Shun Wu

10 kHz accuracy of an optical frequency reference based on (C2H2)-C-12-filled large-core kagome photonic crystal fibers

Saturated absorption spectroscopy reveals the narrowest features so far in molecular gas-filled hollow-core photonic crystal fiber. The 48-68 mum core diameter of the kagome-structured fiber used here allows for 8 MHz full-width half-maximum sub-Doppler features, and its wavelength-insensitive transmission is suitable for high-accuracy frequency measurements. A fiber laser is locked to the (12)C2H2 nu(1); + nu(3) P(13) transition inside kagome fiber, and compared with frequency combs based on both a carbon nanotube fiber laser and a Cr:forsterite laser, each of which are referenced to a GPS-disciplined Rb oscillator. The absolute frequency of the measured line center agrees with those measured in power build-up cavities to within 9.3 kHz (1 sigma error), and the fractional frequency instability is less than 1.2 x 10(-11) at 1 s averaging time.

Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism

The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of approximately 2 x 10(-11) at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3 x 10(-12) for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths.

Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber

We have isolated a single tooth from a fiber laser-based optical frequency comb for nonlinear spectroscopy and thereby directly referenced the comb. An 89 MHz erbium fiber laser frequency comb is directly stabilized to the P(23) (1539.43 nm) overtone transition of (12)C(2)H(2) inside a hollow-core photonic crystal fiber. To do this, a single comb tooth is isolated and amplified from 20 nW to 40 mW with sufficient fidelity to perform saturated absorption spectroscopy. The fractional stability of the comb, ~7 nm away from the stabilized tooth, is shown to be 6 × 10(-12) at 100 ms gate time, which is over an order of magnitude better than that of a comb referenced to a GPS-disciplined Rb oscillator.

Direct comb stabilization to a 12 C 2 H 2 -filled hollow-core fiber via single tooth saturated absorption spectroscopy

Toward an all-fiber system, an erbium fiber laser-based comb is directly stabilized to a ¹²C₂H₂ transition at 1539.4 nm. The comb fractional instability at 1532.8 nm is 6×10^-12 at 100 ms gate time.

Toward an all-fiber based optically referenced frequency comb

A potentially portable optical metrology system is demonstrated by using an acetylene-filled optical fiber frequency reference as an optical reference to a fiber-laser based frequency comb without an intracavity EOM.

Single-mode hollow-core fiber for portable acetylene sub-Doppler frequency reference

A newly-developed, single-mode hollow-core fiber is employed for saturated absorption spectroscopy in a molecular gas. Lack of surface modes, ease of angle splicing, and single-modedness make it promising for portable frequency references.

Acetylene-filled hollow-core kagome fiber toward portable frequency references

A CW fiber laser is stabilized to near-infrared transitions of ¹²C₂H₂ inside kagome fibers and characterized with a frequency comb. ±10 kHz accuracy is achieved, and performance in sealed photonics microcells is explored.

10 kHz accuracy spectroscopy in acetylene-filled hollowcore kagome fiber and improved linewidths

A CW fiber laser is stabilized to the P(13) ν1+ν3 transition of 12C2H2 inside large-core kagome fiber using FM spectroscopy techniques and characterized with a frequency comb. Improved line widths are explored.