Self-heating, thermal lensing, and thermal-conductivity co-design of beam performance in small-aperture VCSELs

In small-aperture vertical-cavity surface-emitting lasers for light detection and ranging, self-heating changes divergence and on-axis intensity through a thermo-optic lens. A transient finite-volume electro-thermal solver computes temperature from literature conductivities and the measured current–voltage characteristic. Its calibrated effective substrate depth reproduces the reference junction-temperature rise, giving a thermal resistance of 235 against the reported 237 K W −1 . A beam-propagation mode solver reads that field: for the reference device (radius 30 μm) over 10–95 mA, the guided-mode radius narrows from 16.6 to 8.4 μm and divergence broadens from 13.6 to 26.4 mrad while the beam-propagation ratio remains near unity. Following a constant-current step, divergence reaches 63% of its excursion in about 9 μs and settles by 30 μs. At small apertures, the model agrees with published far-field broadening and effective-optical-aperture contraction in direction, but under-predicts absolute angles by factors of 1.5–2; temperature-normalized slope comparisons remain conditional on device-specific heating rates. A twenty-four-material screening map based on thermo-optic coefficient divided by thermal conductivity identifies high-conductivity routes to lower thermal sensitivity. The contribution is a forward link from a thermally calibrated model to per-mode transient beam budgets without a fitted optical lens. Predicted divergence drift at 3, 6 and 12 μm radii is 17.9, 21.2 and 45.7%, exceeding a 10% budget; halving thermal resistance reduces it by 44–48% and raises on-axis intensity retention from 50 to 70% to 66–82%. These design estimates apply to specified center-hot structures and heat-source assumptions; transient beam measurements remain necessary.