Stimulated emission in the ultraviolet by optical pumping from photoionization-produced inner-shell states in Cd++

Stimulated emission on three UV transitions in Cd$+$ has been observed by transferring population from inner-shell d-electron states, populated by photoionization, to outer-shell p-electron states using the output from a narrow-frequency dye laser. The use of similar techniques in other elements could eventually result in a number of new lasers in the UV and VUV

Intense plasma discharge source at 13.5 nm for extreme-ultraviolet lithography

Includes bibliographical references (page 36).We measured an emission of 6 mJ/pulse at 13.5 nm produced by the Li2+ Lyman-α transition excited by a fast capillary discharge, using a lithium hydride capillary. 75% of the energy emanated from a spot size of 0.6 mm. The emission is narrow band and would thus be useful in extreme-ultraviolet lithography imaging systems that use Mo:Si multilayer mirrors. The output within the bandwidth of Mo:Si mirrors was comparable with that of a laser-produced plasma (LPP), and the wall plug efficiency of 0.1% was nearly an order of magnitude better than that of a LPP

Broadband and Wide-Angle Invisibility with PT-Symmetric 2D-Weyl Semimetal

Inspired by the magnificent features of two-dimensional (2D) materials which aroused much of the interest in recent materials science research, we study PT-symmetric 2D Weyl semimetal (WSM) to reveal the broadband and wide-angle invisible configurations in a PT-symmetric optical slab system. Desired unidirectional reflectionlessness and invisibility phenomena is obtained by the optimal control of system parameters. We unravel the mystery of broadband and wide-angle invisibility in regular slab materials with finite refractive indices by means of the plenary expressions. We show that materials whose refractive indices relatively small (usually around $\eta =1$) give rise to quite a lot broadband and wide-angle (almost all incidence angles) invisible configurations. This is not observed with any 2D material other than 2D WSMs. Our findings suggest a concrete expedience to experimental realizations in this direction.Comment: 8 pages, 11 figure

Ultimate on-chip quantum amplifier

We report amplification of electromagnetic waves by a single artificial atom in open 1D space. Our three-level artificial atom -- a superconducting quantum circuit -- coupled to a transmission line presents an analog of a natural atom in open space. The system is the most fundamental quantum amplifier whose gain is limited by a spontaneous emission mechanism. The noise performance is determined by the quantum noise revealed in the spectrum of spontaneous emission, also characterized in our experiments.Comment: 4 pages, 4 figures + supplemenntary materials accepted for publication in Phys. Rev. Lett

Optical Spectral Singularities and Coherent Perfect Absorption in a Two-Layer Spherical Medium

An optical spectral singularity is a zero-width resonance that corresponds to lasing at threshold gain. Its time-reversal causes coherent perfect absorption of light and forms the theoretical basis of antilasing. In this article we explore optical spectral singularities of a two-layer spherical medium. In particular, we examine the cases that a gain medium is coated by a thin layer of high-refractive index glass and a spherical glass covered by a layer of gain material. In the former case, the coating reduces the minimum radius required for exciting spectral singularities and gives rise to the formation of clusters of spectral singularities separated by wide spectral gaps. In the latter case, the coating leads to a doubling of the number of spectral singularities.Comment: 19 pages, 1 table, 10 figures, accepted for publication in Proc. R. Soc.

Energy Down Conversion between Classical Electromagnetic Fields via a Quantum Mechanical SQUID Ring

We consider the interaction of a quantum mechanical SQUID ring with a classical resonator (a parallel $LC$ tank circuit). In our model we assume that the evolution of the ring maintains its quantum mechanical nature, even though the circuit to which it is coupled is treated classically. We show that when the SQUID ring is driven by a classical monochromatic microwave source, energy can be transferred between this input and the tank circuit, even when the frequency ratio between them is very large. Essentially, these calculations deal with the coupling between a single macroscopic quantum object (the SQUID ring) and a classical circuit measurement device where due account is taken of the non-perturbative behaviour of the ring and the concomitant non-linear interaction of the ring with this device.Comment: 7 pages, 6 figure

Scattering-induced amplification of two-dimensional plasmons: electromagnetic modeling

Using two rigorous electromagnetic approaches, we study plasmon scattering in two-dimensional systems and show that plasmon amplification is possible in the presence of dc currents. Two scenarios are considered: plasmon scattering from an interface between different two-dimensional channels and plasmon reflection from electric contacts of arbitrary thickness. In each case, the effect of a dc current of the plasmon reflection and transmission coefficients and the plasmon power are both quantified. A resonant system is studied where plasmon roundtrip gain may exceed unity, showing the possibility of plasmon generation

New continuous wave infrared Ar‐Xe laser at intermediate gas pressures pumped by a transverse radio frequency discharge

An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz