Ultrastable laser array at 633 nm for real-time dimensional metrology

We describe a laser system for very-high-accuracy dimensional metrology. A sealed-cavity helium-neon laser is offset locked to an iodine-stabilized la ser in order to realize a secondary standard with higher power and less pha se noise. Synchronous averaging is employed to remove the effect of the fre quency modulation present on the iodine-stabilized laser. Additional lasers are offset locked to the secondary standard for use in interferometry. All servo loops are implemented digitally. The offset-locked lasers have intri nsic linewidths of the order of 2.5 kHz and exhibit a rms deviation from th e iodine-stabilized laser below 18 kHz. The amplitude noise is at the shot- noise limit for frequencies above 700 kHz. We describe and evaluate the sys tem in detail, and include a discussion of the noise associated with variou s types of power supplies. (C) 2001 American Institute of Physics.