C-cut Crystal Research Articles

Spectroscopy and lasing of new mixed Nd-doped (Sc,Y)VO4 crystals

We report the first successful growth of Nd-doped Sc x Y1−x VO4 crystals (0<x≤1) by the Czochralski technique. For a successful synthesis, the upper limit of the Sc concentration in the YVO4 melt was found to be below 10 at%. The spectroscopic characterization of an Nd-doped laser crystal, i.e., Nd:Sc0.011Y1.003V0.986O3.986, is discussed. Diode pumping of a c-cut crystal yielded an output power of 1.1 W at a wavelength of 1.06 μm with a slope efficiency of 43%: The slope efficiency of an a-cut crystal was 37%.

Growth and characterization of Nd:Y_xGd_1−xVO_4 series laser crystals

A series of Nd:YxGd1−xVO4 (x=0.17, 0.37, 0.53, 0.63, 0.70, 0.81) mixed laser crystals with doping concentration of 0.5 at.% Nd were successfully grown by the Czochralski method. Thermal properties including the specific heat, thermal diffusion coefficient, and the thermal conductivity were systematically studied. The material constants Ms were calculated and show that the thermal fracture limit of the mixed crystals should be comparable with that of Nd:YVO4. Diode-pumped continuous-wave (CW) laser performance at 1.34 μm and 1.06 μm with a- and c-cut crystals was demonstrated. The influence of different x values on laser performance and emission cross sections was also discussed. All the results show that Nd:YxGd1−xVO4 represents a new series of crystals suitable for application as high-power diode-pumped lasers.

Piezoelectric properties of lithium modified silver niobate perovskite single crystals

We report the growth and the piezoelectric properties of lead-free perovskite single crystals of Ag1−xLixNbO3. It possesses a rhombohedral structure with high ferroelectric phase transition (Tc=548K for x=0.086) and large spontaneous polarization (Ps∼40μC∕cm2 for x=0.062) along the ⟨111⟩c direction of pseudocubic perovskite structure for x&amp;gt;0.05–0.06. High quasistatic d33∼210pC∕N and low dielectric constant have lead to a very large value of piezoelectric voltage constant g33∼53.9×10−3Vm∕N for the ⟨001⟩c-cut crystal of this simple perovskite. It has been shown that Li substitution might enhance the piezoelectric coefficient of the crystal. The excellent piezo-/ferroelectricity of this system are considered to be facilitated by the strong polarization nature of both Ag and Li in the perovskite structure. Our findings may stimulate further interests in the development of lead-free piezoelectrics.

Ion implantation in 4H–SiC

Silicon carbide offers unique applications as a wide bandgap semiconductor. This paper reviews various aspects of ion implantation in 4H–SiC studied with a view to optimise ion implantation in silicon carbide. Al, P and Si ions with keV energies were used. Channelling effects were studied in both a-axis and c-axis crystals as a function of tilts along major orthogonal planes and off the major orthogonal planes. Major axes such as [0001] and the [112¯0] and minor axis like the [112¯3] showed long channelling tails and optimum tilts for minimising channelling are recommended. TEM analyses of the samples showed the formation of (0001) prismatic loops and the (112¯0) loops as well,in both a and c-cut crystals. We also note the presence of voids only in P implanted samples implanted with amorphising doses. The competing process between damage accumulation and dynamic annealing was studied by determining the critical temperature for the transition between crystalline and amorphous SiC and an activation energy of 1.3eV is extracted.

High-Power Laser Performance of ${\hbox {Yb:}}{\hbox {YAl}}_{3}({\hbox {BO}}_{3})_{4}$ Crystals Cut Along the Crystallographic Axes

High-power continuous-wave laser operation near 1 mum was demonstrated at room temperature with c-cut and a-cut Yb:YAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystals end-pumped by a fiber-coupled diode laser. Using a 2-mm-thick c-cut crystal, 10.6 W of output power was generated with an optical-to-optical efficiency of 65% and a slope efficiency of 72%. The complex polarization state of the generated laser radiation was also studied. With a 2-mm-thick a-cut crystal, sigma-polarized laser oscillation was obtained, producing a maximum output power of 8.1 W; the optical-to-optical and slope efficiencies were 56% and 61%, respectively. Complete absorption and emission cross section spectra of the Yb:YAl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (BO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> crystal were also derived, revealing very strong anisotropy of the spectroscopic properties

CW and Q-switched laser output of LD-end-pumped 1.06μm c-cut Nd:LuVO_4laser

The continuous-wave (cw) and pulsed laser performances of laser-diode (LD)-end-pumped c-cut Nd:LuVO(4) at 1.06 mum were achieved for the first time. Maximum cw output of 2.35W was obtained. Compared with the cw laser output of a-cut Nd:LuVO(4) crystal, the efficient emission cross-section of the c-cut crystal has been calculated to be 3.24x10(-19)cm(2). The largest pulse repetition rate, shortest pulse width, largest pulse energy and highest peak power were measured to be 20 kHz, 12 ns, 84.93 muJ and 7.02 kW, respectively, by using Cr(4+):YAG crystals as the saturable absorbers in the passive pulsed laser output experiments.

High-power laser performance of a-cut and c-cut Yb:LuVO_4 crystals

We report high-power laser operation that was achieved with a-cut and c-cut Yb:LuVO(4) crystals. Up to 8.3 W of pi-polarized output power was generated from an a-cut, 2 mm uncoated crystal with an optical conversion efficiency of 59%. The highest slope efficiency was 80%. Laser oscillation obtained with c-cut crystal was also linearly polarized, with two orthogonal polarization components along [110] and [(-)110] directions. The highest output power achieved was 4.5 W, with an optical conversion efficiency of 33% and a slope efficiency of 40%.

A comparison of extended defect formation induced by ion implantation in (0 0 0 1) and [formula omitted] 4H-SiC

We study the effect of substrate orientation on defect formation in 4H-SiC. Both (112̄0) and (0001) n-type 4H-SiC substrates were implanted with 400keV P. The various samples, both as-implanted samples and annealed, were studied by Rutherford backscattering and channeling and transmission electron microscopy in an attempt to understand the damage evolution and defect structures resulting from different crystal orientations. Secondary ion mass spectrometry (SIMS) was performed for P elemental profiling before and after annealing. We observe a significantly different damage accumulation in the two directions with a broader amorphous layer formed in the c-cut crystal compared to the a-cut crystal. The annealing of the damage results in a range of different defects including dislocation loops and voids in both a-cut and c-cut crystals. The SIMS profiles show in some cases distinct differences between the two crystal directions.

Three-dimensional structuring of sapphire by sequential He + ion-beam implantation and wet chemical etching

We present a method for the selective two- and three-dimensional patterning of sapphire using light ion-beam implantation to generate severe lattice damage to depths exceeding 1 μm and subsequent selective wet chemical etching of the damaged regions by hot H3PO4. C-cut sapphire crystals were implanted through contact masks using ion fluences of 1×1016 to 5×1017 He+/cm2 and energies up to 400 keV. The etching process is characterized by a high selectivity and a rate of approximately 19 nm/min. Whereas an implantation that produces a continuously damaged pathway results in complete etching from the surface, sole in-depth implantation using only high-energy ions leads to under-etching of the crystalline surface layer. By a combination of these processes we have fabricated three-dimensional structures such as channels and bridges in sapphire.

Diode-pumped passively Q-switched c-cut Nd:GdVO 4 laser

We demonstrate a passively Q-switched operation of c-cut Nd:GdVO 4 laser in which a Cr 4+:YAG crystal was used as the saturable absorber for the first time as far as we know. Stable laser pulses 9 ns with 65 μJ energy can be generated with this laser. Compared with a-cut Nd:GdVO 4 crystal, c-cut crystal can produce a peak power much higher than a-cut crystal.

Anisotropic glass freezing in rubidium/ammonium dihydrogen phosphate mixed crystal and its deuterated analogue

Anisotropic glass freezing has been studied via dielectric measurements in the dipole glass systems of rubidium/ammonium dihydrogen phosphate RADP(x) and its perdeuterated analogue D-RADP(x), where x denotes the ammonium concentration. The glass freezing temperatures for a-cut and c-cut crystals are measured, and found to reveal very small anisotropy in the protonated sample of RADP(0.43) but a considerable anisotropy at low frequency in the deuterated sample of D-RADP(0.40). A higher glass freezing temperature was observed along the c-axis as compared with the a-axis freezing temperature for D-RADP(0.40) crystal. This conforms with the prediction of the cluster model theory for . An Arrhenius plot of the logarithmic relaxation frequency versus the reciprocal temperature for D-RADP(0.40) gave the deuteron activation energies along the a-axis and along the c-axis.