The Role of Skew Rays in Biomedical Sensing

Hollow core waveguides are useful tools in biomedical optics both for transmission of radiation to the tissue to perform intervention and to sensing tissue optical parameters for diagnostics. These waveguides can also be used as an interaction chamber for sensing the presence and concentration of different aerosols and gases. To support the design and analyzing of such a device, we developed a computerized, ray tracing simulation. As aerosol particles tend to aggregate near the waveguide's wall, the role of skew rays (i.e., rays that follow a helical path inside the waveguide) is investigated here and compared with merdional rays, which “zig-zag” through the optical axis. To test quantitatively the sensing quality of different types of beam, a measure for the beam-sensing quality is developed. As first step, the validation of the simulation results is presented. Then, a compression between the sensing quality of Guassian, ring-like, and Bessel beam is made. These results allow the optimization of ray coupling to a hollow core waveguide-based, aerosol-sensing devices.