Laser annealing apparatus

A laser annealing apparatus, comprising:

• a laser oscillating structure to emit a first laser beam having a first wavelength and a first beam cross-section to a semiconductor substrate inside a chamber that includes an optical window;
• a laser oscillator to emit a second laser beam to the semiconductor substrate, the second laser beam having a second wavelength different from the first wavelength;
• a beam expanding telescope on an optical path for the second laser beam, the beam expanding telescope to expand a cross-section of the second laser beam to a second beam cross-section;
• a first power meter to measure energy of the second laser beam;
• and
• a second power meter to measure energy of a third laser beam, wherein the third laser beam is generated as the second laser beam is reflected by the semiconductor substrate and wherein an area of the first beam cross-section of the first laser beam that reached the semiconductor substrate is identical to an area of the second beam cross-section.