High-resolution two-photon spectroscopy of rubidium within a confined geometry

Abstract

We present two-photon spectroscopy of a thermal rubidium vapor confined to the hollow core of a photoniccrystal fiber. Linewidths as narrow as 10 MHz were observed on the 5S 1/2 → 5D 5/2 transition enabling the hyperfine splitting of the excited state to be resolved. Very strong nonlinear absorption (>90%) was observed, with substantial absorption maintained over large detunings (9 GHz) from an intermediate state. These attributes make this system ideal for many frequency metrology and quantum optics applications.

Saturation of atomic transitions using subwavelength diameter tapered optical fibers in rubidium vapor

“….1) 10) 10 3 ) 10 5 ) 1) 10 2 ) 10 4 ) It should be noted that the P sat = 61 nW value measured in this way is comparable to a rough order of magnitude estimate of ∼ 100 nW obtained by using the nominal Rb saturation intensity of 1.6 mW/cm 2 [29] multiplied by the mode area seen in Figure 1, and modified by the ratio squared of the natural line width and the measured line widths of Figure 3. The saturation power can also be estimated by measuring the powerbroadened line width; this technique has recently been used in closely related PBGF systems [19,30].…”

High-efficiency cross-phase modulation in a gas-filled waveguide

“…In practice, engineering the atomic dipole moment is difficult, however, the advent of HC-PCF enables constriction of the transverse dimensions of the optical field to several microns over arbitrarily long distances [26][27][28]. In our experiment we achieve an extended, and strong, light-atom interaction using an HC-PCF to confine both an optical field and Rb vapor within the fiber's 45-μm-diameter hollow core [29]. The fiber's kagome lattice cladding [the cross section shown in Fig.…”

“…The frequency detuning from the intermediate state is given by i = ω gi − ω 780 , and the two-photon detuning e = ω ge − (ω 780 + ω 776 ), where ω jk denotes the |j → |k transition frequency. The |g → |e transition was excited using a Dopplerfree configuration [31], providing both strong light-atom interaction (absorption >70% for on-resonance pump laser powers >5 μW) and a narrow linewidth ( e ≈ 10 MHz) [29]. These attributes make this transition ideal for cross-phase modulation experiments, as one can operate at a small detuning which provides simultaneous high interaction but small absorption.…”

Two-color rubidium fiber frequency standard

“…A detuning of Δ ≈ 2 GHz was used which, when compared to the single laser 778 nm based standards [6,7] with Δ ≈ 1 THz, provided a 10 8 enhancement in transition rate [10]. The two-photon transition displayed a spectral full-width at half-maximum of 10.4 MHz, limited predominantly by transit time broadening in combination with residual Doppler and magnetic field broadening [11]. At typical driving powers used here, the transition exhibited ≈5% absorption of the 780 nm laser within the HC-PCF.…”