Ray tracing of optically modified fiber tips. 1: spherical probes

Area of Science:

• Medical Physics
• Optical Engineering
• Biomedical Optics

Background:

• Modified fiber tips are crucial for laser angioplasty procedures.
• Accurate prediction of beam profiles and irradiance is essential for effective treatment.
• Paraxial theory offers a simplified model but may not capture complex optical phenomena.

Purpose of the Study:

• To calculate beam profiles and spatial irradiance distributions of modified fiber tips used in laser angioplasty.
• To compare ray tracing computations with paraxial theory and experimental measurements.
• To evaluate the focusing capabilities of different fiber tip designs in various media.

Main Methods:

• Ray tracing simulations were employed to model beam propagation.
• Assumptions included uniform spatial and weighted angular irradiance distributions.
• Computations were validated against paraxial theory and experimental data in air and water.

Main Results:

• The position of maximum irradiance in water deviated from the paraxial focal point for ball-shaped and hemispherical fiber tips.
• Internal backward reflections and beam divergence limited the maximum irradiance increase.
• Beam focusing is expected to be minimal when fiber tips are in contact with tissue.

Conclusions:

• Ray tracing is a valuable tool for optimizing modified fiber tip designs, especially when paraxial theory is insufficient.
• Standard approximations do not accurately predict the optical performance of these fiber tips in relevant environments.
• Advanced modeling is necessary for the precise design of laser angioplasty fiber optics.