We report the observation of subpicosecond terahertz (T-ray) pulses with energies ≥460 μJ from a laser-driven ion accelerator, thus rendering the peak power of the source higher even than that of state-of-the-art synchrotrons. Experiments were performed with intense laser pulses (up to 5×10(19) W/cm(2)) to irradiate thin metal foil targets. Ion spectra measured simultaneously showed a square law dependence of the T-ray yield on particle number. Two-dimensional particle-in-cell simulations show the presence of transient currents at the target rear surface which could be responsible for the strong T-ray emission.
We experimentally characterize the generation of high-power terahertz radiation (THz) at the rear surface of a target irradiated by multiple laser pulses. A detailed dependence of the THz yield as a function of laser pulse duration, energy, target material and thickness is presented. We studied the THz radiation emitted mainly in two directions from the target rear surface, namely target normal (acceptance angle 0.87 sr) and non-collinear direction (perpendicular to the target normal directionacceptance angle 4.12 sr). Independent measurements based on electro-optic diagnostics and pyroelectric detector were employed to estimate the THz yield. Most of the energy is emitted at large angles relative to the target normal direction. THz yield increases with incident laser intensity and thinner targets are better emitters of THz radiation compared to thicker ones.
We have observed signatures of resonant tunneling in an Al three-junction qubit, inductively coupled to a Nb LC tank circuit. The resonant properties of the tank oscillator are sensitive to the effective susceptibility (or inductance) of the qubit, which changes drastically as its flux states pass through degeneracy. The tunneling amplitude is estimated from the data. We find good agreement with the theoretical predictions in the regime of their validity.PACS numbers: 85.25. Cp, 85.25.Dq, 84.37.+q, 03.67.Lx Several groups, using different devices, have by now established that superconductors can behave as macroscopic quantum objects.1-3 These are natural candidates for a qubit, the building block of a quantum computer. Qubits are effectively two-level systems with timedependent parameters. One of them is a superconducting loop with low inductance L, including three Josephson junctions (a 3JJ qubit).4 Its potential energy, U = For suitable parameters, U (φ 1 , φ 2 ) has two minima corresponding to qubit states Ψ l and Ψ r , carrying opposite supercurrents around the loop. These become degenerate for Φ x = 1 2 Φ 0 . The Coulomb energy E C (≡ e 2 /2C, with C the capacitance of junction 1) introduces quantum uncertainty in the φ j . Hence, near degeneracy the system can tunnel between the two potential minima.(Since E C ≪ E J ≡ E J1 , we deal with a flux qubit; E C ≫ E J yields a charge qubit. Coherent tunneling was demonstrated in both.)In the basis {Ψ l , Ψ r } and near Φ x = 1 2 Φ 0 , the qubit can be described by the Hamiltonian∆ is the tunneling amplitude. At bias ǫ = 0 the two lowest energy levels of the qubit anticross [ Fig. 1(a)], with a gap of 2∆. Increasing ǫ slowly enough, the qubit can adiabatically transform from Ψ l to Ψ r , staying in the ground state E − . Since dE − /dΦ x is the persistent loop current, the curvature d
We report the first experimental observation of terahertz (THz) radiation from the rear surface of a solid target while interacting with an intense laser pulse. Experimental and two-dimensional particle-in-cell simulations show that the observed THz radiation is mostly emitted at large angles to the target normal. Numerical results point out that a large part of the emission originates from a micron-scale plasma sheath at the rear surface of the target, which is also responsible for the ion acceleration. This opens a perspective for the application of THz radiation detection for on-site diagnostics of particle acceleration in laser-produced plasmas.
Laser-produced solid density plasmas are well-known as table-top sources of electromagnetic radiation. Recent studies have shown that energetic broadband terahertz pulses (T rays) can also be generated from laser-driven compact ion accelerators. Here we report the measurement of record-breaking T-Ray pulses with energies no less than 0.7 mJ. The terahertz spectrum has been characterized for frequencies ranging from 0.1-133 THz. The dependence of T-Ray yield on incident laser energy is linear and shows no tendencies of saturation. The noncollinear emission pattern and the high yield reveal that the T rays are generated by the transient field at the rear surface of the solid target.
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