Apparatus and Method for Controlling Laser Processing of a Remote Material

Apparatus for controlling laser piercing of a remote material (10), which apparatus comprises: at least one piercing laser (1) for emitting laser radiation (2) for piercing the remote material (10), which laser radiation (2) is characterized by a first wavelength (16); a probe laser (3) for emitting a probe signal (4) for monitoring the piercing of the remote material (10); beam delivery optics (5) configured to direct the laser radiation (2) and the probe signal (4) onto the material (10); at least one detector (6) for detecting optical radiation (7) that is emitted or reflected by the material (10) in response to the probe signal (4); and an electronic filter (8) for filtering an electronic signal (9) emitted by the detector (6) in response to the detector (6) detecting the optical radiation (7); and the apparatus being characterized in that the probe laser (3) is configured such that the probe signal (4) is able to be modulated by a modulation signal (13); and the electronic filter (8) comprises a phase sensitive detector (14) which is configured to receive the electronic signal (9) and the modulation signal (13) and to provide phase sensitive detection of the electronic signal (9), which phase sensitive detection is used to improve a signal to noise ratio of an amplitude of the electronic signal (9), thereby enabling detection of a reduction in the amplitude of the electronic signal (9), which reduction is indicative of the laser radiation (2) piercing the remote material (10).