# Research on Low Numerical Aperture 808 nm Fiber-Coupled Semiconductor Laser

## TL;DR

Researchers developed a high-efficiency fiber coupling system for 808 nm semiconductor lasers, achieving high power output and stable performance.

## Contribution

A novel fiber coupling system combining FAC/SAC with a focusing lens for low-NA fibers is proposed and experimentally validated.

## Key findings

- The coupling module achieved 95% efficiency with a continuous output power of 9.59 W and slope efficiency of 1.1 W/A.
- The system demonstrated a maximum output numerical aperture of 0.116 and a wavelength temperature drift of 0.2 nm/°C.
- The approach is validated for high-brightness laser systems with applications in solid-state laser pumping and long-distance transmission.

## Abstract

This article investigates fiber coupling techniques for low numerical aperture 808 nm semiconductor lasers. A coupling optical system combining fast-axis/slow-axis collimators (FAC/SAC) with a focusing lens was designed, achieving efficient coupling through high-precision optical integration packaging. First, a high-power GaAs-based 808 nm semiconductor laser chip was designed and fabricated. Its thermal performance and operational stability were enhanced by optimizing packaging materials and structures. The coupling system employs a fast-axis collimating lens, slow-axis collimating lens, and aspheric focusing lens to shape the beam and focus it into a 200 μm/0.12 NA fiber. Experimental results show that the developed coupling module achieves the threshold current of 1.2 A at 298 K, the continuous output power of 9.59 W, with the slope efficiency of 1.1 W/A, a coupling efficiency of 95%, the maximum output numerical aperture of 0.116, the wavelength temperature drift coefficient of approximately 0.2 nm/°C, and the peak brightness of 0.72 MW/cm2·sr. This study validates the feasibility and superiority of the FAC/SAC combined with focusing lens approach for low-NA fiber coupling. It provides theoretical and practical foundations for fiber coupling in high-brightness, high-power laser systems, offering promising applications in solid-state laser pumping, enhancing system integration, and enabling long-distance, high-brightness transmission.