Matthew C. Stowe

Direct frequency comb spectroscopy

We summarize recent developments in direct frequency-comb spectroscopy that allowed high-resolution, broad-bandwidth measurements of multiple atomic and molecular resonances using only a phase-stabilized femtosecond laser, opening the way for merging precision spectroscopy with coherent control.

Precise Control of Molecular Dynamics with a Femtosecond Frequency Comb

We present a general and highly efficient scheme for performing narrow-band Raman transitions between molecular vibrational levels using a coherent train of weak pump-dump pairs of shaped ultrashort pulses. The use of weak pulses permits an analytic description within the framework of coherent control in the perturbative regime, while coherent accumulation of many pulse pairs enables near unity transfer efficiency with a high spectral selectivity, thus forming a powerful combination of pump-dump control schemes and the precision of the frequency comb. Simulations verify the feasibility and robustness of this concept, with the aim to form deeply bound, ultracold molecules.

Control of Four-Level Quantum Coherence via Discrete Spectral Shaping of an Optical Frequency Comb

We present experiments demonstrating high-resolution and wide-bandwidth coherent control of a four-level atomic system in a diamond configuration. A femtosecond frequency comb is used to excite a specific pair of two-photon transitions in cold 87Rb. The optical-phase-sensitive response of the closed-loop diamond system is studied by controlling the phase of the comb modes with a pulse shaper. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.

Tapered semiconductor amplifiers for optical frequency combs in the near infrared

A tapered semiconductor amplifier is injection seeded by a femtosecond optical frequency comb at 780 nm from a mode-locked Ti:sapphire laser. Energy gains of more than 17 dB(12 dB) are obtained for 1 mW(20 mW) of average input power when the input pulses are stretched into the picosecond range. A spectral window of supercontinuum light generated in a photonic fiber has also been amplified. Interferometric measurements show sub-Hertz linewidths for a heterodyne beat between the input and amplified comb components, yielding no detectable phase-noise degradation under amplification. These amplifiers can be used to boost the infrared power in f-to-2f interferometers used to determine the carrier-to-envelope offset frequency, with clear advantages for stabilization of octave-spanning femtosecond lasers and other supercontinuum light sources.

High Resolution Atomic Coherent Control via Spectral Phase Manipulation of an Optical Frequency Comb

We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.