Second-harmonic generation for critical dimensional metrology

A system for characterizing a sample using second harmonic generation, the system comprising:

• a sample holder configured to support a sample;
• at least one optical source configured to direct a light beam onto said sample to produce second harmonic generation (SHG) signals;
• an optical detection system comprising at least one optical detector configured to receive the SHG signals emitted from said sample and generate detected SHG signals;
• one or more hardware processors in communication with the optical detection system, the one or more hardware processors configured to:
• receive at least one detected SHG signal;
• and
• determine a geometric feature of the sample or a variation in a geometric feature of the sample based on the at least one detected SHG signal.