Stimulated Brillouin scattering (SBS) gain profiles were recorded for Kr, Ar, and N2 at a pumping wavelength of 266 nm. Use of low-pressure (<10 atm) gas shows a transition from the typical hydrodynamic regime into the kinetic regime.

Two classes of higher-order, fractal spatial eigenmodes have been predicted computationally and observed experimentally in microlasers. The equatorial plane of a close-packed array of microspheres, lying on one mirror within a Fabry-Pérot resonator and immersed in the laser gain medium, acts as a refractive slit array in a plane transverse to the optical axis. Edge diffraction from the slit array generates the high spatial frequencies (>10 4 cm −1 ) required for the formation of high-order laser fractal modes, and fractal transverse modes are generated, amplified, and evolve within the active medium. With a quasi-rectangular (4-microsphere) aperture, the fundamental mode and several higher-order eigenmodes ( m = 2,4,5) are observed in experiments, whereas only the m = 1,2 modes are observed experimentally for the higher-loss resonators defined by triangular (3-microsphere) apertures. The fundamental and 2 nd -order modes ( m = 1,2) for the 4-sphere aperture are calculated to have qualitatively similar intensity profiles and nearly degenerate resonant frequencies that differ by less than <0.1% of the free-spectral range (375 GHz) but exhibit even and odd parity, respectively. For all of the observed fractal modes, the fractal dimension (D) rises rapidly beyond the intracavity aperture array as a result of the high spatial frequencies introduced into the mode profile. Elsewhere, D varies gradually along the resonator axis and 2.2 < D < 2.5. Generating fractal laser modes in an equivalent optical waveguide is expected to allow the realization of new optical devices and imaging protocols based on the spatial frequencies and variable D values available.

Spectroscopic measurements of the 3H4 →3H6 transition in Tm:YLF were conducted. Absorption spectra, emission spectra, and spontaneous emission lifetime are reported as a function of both temperature and doping concentration.

Oxide films of the quality required for the fabrication of electronic and photonic devices are typically deposited at elevated temperatures and thermal equilibrium, thereby adversely impacting thermal budgets. We report the deposition and patterning of silicon dioxide (SiO2) films of high electrical and optical quality on Si(100) or polymer substrates in a N2 atmosphere and at 300 K by the photochemical conversion of thin liquid tetraethoxysilane (TEOS) layers with narrowband vacuum ultraviolet radiation [vacuum ultraviolet (VUV), 172 nm] provided by efficient microplasma lamps. Irradiating liquid TEOS layers, produced by spin-coating the precursor onto a substrate, with a VUV intensity of 13 mW cm−2, yields 40 nm-thick SiO2 films having a dielectric breakdown strength (Eb) of 5 MV cm−1, for which no precedent exists in the deposition of oxide films at 300 K. If room temperature-deposited films are post-annealed at 200 °C, Eb rises to 7.5 MV cm−1, which is <12% below the measured value (8.5 MV cm−1) for 40 nm SiO2 films grown by thermal oxidation. The deposition of 1 µm thick, stoichiometric SiO2 films requires only 20 min of VUV illumination at low optical fluences, and films with thicknesses of ∼35–60 nm exhibit a refractive index of 1.45 (633 nm). X-ray photoelectron spectrometry and Rutherford backscattering analysis indicate that, despite the deposition temperature, hydrocarbon impurity levels are near or below the detection limit. The capability for depositing 960 nm-thick SiO2 films uniformly (to within 0.6%) by liquid → solid photochemical conversion over a 5 cm diameter Si substrate and patterning films onto flexible polymer substrates has also been demonstrated.

Investigatingthe potential of a new microcavity-plasmalamp with a phosphor wavelength converter film for advanced watertreatment. A longstandingobstacle to the application of vacuum ultraviolet(VUV) radiation for advanced water treatment is the absence of efficient,affordable, and powerful lamps. A custom Xe-2 microcavityplasma (McP) lamp with an internal phosphor film, generating broadbandemission in the 165-200 nm interval, is presented here as anoptical source for the degradation of dissolved contaminants. Theperformance of this lamp was evaluated by comparing measured photodegradationrates for carbamazepine (CBZ, a model compound) with correspondingdata obtained with a conventional 254/185 nm Hg lamp. While the oxidantproduction rate was lower for the McP lamp, it was found to be moreeffective in photodegrading CBZ for a given energy dosage absorbedby the water. The McP lamp also produced higher concentrations ofthe byproduct acridine (ARD) but normalization to effective fluenceexposure reveals it produced and removed ARD more efficiently thandid the Hg lamp. The flat form factor and ability to produce outputpowers >10 W from a 100 cm(2) aperture make the McP lamppromising for photochemical water treatment. Although its emissionspectrum is not currently optimized, the data indicate that the lampspectrum can be engineered to efficiently photodegrade a wide rangeof challenging water pollutants.

Optical quantum memory describes the process of on-demand storage and retrieval of single photon-level quantum states, and is a critical enabling technology for many quantum applications. Memory bandwidth plays an important role in these applications, as it determines the pulse durations compatible with the memory and places an upper bound on the clock rate and processing speed of a quantum device. Here we present experimental results of an atomic barium quantum memory that enables storage and retrieval of ultra-broadband $(> 800$ GHz) signal photons with high storage efficiency [95.6(3)%] and low noise [3.8(6) $\times 10^{-5}$ noise photons]. Experimental Results.- The quantum memory operation is based on the ground $(6s^{2}\ {}^{1}S_{0})$ , excited $(6s6p \ {}^{1}P_{1})$ , and metastable $(6s5d \ {}^{1}D_{2})$ orbital states of atomic barium in a $\Lambda$ -type configuration. The barium vapor is created in an 800–900 °C barium heat pipe oven with 0–1000 torr tunable argon buffer gas pressure. The ground-excited transition at 553.5 nm features large and tunable homogeneous collisional broadening due to the argon buffer gas and a peak optical depth of $d=50$ . The memory operates in the so-called absorb-then-transfer (ATT) regime, in which the signal field is linearly absorbed along the ground-excited transition, whose collisionally broadened lineshape enables efficient absorption of ultra-broadband photons; the resulting atomic polarization is transferred into a so-called spin wave by application of a strong $[O(10 \ \text{uJ}),100\ \text{fs}]$ control pulse along the excited-metastable transition at 1500 nm. The storage state has a 0(0.1) second coherence lifetime in the bare atom [1], but this is reduced to the $O(\text{ns})$ level due to motional dephasing [0.49(1) ns measured memory lifetime]. The memory experiment is repeated at a repetition rate of 1 kHz. The total end-to-end efficiency of the memory at 900°C is 31(1)%, which is limited by available control field power.

We measure 95.6±0.3% storage efficiency of ultrafast photons in a collisionally broadened barium vapor quantum memory. We measure 31±1% total efficiency, limited by control field power, and a 0.515(6) ns lifetime, limited by motional dephasing.

We present a demonstration of simultaneous high-efficiency, high-speed, and low-noise operation of a photonic quantum memory. By leveraging controllable collisional dephasing in a neutral barium atomic vapor, we demonstrate a significant improvement in memory efficiency and bandwidth over existing techniques. We achieve greater than 95% storage efficiency and 26% total efficiency of 880 GHz bandwidth photons, with $\mathcal{O}(10^{-5})$ noise photons per retrieved pulse. These ultrabroad bandwidths enable rapid quantum information processing and contribute to the development of practical quantum memories with potential applications in quantum communication, computation, and networking.

In honor of Professor Kurt Becker’s pioneering contributions to microplasma physics and applications, we report the capabilities of arrays of microcavity plasmas in two emerging and disparate applications. The first of these is the generation of ultrasound radiation in the 20–240 kHz spectral range with microplasmas in either a static or jet configuration. When a 10× 10 array of microplasma jets is driven by a 20-kHz sinusoidal voltage, for example, harmonics as high as m = 12 are detected and fractional harmonics are produced by controlling the spatial symmetry of the emitter array. The preferential emission of ultrasound in an inverted cone having an angle of ± 45^∘ with respect to the surface normal of the jet array’s exit face is attributed to interference between spatially periodic, outward-propagating waves generated by the arrays. The spatial distribution of ultrasound generated by the arrays is analogous to the radiation patterns produced by Yagi-Uda phased array antennas at RF frequencies for which radiation is emitted broadside to arrays of parallel electric dipoles. Also, the nonperturbative envelope of the ultrasound harmonic spectrum resembles that for high-order harmonic generation at optical frequencies in rare gas plasmas and attests to the strong nonlinearity provided by the pulsed microplasmas in the sub-250-kHz region. Specifically, the relative intensities of the second and third harmonics exceed that for the fundamental, and a “plateau” region is observed extending from the 5th through the 8th harmonics. A strong plasma nonlinearity appears to be responsible for both the appearance of fractional harmonics and the nonperturbative nature of the acoustic harmonic spectrum. Multilayer metal-oxide optical filters designed to have peak transmission near 222 nm in the deep-UV region of the spectrum have been fabricated by microplasma-assisted atomic layer deposition. Alternating layers of ZrO _2 and Al _2 O _3 , each having a thickness in the 20–50 nm range, were grown on quartz and silicon substrates by successively exposing the substrate to the Zr or Al precursor (tetrakis(dimethylamino) zirconium or trimethylaluminum, respectively) and the products of an oxygen microplasma while maintaining the substrate temperature at 300 K. Bandpass filters comprising 9 cycles of 30-nm-thick ZrO _2 /50-nm-thick Al _2 O _3 film pairs transmit 80

Interference between coherences established at 384 and 386 THz in atomic Rb (5d 5/2 - 5p 3/2 and 5p 3/2 -5s 1/2 , respectively) is observed at the 2.1 THz difference frequency. Interaction between the two coherences is observed in the spectral domain in the form of a Fano resonance, and the characteristics of the coupled oscillator are described.

Low-temperature microplasmas are efficient sources of ions, electrons, active species, and photons. In particular, Photon generation of microcavity plasma arrays offers differentiated performance in various photonics applications that were previously unavailable. In this paper, we will discuss recent developments in microplasma photonics in three areas.

A KXe amplifier was engineered through excitation of K-Xe collisional pairs. Amplification on the K D1 line along with stimulated electronic and molecular Raman peaks are observed.

A KXe laser was engineered through excitation of K-Xe collisional pairs and populating K atomic levels. Lasing occurred on the K D 1 line.

Modern communication and navigation systems are increasingly relying on atomic clocks. As timing precision requirements increase, demands for lower SWaP (size, weight, and power) clocks rise. However, it has been challenging to break through the general trade-off trend between the clock stability performance and SWaP. Here we demonstrate micro mercury trapped ion clock (M2TIC) prototypes integrated with novel micro-fabricated technologies to simultaneously achieve high performance and low SWaP. The M2TIC prototypes could reach the 10^-14 -stability level in 1 day with a SWaP of 1.1 L, 1.2 kg, and under 6 W of power. This stability level is comparable to the widely used rack-mount Microchip 5071A cesium frequency standard. These standalone prototypes survived regular commercial shipping across the North American continent to a government laboratory, where their performance was independently tested. The M2TIC sets a new reference point for SWaP and performance and opens opportunities for high-performance clocks in terrestrial and space applications.

Modern communication and navigation systems are increasingly relying on atomic clocks. As timing precision requirements increase, demands for lower SWaP (size, weight, and power) clocks rise. However, it has been challenging to break through the general trade-off trend between the clock stability performance and SWaP. Here we demonstrate micro mercury trapped ion clock (M2TIC) prototypes integrated with novel micro-fabricated technologies to simultaneously achieve high performance and low SWaP. The M2TIC prototypes could reach the [Formula: see text]-stability level in 1 day with a SWaP of 1.1 L, 1.2 kg, and under 6 W of power. This stability level is comparable to the widely used rack-mount Microchip 5071A cesium frequency standard. These standalone prototypes survived regular commercial shipping across the North American continent to a government laboratory, where their performance was independently tested. The M2TIC sets a new reference point for SWaP and performance and opens opportunities for high-performance clocks in terrestrial and space applications.

We demonstrate quantum memory of single-photon-level coherent pulses of 880 GHz bandwidth with 95.6(3)% storage efficiency in collisionally broadened barium vapor. We measure 26(1)% total efficiency, limited by control field power; 0.49(1) ns memory lifetime, limited by motional dephasing; and a signal-to-noise ratio of ${O}(10^{3})$, limited by two-photon control field scattering. To the best of the authors’ knowledge, this represents the best efficiency, lifetime, and noise performance of atomic quantum memories in the ultrabroadband regime $(\gt100$ GHz bandwidth) to date.

Interatomic potentials for the B2Σ1/2+ states of CsAr, CsXe, and RbXe have been determined through comparisons of experimental B ← X absorption spectra for alkali vapor–rare gas mixtures with calculations of the Franck–Condon factors (FCFs) associated with free–free transitions of thermal atomic pairs. Simulations of optical transitions of alkali-rare gas atomic pairs between the thermal and vibrational continua of the X2Σ1/2+ and B2Σ1/2+ states of the molecule, responsible for the blue satellites of the Cs and Rb D2 resonance lines in a rare gas background, require the incorporation of ground-state J values above ∼400 into the FCF calculations and proper normalization of the free-particle wave functions. Absorption spectra computed on the basis of several X and B state interatomic potentials available in the literature were found to be sensitive to the height of the B2Σ1/2+ state barrier, as well as the X2Σ1/2+ state repulsive wall contour and the location of the van der Waals minimum. Other spectral simulations entailed iterative modifications to a selected B2Σ1/2+ interatomic potential, again coupled with comparison to experimental B ← X spectra. Comparisons of calculated spectra with experiment yield a CsXe B2Σ1/2+ potential, for example, exhibiting a barrier height of 76 cm–1 at 5.2 Å and yet is nearly flat at smaller values of internuclear separation (R). The latter contrasts with previous theoretical calculations of VB(R) in the vicinity of the barrier maximum. For the CsAr molecule, the B2Σ1/2+ barrier height was found to be 221 cm–1, which is within 3% of the value determined from pseudopotential calculations incorporating the spin–orbit effect. Reproducing Cs-rare gas experimental absorption spectra also requires the existence of a broad, shallow potential well lying beyond the B2Σ1/2+ barrier that, for CsAr, has a dissociation energy (De ∼ 24 cm–1) a factor of 3 larger than values predicted by theory. Similar results are obtained for the RbXe and CsXe complexes.

The confinement of low temperature plasma to cavities having dimensions below 1 mm has provided access to a new realm of parameter space and plasma-surface interactions that, in turn, has given rise to a broad range of commercial applications. This presentation will briefly review the history of the development of microcavity plasma arrays, followed by a description of several current and emerging commercial applications. The most prominent of the former are: the introduction of a family of VUV/UV lamps of unprecedented power and efficiency, VUV photolithography and photopatterning systems, the disinfection of air and surfaces during the COVID-19 pandemic, materials analysis and identification products, and solar-powered, microplasma ozone generator units for the disinfection of drinking water. Emerging applications such as optical drivers for atomic clocks, plasma-assisted atomic layer deposition (ALD) systems, and the deactivation of biofilms in the human ear, as well as in municipal water distribution systems, will also be discussed briefly.

We report record storage efficiencies in the first atomic THz-bandwidth quantum memory. Near-off-resonant orbital transitions in collisionally broadened hot atomic barium vapor allow for 83% storage efficiency, 25% total efficiency, and a time-bandwidth-product of 800.