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Properties of Buried Heterostructure Single Quantum Well (Al,Ga)As Lasers


Derry, Pamela Louise (1989) Properties of Buried Heterostructure Single Quantum Well (Al,Ga)As Lasers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WSZC-4R60.


Unlike conventional semiconductor lasers, single quantum well (SQW) lasers with high reflectivity end facet coatings have dramatically reduced threshold currents as a result of the smaller volume of the (active) quantum well region. A cw threshold current of 0.55 mA was obtained for a buried graded-index separate-confinement heterostructure SQW laser with facet reflectivities of ~80%, a cavity length of 120 µm, and an active region stripe width of 1 µm. This is believed to be the lowest threshold current so far reported for any semiconductor laser at room temperature.

The submilliampere threshold currents of these lasers allow them to be modulated at high speed without any current prebias or feedback monitoring. The relaxation oscillation frequency for these lasers was also measured. Values of differential gain derived from these measurements demonstrated that the differential gain in the uncoated lasers is less than in the coated devices. This result was expected because of gain saturation.

As predicted, SQW lasers have substantially narrower spectral linewidths than bulk double heterostructure lasers. This result is attributed to lower internal loss, linewidth enhancement factor, and spontaneous emission factor. A further major reduction (< 3x) in the linewidth of these SQW lasers was observed when the facet reflectivities were enhanced. This observation is explained theoretically on the basis of the very low losses in coated SQW lasers and the value of the spontaneous emission factor.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Condensation; Optics; Applied Physics
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Yariv, Amnon (advisor)
  • Bellan, Paul Murray (co-advisor)
Thesis Committee:
  • Yariv, Amnon (chair)
  • Vahala, Kerry J.
  • Bridges, William B.
  • Gould, Roy Walter
  • Culick, Fred E. C.
  • Bellan, Paul Murray
Defense Date:8 June 1988
Additional Information:Title in 1989 commencement program -- Properties of Buried Heterostructure Single Quantum Well (Al,Ga) as Lasers -- is misprinted.
Funding AgencyGrant Number
Office of Naval Research (ONR)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Record Number:CaltechETD:etd-02052007-093221
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:501
Deposited By: Imported from ETD-db
Deposited On:23 Feb 2007
Last Modified:08 Jul 2021 21:39

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