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Title:Improving the efficiency and threshold current of photonic crystal vertical-cavity surface-emitting lasers
Author(s):Tan, Meng Peun
Advisor(s):Choquette, Kent D.
Contributor(s):Choquette, Kent D.
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Vertical-cavity surface-emitting laser (VCSEL)
oxide-confined photonic crystal vertical-cavity surface-emitting laser (VCSEL)
proton-implanted photonic crsytal vertical-cavity surface-emitting laser (VCSEL)
single mode operation
differential quantum efficiency
threshold current.
Abstract:This work focuses on how to achieve high power, low threshold, and high efficiency single mode VCSELs. Various mechanisms that affect the differential quantum efficiency and threshold current of the proton-implanted and oxide-confined photonic crystal vertical-cavity surface-emitting lasers (VCSELs) are studied. Three degrees of freedom in designing the photonic crystal VCSELs to maximize the laser performance in terms of efficiency and threshold current are considered: the epitaxial structure, the relative size of the current aperture and the transverse optical mode, and the photonic crystal design. The theoretical background regarding the differential quantum efficiency and threshold current of the photonic crystal VCSELs is presented. Proton-implanted 850 nm VCSELs intended for high efficiency single mode lasing are fabricated and characterized, and then the experimental results are compared with the theories. It is found that spectral and spatial mode-gain overlap, optical loss, and thermal effects affect the laser efficiency and threshold current. The thermal effects also affect the dynamical change of differential quantum efficiency with the injected current. The epitaxial structure determines the spectral mode-gain overlap and the modal properties of the VCSELs, while the relative size of the current aperture and the optical mode sets the spatial mode-gain overlap factor. The photonic crystal air hole fill-factor has an impact on all the mechanisms mentioned above. By etching the photonic crystal into proton-implanted VCSELs, stronger index guiding is introduced and consequently the wide distribution of efficiency and threshold current between devices and the discontinuity in measured output power versus current are eliminated, and the threshold current is reduced. Single mode power of 2.5 mW is obtained from proton-implanted photonic crystal VCSELs.
Issue Date:2010-01-06
URI:http://hdl.handle.net/2142/14614
Rights Information:Copyright 2009 Meng Peun Tan
Date Available in IDEALS:2010-01-06
Date Deposited:December 2


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