Methods and Systems for Coherent Imaging and Feedback Control for Modification of Materials Using Dynamic Optical Path Switch in the Reference Arms

An apparatus, comprising:

• an optical imaging source that produces imaging light;
• a laser head configured to focus a processing laser beam onto a sample in a material modification process, and direct the imaging light to the sample such that the imaging light illuminates multiple reflective features of the sample that are different axial heights;
• an optical interferometer that produces a interferometry output based at least in part on imaging light that is reflected from the multiple reflective features;
• and
• an interferogram processor that processes the interferometry output to determine a depth of at least one reflective feature of the multiple reflective features.

A method, comprising:

• applying a processing laser beam to a sample in a material modification process;
• directing imaging light to the sample such that the imaging light illuminates multiple reflective features to the sample that are different axial heights;
• generating an interferometry output based at least in part on imaging light that is reflected from the multiple reflective features;
• and
• determining a depth of at least one reflective feature of the multiple reflective features based on the interferometry output.

A method, comprising:

• applying a processing laser beam to a sample in a material modification process;
• directing imaging light to the sample such that the imaging light illuminates at least one subsurface interface in the sample;
• generating an interferometry output based at least in part on imaging light that is reflected from the at least one subsurface interface;
• and
• controlling at least one of the processing laser beam and a processing laser source that generates the processing laser beam based on the interferometry output.