Carrier-envelope Phase Control Research Articles

Grism compressor for carrier-envelope phase-stable millijoule-energy chirped pulse amplifier lasers featuring bulk material stretcher

We demonstrate compression of amplified carrier-envelope phase (CEP)-stable laser pulses using paired transmission gratings and high-index prisms, or grisms, with chromatic dispersion matching that of a bulk material pulse stretcher. Grisms enable the use of larger bulk stretching factors and thereby higher energy pulses with lower B-integral in a compact amplifier design suitable for long-term CEP control.

High-speed carrier-envelope phase drift detection of amplified laser pulses

An instrument for measuring carrier-envelope phase (CEP) drift of amplified femtosecond laser pulses at repetition rates up to the 100-kHz regime is presented. The device can be used for real-time pulse labeling and it could also enable single-loop CEP control of future high-repetition rate laser amplifiers. The scheme is demonstrated by measuring the CEP drift of a 1-kHz source.

Forty-photon-per-pulse spectral phase retrieval by shaper-assisted modified interferometric field autocorrelation

We retrieve the spectral phase of 400 fs pulses at 1560 nm with 5.2 aJ coupled pulse energy (40 photons) by the modified interferometric field autocorrelation method, using a pulse shaper and a 5 cm long periodically poled lithium niobate waveguide. The carrier-envelope phase control of the shaper can reduce the fringe density of the interferometric trace and permits longer lock-in time constants, achieving a sensitivity of 2.7×10(-9) mW(2) (40 times better than the previous record for self-referenced nonlinear pulse measurement). The high stability of the pulse shaper allows for accurate and reproducible measurements of complicated spectral phases.

Experimental observation of carrier-envelope-phase effects by multicycle pulses

We present an experimental and theoretical study of carrier-envelope phase (CEP) effects on the population transfer between two bound atomic states interacting with pulses consisting of many cycles. Using intense radio-frequency pulse with Rabi frequency of the order of the atomic transition frequency, we investigated the influence of CEP on the control of phase dependent multi-photon transitions between the Zeeman sub-levels of the ground state of $^{87}$Rb. Our scheme has no limitation on the duration of the pulses. Extending the CEP control to longer pulses creates interesting possibilities to generate pulses with accuracy that is better then the period of optical oscillations.

Carrier-envelope phase control using linear electro-optic effect

We present a new method to control the Carrier-Envelope Phase of ultra-short laser pulses by using the linear Electro-Optic Effect. Experimental demonstration is carried out on a Chirped Pulse Amplification based laser. Phase shifts greater than π radian can be obtained by applying moderate voltage on a LiNbO3 crystal with practically no changes to all other parameters of the pulse with the exception of its group delay. Time response of the Electro-Optic effect makes possible shaping at a high repetition rate or stabilization of the CEP of ultra short CPA laser systems.

Few‐optical‐cycle light pulses with passive carrier‐envelope phase stabilization

AbstractOne of the most advanced frontiers of ultrafast optics is the control of carrier‐envelope phase (CEP) ϕ of light pulses, which enables the generation of optical waveforms with reproducible electric field profile. Such control is important for pulses with few‐optical‐cycle duration, for which a CEP variation produces a strong change in the waveform, so that strongly nonlinear optical phenomena, such as multiphoton absorption, above‐threshold ionization and high‐harmonic generation become CEP‐dependent. In particular, CEP control is the prerequisite for the production of isolated attosecond pulses. Standard laser systems generate pulses that are CEP unstable; the CEP can be stabilized using either active or passive methods. Passive, all‐optical schemes rely on difference‐frequency generation (DFG) between two pulses sharing the same CEP: in this process the phases of the two pulses add up with opposite signs, leading to cancellation of the shot‐to‐shot CEP fluctuations. This paper presents an overview of passive CEP stabilization schemes, starting from the basic concepts and progressing to the details of the practical implementations of the idea. The passive approach allows the generation of CEP‐controlled few‐optical‐cycle pulses covering a very broad range of parameters in terms of carrier frequency (from visible to mid‐IR), energy (up to several mJs) and repetition rate (up to hundreds of kHz)

Calculation of the probability of photoprocesses induced by ultrashort electromagnetic pulses

An expression for the total probability of photoprocesses induced by ultrashort electromagnetic pulses in terms of the excited transition cross-section has been derived by using perturbation theory. The expression obtained is valid for any radiation spectral width and for various types of transition: bound-bound and bound-free. By way of illustration the excitation of a two-level system by an ultrashort pulse with a controlled carrier-envelope phase and the photoionization of a hydrogen atom under the action of a sequence of two-cycle electromagnetic pulses are considered.

Carrier-Envelope Phase Control of Few-Cycle Parametric Chirped-Pulse Amplifier

We demonstrate the carrier-envelope phase (CEP) stabilization of the 5-fs, multi-mJ parametric chirped-pulse amplification system. The slow CEP drift induced in the parametric chirped-pulse amplifier was precompensated in the phase-control loop of the seed oscillator, and arbitrary CEP control of the whole system was realized over a few hours. We discuss several possible origins that induce CEP noise of the amplified pulses.

Closed-loop carrier-envelope phase stabilization with an acousto-optic programmable dispersive filter

We demonstrate arbitrary carrier-envelope (CE) phase control of femtosecond laser pulses by an acousto-optic programmable dispersive filter (AOPDF), with an accuracy better than pi/100 at a repetition rate of 1 kHz. We also demonstrate, for the first time to the best of our knowledge, 15 Hz closed-loop CE phase stabilization using an AOPDF inside a 1 kHz chirped pulse amplifier to correct for slow CE phase drifts.

Carrier-envelope phase stabilization and control of 1 kHz, 6 mJ, 30 fs laser pulses from a Ti:sapphire regenerative amplifier

Carrier-envelope (CE) phase stabilization of a two-stage chirped pulse amplifier laser system with regenerative amplification as the preamplifier is demonstrated. The CE phase stability of this laser system is found to have a 90 mrad rms error averaged over 50 laser shots for a locking period of 4.5 h. The CE phase locking was confirmed unambiguously by experimental observation of the 2pi periodicity of the high-order harmonic spectrum generated by double optical gating.

Carrier-envelope phase stabilization and control using a transmission grating compressor and an AOPDF

Carrier-envelope phase (CEP) stabilization of a femtosecond chirped-pulse amplification system featuring a compact transmission grating compressor is demonstrated. The system includes two amplification stages and routinely generates phase-stable (approximately 250 mrad rms) 2 mJ, 25 fs pulses at 1 kHz. Minimizing the optical pathway in the compressor enables phase stabilization without feedback control of the grating separation or beam pointing. We also demonstrate for the first time to the best of our knowledge, out-of-loop control of the CEP using an acousto-optic programmable dispersive filter inside the laser chain.

Isochronic carrier-envelope phase-shift compensator

A concept for orthogonal control of phase and group delay inside a laser cavity by a specially designed compensator assembly is discussed. Similar to the construction of variable polarization retarder, this assembly consists of two thin wedge prisms made from appropriately chosen optical materials. Being shifted as a whole, the assembly allows changing the phase delay with no influence on the cavity round-trip time, whereas relative shifting of the prisms enables adjustment of the latter. This scheme is discussed theoretically and verified experimentally, indicating a factor 30 reduction of the influence on the repetition rate compared to the commonly used silica wedge pair. For a 2pi adjustment of the carrier-envelope phase shift, single-pass timing differences are reduced to the single-femtosecond regime. With negligible distortions of timing and dispersion, the described compensator device greatly simplifies carrier-envelope phase control and experiments in extreme nonlinear optics.

5-fs, multi-mJ, CEP-locked parametric chirped-pulse amplifier pumped by a 450-nm source at 1 kHz

We report on the development of an optical parametric chirpedpulse amplifier at a 1-kHz repetition rate with a 5.5-fs pulse duration, a 2.7-mJ pulse energy and carrier-envelope phase-control. The amplifier is pumped by a 450-nm pulse from a frequency-doubled Ti:sapphire laser.

Electron dynamics in molecules: a new combination of nuclear quantum dynamics and electronic structure theory

An efficient approach to describe electron dynamics in molecules is developed which exploits quantum dynamics and quantum chemistry in a new way. The photodissociation of D+2 which can be controlled via the carrier-envelope phase of an ultrashort laser pulse is chosen as a test system. In this system, the approach is checked against more rigorous theories as well as experiments which show excellent agreement. The electron dynamics is visualized in several ways including the phase information of the electronic wavefunction. The detailed analysis of the electron motion after different ionization events reveals the underlying complex dynamics which are hidden in the experiment. The interplay between the carrier-envelope phase and electron control is elucidated. The ansatz is based on the highly developed electronic structure theory and can be implemented quite easily. The method allows for a successive extension to multi-electron systems and simultaneously enables a quantum-dynamical description of the nuclear motion.

Frequency comb generation and carrier-envelope phase control in femtosecond optical parametric oscillators

We describe progress in the measurement and control of the carrier-envelope phase-slip frequencies of pulses generated by a femtosecond optical parametric oscillator. Example applications of such control are presented and include the generation of a frequency comb spanning nearly three optical octaves, and the creation of a train of 30-fs pulses via coherent pulse synthesis. Future prospects for frequency combs based on femtosecond optical parametric oscillators are discussed.

Carrier-envelope phase control of carrier-wave Rabi flopping in asymmetric semiparabolic quantum well

We investigate the carrier-wave Rabi flopping effects in an asymmetric semiparabolic semiconductor quantum well (QW) with few-cycle pulse. It is found that higher spectral components of few-cycle ultrashort pulses in the semiparabolic QW depend crucially on the carrier-envelope phase (CEP) of the few-cycle ultrashort pulses: continuum and distinct peaks can be achieved by controlling the CEP. Our results demonstrate that by adjusting the CEP of few-cycle ultrashort pulses, the intersubband dynamics in the asymmetric semiparabolic QW can be controlled in an ultrashort timescale with moderate laser intensity.

Nonsequential Double Ionization of Atoms in Strong Laser Pulses

It is now possible to produce laser pulses with reproducible pulse shape and controlled carrier envelope phase. It is discussed how that can be explored in double ionisation studies. To this end we solve numerically the Schrodinger equation for a limited dimensionality model which nevertheless treats electron repulsion qualitatively correctly and allows to study correlation effects due to the Coulomb repulsion.

Control of carrier-envelope phase offset in femtosecond laser with PLL and TV-Rb clock

With the fast development of the cycle-pulse lasers, the control of the carrier-envelope phase offset (CEO) frequency has been an important research subject in such fields as femtosecond optical frequency metrology, strong field physics and high harmonic generation. In this paper, a different measurement method for CEO is demonstrated and subsequently a better beat frequency signal with the signal-to-noise ratio greater than 40 dB is obtained. Based on this optimized beat frequency signal, the CEO of the Ti:sapphire laser is stabilized to the standard signal of 10 MHz of the microwave reference source TV-Rb clock by using the electronic phase-locked loop techniques and the piezo-transducers which are mounted on the mirror inside the laser cavity to change the frequency and phase. The repetition rate of the Ti:sapphire laser is locked to the same TV-Rb clock simultaneously. The experimental results showed that the stability of the repetition rate reached the same level as the TV-Rb clock and that of the CEO frequency was increased by three orders.

Generation of optical-field controlled high-intensity laser pulses

We demonstrated control of electric fields of optical pulses by combining the pulse shaper with carrier-envelope phase (CEP) stabilized lasers. We employed spectral phase controller known as the pulse shaper for controlling the pulse envelope and the CEP. In order to evaluate the accuracy of the device, we measured the CEP shift, and delay shift by the spectral interferometry method and confirmed that the CEP and the delay were precisely controlled by the pulse shaper independently. We demonstrated control of the CEP and the relative spectral phase of amplified high-intensity laser pulses by installing the pulse shaper in a CEP stabilized amplifier system. The pulse shaper worked as an ideal CEP shifter because it controlled the phase of very broad spectrum precisely, and independent control of CEP was achieved.

Carrier-envelope phase control by a composite plate

We demonstrate a new concept to vary the carrier-envelope phase of a mode-locked laser by a composite plate while keeping all other pulse parameters practically unaltered. The effect is verified externally in an interferometric autocorrelator, as well as inside the cavity of an octave-spanning femtosecond oscillator. The carrier-envelope frequency can be shifted by half the repetition rate with negligible impact on pulse spectrum and energy.