| Photodynamic therapy (PDT) is a promising method of cancer treatment with minimal side effects. It uses a photosynthesizing drug (typically porfimer sodium) that becomes toxic after it is activated by 635 nm red light. The drug is administered to the patient 10--48 hours before the treatment. During that time the drug accumulates mainly in cancerous cells. The 635 nm red light illuminates the cancerous area, activating the drug that destroys the cancerous cells without damaging surrounding healthy tissues, and without the cumulative toxicity associated with ionizing radiation.; In this dissertation a new type of light delivery system for esophageal cancer treatment is proposed. This system uses semiconductor red laser diodes similar to the newly emerging systems that have largely come to replace huge and expensive gas lasers. However, in the proposed system, laser diodes are activated inside a balloon catheter that is inserted inside the patient's esophagus, in contradistinction to the fiber based light delivery systems being used now.; The proposed system is portable, selfcontained, and inexpensive. It combines most advantages of the up-to-date laser diode systems with some unique features. It provides the same, or even higher optical power than existing systems, since no fiber coupling is necessary. This system allows greater flexibility to adjust the lighting pattern to the size of the tumor by turning on and off individual lasers and laser sections.; The design of the system required a multidisciplinary study in many areas including diode laser design, optoelectronic packaging, heat transfer, optics and light scattering. The main problems solved in this work include: (i) the design and fabrication of a high power ridge waveguide laser array that can reliably provide the necessary amount of optical power at 635nm, (ii) design and construction of a package sufficiently small and flexible enough to fit the human esophagus, yet capable of providing mechanical strength and the necessary laser cooling, (iii) optimization of the laser array and the laser submount for efficient heat transfer, (iv) design of a scattering element that can convert a narrow laser beam into uniform lighting required for photodynamic therapy, (v) optimization of the scattering element for maximum scattering and minimum loss, and (vi) optimization of the package to achieve the maximum lighting uniformity and to avoid shadows. |
