High-precision 3D surface topography measurement using high-stable multi-wavelength digital holography referenced by an optical frequency comb

High-stable, two-wavelength, digital holography referenced by an optical frequency comb is presented. The technique is demonstrated by using optical waves from an external cavity laser diode phase-locked to a mode-locked Er-doped fiber comb laser light. The mixed beat signal is stabilized at 30 MHz by a sensitive proportional integral derivative controller. The tunable continuous-waves stabilized with frequency uncertainty of 5×10−11 are employed to investigate large stepped structures.