A haloscope amplification chain based on a traveling wave parametric amplifier.

In this paper, we will describe the characterization of an RF amplification chain based on a traveling wave parametric amplifier. The detection chain is meant to be used for dark matter axion searches, and thus, it is coupled to a high Q microwave resonant cavity. A system noise temperature Tsys = (3.3 ± 0.1) K is measured at a frequency of 10.77 GHz, using a novel calibration scheme, allowing for measurement of Tsys exactly at the cavity output port.

Axion dark matter detection by laser induced fluorescence in rare-earth doped materials.

We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy m a c 2. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy (~hundreds of µeV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of 4f N electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range 1.9 - 4.2 K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.

Optomechanical Rydberg-atom excitation via dynamic Casimir-Polder coupling.

We study the optomechanical coupling of a oscillating effective mirror with a Rydberg atomic gas, mediated by the dynamical atom-mirror Casimir-Polder force. This coupling may produce a near-field resonant atomic excitation whose probability scales as ∝(d(2)an(4)t)(2)/z(0)(8), where z(0) is the average atom-surface distance, d the atomic dipole moment, a the mirror's effective oscillation amplitude, n the initial principal quantum number, and t the time. We propose an experimental configuration to realize this system with a cold atom gas trapped at a distance ∼2×10 µm from a semiconductor substrate whose dielectric constant is periodically driven by an external laser pulse, hence realizing an effective mechanical mirror motion due to the periodic change of the substrate from transparent to reflecting. For a parabolic gas shape, this effect is predicted to excite about ∼10(2) atoms of a dilute gas of 10(3) trapped Rydberg atoms with n=75 after about 0.5 µs, which is high enough to be detected in typical Rydberg gas experimental conditions.

Laser system generating 250-mJ bunches of 5-GHz repetition rate, 12-ps pulses.

We report on a high-energy solid-state laser based on a master-oscillator power-amplifier system seeded by a 5-GHz repetition-rate mode-locked oscillator, aimed at the excitation of the dynamic Casimir effect by optically modulating a microwave resonator. Solid-state amplifiers provide up to 250 mJ at 1064 nm in a 500-ns (macro-)pulse envelope containing 12-ps (micro-)pulses, with a macro/micropulse format and energy resembling that of near-infrared free-electron lasers. Efficient second-harmonic conversion allowed synchronous pumping of an optical parametric oscillator, obtaining up to 40 mJ in the range 750-850 nm.

High-gain diode-pumped amplifier for generation of microjoule-level picosecond pulses.

A diode-pumped single-pass amplifier system relying on two grazing-incidence Nd:YVO(4) slabs was developed to increase the energy of low-repetition-rate pulses from a decimated low-power cw mode-locked oscillator. Single-pass unsaturated gain up to 1.3x10(5) was achieved, and amplified pulses of 10-muJ energy and 8.0-ps duration were obtained. Efficient second harmonic generation (SHG) at 532 nm was achieved, as well as traveling-wave parametric conversion in the range 770-1020 nm (signal) and 1110-1720 nm (idler).

Multi-GHz tunable-repetition-rate mode-locked Nd:GdVO4 laser.

We report on a simple design for a multi-GHz tunable-repetition-rate diode-pumped picosecond laser. Using a plano-Brewster Nd:GdVO4 crystal in a V-folded cavity employing only readily available commercial components, we achieved passive mode-locking with 4.4-ps pulses tunable in the range 2.5-2.7 GHz. This laser is meant to be employed in the MIR experiment that aims at the detection of the Schwinger radiation (dynamical Casimir effect).