Saturated Optical Absorption by Slow Molecules in Hollow-Core Photonic Band-Gap Fibers

Abstract

We report on saturated absorption in a hollow-core photonic band-gap fiber filled with 12C2H2 molecules. We find that slow molecules provide a major contribution to the signal in the limit of low optical power and low pressure where the signal deviates significantly from the usual Lorentzian line shape. In particular, we observe a linewidth reduction of about 3 times as compared to the transit-time limited linewidth.

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

“…The long-term performance (τ ≥ 100 s) confirms the remarked difference between the C7 S and the other fibers: the multimode fibers follow the same trend (increased instability), while the C7 S presents an instability below 4 × 10 −12 for 1 < τ < 10 4 s. In the short term (τ < 100 s), the instability is inversely proportional to the MFD: the noise of the locked-laser depends on the slope of the error signal produced for locking, which is inversely proportional to the linewidth (FWHM) of the transition addressed. The linewidth is dominated by the transit-time broadening caused by the small beam diameter [20,21]. The measured instability confirms this effect within the experimental uncertainties, except for the PM fiber, since the MFD of the C7 PM is larger than the C7 S. The second phase of the test could help to clarify this unexpected performance.…”

“…As previously mentioned, the transit-time broadening is the major limiting factor for SAS in HC fibers, because the mode field diameter (MFD) is one order of magnitude smaller than what is typically used in bulk vapour cell systems. This effect is inversely proportional to the MFD and the FWHM contribution is about 15 to 30 MHz, depending on the fiber tested [20,21].…”

“…Taking into account the transit-time and the pressure broadening effect, the FWHM for the fiber considered is Γ 0 ≈ 26 MHz [20,21]. Depending on the I i j , Δν i j and Γ 0 , the maximum of the line-shape I(ν) could experience a shift (Δν TOT ).…”

Slow-light enhanced absorption in a hollow-core fiber

“…Such a mode has been recently proposed for slow-light enhanced absorption [17], which could be interesting in the context of previous studies of gases infiltrated in hollow-core fibers [18,19]. The right panel of Fig.…”

Cladding defects in hollow core fibers for surface mode suppression and improved birefringence

“…fiber optic gyroscopes and gas spectroscopy [1,2]. Even though they offer unique properties, like very high optical depth [3] and low non-linearity, they also show some limitations.…”