High power red diode laser systems for medical applications

Abstract

Diode lasers in the wavelength range of 630 to 740 nm are ideally suited for photodynamic therapy (PDT) and dermatological applications. Turnkey laser systems based on multiple discrete diode lasers offer significant advantages over other laser technologies, including dye, ruby and tunable lasers with respect to simplicity, cost, size reliability and maintenance. Applied Optronics Corp. has developed laser system platforms that permit the use of multiple diode lasers, each fiber-coupled to a single emitter, wired in series and mounted in a sealed aluminum module with its fiber bundle exiting and terminating in an SMA 905 connector. Low numerical aperture bundle fibers with core diameters less than 100 /spl mu/m permit the use of a large number of individually selected diode lasers to be used while maintaining a tight bundle packing ratio. The bundle output is re-imaged through an optical relay to decrease spot size while increasing numerical aperture. The laser system can use of wide variety of standard 400-1,000 micron, NA 0.37 PDT diffuser and other fibers. For PDT applications, light of a specific wavelength that is highly absorbed by a photosensitizer drug (dye) is required for optimal efficacy. Activation of the photosensitizer causes the release of singlet oxygen radicals that cause cell death. The photosensitizer is selectively absorbed by rapidly reproducing or abnormal cells (e.g., cancer cells) and, if a lesion or tumor can be exposed to the specific wavelength of light required, a cancerous tumor can be eliminated while preserving normal tissue. PDT has been largely successful as a treatment for cancer and pre-cancerous conditions in the lung, esophagus, oral cavity and skin. PDT is also being investigated for use in noncancerous treatment in ophthalmology for age related macular degeneration.