A. Baltuska

Optical pulse compression to 5 fs at a 1-MHz repetition rate

We report on the characterization and compression of the white-light continuum produced by injection of a 13-fs pulse from a cavity-dumped self-mode-locked Ti:sapphire laser into a single-mode fiber. Pulses as short as 5 fs were generated at repetition rates up to 1 MHz.

Autocorrelation measurement of 6-fs pulses based on the two-photon-induced photocurrent in a GaAsP photodiode

We experimentally characterize the two-photon response of a GaAsP photodiode by use of a femtosecond Ti:sapphire laser tuned below the diode bandgap. The photodiode is shown to be highly suitable for real-time second-order autocorrelation measurements of pulses as short as 6fs in duration and with energies as small as a few picojoules.

Second-harmonic generation frequency-resolved optical gating in the single-cycle regime

The problem of measuring broad-band femtosecond pulses by the technique of second-harmonic generation frequency-resolved optical gating (SHG FROG) is addressed. We derive the full equation for the FROG signal, which is valid even for single-optical-cycle pulses. The effect of the phase mismatch in the second-harmonic crystal, the implications of the beam geometry, and the frequency-dependent variation of the nonlinearity are discussed in detail. Our numerical simulations show that, under carefully chosen experimental conditions and with a proper spectral correction of the data, the traditional FROG inversion routines work well even in the single-cycle regime. The developed description of the SHG FROG signal was applied to measure the white-light continuum pulses in the spectral region of 500-1100 nm. The obtained spectral phase of these pulses served as a target function for the pulse compressor design. The pulses produced by compression around 800 nm were also characterized by SHG FROG. The resulting pulse duration measures 4.5 fs which corresponds to /spl sim/2.5 optical cycles.

Amplitude and phase characterization of 4.5-fs pulses by frequency-resolved optical gating

The technique of second-harmonic generation frequency-resolved optical gating is applied to measure the intensity and the phase of 4.5-fs pulses resulting from the fiber-compressed output of a cavity-dumped Ti:sapphire laser. Characterization of even shorter optical pulses by this method should also be feasible.

Frequency-resolved pump–probe characterization of femtosecond infrared pulses

A novel method for ultrashort IR pulse characterization is presented. The technique utilizes a frequency-resolved pump-probe geometry that is common in applications of ultrafast spectroscopy, without any modifications of the setup. The experimental demonstration of the method was carried out to characterize 70-fs IR pulses centered at 3 microm .

Sub-5-fs Pulses: Generation, Characterisation, and Experiments

We present a sub-5-fs 1-MHz-repetition-rate all-solid-state laser system based on the fibre-compression of the output of a cavity-dumped Ti:sapphire oscillator. Frequency-resolved optical gating is applied to measure precisely the phase correction needed for the compression, and to characterise the 4.5-fs pulses. The applications of the developed laser in nonlinear experiments on liquid-phase dynamics are discussed.

Rapid amplitude-phase reconstruction of femtosecond pulses from intensity autocorrelation and spectrum

Summary form only given. The retrieval of time-dependent intensity and phase of femtosecond laser pulses is a long standing problem. To date, frequency-resolved optical gating (FROG) is probably the most trustworthy pulse measurement method. However, it requires a substantial experimental and numerical involvement. This motivates the quest for other simpler high-fidelity pulse measuring techniques. We present a new method of deciphering the pulse structure from the intensity autocorrelation trace and the intensity spectrum. We show that such a set of data is sufficient to restore the intensity and phase of a femtosecond pulse except for the typical uncertainties concerning the time shift and direction. The main feature of the proposed method is its robustness and swift convergence. Unlike a two-step pulse reconstruction, our algorithm employs the time- and frequency-domain data simultaneously, which in general provides a much faster convergence.

Hydrated electron dynamics on a 5-fs timescale

We report on frequency-resolved pump-probe and photon echo experiments on the equilibrated aqueous electron using 5-fs pulses. All experiments exhibit a signature of wave packet dynamics attributed to librational motions of water molecules.

Frequency-resolved pump-probe for ultrashort pulse characterization

Summary form only given. In recent years, frequency-resolved optical gating (FROG) technique has been widely applied for ultrashort pulse characterization. A number of outstanding qualities such as experimental simplicity, uniqueness of the retrieved amplitude and phase, and independent data checks make FROG an invaluable tool in ultra-fast spectroscopy In this contribution we introduce a new member of the FROG family: frequency-resolved pump-probe (FRPP). Unlike optically heterodyne detected (OHD) FROG, which requires additional polarizers, FRPP employs unmodified pump-probe geometry widely used in ultrafast spectroscopic experiments. Furthermore, a FRPP trace carries both positive and negative values, which should substantially improve the noise stability of the retrieval procedure.

Ultrashort pulse characterization by frequency-resolved pump-probe

We present a novel method for measuring amplitude and phase of ultrashort optical pulses. The technique makes use of frequency-resolved pump-probe geometry that is widely used in femtochemistry and femtobiology. The experimental realization of the method is demonstrated.