Enhanced beam quality and polarization stability in oxide-confined Vertical-Cavity Surface-Emitting Lasers via anti-phase optical coatings and disorder-defined apertures

The Vertical-Cavity Surface-Emitting Laser (VCSEL) has become ubiquitous in the modern world, with applications spanning the optical telecommunications infrastructure in the form of short-haul optical transceivers, optical printers, and optical “mice.” This is a result of its energy-efficient operation, small footprint, and capability for packaging into 2-dimensional arrays. Emerging technologies in 3D-sensing for consumer handheld products, augmented reality/virtual reality (AR/VR) headsets, and light detection and ranging (LiDAR) have begun to reach operational limits of current VCSELs. The development of VCSELs capable of operating in a single-transverse mode with a stable single polarization and high output optical powers is paramount. Operation in this regime is advantageous for many reasons, including less divergence in the optical beam leading to a smaller spot size, higher optical signal-to-noise ratio (SNR), and spectral purity and stability. The anti-phase coating introduced in this work accomplishes these operational objectives via the deposition of a single layer of silicon atop the VCSEL patterned with a circular or elliptical aperture. This creates a radially-varying threshold modal gain, sufficient for suppressing higher-order transverse modes or unpreferred polarization states without disrupting the cylindrically-symmetric transverse optical modes defined by the circular oxide aperture, maintaining the symmetrical integrity of the modes. Another mode- and polarization-control technique discussed in this dissertation is impurity-induced layer disordering for the formation of disorder-defined apertures. By diffusing zinc into the periphery of a VCSEL top DBR, the number of DBR pairs is reduced, raising the threshold modal gain for the modes overlapping with the zinc difused region, mainly the higher-order transverse modes. The following dissertation primarily investigates the anti-phase coating as a mode- and polarization-control method in 850 nm GaAs-based oxide-cofined VCSELs, both discrete devices and arrays. The VCSEL structure is simulated to develop an optimal anti-phase coating structure, and the devices are then fabricated following a standard oxide-confined VCSEL process flow. The VCSELs are then characterized for output power and spectral performance via light-current-voltage (LIV) curves and optical spectra measurements. To realize single-polarization operation, polarization-resolved LIV (PR-LIV) measurements are taken. This dissertation also investigates the use of disorder-defined apertures for single-mode, single-polarization operation in 2D-arrays and how the combination of both techniques can result in single-mode performance in multimode VCSELs utilizing only one technique. To conclude, an overview of long-wavelength VCSELs will occur, followed by the simulation of several epitaxial materials and design of a novel long wavelength VCSEL structure.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Pikul, Kevin Peter

Contributors dc:contributor

• Dallesasse, John M
• Feng, Milton
• Lee, Minjoo
• Dragic, Peter D

• VCSEL
• single-transverse mode
• single-polarization state
• anti-phase optical coating
• silicon optical coating
• impurity-induced disordering
• disorder-defined aperture

Statement dc:rights

• Copyright 2025 Kevin Pikul

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129750

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129750