Development of High-Power VECSELs for Medical Applications

Vertical-external-cavity surface-emitting lasers (VECSELs) are versatile lasers sources that have become particularly appealing for different applications due to the unique features they can offer. They combine the wide wavelength coverage of semiconductor laser technology with the good beam quality and power scalability of solid-state thin-disk lasers. The external cavity architectures also allow for efficient frequency conversion from infrared to visible and UV wavelengths. In this way, VECSELs can provide high-power emission with good beam quality at the most challenging wavelengths, such as the yellow spectral region. Moreover, one of their major benefits is the compact design, which is particularly important for applications.

Potential applications for VECSELs are manifold and include fields such as medicine, astronomy and quantum optics research. This thesis is concerned with the medical applications, and particularly focuses on dermatologic applications requiring yellow lasers. The yellow spectral range is challenging for any laser technology, which is why not that many yellow lasers exist on the laser market. The first main objective of this thesis was to demonstrate frequency converted yellow-orange-red VECSELs in laboratory set-ups. This was followed by the development of a fully functional yellow laser based on VECSEL-technology and designed for medical use. Finally, the work was focused on performing a clinical trial designed to test the feasibility of VECSEL-technology in a dermatologic medical application.

As a result of this thesis work, we have demonstrated record high output powers from laboratorybased VECSELs: 20 W at 585 nm, 10 W at 615 nm and 72 W at 1180 nm. Moreover, the performed clinical trial showed that the developed yellow VECSEL system is at least as good as the traditionally used laser in the treatment of vascular lesions (specifically telangiectasia) in terms of the treatment efficacy. In addition, the treatment times were significantly shorter with the VECSEL system than with the traditional laser thanks to the fast scanning of the light application device. With further improvements arising from the full exploitation of the laser’s power reserve, the system has the potential to be a breakthrough in the treatment of vascular-related skin conditions.