Lia Matos

Self-Referenced 200 MHz Octave-Spanning Ti:Sapphire Laser with 50 Attosecond Carrier-Envelope Phase Jitter

Carrier-envelope phase stabilization of a 200MHz octave-spanning Ti:sapphire laser without external broadening is demonstrated. The individual comb lines spaced by 200MHz can conveniently be resolved using commercial wavemeters. The accumulated in-loop carrier-envelope phase error (integrated from 2.5 mHz to 10 MHz) using a broadband analog mixer as phase detector is 0.117 rad, equivalent to 50 attosecond carrier-envelope phase jitter at 800 nm.

Inelastic collision rates of trapped metastable hydrogen

We report the first detailed decay studies of trapped metastable (2S) hydrogen. By two-photon excitation of ultracold H samples, we have produced clouds of at least 5x10(7) magnetically trapped 2S atoms at densities greater than 4x10(10) cm(-3) and temperatures below 100 muK. At these densities and temperatures, two-body inelastic collisions of metastable atoms are evident. Experimental values for the total two-body loss rate constant are K-2=1.8(-0.7)(+1.8)x10(-9) cm(3) s(-1) at 87 muK and K-2=1.0(-0.5)(+0.9)x10(-9) cm(3) s(-1) at 230 muK. These results are in the range of recent theoretical calculations for the total 2S-2S inelastic rate constant. The metastable clouds were excited in a gas of ground-state (1S) hydrogen with peak densities reaching 7x10(13) cm(-3). From the one-body component of the metastable decay, we derive experimental upper limits for K-12, the rate constant for loss due to inelastic 1S-2S collisions.

Towards single-cycle optical pulses

Single-cycle optical pulses, the never-before-achieved regime, have a great potential for attosecond science and phase-sensitive nonlinear optics. To achieve single-cycle optical pulses by active synchronization, three major steps are required. Firstly, two very stable and broadband mode-locked lasers with overlapping spectra are necessary. Secondly, a tight timing synchronization with timing jitter under one-tenth of the synthesized pulsewidth has to be implemented. Finally, the carrier-envelope offset frequency lock between two lasers completes the coherent pulse synthesis process. In this thesis, the major ideas, techniques, and experimental results for single-cycle optical pulse synthesis are presented. A broadband Cr:forsterite laser mode-locked by a semiconductor saturable absorber is designed and implemented. The output spectrum spans from 1080 nm to 1500 nm range, and has a 3-dB bandwidth of 90 nm. This is the broadest spectrum from a prismless Cr:forsterite laser to our best knowledge, and corresponds to a sub-20 fs Fourier-transform limited pulsewidth. A new broadband output coupler is designed to optimize the output spectrum of an octavespanning Ti:sapphire laser. The resulting combined spectrum covers 1.5 octave from 600 nm to 1500 nm and has a strong overlap in 1100 to 1200 nm range, which enables a strong beat-note signal between the two lasers. A tight timing synchronization between the two lasers is achieved by balanced cross-correlation. The resulting timing jitter is 300 attoseconds, which is less than one-tenth of the synthesized pulsewidth. For a high-quality pulse synthesis, an ultra-broadband 50:50 beam splitter, a bandpass filter beam splitter, and a tapping beam splitter are designed with optical thin-film multilayer structures. A novel scheme for synchronization of an RF-signal to the pulse train of a mode-locked laser is proposed. Currently the isolation of cross-talk between two locking loops for repetition rate and carrier-envelope phase is under investigation, and it is expected to generate true singlecycle optical pulses in the near future. Future work will include full characterization of the synthesized pulses with SPIDER (spectral phase interferometry for direct electric-field reconstruction) and novel phase-sensitive nonlinear optic experiments. Thesis Supervisor: Franz X. Kaertner Title: Associate Professor of Electrical Engineering and Computer Science

Phase-coherent Spectrum from Ultrabroadband Ti:sapphire and Cr:forsterite Lasers Covering the Visible to the Infrared

Few-cycle optical pulses open up new possibilities to investigate various extreme light-matter interactions, which depend on the light electric-field oscillation itself, for example, high-harmonic generation (HHG) for extreme ultraviolet and soft X-ray pulse generation [1]. For further investigations and applications of such phase-sensitive phenomena, single-cycle optical pulse, comprised of only one cycle of the light oscillation, is currently pursued in many laboratories.

Carrier-envelope phase dynamics and noise analysis in octave-spanning Ti:sapphire lasers

The intensity-related carrier-envelope phase dynamics of octave-spanning Ti:sapphire lasers is investigated. Taking the laser gain dynamics into account, quantitative agreement between the measured and predicted carrier-envelope phase noise resulting from pump laser noise is achieved.

Solid-state lasers for frequency metrology

The unique properties of solid-state laser materials such as ultrawide bandwidth and long upper-state lifetimes enable unique tools for frequency metrology. We report on recent progress in femtosecond laser frequency combs from octave-spanning Ti:sapphire lasers and single-frequency microchip lasers.