Development of an integrated multispectral LIDAR in silicon photonics

  • Pierre Maidment

Student thesis: Doctoral ThesisDoctor of Philosophy

Abstract

The main objective of this thesis was the development of a multi-wavelength beam-steering device to be incorporated into an integrated lidar chip in the silicon-on-insulator (SOI) platform. Chip-scale LIDAR has been targeted for self-navigation technology but the addition of multiple wavelengths enables enhanced feature recognition and spectral analysis for use in food monitoring and agriculture. The development of an optical phased array capable of beam-steering was preceded by the optimisation of several components for broadband operation at the two key telecom wavelengths of 1.31µm and 1.55µm for targeting moisture sensing.

Waveguides were designed for broadband operation with propagation losses of 1 − 2dB/cm for the two wavelengths. Phased arrays were fabricated with 4-64 emitting elements to steer light from both wavelengths across an alias-free but measurement-limited field-of-view. Alias-free steering was enabled by a half-wavelength (775nm) array spacing across phase-mismatched emitter waveguides to suppress optical crosstalk to < 12dB over propagation lengths of > 250µm. The side-lobe level below the main steered beam was decreased from around 1dB to 6 − 10dB after a phase alignment process. The far-field beam widths were < 3.5◦ for the 64-element array, equating to a scanning resolution of about 60 individual spots. Finally, a flip-chip bonding process is initially demonstrated to integrate III-V laser diodes to the SOI platform with coupling efficiency and thermal resistance tested. The in-plane laser alignment is achieved using complementary markers on the laser p-contact and silicon substrate while vertical alignment is considered by matching the thickness of the laser epilayer stack with the active region to the position of the passive waveguides.
Date of AwardJul 2024
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsUniversity of Glasgow
SupervisorMarc Sorel (Supervisor) & Amit Kumar (Supervisor)

Keywords

  • LiDAR
  • photonics
  • integrated photonics
  • silicon photonics
  • Finite Difference simulation
  • optical phased array

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