUBLE HETEROSTRUCTURES AND A DESIGN OF FAR-INFRARED LASERS BASED ON GALLIUM ARSENIDE/ALUMINUM(X) GALLIUM(1-X) ARSENIC MULTIPLE QUANTUM WELLS (ZINC SULFUR SELENIDE;
- ALUMINUM GALLIUM ARSENIDE;
- GALLIUM ARSENIDE;
- Engineering: Electronics and Electrical; Engineering: Materials Science; Physics: Condensed Matter