Abstract: There is provided an intracavity module (150) arranged to be replaceably-mounted inside a laser resonator cavity. The intracavity module comprises a first optical element (104), a second optical element (102) and a frequency conversion element (107). The frequency conversions element is arranged to receive light at a first frequency and output light at a second frequency. The first optical element is at least partially transmissive at the first frequency. The frequency conversion element is encapsulated by at least the first optical element and the second optical element.

Abstract: A method and apparatus for machining, or forming a feature in, a patterned silicon wafer includes removing portions of surface layers on the wafer using a first pulsed laser (4) beam with a pulse width between 1 ps and 1000 ps; and removing portions of bulk silicon (1) underlying the surface layers from the wafer using a second pulsed laser (5) beam with a wavelength between 200 nm and 1100 nm. Re-deposited silicon may be removed from the wafer by etching.