Laser modulation for coagulation

An apparatus (100) comprising:

• a pump module (104) providing pump energy;
• a resonator (106) comprising:
• a gain medium (102)receiving the pump energy from the pump module and producing light;
• at least two at least partially reflective surfaces (110, 156, 158, 160, 162) reflecting light produced by the gain medium back toward the gain medium;
• a variable light attenuator (152) receiving light produced by the gain medium;
• a controller (187) that controls the amount of light attenuated by the variable light attenuator such that the apparatus emits windows (306, 308, 310) of pulses of laser light at spaced time intervals, each window containing a plurality of pulses of laser light and each interval (326, 327) between windows being larger than an interval (318) between pulses within a window, the duration (324) of the windows and the duration (328) of the intervals between windows being such that the emitted windows of pulses (320, 322) of laser light heat tissue to a temperature that causes coagulation.