title: Development and optimization of a diode laser for photodynamic therapy.
abstract: OBJECTIVE
  This study demonstrated the development of a laser system for cancer treatment with photodynamic therapy (PDT) based on a 635 nm laser diode. In order to optimize efficacy in PDT, the ideal laser system should deliver a homogeneous nondivergent light energy with a variable spot size and specific wavelength at a stable output power.
  
  
  METHODS
  We developed a digital laser beam controller using the constant current method to protect the laser diode resonator from the current spikes and other fluctuations, and electrical faults. To improve the PDT effects, the laser system should deliver stable laser energy in continuous wave (CW), burst mode and super burst mode, with variable irradiation times depending on the tumor type and condition.
  
  
  RESULTS
  The experimental results showed the diode laser system described herein was eminently suitable for PDT. The laser beam was homogeneous without diverging and the output power increased stably and in a linear manner from 10 mW to 1500 mW according to the increasing input current. Variation between the set and delivered output was less than 7%.
  
  
  CONCLUSIONS
  The diode laser system developed by the author for use in PDT was compact, user-friendly, and delivered a stable and easily adjustable output power at a specific wavelength and user-set emission modes.
authors.affiliation: Department of Biomedical Engineering, College of Medicine, Chungnam National University, Daejeon, Korea.
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Lim
keywords: Photodynamic Therapy; beam emission mode; beam stability; diode laser, beam homogeneity