High-power and high-efficiency wide-aperture lasers for material processing
Fig. 1: Voltage, optical power, and power conversion efficiency as a function of drive current for a W = 1200 µm single-emitter under QCWand CW operation.
Fig. 2: Schematic of a wide-aperture single emitter with buried-regrown-implant-structure (BRIS) periodic current structuring.
Fig. 3: Lateral far-field profile of W = 1200 µm single emitters comparing a device with BRIS and a reference device.
Fig. 4: Broad-area laser: Single-emitter with double-sided cooling
High-power broad-area diode lasers are a crucial component for applications in material processing, medicine, automotive, and more. Continually higher powers are required from single devices, in particular for use in fiber-coupled modules for material processing applications. A trend in recent years is to move to wider aperture single emitters, with lateral stripe width larger than 100 µm, in order to reduce cost per component.
Scientists from FBH have recently realized very wide-aperture GaAs-based broad area lasers emitting at a wavelength of 915 nm that achieve exceptionally high output power and efficiency at the same time. Fig. 1 shows voltage, optical power, and power conversion efficiency of a single emitter laser with a stripe width of W = 1200 µm and a resonator length of L = 4 mm, mounted on a compact passively cooled heatsink. Under quasi-continuous wave (QCW) operation, we reached a peak efficiency of 70% with 93 W of output power per emitter, with a peak power of over 225 W. In continuous wave (CW) operation, we achieved a peak power of 62 W at 62% efficiency. By varying the stripe width of the device in the range of W = 1000 … 1500 µm, the peak efficiency of the devices can be shifted to lower or higher output powers to match the desired application.
Further, utilizing FBH’s novel buried regrown implant structure (BRIS) technology, we were able to improve the far-field divergence of these devices, at the cost of a small penalty to device efficiency. The schematic in Fig. 2 depicts a W = 1200 µm device with BRIS periodic current structuring close to the active region. In Fig. 3, a far-field profile of an exemplary device is shown for an optical power of 100 W under QCW operation, which exhibits considerable narrowing of the far-field using BRIS current structuring compared to a reference device. This technology allows for wider, higher power devices to be efficiently coupled into a standard 1 mm core optical fiber, suitable for use in direct material-processing applications. We recently shared preliminary results at the CLEO Conference in Munich [1] and will present an extended overview at Photonics West in 2024 [2].
We thank the Federal Ministry of Education and Research (BMBF) for funding within the European Union Eurostars Project, BRISCL, under contract number: 01QE2103D.
Publications
[1] B. King, S. Arslan, A. Boni, P. S. Basler, C. Zink, P. Della Casa, D. Martin, A. Thies, A. Knigge, and P. Crump. "GaAs-based wide-aperture single emitters with 68 W output power at 69% efficiency realized using a periodic buried-regrown-implant-structure." The European Conference on Lasers and Electro-Optics, Munich, Germany, 2023.
[2] B. King, S. Arslan, P. Della Casa, D. Martin, A. Boni, P. S. Basler, A. Thies, A. Knigge, and P. Crump. "Ultra-wide-aperture diode lasers with high brightness through use of buried periodic current structuring." Accepted talk, High-Power Diode Laser Technology XXII Conference, SPIE Photonics West, San Francisco USA, 2024.