The safe therapeutic window for laser medicine tends to decrease as pulse length decreases. This problem is addressed by use of beam shapes and/or pulse shapes that improve temperature uniformity in the treated tissue. A beam shape with an adjustable on-axis intensity minimum improves spatial temperature uniformity in treated tissue. A pulse shape with a relatively intense early part (to set the temperature rise), followed by a less intense late part having decreasing intensity with time (to maintain a constant or nearly constant temperature rise) improves temporal temperature uniformity in the treated tissue. A therapeutic window (TW) of at least 3 is often required to provide a sufficient safety margin in practice. In one experiment, it was demonstrated that the minimum pulse length to provide a TW of 3 could be decreased from 20 ms to 10 ms following these principles.
