Karl A. Tillman

A phase-stabilized carbon nanotube fiber laser frequency comb

A frequency comb generated by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber is phase-stabilized for the first time. Measurements of the in-loop phase noise show an integrated phase error on the carrier envelope offset frequency of 0.35 radians. The carbon nanotube fiber laser comb is compared with a CW laser near 1533 nm stabilized to the nu(1) + nu(3) overtone transition in an acetylene-filled kagome photonic crystal fiber reference, while the CW laser is simultaneously compared to another frequency comb based on a Cr:Forsterite laser. These measurements demonstrate that the stability of a GPS-disciplined Rb clock is transferred to the comb, resulting in an upper limit on the locked combs frequency instability of 1.2 x 10(-11) in 1 s, and a relative instability of <3 x 10(-12) in 1 s. The carbon nanotube laser frequency comb offers much promise as a robust and inexpensive all-fiber frequency comb with potential for scaling to higher repetition frequencies.

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.

Phase-stabilized Prism-based Cr:forsterite Laser Frequency Comb for Absolute Frequency Measurements

A prism-based Cr:forsterite frequency comb is stabilized, with a repetition rate of 116 MHz. The flexibility of the prism-based system aids in achieving the carrier-envelope-offset frequency (f0) beat note width of ~1.5 MHz.

Stability of an acetylene frequency reference inside kagome structured hollow-core photonic crystal fiber

A continuous-wave laser has been stabilized to an acetylene transition inside kagome photonic crystal fiber. Stability as measured with a carbon nanotube fiber laser frequency comb is better than 1×10⁻¹¹ at 10 s.

Significant carrier envelope offset frequency linewidth narrowing in a prism-based Cr:forsterite frequency comb

We report a dramatic reduction in the linewidth of the carrier envelope offset frequency of a frequency comb generated by a femtosecond prism-based Cr:forsterite laser due to changes in the wavelength-dependent intracavity loss.

Stability of Optical Frequency References Based on Acetylene-Filled Kagome-Structured Hollow Core Fiber

A fiber laser at 1532 nm is stabilized to a sub-Doppler feature in acetylene inside hollow core kagome structured photonic crystal fiber. Short term stability is evaluated by beating against a Cr:forsterite laser-based frequency comb.

Carrier-envelope offset frequency dynamics in a self-referenced prism-based Cr: forsterite frequency comb

Carrier-envelope offset frequency (f0) dynamics of a prism-based modelocked Cr:forsterite laser are investigated in the context of a self-referenced frequency comb. Ultimately, this comb will be used in developing acetylene-filled fibers for portable frequency references.

Idler-resonant tandem femtosecond optical parametric oscillator operating at 2.3/spl mu/m

In a tandem optical parametric oscillator (OPO) a quasiphasematched crystal is fabricated by cascading two or more gratings in series so that the light generated in the first grating undergoes further frequency conversion in the second grating and this approach should make it possible to obtain high-quantum-efficiency conversion from a near-infrared pump to a mid-infrared idler. Self-modelocked Ti:sapphire laser was used as pump source for OPO. The tuning and characterisation data from the OPO and its performance such as threshold and conversion efficiency is discussed.In a tandem optical parametric oscillator (OPO) a quasiphasematched crystal is fabricated by cascading two or more gratings in series so that the light generated in the first grating undergoes further frequency conversion in the second grating and this approach should make it possible to obtain high-quantum-efficiency conversion from a near-infrared pump to a mid-infrared idler. Self-modelocked Ti:sapphire laser was used as pump source for OPO. The tuning and characterisation data from the OPO and its performance such as threshold and conversion efficiency is discussed.