Carrier-envelope Phase Variation Research Articles

Carrier-envelope-phase measurement of sub-cycle UV pulses using angular photofragment distributions

Carrier-envelope-phase (CEP) of sub-cycle ultraviolet (UV) pulse strongly influences the dynamics of quantum systems, but its characterization is not accessible experimentally. Here we investigate photodissociation of a diatomic molecule from its ground-rovibrational state in a linearly polarized weak sub-cycle UV pulse with a controlled CEP. The angular distribution of photofragments shows an asymmetric profile deviating from the well-known {cos }^{2}- or {sin }^{2}-like ones, which can be identified as a way to imprint CEP. We unveil that such an effect stems from the temporal neighboring rotational excitation by molecular permanent dipole interaction through the joint contributions between counter-rotating and rotating terms. This in turn, opens different pathways in photodissociation dynamics. Given that the temporal excitation between various states with close energies can be manipulated by CEP of sub-cycle UV pulses, our results pave ways for understanding and manipulating electron, nuclear and their joint dynamics with variation of CEP of attosecond pulses.

Space-time coupling of the carrier-envelope phase in ultrafast optical pulses.

The carrier-envelope phase (CEP) plays an increasingly important role in precise frequency comb spectroscopy, all-optical atomic clocks, quantum science and technology, astronomy, space-borne-metrology, and strong-field science. Here we introduce an approach for space-time calculation of the CEP in the spatially defined region of interest. We find a significant variation of CEP in the focal volume of refracting focusing elements and accurately calculate its value. We discuss the implications and importance of this finding. Our method is particularly suitable for application to complex, real-world, optical systems thereby making it especially useful to applications in research labs as well as in the engineering of innovative designs that rely on the CEP.

Carrier-envelope-phase-stable soliton-based pulse compression to 4.4 fs and ultraviolet generation at the 800 kHz repetition rate.

In this Letter, we report the generation of a femtosecond supercontinuum extending from the ultraviolet to the near-infrared spectrum and detection of its carrier-envelope-phase (CEP) variation by f-to-2f interferometry. The spectrum is generated in a gas-filled hollow-core photonic crystal fiber, where soliton dynamics allows the CEP-stable self-compression of the optical parametric chirped-pulse amplifier pump pulses at 800nm to a duration of 1.7 optical cycles, followed by dispersive wave emission. The source provides up to 1μJ of pulse energy at the 800kHz repetition rate, resulting in 0.8W of average power, and it can be extremely useful, for example in strong-field physics, pump-probe measurements, and ultraviolet frequency comb metrology.

An overview of LabVIEW-based f-to-2f spectral interferometer for monitoring, data acquiring and stabilizing the slow variations in carrier-envelope phase of amplified femtosecond laser pulses

We are presenting an overview of designed and implemented LabVIEW-based f-to-2f spectral interferometer for carrier-envelope phase (CEP) monitor and stabilization of high-power femtosecond laser system. This automated method applied successfully to the femtosecond laser system working at 1-kHz repetition rate and focused on the amplified pulses. The slow CEP variations observed and suppressed using LabVIEW software and hardware by generating feedback to the direct locking electronics of the CEP stabilized oscillator. The LabVIEW code designed efficiently to acquire the data, filter the signal to minimize the noise and to generate a feedback signal from the slow CEP variations of consecutive pulses. The multitask coding technique adopted in LabVIEW coding to enhance the speed of data acquisition and the feedback generation. The CEP variation monitored and controlled precisely in real-time.

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)

Robust generation of isolated attosecond pulse against the variation of carrier envelope phase of driving laser pulses

We propose a scheme for generating isolated attosecond pulse (IAP) via high-order harmonic generation in gases using a chirped two-color laser field of multicycle duration. In contrast to previous techniques where the stable carrier-envelope phase (CEP) of the driving laser pulses is a prerequisite for IAP generation, the proposed scheme is robust against the large variation of CEP. We show the generation of IAP with an intensity fluctuation less than $50%$ and an intensity contrast ratio higher than $5:1$ when the CEP shift is as large as $1.35$$\ensuremath{\pi}$.