Chip-scale electrically focus-tunable VCSEL with large dynamic zoom enabled by liquid crystal phase gradients

Focusing and collimation capabilities are essential for vertical-cavity surface-emitting lasers (VCSELs), enabling applications such as short-range sensing, scanning imaging, and high-speed optical communications. In this work, we demonstrate a highly compact, electrically focus-tunable VCSEL accomplished by directly integrating a liquid crystal (LC) optical module onto the emission aperture. This structure enables wide-range focal control along the Z-axis, providing a continuous focal-length tuning range of 25 mm under driving voltages between 3 V and 10 V. At the focal plane, it reduces the far-field spot size to a 1/e² diameter of 4 mm × 4 mm, corresponding to a full width at half maximum (FWHM) of 2 mm × 2 mm. This represents a maximum beam area reduction of 66%, with a 40% suppression of the FWHM-based effective numerical aperture (NA) down to 0.081. Meanwhile, the device consistently maintains a high power density exceeding 42 W/m², with spatial power variation below 0.005 mW/mm across the entire zoom range. The integrated structure has a volume of only 60 µm³, providing a practical solution for ultra-compact integrated optical shaping of VCSEL arrays.