Eric Cunningham

Generation of high-flux attosecond extreme ultraviolet continuum with a 10 TW laser

We report a laser system that delivers 15 fs pulses with 200 mJ energy at a 10 Hz repetition rate. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two-stage Ti:sapphire chirped-pulse power amplifier with sub-mJ white-light pulses from a gas-filled hollow-core fiber. With this laser, an extreme ultraviolet (XUV) super-continuum supporting 230 as isolated attosecond pulses at 35 eV was generated using the generalized double optical gating technique. The XUV pulse energy was ∼100 nJ at the exit of the argon gas target.

High-efficiency optical parametric chirped-pulse amplifier in BiB 3 O 6 for generation of 3 mJ, two-cycle, carrier-envelope-phase-stable pulses at 1.7 μm

We produce a 3 mJ, two-cycle (11.4 fs), 1 kHz, carrier-envelope phase (CEP)-stable laser source at 1.7 μm via a three-stage Ti:sapphire-pumped optical parametric chirped-pulse amplifier in BiB3O6. We achieve a pump-to-signal conversion efficiency of 18% in the last stage, which is, to the best of our knowledge, the highest yet achieved for near-octave bandwidth amplification. A f-to-2f measurement shows a CEP instability of 165 mrad over 1 h. This is an ideal light source for generating isolated attosecond pulses in the soft x-ray region.

Polarization gating of high harmonic generation in the water window

High harmonic spectrum from 50-350 eV is achieved via polarization gating technique using an OPCPA laser at 1.7 μm. The driving lasers carrier-envelope phase influence on the high harmonic generation yield indicates that isolated attosecond pulses are generated.

53-attosecond X-ray pulses reach the carbon K-edge

The motion of electrons in the microcosm occurs on a time scale set by the atomic unit of time—24 attoseconds. Attosecond pulses at photon energies corresponding to the fundamental absorption edges of matter, which lie in the soft X-ray regime above 200 eV, permit the probing of electronic excitation, chemical state, and atomic structure. Here we demonstrate a soft X-ray pulse duration of 53 as and single pulse streaking reaching the carbon K-absorption edge (284 eV) by utilizing intense two-cycle driving pulses near 1.8-μm center wavelength. Such pulses permit studies of electron dynamics in live biological samples and next-generation electronic materials such as diamond.Isolated attosecond pulses are produced using high harmonic generation and sources of these pulses often suffer from low photon flux in soft X-ray regime. Here the authors demonstrate efficient generation and characterization of 53 as pulses with photon energy near the water window.

Suppression of driving laser in high harmonic generation with a microchannel plate.

Separating the infrared driving laser from the extreme ultraviolet (XUV) pulses after high-order harmonic generation has been a long-standing difficulty. In this Letter, we propose and demonstrate that the driving laser can be blocked by simply installing a microchannel plate (MCP) into the beam line. In addition to its high damage threshold, the MCP filter also transmits photons over the entire XUV region. This paves the way for attosecond pulse generation with unprecedented bandwidth.

Optical Gating With Asymmetric Field Ratios for Isolated Attosecond Pulse Generation

A technique to improve double optical gating for generating isolated attosecond pulses is introduced. In this method, the ratio between the amplitudes of the counter-rotating pulses is altered to decrease the field strength prior to the linearly-polarized gate cycle. The result is a decrease in the preionization of the gas target used for generating high-order harmonics. In addition to improving phase matching and increasing the saturation intensity, this development also allows isolated attosecond pulse production with longer driving laser pulses.

Carrier-envelope phase control of a 10 Hz, 25 TW laser for high-flux extreme ultraviolet quasi-continuum generation

A scheme for stabilizing the carrier-envelope phase (CEP) of low-repetition rate lasers was demonstrated using a 350 mJ, 14 fs Ti:Sapphire laser operating at 10 Hz. The influence of the CEP on the generation of a quasi-continuum in the extreme ultraviolet was observed.

Photoemission by Large Electron Wave Packets Emitted Out the Side of a Relativistic Laser Focus

We provide an update on an experimental effort to measure the radiation from individual electron wave packets that are spread over an area on the scale of an optical wavelength.

Erratum: 53-attosecond X-ray pulses reach the carbon K-edge

Nature Communications8:186 10.1038/s41467-017-00321-0 (2017); Article published online: 4 August 2017

Attosecond pulse generation isolated with an asymmetric polarization gating

Abstract High harmonics generated using the polarization gating technique are simulated under the strong-field approximation for the cases of equal and unequal ratios between the amplitudes of the two counter-rotating pulses. The effect of the field asymmetry is observed on the high harmonic yield and cut-off in the frequency domain and on the attosecond pulse duration and satellite peak contrast in the time domain. The case where the strong pulse comes later is more favourable in terms of generating a higher cut-off and a shorter pulse duration. It is predicted that thin metal filters can reduce the impact of satellite pulses while simultaneously reducing the pulse duration.