High-accuracy frequency atlas of 13C2H2 in the 1.5 μm region

Abstract

A pair of 1.5 μm semiconductor laser frequency standards have been developed for optical telecommunications use, stabilised to Doppler-free transitions of the ν1 + ν3 and ν1 + ν2 + ν4 + ν5 combination bands of 13C2H2. The Allan deviation σ/f for a laser locked to line P(10) of the former band follows a slope of 1.6 × 10−12τ−1/2, reaching a minimum of 5.7 × 10−14 at τ = 4000 s. The absolute frequencies of 61 lines of the ν1 + ν3 band and 43 lines of the ν1 + ν2 + ν4 + ν5 band, covering the spectral region 1520 nm to 1552 nm, have been measured by use of a combined frequency chain and femtosecond comb, together with a passive optical frequency comb generator. The mean uncertainties for the line frequencies within each band are 1.4 kHz for the ν1 + ν3 band and 1.9 kHz for the ν1 + ν2 + ν4 + ν5 band, representing improvements on the precision of previously published data by factors of 100 and 104, respectively. Improved values of the rotational constant B″ and centrifugal distortion coefficients D″, H″ and L″ of the vibrational ground state are presented.