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

Area of Science:

• Photonics and Laser Technology
• Optoelectronics
• Materials Science

Background:

• Vertical-cavity surface-emitting lasers (VCSELs) require precise focusing and collimation for applications like sensing and optical communications.
• Existing VCSEL solutions often lack integrated, tunable focusing capabilities, limiting their compactness and versatility.

Purpose of the Study:

• To demonstrate a highly compact, electrically focus-tunable VCSEL by integrating a liquid crystal (LC) optical module.
• To achieve wide-range focal control and assess its performance in terms of spot size, numerical aperture, and power density.

Main Methods:

• Direct integration of a liquid crystal optical module onto the VCSEL emission aperture.
• Electrical tuning of the focal length using driving voltages from 3V to 10V.
• Characterization of far-field spot size, numerical aperture (NA), power density, and spatial power variation across the tuning range.

Main Results:

• Achieved a continuous focal-length tuning range of 25mm.
• Reduced far-field spot size to a 4mm x 4mm diameter (1/e^2), with a 2mm x 2mm FWHM.
• Maximized beam area reduction of 66% and suppressed FWHM-based NA to 0.081.
• Maintained high power density (>42 W/m^2) with low spatial variation (<0.005 mW/mm).

Conclusions:

• The integrated LC-VCSEL offers a practical solution for ultra-compact optical shaping.
• This technology enables advanced functionalities for VCSEL arrays in sensing, imaging, and communication systems.
• The device provides wide-range, electrically controlled focusing in a minimal volume (60 μm^3).