Shaping Of Ultrashort Laser Pulses Research Articles

Optimal control of ultrafast selection.

Optimal laser control for ultrafast selection of closely lying excited states whose energy separation is smaller than the laser bandwidth is reported on the two-photon transition of atomic cesium; Cs(6S-->7D(J), J=5/2 and 3/2). Selective excitation was carried out by pulse shaping of ultrashort laser pulses which were adaptively modulated in a closed-loop learning system handling eight parameters representing the electric field. Two-color fluorescence from the respective excited states was monitored to measure the selectivity. The fitness used in the learning algorithm was evaluated from the ratio of the fluorescence yields. After fifty generations, a pair of nearly transform-limited pulses were obtained as an optimal pulse shape, proving the effectiveness of the "Ramsey fringes" mechanism. The contrast of the selection ratio was improved by approximately 30% from the simple "Ramsey fringes" experiment.

Spectrum-Holographic Formation of Fine Etching Patterns on a Silicon Surface with Pulse-Shaped Femtosecond Laser Pulses

We demonstrate a novel method of material processing to create flexible periodic structures using temporal pulse shaping of ultrashort laser pulses and spectral interferometry. This scheme is based on the idea that the interferometric fringe pattern at a Fourier spectral plane can be varied by programming temporal amplitude, relative phase and the interval of two collinearly incident pulses. Various periodical patterns are formed on a silicon surface located at the Fourier plane with laser ablation.

Adaptive Shaping of Ultrashort Laser Pulses and Its Application for Photo Excitation.

Fourier shaping of ultrashort laser pulses can offer additional functions to mode-lock lasers, and opens upvarious applications, including optical information processing, coherent spectroscopy, and quantum molecularcontrol. Furthermore, using light waves whose temporal aspects can be almost-arbitrarily programmed, wecan introduce optimization algorithms into the temporal domain of optical systems and even into quantumsystems. In this tutorial review, first, basic concept of Fourier pulse shaping is described, then, special emphasisis placed on adaptive shaping for controlling unknown light-matter interactions.

Preface for Topical Papers on Characterization and Shaping of Ultrashort Laser Pulses

Preface for Topical Papers on Characterization and Shaping of Ultrashort Laser Pulses

Pulse Shaping of Ultrashort Laser Pulses with Nonlinear Optical Crystals

We present a detailed description of the pulse shaping of ultrashort laser pulses with nonlinear optical crystals by introducing a time delay between two fundamental pulses. We demonstrate that the frequency reconversion process from a second-harmonic pulse to fundamental pulses will play an important role in fundamental pulse compression and train pulse generation. A collinear type II potassium dihydrogen phosphate (KDP) crystal can be used to achieve complete pulse shaping for a 1053 nm wavelength. Under conditions of a 50 GW/cm2 fundamental intensity, a 1.0 ps fundamental pulse duration and a 0.7 ps delay time, the second-harmonic pulse can be compressed to 0.14 ps. In addition, the fundamental pulse can be compressed to 0.3 ps by introducing an intensity unbalance into the two fundamental pulses. Furthermore, the train pulse can be generated by increasing the fundamental intensity over 20 GW/cm2. A train pulse with three 0.1 ps individual pulses with a 2.5 THz frequency interval can be generated for a 100 GW/cm2 fundamental intensity. We also demonstrate that pulse shaping with a noncollinear type I BBO crystal can be achieved at wavelengths near 800 nm.

Characterization of short-pulse oscillators by means of a high-dynamic-range autocorrelation measurement

A high-dynamic-range autocorrelation technique was used to characterize the temporal pulse shape of ultrashort laser pulses produced from four separate oscillators. These lasers included two Kerr-lens mode-locked Ti:sapphire oscillators as well as a Nd:glass and a Ti:sapphire oscillator, each passively mode locked by an antiresonant Fabry-Perot semiconductor saturable absorber. It was shown that the Nd:glass oscillator supported a pulse that was temporally clean over 8 orders of magnitude.

Measurement of ultrashort laser pulses

A proposal for measuring the pulse shape of ultrashort laser pulses is described. The proposed method consists of a Gamo triple intensity-interferometer to measure the triple-correlation function of the light pulses. A subsequent signal processing algorithm is used to reconstruct the true shape of the light pulses out of their triple-correlation function. The suggested method is quite insensitive to noise, as shown by means of computer simulations.