A
catheter enables real-time light measurements, for example, without limitation, diffuse reflectance,
fluorescence, etc., from
biological materials, such as tissue (including blood), while performing
RF ablation. The
catheter tip design isolates illumination and collection paths such that light exits the
catheter tip and travels through the tissue of interest (e.g., cardiac tissue or blood) before returning to the catheter tip. Such a design advantageously avoids saturation of the
optical detector, and ensures
diffusion of the illumination light within the medium of interest. The catheter has a catheter body and a tip
electrode. The tip
electrode has an exterior shell, an inner layer of diffuse material and a hollow cavity, wherein the inner layer is configured to transmit light outside the tip
electrode to a tissue via a set of illumination openings in the shell wall and the hollow cavity is configured to receive light from the tissue via a set of collection openings in the shell wall and the inner layer. An inner surface of the inner layer has a reflective
coating to isolate light injected into the inner layer from light collected in the hollow cavity. There are a first optical
waveguide extending between the catheter body and the tip electrode to inject light into the inner layer and illuminate the tissue, and a second optical
waveguide extending between the catheter body and the tip electrode to collect the recaptured light in the hollow cavity.