2026-09-23T06:35:28Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/129750 2026-02-05 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2027-05-01 The student, Kevin Pikul, accepted the attached license on 2025-04-29 at 12:29. The student, Kevin Pikul, submitted this Dissertation for approval on 2025-04-30 at 11:41. This Dissertation was approved for publication on 2025-04-30 at 12:58. DSpace SAF Submission Ingestion Package generated from Vireo submission #22084 on 2025-10-19 at 19:54:37 Enhanced beam quality and polarization stability in oxide-confined Vertical-Cavity Surface-Emitting Lasers via anti-phase optical coatings and disorder-defined apertures Pikul, Kevin Peter 2025-04-30 Dallesasse, John M 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 eng 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. 2025-05 Thesis https://hdl.handle.net/2142/129750 Copyright 2025 Kevin Pikul Electrical & Computer Eng Electrical & Computer Engr University of Illinois Urbana-Champaign Ph.D. Dissertation