Characterisation of photonic crystal surface emitting laser devices and materials

Zhao, Xingyu (2026) Characterisation of photonic crystal surface emitting laser devices and materials. PhD thesis, University of Glasgow.

Abstract

This thesis presents the detailed characterisation of photonic crystal surface emitting laser (PCSEL) devices and materials.

Initially, the muti-wavelength gain material (InGaAs/GaAs) for PCSEL arrays is achieved through selective area regrowth technology. The square masked region with widths in the range of 100-300 μm are presented to match the requirement of PCSEL. The details of the measurement apparatus and the system alignment process is presented before the sample characterization. Spatially resolved photoluminescence is used to measure the emission wavelength and white light interferometry is used to determine the thickness enhancement factor, which is combined with simulation. The results indicate that over 100 μm uniform emission area and total 86nm wavelength shift was achieved, and a thickness enhancement factor ranging from 1.19 to 2.23 at the centre of the masked region was obtained across all investigated patterns. Even for 300 x 300 μm masked region, the growth rate enhancement and wavelength variation is still observed due to the selective area regrowth effect. The result shows the potential of application of large area two-dimensional selective area growth technology for monolithically integrated multi-wavelength PCSEL arrays.

The detailed characteristics of the REPCSELs (and their associated PCSELs) are also presented. The reduction of threshold current and increased slope efficiency through surrounding the PCSEL with a DBR is demonstrated, with the REPCSEL device exhibiting a threshold of 324 mA (860 A/cm2 ), whereas no PCSEL device showed lasing operation up to 1.1A for 200 μm device. The effect of detuning with respect to the gain spectrum by change the PC and DBR period are presented. The minimum threshold current density is achieved when the lasing wavelength of the PCSEL is aligned with the peak material gain. The temperature dependent current power characteristics and spectral measurements are analysed. A wavelength selective enhancement through the resonator effect is demonstrated. This is followed by a detailed current dependent band structure analysis of PCSELs. The measurement results indicate that the in-plane loss parameters associated with the leaky and non-leaky modes are selectively modified by the perimeter DBR. The result demonstrates the potential to achieve a wavelength selectivity mechanism for lower threshold and high efficiency PCSELs.

Spatially resolved band structure for the quantitative analysis of PCSELs is presented. The details of measurement strategy for different methods before characterization is presented. The current dependent measurement at the zone centre about the influence of collected wavevector Δ k on spectral linewidth is presented, and the reduction of linewidth for each mode is observed for a reduced collected wavevector Δk. Spatially resolved band structure allows the threshold gain to be estimated, and the role of inhomogeneity to be explored. The result indicated that the lasing mode with the lowest threshold had been observed and the estimated threshold gain is ~ 110 cm⁻¹. Spectral measurements of the PCSEL image plane indicate that the scale of inhomogeneous photonic crystal is smaller than 30 μm. The image plane mapping result elucidates how the PCSEL develops a spatially extended optical mode, formed through the coherent integration of numerous localized, would-be lasing regions with increasing current.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Sweeney, Professor Stephen J.
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85998
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 12 Jun 2026 09:23
• Last Modified: 12 Jun 2026 09:25
• Thesis DOI: 10.5525/gla.thesis.85998
• URI: https://theses.gla.ac.uk/id/eprint/85998

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