Improved wavelength meter calibration in near infrared region via Doppler-free spectroscopy of molecular iodine

A laser wavelength meter was calibrated to ±1 MHz 1 $$\sigma$$ using transitions in molecular iodine at around 700 nm, where precise experimental measurements of iodine lines are sparse. Two saturation absorption spectroscopy systems were used to measure and characterize the R(118)(2-8) a10, R(54)(3-9) a1, and P(48)(3-9) a15 hyperfine lines of molecular iodine near 700 nm. The transition frequencies were measured using a frequency comb and used to calibrate the wavelength meter. Additionally, the full hyperfine spectrum of the R(54)(3-9) transition was obtained and fitted using a theoretical model allowing for hyperfine coupling constants to be deduced, which agreed with theoretical values.