Strain-controlled disorder-defined apertures for optical mode control in vertical-cavity surface-emitting lasers

Su, Patrick

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https://hdl.handle.net/2142/117524 Copy

Description

Title

Strain-controlled disorder-defined apertures for optical mode control in vertical-cavity surface-emitting lasers

Author(s)

Su, Patrick

Issue Date

2022-08-23

Director of Research (if dissertation) or Advisor (if thesis)

Dallesasse, John M

Doctoral Committee Chair(s)

Dallesasse, John M

Committee Member(s)

• Feng, Milton
• Nahrstedt, Klara
• Lee, Minjoo L

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Vertical-cavity surface-emitting lasers, impurity-induced disordering, single-fundamental-mode, optical mode-control

Abstract

Vertical-Cavity Surface-Emitting Lasers (VCSELs) have become ubiquitous in modern consumer markets. Owing to their small footprint, circular-beam profile, on-wafer probing capability, and high reliability, VCSELs have been widely deployed for optical transceivers and consumer facial recognition systems. In the advent of emerging applications such as autonomous driving, AR/VR systems, and automated robotics, high-power 2D VCSEL arrays are being used as the premier illumination source for optical depth sensing modules. Through the initiation of Zn diffusion, impurity-induced disordering (IID) has been demonstrated to enable optical mode control and increased modulation frequencies, and provide carrier and photon confinement in vertical-cavity surface-emitting lasers. While disordering provides a wafer-scale method of improving device performance, the regions of disordering must be carefully controlled. Adverse effects can overshadow the benefits of disordering if it is not properly managed. Due to the isotropic nature of diffusion, undesirable lateral undercutting can occur during deep disordering processes where the severity of this effect is defined by the initial diffusion front formed. In this work, the fine control of Zn diffusion fronts in apertures formed using impurity-induced disordering is presented. By tailoring the diffusion mask strain, the diffusion front curvature of the impurity-induced disordering aperture can be controlled. Through modifying the composition of SiN$_{x}$ diffusion masks, various film stresses can be achieved. When employed for disordering, these form a variety of disordering apertures with differing diffusion fronts. Through utilizing tensile-strained diffusion masks, a disordering front with reduced lateral and enhanced vertical disordering is formed. Conversely, a compressive-strained diffusion mask yields a disordering front with enhanced lateral and reduced vertical disordering. Tensile-strained diffusion masks yield the most desirable disordering front profile, as it enables maximum higher-order mode suppression while mitigating the encroachement of the disordering front onto the fundamental-mode. Using tensile-strained diffusion masks, record high-power single-fundamnetal-mode emission in an oxide-VCSEL is presented. A comparison of the tensile-strained, unstrained, and compressive-strained diffusion masks utilized to fabricate disorder-defined VCSELs designed for single-fundamental-mode operation is also investigated. Lastly, the strain-controlled disorder-defined apertures designed for single-fundamental-mode emission is then extended to achieve single-polarization state emission. Through designing an asymmetric disorder-defined aperture, the symmetrical threshold modal gain profile is eliminated, thus leading to a preferential polarization state. This body of work demonstrates the high-performance capabilities of VCSELs utilizing strain-controlled disorder-defined apertures. Through tailoring the diffusion mask, performance characteristics such as high-power, single-mode, and single-polarization emission in an oxide-aperture VCSEL is achieved.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

@2022 Patrick Su

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