Use of aluminum bearing III-V semiconductor native oxides for optical and current confinement in waveguides and lasers
Caracci, Stephen Joseph
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https://hdl.handle.net/2142/21228
Description
Title
Use of aluminum bearing III-V semiconductor native oxides for optical and current confinement in waveguides and lasers
Author(s)
Caracci, Stephen Joseph
Issue Date
1993
Doctoral Committee Chair(s)
Holonyak, Nick, Jr.
Department of Study
Electrical and Computer Engineering
Discipline
Electrical and Computer Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
Language
eng
Abstract
Data are presented on various laser and optical devices that utilize native oxidation of Al bearing III-V semiconductors to effect large lateral index steps. These large index steps are due to the low refractive index of the Al bearing native oxide (n $\sim$ 1.5), making possible the fabrication of high-quality optical waveguides.
To process epitaxial III-V crystals at higher resolution (e.g., laser devices with small output apertures and lower threshold currents), it is often desirable to shrink the thickness of the upper confining layer (UCL). The effect of thin upper confining layers on laser performance is studied by reducing the thickness to 0.2, 0.3, 0.45, and 0.6 $\mu$m. Data presented show that device performance is not significantly degraded until the UCL thickness is reduced $\sim$0.2 $\mu$m.
Planar native-oxide index-guided lasers with high-performance operation are described. These lasers use a relatively thick native oxide to form a lateral waveguide with an effective index step of $\rm\Delta n \sim 5\times10\sp{-3}.$ Index-guided devices, as opposed to gain-guided devices, exhibit improved output beam quality, lower threshold current, and narrower spectra.
"With even larger lateral index steps it is possible to ""steer"" photons. To investigate very large index steps formed from native oxides, three types of devices are used: planar native-oxide defined waveguides, ""teardrop""-shaped lasers and ring lasers. Data presented on native-oxide defined S-bend waveguides indicate extremely low optical losses are achieved even for ""tight"" bending. Further data on half- and full-ring lasers demonstrate that the radiation losses due to bending are low enough to still have high output power and low threshold current laser operation. It is even possible to select the polarization of the emitted light due to asymmetric losses for TE and TM light. This is accomplished by using a ""teardrop""-shaped resonator consisting of a single output stub which is split into a y-section that is then closed with a half ring. Laser devices using this geometry exhibit TM polarized output light with low threshold currents and high output powers."
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