A wire, comprising a shape memory alloy, is shaped to define a perimeter of an aperture having an adjustable size. The wire is responsive to current flow through the wire to vary the length of the wire, and thereby the length of the perimeter of the aperture. A controllable power supply is coupled to the wire, for supplying a controllable current through the wire to adjust its length, and thereby to adjust the size of the aperture. The aperture is suited for controlling transverse modes in a laser by controlling diffraction losses in the laser resonant cavity. Also, the shape memory alloy aperture is suitable for mounting within a sealed cavity laser.
A gas turbine engine component includes a wall portion with at least one compound cooling hole formed therein between an external surface of the component and an interior plenum. The at least one compound cooling hole includes a non-circular diffuser opening formed by a laser beam with a non-circular cross-sectional area, and a channel with a substantially circular cross-section connecting the diffuser opening and the interior plenum. The channel is also formed by the non-circular laser beam in the same laser drilling operation as the diffuser opening. The cooling hole further includes a transition point at which the compound hole begins to convert from a substantially non-circular cross-section to a substantially circular cross-section. The location of the transition point is controlled by positioning a focal point of the non-circular laser beam to undershoot the external surface of the component by a predetermined distance.
