Field-tuned ferroquadrupolar quantum phase transition in the insulator TmVO.

We report results of low-temperature heat-capacity, magnetocaloric-effect, and neutron-diffraction measurements of TmVO, an insulator that undergoes a continuous ferroquadrupolar phase transition associated with local partially filled 4 orbitals of the thulium (Tm[Formula: see text]) ions. The ferroquadrupolar transition, a realization of Ising nematicity, can be tuned to a quantum critical point by using a magnetic field oriented along the axis of the tetragonal crystal lattice, which acts as an effective transverse field for the Ising-nematic order. In small magnetic fields, the thermal phase transition can be well described by using a semiclassical mean-field treatment of the transverse-field Ising model.

An apparatus for studying scintillator properties at high isostatic pressures.

We describe the design and operation of a unique hydraulic press for the study of scintillator materials under isostatic pressure. This press, capable of developing a pressure of a gigapascal, consists of a large sample chamber pressurized by a two-stage hydraulic amplifier. The optical detection of the scintillation light emitted by the sample is performed, through a large aperture optical port, by a photodetector located outside the pressure vessel.

High-throughput combinatorial database of electronic band structures for inorganic scintillator materials.

For the purpose of creating a database of electronic structures of all the known inorganic compounds, we have developed a computational framework based on high-throughput ab initio calculations (AFLOW) and an online repository (www.aflowlib.org).

Generation of tunable 187.9-196-nm radiation in beta-Ba(2)BO(4).

Tunable 187.9-196-nm vacuum-ultraviolet radiation was generated at room temperature in a beta barium borate crystal by sum-frequency mixing of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the second harmonic of the same Nd:YAG laser. By use of the advantageous noncollinear phase-matching configuration, a peak power of 1.

16-microm infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs.

Tunable 90-ps 15.6-17.6-microm coherent radiation was generated by means of difference-frequency mixing in diffusion-bonded-stacked GaAs.

Generation of tunable 187.9-196-nm radiation in beta-BaB(2)O(4): errata.

In Ref. 1, the first full sentence in the right-hand column of p. 1608 should read as: 'Although BBO is phase matchable down to 187 nm and shorter in this configuration without a very large (2-4 degrees ) change in theta (and hence in d(eff)), and B2 is also suitable to accommodate the phase matching, tunability below 187.

Waveguides formed by incoherent dark solitons.

We demonstrate experimentally optical guidance of coherent light beams, using incoherent light. Such guidance is made possible by generation of partially spatially incoherent self-trapped dark beams (dark incoherent solitons) in a noninstantaneous nonlinear medium. In the one-dimensional case, the incoherent solitons induce single and Y-junction planar waveguides, whereas in the two-dimensional case, they form circular waveguides.

Photoluminescence of n-type CdGeAs.

Samples of n-type CdGeAs were produced by intentional doping with indium, selenium, or tellurium impurities. A near-edge photoluminescence (PL) band from heavily In-doped CdGeAs samples shifts to higher energy and becomes broader with increasing electron concentration. The observed shifts in peak energies are compared to predictions for donor-acceptor pair and free-to-bound (electron-acceptor) recombinations including band filling, band tailing, and band gap shrinkage effects due to the high doping levels.

Observation and thermal fixing of holographic gratings in lead barium niobate crystal.

We report what we believe to be the first observation of photorefractive gratings in lead barium niobate (Pb(1-x)Ba (x)Nb(2)O>( 6) ; PBN). A diffraction efficiency of 9% and a beam-coupling coefficient of 9 cm(-1) are obtained. After thermal fixing a grating of 0.

Mid-IR absorption in AgGaSe(2) optical parametric oscillator crystals.

We report new experimental results on the spectral, thermal, and orientational characteristics of stoichiometry-dependent mid-IR absorption in AgGaSe(2) crystals. In currently available material, this absorption poses an obstacle to the power scaling of the 2-µm-pumped AgGaSe(2) optical parametric oscillator (OPO). Preliminary experiments have indicated that this absorption could be substantially reduced by optimization of the process parameters during crystal growth and annealing.

6.5-W, 532-nm radiation by cw resonant external-cavity second-harmonic generation of an 18-W Nd:YAG laser in LiB(3)O(5).

We report 6.5 W of TEM(00) cw 532-nm radiation generated by external resonant doubling in a LiB(3)O(5) crystal. An 18-W, cw, injection-locked single-frequency Nd:YAG laser was used to generate 532-nm second-harmonic output with a 3-dB heterodyne linewidth of 15 kHz.

Photorefractive-damage-resistant Zn-diffused waveguides in MgO:LiNbO(3).

Planar waveguides were fabricated by diffusing Zn into MgO:LiNbO(3) and LiNbO(3). Zn-diffused waveguides in MgO:LiNbO(3) guide both the ordinary and extraordinary polarization and have propagation losses at 633 nm in the range of 0.4-1.

Superconducting bi-ca-sr-cu-o fibers grown by the laser-heated pedestal growth method.

Superconducting fibers of several compositions including the nominal composition Bi(2)CaSrCu(2)O(8) have been grown by means of the laser-heated pedestal growth method. The influence of starting composition and growth conditions on structure and superconducting properties is discussed. The a-b planes of the material are parallel to the fiber axis (along the growth direction), providing the ideal condition for conduction along the copper-oxygen planes.

Second harmonic generation and accurate index of refraction measurements in flux-grown KTiOPO(4).

Accurate index of refraction measurements have been performed in flux-grown KTiOPO(4). These measurements give good agreement between experiment and theory for angle phase matching in Type II second harmonic generation at 1.064 microm.

Research on nonlinear optical materials: an assessment.

The seven papers making up this assessment are based on the Workshop on Nonlinear Optical Materials held in April 1986.