Paraxial application of auxiliary devices with waveguide mediated laser irradiation for applications in medical biophotonics

Abstract

Laser-based medical applications offer minimally-invasive alternatives to traditional procedures; however, the simplistic method of open-air laser transmission poses ocular hazards and negative side effects, along with a fundamentally limited efficacy for patients of darker complexion due to strong optical absorption in the epidermis. Additionally, the traditional irradiation method also inhibits the incorporation of additional technologies that might otherwise enhance therapeutic effects or provide diagnostic benefits, as doing so would otherwise occlude the laser beam path. The research presented herein addresses each of these considerations individually, first by transmitting laser light into tissue through direct contact with a selective-release waveguide, and thereafter incorporating auxiliary equipment on its rear face. Metal clad planar optical waveguides are demonstrated for the transmission of laser light into samples of porcine skin through direct transmission, governed by scaling evanescent leaking through a designated active area by controlling thin film thickness. In one manifestation, an ultrasonic pulser was incorporated to modulate tissue optical properties and thereby improve transmission of light through epidermal and dermal tissues by increasing forward anisotropy; whereas in another, a high frequency ultrasonic transducer was incorporated to detect photoacoustically generated pressure waves to determine depth profiles of chromophores in skin as a foundation for clinical backward-mode photoacoustic tomography.