C-cut Crystal Research Articles

Lasing properties and their anisotropy of Yb:CaWO[formula omitted] crystal

Continuous-wave lasing properties of the tetragonal Yb:CaWO4 crystal were investigated with a- and c-cut crystals under 976-nm diode pumping, revealing a strong anisotropy in many output characteristics. Depending on the resonator output coupling, the laser oscillation realized with the a-cut crystal could be σ- or π-polarized; it could also consist of σ and π polarization states simultaneously. An output power of 2.01 W was generated at 1025.1–1027.8 nm in dual-polarization laser operation, with an optical-to-optical efficiency of 24.1% and a slope efficiency of 28%; the σ- and π-polarized components were measured to be 1.05 and 0.96 W, respectively. The laser emission generated with the c-cut crystal could only be unpolarized; while the maximum output power, which was limited by the output saturation behavior, amounted only to 1.61 W.

2.3–2.5 μm laser operation of LD-pumped Tm:YAP on the 3H4→3H5 transition

Abstract 2.3–2.5 μm laser operation of LD-pumped Tm:YAP on the 3H4→3H5 transition is reported. The a-cut, b-cut and c-cut Tm:YAP crystals with 2 at.% doping concentration were used to characterize the laser performance. All the laser outputs were found to be linearly polarized that is induced by the gain anisotropy of Tm:YAP. First laser oscillation of Tm-doped laser on the 3H4→3H5 transition beyond 2.4 μm in Tm:YAP was realized by using a specially designed output coupler with a high transmittance at 2200–2350 nm and partial reflection at 2400–2500 nm. 736 mW at 2446 nm and 189 mW at 2482 nm are obtained from the a-cut and b-cut crystal, respectively. Furthermore, continuous-wave and passively Q-switched dual-wavelength Tm:YAP laser at 2274 and 2383 nm were realized with the a-cut crystal. 538 mW at 2353 nm with a slope efficiency of 8.3% is achieved from the c-cut crystal. Our work demonstrates the multi-wavelength emitting ability of LD-pumped Tm:YAP laser on the 3H4→3H5 transition, which can further expand the application of Tm-doped lasers.

Model-free determination of the birefringence and dichroism in c-cut crystals from transmission ellipsometry measurements.

In this work, we derive closed-form expressions for determination of the linear birefringence and linear dichroism of uniaxial crystals utilizing transmission ellipsometry measurements at small angles of incidence in $ c $c-cut crystal substrates. The model-free method we use is an algebraic generalization of the method reported in Appl. Opt.44, 3153 (2005).APOPAI0003-693510.1364/AO.44.003153 The optical anisotropy of substrates of sapphire, 4H-SiC, and 6H-SiC single crystals is measured for illustration.

Efficient continuous-wave and passively Q-switched lasers based on disordered Nd:Ca0.7La0.3Al12O19 crystals

A new neodymium-doped (Nd3+-doped) Ca0.7La0.3Al12O19 (Nd:CLA) disordered crystal was successfully grown by the Czochralski method. The performance of diode-pumped Nd:CLA (a-cut and c-cut) lasers was demonstrated for the first time. For the c-cut crystal continuous-wave (CW) operation, we obtained the highest output power of 2.08 W at the wavelength of 1053.2 nm, and the slope efficiency was 23% versus the incident pump power. By inserting a Cr4+:YAG absorber, we successfully achieved a passively Q-switched laser, and the shortest pulse width was 18.36 ns with a peak power of 364.6 W. Compared with a-cut crystal, c-cut crystal has superior laser characteristics.

Spectroscopic properties and continuous-wave laser performance of Yb:Gd2SrAl2O7 crystal

In this paper, the crystal growth, spectral properties, and laser performance of 5 at.% Yb doped Gd2SrAl2O7 (Yb:GSAO) crystal were reported. The peak absorption cross-section is 5.22 × 10−20 cm2 at 979 nm and the peak stimulated emission cross section calculated by Füchtbauer-Ladenburg (FL) method is 1.22 × 10−20 cm2 at 1062 nm for the π polarization. Efficient continuous-wave (cw) laser action was demonstrated in the range of 1060.2–1069.5 nm with a c-cut crystal sample end pumped by a 980 nm laser diode, generating a maximum output power of 7.345 W with an optical-to-optical efficiency of 47.5% and a slope efficiency of 53.7%. The results indicate that Yb:GSAO is a good Yb laser material.

Investigations on the spectroscopic properties and laser performance of Tm3+/Ho3+-SrLaGa3O7 crystal

The Tm3+/Ho3+-SrLaGa3O7 crystal was grown using the Czochralski (CZ) method. The absorption spectra, the fluorescence spectra around 2.0 μm and energy-transfer (ET) schemes between Tm3+ ions and Ho3+ ions has been studied. The lasing performance of Tm3+/Ho3+-SrLaGa3O7 crystal for a-cut and c-cut pumped by a fiber-coupled laser diode laser are presented in this paper. The maximum output powers of 6.15 W for a-cut crystal at 2041 nm and 2.51 W for c-cut crystal at 2044 nm have been obtained, respectively. The maximum slope efficiency in terms of absorbed pump power nearly reached 36.5% for the a-cut crystal and about 18.8% for the c-cut crystal. In addition, the width of tuning can reach about 450 nm, suggesting the potential of these crystals for ultrashort pulse generation by mode-locking.

Crystal growth, spectroscopy and first laser operation of a novel disordered tetragonal Tm:Na2La4(WO4)7 tungstate crystal

Tm3+:Na2La4(WO4)7, a disordered tetragonal scheelite-type tungstate crystal, is grown by the Czochralski method. The polarized absorption, stimulated-emission and gain cross-section spectra are determined. The maximum σSE is 1.62 × 10–20 cm2 at 1788.6 nm for σ-polarization. The Judd-Ofelt parameters for Tm3+ are Ω2 = 10.321, Ω4 = 0.183 and Ω6 = 2.122 [10–20 cm2]. The radiative lifetime of the 3F4 state is 1.63 ms. Raman spectroscopy reveals a maximum phonon energy of 923 cm−1. Laser operation under diode-pumping is achieved with both a-cut and c-cut Tm:Na2La4(WO4)7 crystals, reaching a maximum output power for the a-cut of 715 mW at ~ 1937 nm with a slope efficiency of 34%. Microchip laser operation using the c-cut crystal yields a slope efficiency of 41%. The Tm:Na2La4(WO4)7 crystal is promising for mode-locked lasers due to its broadband emission.

Crystal growth, spectral properties and continuous wave laser operation of new mixed Nd:GdYNbO4 laser crystal

A new mixed laser crystal Nd:Gd0.69Y0.3NbO4 (Nd:GYNO) with high quality was grown successfully by Czochralski method. Its structure parameters are obtained by the X-ray Rietveld refinement method. The effective segregation coefficient of Nd3+ ions is 0.61 in GYNO host. The maximum absorption cross section at 809 nm and peak emission cross section at 1065.6 nm of Nd:GYNO crystal are 11.6 × 10−20 and 20.5 × 10−20 cm2, respectively. The fluorescence lifetime of 4F3/2 manifold for Nd3+ in Nd:GYNO crystal is fitted to be 156 μs. Diode-pumped continuous-wave laser operations at 1.06 μm with Nd:GYNO crystals cut perpendicular to crystallographic a, b, and c axes (denoted as a-, b- c-cut, respectively) were demonstrated. A maximum output power of 0.98 W was obtained with c-cut crystal, corresponding to an optical-to-optical conversion efficiency of 31.3% and a slope efficiency of 30.4%. All these results imply that the Nd:GYNO crystal has great potential application in low and even moderate lasers.

Growth, thermal and laser properties of a new self-frequency-doubling Yb:CNGS crystal

A new optical single-crystal Yb:CNGS (Yb:Ca3NbGa3Si2O14) was grown successfully for self-frequency-doubling with the sizes of 25 mm in diameter and 50 mm in length using the Czochralski methods. We studied the thermal properties of these crystals systematically, including the thermal expansion coefficient, specific heat, thermal diffusion coefficient, and the thermal conductivity. The absorption and fluorescence spectra of Yb:CNGS crystal were measured. The absorption spectra show a broad transmission range from 350 to 3500 nm. The continuous-wave (CW) laser output at 1060 nm was demonstrated with a- and c-cut crystal. The maximum output power was about 1.53 W under a 4.03 W incident power with z-cut crystals. The slope efficiency was as high as 47.8%. An efficient CW self-frequency-doubling (SFD) green laser was performed with a diode-pumped Yb:CNGS laser. The CW green output power was 37.1 mW and the wavelength tunability from 526 to 532 nm with input pump power as been demonstrated.

Thermal stresses in the laser disc from a tetragonal c-cut crystal

Analytical expressions for thermal stresses and strains, as well as displacements, are obtained for the laser disc from a tetragonal crystal cut along the [001] axis under plane stress approximation, for the first time, to our knowledge. This study illustrates that, in polar coordinates, the normal stresses, σr and σθ, are angular independent, while the shear one τrθ is zero. The thermal strains, εr and εθ, and displacements, u and υ, depend on both radial and tangential coordinates; this dependence has the shape of a four-leaf rose. For considered crystal cutting with isotropic in-plane thermal expansion, the displacements are not pure radial (υ≠0). The values of stresses, strains and displacements are calculated for the disc from a c-cut yttrium vanadate laser crystal, Nd:YVO4. The thermal fracture issues are analyzed for this crystal.

Passive mode-locking performance of mixed Nd:La_011Y_089VO_4 crystal

Passive mode locking of a diode pumped Nd:La(0.11)Y(0.89)VO(4) mixed crystal laser with a semiconductor saturable absorber mirror (SESAM) was experimentally investigated for the first time to our knowledge. Stable CW mode-locking has been achieved on both a-cut and c-cut mixed crystals. In case of the a-cut crystal, when a 2% output coupler (OC) was used, the shortest pulse obtained was 4.5 ps and the highest output power was 0.94 W, while when a 6% OC was used, the shortest pulse obtained was 6.8 ps and the highest output power was 5.16 W. In the latter case the optical conversion efficiency is 38% and the slope efficiency is 40.3%, respectively; with the c-cut crystal the shortest pulse achieved was 5.5 ps. Moreover, simultaneous mode locking at two close wavelengths of 1064.3 nm and 1066.2 nm was observed on the c-cut crystal. The mode locked pulse beating generated temporal interference fringe of 0.5 THz repetition rate.

Thermal, spectral and laser characteristics of Nd doped La0.05Lu0.95VO4 crystal

A 0.25at% Nd doped La0.05Lu0.95VO4 mixed crystal was grown by the Czochralski method. The thermal properties including thermal expansion, specific heat, thermal diffusion, and thermal conductivity were systematically studied. Meanwhile the reasons for cracking of this mixed crystal were also discussed. The refractive index at wavelengths of 633nm and 1539nm were obtained with the prism coupling method. The polarized absorption and fluorescence spectra of the crystal were also measured at room temperature. It was found that the fluorescence lifetime of 4F3/2 manifold for Nd3+ in Nd:La0.05Lu0.95VO4 is about 90μs. Diode-pumped continuous-wave (CW) laser operations at 1.06μm with a- and c-cut crystals were demonstrated. For the a-cut crystal a maximum output power of 5.41W was obtained at an incident pump power of 12.9W. Different from the a-cut crystal, the laser spectrum of the c-cut crystal was found to be dual-wavelength.

LD端面泵浦Nd∶LiGd(MoO4)2晶体的主动调Q脉冲激光特性

The Nd∶LiGd(MoO4)2 crystal samples with different orientations were machined,and their Continuous Wave(CW) and actively modulation laser characteristics were measured and analyzed.A laser diode(LD) end-pumped double mirror cavity was used in the experiment,in which the coupling transmittance of the output mirror was 2%.In CW operation conditions,the maximum output powers of a-cut and c-cut crystals were 733 mW and 550 mW,respectively,corresponding optical conversion efficiencies of 11.3% and 6.7%.In acousto-optic(A-O) operation conditions,the maximum output powers of a-cut and c-cut crystals were 180 mW and 135mW,respectively,corresponding optical conversion efficiencies of 2.8% and 1.7%.The optimum pulse experimental results are obtained when the pulse repetition frequency(PRF) is 10 kHz.It is shown that the largest pulse energy and the highest peak power are 15.8 J and 85 W,respectively,which come from the a-cut sample.The shortest pulse width is 153 ns,which comes from the c-cut sample.Experimental results indicate that Nd∶LiGd(MoO4)2 crystals with different orientations can output different wavelengths in 1061 nm for the a-cut sample and in 1 068 nm for c-cut sample.The multi-wavelength emission property of the Nd∶LiGd(MoO4)2 crystal will help its applications to the THz-wave domain.

Diode-Pumped Actively Q-Switched Nd:Lu0.1Y0.9VO4Laser at 1.34 µm

The continuous-wave (CW) and acoustooptic (AO) Q-switched 1.34 µm laser performance of Nd:Lu0.1Y0.9VO4 crystals was demonstrated. In all operations, an a-cut crystal behaved better than a c-cut crystal. With a T = 3.9% output coupler, the maximum CW output power was 2 W, which corresponded to an optical conversion efficiency of 30.8%. At a pulse repetition frequency (PRF) of 5 kHz, the shortest pulse width, largest pulse energy, and highest peak power were 23.8 ns, 124 µJ, and 5.21 kW, respectively. As we have known, these are the best results obtained for a 1.34 µm pulsed laser based on mixed vanadate crystals.

Tm^3+/Ho^3+ co-doped LiGd(MoO_4)_2 crystal as laser gain medium around 20 μm

Tm3+/Ho3+ co-doped LiGd(MoO4)2 (LGM) crystals were investigated as gain media for the Ho3+ laser around 2.0 μm. Polarized spectroscopic parameters of Ho3+ ions in the crystals were calculated based on the absorption spectra by the Judd-Ofelt theory. Related fluorescence spectra and decay curves were measured and analyzed for the crystals with different Tm3+/Ho3+ co-doped concentrations, 5.4/1.4 and 4.6/0.6 at.%. Stimulated emission cross sections of the 5I7→5I8 transition of Ho3+ ions were derived according to the Fuchtbauer-Ladenburg formula. End-pumped by a pulsed diode laser at 795 nm, the Ho3+ laser at 2.05 μm with a slope efficiency of 20% was realized in a c-cut crystal sample with the Tm3+/Ho3+ concentrations of 4.6/0.6 at.%.

Diode-Pumped Actively Q-Switched Nd:Lu0.1Y0.9VO4 Laser at 1.34 µm

The continuous-wave (CW) and acoustooptic (AO) Q-switched 1.34 µm laser performance of Nd:Lu0.1Y0.9VO4 crystals was demonstrated. In all operations, an a-cut crystal behaved better than a c-cut crystal. With a T = 3.9% output coupler, the maximum CW output power was 2 W, which corresponded to an optical conversion efficiency of 30.8%. At a pulse repetition frequency (PRF) of 5 kHz, the shortest pulse width, largest pulse energy, and highest peak power were 23.8 ns, 124 µJ, and 5.21 kW, respectively. As we have known, these are the best results obtained for a 1.34 µm pulsed laser based on mixed vanadate crystals.

Thermal and laser characteristics of Nd doped La011Y089VO4 crystal

A 0.3 at% Nd doped La0.11Y0.89VO4 mixed crystal was grown by the Czochralski method. The thermal properties including the thermal expansion coefficient, specific heat, thermal diffusion coefficient, and the thermal conductivity were systematically studied. Diode-pumped continuous-wave (CW) laser performance at 1.06 μm with a- and c-cut crystal were demonstrated, and the maximum output power is about 8.76 W, which is obtained at the incident power of 19.15 W. All the results show that Nd:La0.11Y0.89VO4 is an excellent crystal for application as high-power lasers. What’s more, different with the a-cut crystal, the laser spectrum of c-cut one is found to be dual-wavelength.

Experimental study on the widely tunable performances of Tm:YAP laser under different output transmittance

Using by different output transmittances of 2%, 5%, and 10%, we have investigated the continuously tunable laser performance of c-cut Tm:YAP crystal. The 5-mm long c-cut crystal with 4 at.% thulium ion was used. Without a tuning element, the slope efficiency respect to the absorbed pump power reached 44.1% with transmittance of 5%, corresponding to the conversion efficiency of 35.3%. The laser operated at TEM00 mode with a beam quality factor of M2 ∼ 1.3, which was demonstrated by a 90/10 knife-edge method. A 3-mm thick birefringent plate was used as a tuning element. At transmittance of 5%, the widest tunable range of 159 nm extended from 1899 to 2058 nm. For transmittances of 2% and 10%, the tunable ranges of 150 and 68 nm were achieved, respectively.

Diode-pumped continuous wave and Q-switched operation of Nd:CaYAlO_4 crystal

The continuous wave (CW) and passively Q-switched performances of Nd:CaYAlO(4) crystal with both a- and c-cut were demonstrated. The CW output powers of 1.15 W and 1.26 W were obtained under the pump power of 8.96 W with slope efficiencies of 15.2% and 16.8% for a- and c-cut samples, respectively. As a result, new dual-wavelength all-solid-state lasers at 1080 nm and 1081 nm were achieved with c-cut crystal. By using Cr(4+):YAG wafer as saturable absorber, we performed Q-switching experiments. The highest average output powers and shortest pulse widths were measured to be 0.798 W, 10.6 ns and 0.537 W, 9.6 ns for a- and c-cut samples, respectively.

Spectroscopic and laser properties of Er^3+:Yb^3+:LuAl_3(BO_3)_4 crystal at 15-16 μm

An Er(3+):Yb(3+):LuAl(3)(BO(3))(4) crystal doped with 24.1 at.% Yb(3+) and 1.1 at.% Er(3+) ions was grown by the flux method. The polarized spectroscopic properties related to the operation of 1.5-1.6 microm laser of the crystal were evaluated at room temperature. The laser properties of a 0.7-mm-thick, c-cut crystal were investigated in diode-end-pumped hemispherical and plano-plano cavities, respectively. Compared with those of Er(3+):Yb(3+):YAl(3)(BO(3))(4) crystal obtained under similar experimental conditions, higher maximum output peak power, higher slope efficiency, and lower threshold were achieved in the Er(3+):Yb(3+):LuAl(3)(BO(3))(4) crystal.