The advantages of the unsta ble resonator concept, when the necessary conditions are met then include Large and controllable. mode volume Controllable diffractive output coupling Good transverse mode discrimination automatically collimated output beams Ease of alignment and adjustment Efficient power extraction Good far-field beam patterns endThe advantages of the unstable resonator concept, when the necessary conditions are met, then include: • Large, and controllable, mode volume • Controllable diffractive output coupling • Good transverse mode discrimination • Automatically collimated output beams • Ease of alignment and adjustment • Efficient power extraction • Good far-field beam patterns end