Embodiments of a laser ablation system include a shaft, a balloon and a laser fiber. The shaft has a proximal end and a distal end. The balloon is attached to the distal end of the shaft, a portion of which is disposed within the balloon. A light dispenser at a distal end of the laser fiber is configured to deliver laser light through the balloon. A central axis of the balloon is aligned with a longitudinal axis of the shaft. The balloon has a variable transparency such that the transmission of laser light through the balloon is non-uniform along the central axis. Accordingly, an energy of laser light transmitted from the light dispenser through the balloon to the targeted tissue varies due to the variable transparency of the balloon.