Generation of 10 fs Ti:sapphire laser at repetition rate of 525 MHz and measurement of carrier-envelope phase frequency

This paper presents a Kerr-lens mode-locked Ti：sapphire laser at the repetition rate of 525 MHz, stable laser pulse as short as 10 fs with average output power of 480 mW is obtained. By injecting the pulse into photonics crystal fibre, octave-spanning spectrum covered from 500 to 1050 nm is generated, carrier-envelope phase frequency with signal-to- noise ratio of 31dB is measured, which paves the way for the generation of a compact frequency comb.

Carrier-envelope phase measurement using plasmonic-field-enhanced high-order harmonic generation of H atom in few-cycle laser pulses

We investigate the plasmonic-field-enhanced high-order harmonic generation（HHG） of H atom driven by few-cycle laser pulses, by solving the time-dependent Schr？dinger equation（TDSE）. Compared with the homogeneous field, HHG spectra generated by inhomogeneous field exhibit two-plateau structure. We analyze the origin of the two plateaus by using the semiclassical trajectory method. Our results from both classical and TDSE simulations show that the cutoffs of the two plateaus are dramatically affected by the carrier-envelope phase（CEP） of laser pulse in the inhomogeneous field, even for a little longer pulse. Thus, we can determine the CEP of driving laser based on the cutoff position of HHG generated in the inhomogeneous field.

Carrier-Envelope Phase-Dependent Atomic Coherence and Its Detection Scheme

The carrier-envelope phase （CEP） of few-cycle laser pulses is shown to have profound effects on the bound- state atomic coherence even in the weak-field regime where ionizations hardly take place, and a simple scheme is proposed to measure such CEP-dependent atomic coherence.

Carrier-envelope phase effects for a dipolar molecule interacting with ultrashort laser pulse

In this paper the phase-dependent features of ultrashort laser pulse resonant propagation in a two-level dipolar molecule are demonstrated by solving full Maxwell-Bloch equations. The electronic properties of dipolar molecule 4-trans-[p-（N, N-Di-n-butylamino）-p-stilbenylvinyl] pyridine （DBASVP） molecule, one-dimensional asymmetric organic molecule, is calculated by density functional theory at ab initio level. The numerical results show that the carrier propagation and the spectrum evolution of the pulse are sensitive to its initial phase and the phase sensitivity is more obvious for larger area pulse. The phase-dependent feature is more evident in dipolar molecule because the permanent dipole moment makes the nonlinear effects stronger.

Carrier-envelope phase effects on high-harmonic generation driven by mid-infrared laser field

The influence of the carrier-envelope phase on high-harmonic generation is investigated, both experimentally and theoretically, for three different interaction gas media, driven by mid-infrared, few-cycle and CEP-stabiUzed laser pulses. Different patterns of harmonic spectra with varying CEP for the three interaction gas media are observed. Furthermore, in comparing our experiment results to the previous works driven by near-infrared laser pulses, different phenomena are found. Through numerical simulation, we find that for the two different kinds of driving fields, i.e. mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics.

Carrier-Envelope Phase-Dependent Phase Matching of Terahertz Emission in Laser Plasma

We investigate off-axis phase-matched terahertz(THz)radiation in laser plasma pumped by few-cycle laser pulses.We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse’s focal carrier-envelope phase(CEP).Ring-like profiles of THz radiation are obtained at CEP values of 0.5πand 1.5π,due to the inversely symmetric local THz waveforms emitted before and after laser focus.Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.

Monolithic CEO-stabilization scheme-based frequency comb from an octave-spanning laser

We demonstrate a carder-envelope phase-stabilized octave-spanning oscillator based on the monolithic scheme. A wide output spectrum extending from 480 nm to 1050 nm was generated directly from an all-chirped mirror Ti：sapphire laser. After several improvements, the carder-envelope offset （CEO） beat frequency accessed nearly 60 dB under a reso- lution of 100 kHz. Using a feedback system with 50-kHz bandwidth, we compressed the residual phase noise to 55 mrad （integrated from 1 Hz to 1 MHz） for the stabilized CEO, corresponding to 23-as timing jitter at the central wavelength of 790 nm. This is, to the best of our knowledge, the smallest timing jitter achieved among the existing octave-spanning laser based frequency combs.

All optical method for measuring the carrier envelope phase from half-cycle cutoffs

An all optical method is demonstrated for measuring the carrier-envelope phase （CEP） of few-cycle laser pulses. It is found that, in the few-cycle regime, the high harmonic spectrum generated from asymmetric molecules shows several half-cycle cutoffs that change their positions as the CEP varies. Such half-cycle cutoffs represent the fingerprint of different quantum trajectories and the waveform of the driving pulse. In this case, the CEP can be accurately measured from the half-cycle cutoffs.

Asymmetry in the Strong-field Photodetachment of H- by Linearly Polarized Few-cycle Pulses

Photodetachment of H- irradiated by linearly polarized few-cycle laser field is investigated by time-dependent SchrSdinger equation numerically. The photo-electron left-right asymmetry parameter as a function of carrier-envelop （CE） phase of few-cycle pulses is attained. We confirm the asymmetry of photoelectron distribution in H- photodetachment and find that the maximal asymmetry parameter of H- is equal to that of H atom under the same conditions but the corresponding CE phases are quite different. Thus a CE phase shift appears. Compared to that of H atom and field free electron, the zero asymmetry CE phase shift is sensitively affected by Coulomb field. The Coulomb effect on the asymmetry of H- photodetachment mainly behaves in the CE phase shift of H- instead of the amplitude of asymmetry parameter curve.

Isolated attosecond pulse generation with few-cycle two-color counter-rotating circularly polarized laser pulses

Most of the schemes for generating isolated attosecond pulses（IAP） are sensitive to the carrier-envelope phase（CEP）of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized（TCCRCP） laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.

High-Conversion-Efficiency and Broadband Tunable Femtosecond Noncollinear Optical Parametric Amplifier

We build a compact high-conversion-efficiency and broadband tunable noncollinear optical parametric amplifier （OPA） in the infra-red （IR） pumped by a femtosecond Ti：sapphire CPA laser. The OPA consists of an internal seed of white-light continuum generator （WLG） and two noncollinear optical parametric amplifiers. The tunable wavelength range is from 1.2μm to 2.4μm for both signal and idle pulses. The total OPA efficiency in the last OPA stage reaches about 40% in a wider tunable spectral range （from 1.3μm to 1.7μm for signal pulse, from 1.5μm to 2.0 μm for idle pulse respectively）.