A laser 10 comprises a pump source 11, a resonator 13 including an etalon of gain material 15, and means 12 to focus the pump source 11 output onto one end 14 of the resonator 13 as a spot having a diameter in the range 50-150 .mu.m. The resonator 13 includes substantially parallel end faces 14,19 having a relative taper better than 0.25 milliradians, and the end faces 14,19 are substantially free of scratches greater than 10 .mu.m in size and pits greater than 5 .mu.m in size. A thermally induced microlens 22 is formed at the surface 14 of the gain material 15.