Acetylene frequency references in gas-filled hollow optical fiber and photonic microcells

Abstract

Gas-filled hollow optical fiber references based on the P(13) transition of the ν1+ν3 band of 12C2H2 promise portability with moderate accuracy and stability. Previous realizations are corrected (<1σ) by using proper modeling of a shift due to line-shape. To improve portability, a sealed photonic microcell is characterized on the 12C2H2 ν1+ν3 P(23) transition with somewhat reduced accuracy and stability. Effects of the photonic crystal fiber, including surface modes, are explored. Both polarization-maintaining (PM) and non-PM 7-cell photonic bandgap fiber are shown to be unsuitable for kilohertz-level frequency references.

Optical frequency standard using acetylene-filled hollow-core photonic crystal fibers

“…The performance achieved improves previously published results [12,15] for gas-filled HC fibers both in terms of frequency stability and lock-point repeatability, reducing the gap with respect to the performance achieved with bulk glass cells [7].…”

“…Previously published works ascribe this effect to the presence of high order modes (HOMs) [12], surface modes [15] inside the band gap or polarization instability between the pump and probe beams [16]. The mechanism ascribed to the lock-point inaccuracy presented in [12] suffers a lack of universality and it cannot explain some of the effects presented in these paper.…”

“…However, developing a portable and user-friendly optical frequency standard is not free of challenges; although fiber gas-filling and other main technical issues have already been characterized [14], targeting the most suitable fiber for this technology is still under debate. State of the art research suggest that kagome fibers produce better performance than more common hollow core photonic crystal fibers (HC-PCF), both in terms of lock-point repeatability and stability [12,15]. Limited transit-time broadening due to larger core size and absence of surface modes are the key-features of the kagome fibers.…”

S2 Measurement of Higher Order Mode Content in Low Loss Hypocycloid Kagomé Hollow Core Photonic Crystal Fiber

“…KHCFs can exhibit an extremely low overlap between the core guided light and the surrounding silica microstructured cladding, and thus offer ultralow nonlinearity and considerably higher damage thresholds as compared to solid fibers. Furthermore, the antiresonant guidance mechanism demonstrated by KHCFs enables fabrication of fibers with large core diameters (and correspondingly large mode field diameters (MFDs)), low group velocity dispersion and broad transmission bandwidths; these factors, in combination with this recent loss reduction, make these fibers excellent candidates for high power pulse delivery [1] and frequency standard [2] experiments. Despite 7 and 19 cell KHCF being implemented in experiments which typically require high modal purity, no thorough investigation of the modal content in this class of fibers has yet been reported to date.…”

Frequency-stabilized laser system at 1572 nm for space-borne CO2 detection LIDAR

“…However, the absorption of the 1572.0179 nm line is very weak, so in order to get enough absorption, the length of the reference cell should be very long (typically >10 m). During the last decade, gas-filled hollow-core fibers have been widely investigated and could be used to build the light, compact reference cells [15][16][17] . But, the surface and high-order modes exhibited in these fibers lead to higher power loss and wavelength-dependent coupling to core modes, causing strong multipath interference (MPI), which limited the frequency stability to the MHz level, which is insufficient for the CO 2 LIDAR application.…”