Selection of modes perpendicular to the junction plane in GaAs large-cavity double-heterostructure lasers
The gains and reflectivities of the transverse-electric (TE) modes of GaAs large-cavity double-heterostructure (DH) (P-p-n'-N) lasers have been calculated in order to study mode selection perpendicular to the junction plane. The GaAs laser is modeled as a passive dielectric-slab waveguide composed of four layers whose optical constants are taken from recent literature. In lasers having a cavity thickness of a few microns, a small difference in refractive index between the p- and n'-region leads to the fundamental mode being confined to the p-region. Discrimination in favor of this mode without significant penalty in threshold gain may be achieved by utilizing the mode-dependent loss in the n'-layer. It is found that optimum mode discrimination in favor of the fundamental mode is governed by a suitable combination of the p-layer thickness, loss in the n'-region, and the difference of refractive indices of the p- and n'- layers. This analysis contrasts with an earlier analysis of the case of uniform refractive index in which it was found that the p-layer should be twice as thick as the n-layer for optimum mode discrimination. The calculated mode shapes in P- p-n'-N lasers are found to be in qualitative agreement with those observed recently by Hakki, and also with earlier observations that catastrophic mirror damage in P-p-n'-N lasers is confined to the p-region. Contrary to experimental observation, the model predicts that lasers having cavity thicknesses as large as 3 $mu$m should operate stably in the fundamental mode. Possible reasons for this discrepancy are advanced. A simplification of the P-p-n'-N laser, which consists of omitting the N-layer thus yielding an asymmetric double-heterostructure laser, is suggested, and the merits and drawbacks of such a design are discussed. (auth)
- Research Organization:
- Bell Labs., Murray Hill, NJ
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-007200
- OSTI ID:
- 4152624
- Journal Information:
- IEEE J. Quant. Electron., v. QE-11, no. 7, pp. 390-400, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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