Laser ablation catheters having expanded distal tip windows for efficient tissue ablation

A laser ablation catheter to ablate blockages in body lumens, comprising:

• a liquid filled waveguide including an elongate catheter body tube having an inner layer with a first index of refraction and an optical fluid disposed within an inner lumen of the elongate catheter body tube, with the optical fluid having a second index of refraction which is greater than the first index of refraction;
• and
• a distal optical window disposed in liquid sealed relation to a surface of the elongate catheter body tube at a distal end of the elongate catheter body tube, the distal optical window including:
• an insert segment which is disposed within the inner lumen of a distal section of the elongate catheter body tube, and
• an expanded segment which is disposed distally of the insert segment, which comprises a material configured to efficiently transmit optical energy for ablation of blockages in body lumens, which has an outer diameter which is greater than an outer diameter of the insert segment, and which has an axial length sufficient to allow optical energy expansion within the expanded segment.