Development of an integrated multispectral LIDAR in silicon photonics

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. <br> <br>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.