S. Thomas

Cardiff University

  • 11A.1 – A Hybrid Electron Beam Lithography Approach to Wafer Scale Up of 150mm InP Ridge Lasers

    Thomas Peach, Cardiff University
    T. Jones, Cardiff University
    B. Salmond, Cardiff University
    S. Thomas, Cardiff University
    E. Beaumont, Cardiff University
    A. Sobiesierski, Cardiff University
    Samuel Shutts, Cardiff University

    11A.1 Final.2025

    Abstract – The utilization of electron beam lithography (EBL) as a wafer scale technique for the fabrication of compound semiconductor devices provides unique challenges in terms of both application and throughput. We report on wafer scale EBL in the context of fabricating edge emitting lasers on 150mm indium phosphide (InP) substrates. A hybrid electro-optical lithography process is used to pattern typical ridge waveguide (RWG) laser structures, while overcoming some of the practical challenges associated with fabricating these devices on large wafer platforms.

  • 12.7 – Regrowth-Free 1st-Order Gratings for Photonic Integrated Circuits using Focused Ion Beam Nanofabrication and Electron Beam Lithography

    B. Salmond, Cardiff University
    Thomas Peach, Cardiff University
    S. Thomas, Cardiff University
    Sara Gillgrass, Cardiff University
    D. D. John, University of California Santa Barbara
    W. J. Mitchell, University College London
    B. J. Thibeault, University of California Santa Barbara
    M. J. Wale, University College London
    W. Meredith, Compound Semiconductor Centre Ltd.
    Peter M. Smowton, Cardiff University
    D. Read, Cardiff University, University of California Santa Barbara
    Samuel Shutts, Cardiff University

    12.7 Final.2025

    Abstract
    We present and compare two methods for fabricating grating structures for photonic integrated circuits. The first method uses a two-step electron beam lithography (EBL) and dry etch process, while the second uses direct milling of the grating structures using focused ion beam (FIB) nanofabrication. In both cases 1st order periodic structures with a pitch of 238 nm were successfully positioned adjacent to the ridge waveguide. Using the EBL method, a final grating depth of 10 nm was observed with an estimated coupling coefficient of 40 cm-1. Direct milling using FIB provided grating features milled to a depth of up to 350 nm, achieving maximum coupling strengths of over 200 cm-1.