First Achievement of Yellow Laser Operation in Dy-Doped Borate Crystals.

Continuous-wave (CW) yellow lasers have been demonstrated successfully by using a GaN laser-diode (LD) pumping in borate crystals for the first time. The Dy:GdMgBO (Dy:GMB) crystal with dimensions up to 33 × 19 × 15 mm is grown by the top-seeded solution growth method, and the polarized spectroscopic properties are investigated systematically at room temperature. The line strengths, Judd-Ofelt (J-O) intensity, spontaneous transition rates, fluorescence branching ratios, and radiative lifetimes are calculated in detail by the Judd-Ofelt theory.

NaKLa(SO): Enhanced Birefringence of Multiple-Alkali Metal Sulfate Systems via Rare Earth Metal-Centered Polyhedra.

Polarization modulation of ultraviolet (UV) birefringent crystals is crucial for various applications. Here, we introduce distorted La-O polyhedra into alkali metal sulfates to synthesize a novel birefringent material with excellent UV transmission and birefringence. The incorporation of distorted La-O polyhedra significantly increases the birefringence to 0.

Two UV optical crystals with strong optical anisotropy, large band gaps and an α-BBO type structure.

The [BO] group has attracted a lot of attention as α-BaBO (α-BBO) is composed of the [BO] group showing a short UV cut-off edge and a large birefringence. However, it is difficult to synthesize novel crystals with properties beyond α-BBO using [BO] as a fundamental building block (FBB). Hence, we successfully synthesized two cases of α-BBO-type organic-inorganic hybrid compounds using α-BBO as the template and melamine [CNH] as the fundamental building block.

[C(NH)]Zn(CO): A Guanidinium-Templated Ultraviolet Nonlinear Optical Material.

A novel guanidinium-templated ultraviolet (UV) nonlinear optical zinc carbonate crystal, [C(NH)]Zn(CO) (GZCO), has been synthesized in a closed system at low temperatures. GZCO crystallizing in the tetragonal noncentrosymmetric nonpolar space group, 422 exhibits a three-dimensional anionic framework constructed by interconnected [ZnCO] 12-membered ring channels with inorganic CO triangles and ZnO tetrahedra. Notably, the anhydrous GZCO shows a very high thermal stability among guanidine-based hybrid NLO materials benefiting from the confinement effect of the organic cations within inorganic channels.

Enhanced Electron-Phonon Coupling Effect in Rare-Earth Borate Crystals Containing a "Quasi-Free-Oxygen" Motif.

Revealing the interaction between electrons and phonons, e.g., electron-phonon coupling or decoupling, is a great challenge for physics and functional material communities.

SESAM mode-locked Yb:SrY(BO) laser.

We demonstrate the first sub-40 fs soliton pulse generation from a diode-pumped Yb:SrY(BO) laser passively mode-locked by a semiconductor saturable absorber mirror. Pulses as short as 38 fs at a central wavelength of 1051.7 nm were achieved with an average output power of 115 mW and a pulse repetition rate of 67.

Hybrid organic-inorganic triguanidine arsenate dihydrate for ultraviolet nonlinear optical application.

Introduction of the planar organic cation [C(NH)] into tetrahedronal inorganic arsenate generates a new ultraviolet nonlinear optical crystal triguanidine arsenate dihydrate, [C(NH)]AsO·2HO, which exhibits a short ultraviolet absorption edge (210 nm), suitable second-harmonic generation response (0.9 × KDP), and moderate birefringene (0.0387 at 546 nm).

To improve the key properties of nonlinear optical crystals assembled with tetrahedral functional building units.

Nonlinear optical (NLO) crystals assembled with conventional non-π-conjugated tetrahedral functional building units (FBUs), generally referring to [PO] and [BO], usually exhibit weak nonlinearity and poor birefringence. It is currently proposed that partially substituting oxygen atoms with fluoride atoms in these FBUs could enhance these crucial properties. Hence, we investigated for the first time the NLO-related properties of NHBAsOF (ABAF), which was constructed from tetrahedral [BOF] and [AsO] FBUs, and enhancements of these properties were observed in this material, that is large second-harmonic generation (SHG) response (2 × KDP) and improved birefringence (0.

Struvite-type AMgPO·6HO (A = NH, K): Two Natural Deep-Ultraviolet Transparent Nonlinear Optical Crystals.

Deep-ultraviolet (DUV) nonlinear optical (NLO) materials play vital roles in diverse fields. Unfortunately, only the KBeBOF crystal has found commercial applications so far. Therefore, the discovery of new DUV NLO crystals is still urgent.

Diode-pumped sub-50-fs Kerr-lens mode-locked Yb:GdYCOB laser.

We present a sub-50-fs diode-pumped Kerr-lens mode-locked laser employing a novel "mixed" monoclinic Yb:Ca(Gd,Y)O(BO) (Yb:GdYCOB) crystal as a gain medium. Nearly Fourier-limited pulses as short as 43 fs at 1036.7 nm are generated with an average power of 84 mW corresponding to a pulse repetition rate of ∼70.

Single-walled carbon-nanotube saturable absorber assisted Kerr-lens mode-locked Tm:MgWO laser.

We demonstrate sub-100-fs Kerr-lens mode-locking of a : laser emitting at ∼2µ assisted by a single-walled carbon-nanotube saturable absorber. A maximum average output power of 100 mW is achieved with pulse duration of 89 fs at a pulse repetition rate of ∼86. The shortest pulse duration derived from frequency-resolved optical gating amounts to 76 fs at 2037 nm, corresponding to nearly bandwidth-limited pulses.

2(CHN)·2Cl·HO: an ultraviolet nonlinear optical crystal with large birefrigence and strong second-harmonic generation.

Large birefringence (Δn = 0.277 at 546 nm) and strong second-harmonic generation (SHG) intensity (4.3 × KDP) achieved a remarkable balance in a potential ultraviolet nonlinear optical crystal: 2(CHN)·2Cl·HO.

[Al(HO)](IO)(NO): a material with enhanced birefringence induced by synergism of two superior functional motifs.

We report a new strongly birefringent material, [Al(HO)](IO)(NO) (AINO). Based on a detailed analysis, we concluded that its enhanced birefringence (0.253 at 546 nm) predominantly resulted from a synergy of the effects of its (NO) and (IO) functional motifs, combined with an equally important and indispensable optimal arrangement of these two groups in the structure.

Low-loss fs-laser-written surface waveguide lasers at >2 µm in monoclinic Tm:MgWO.

Surface channel waveguides (WGs) based on a half-ring (40-60-µm-diameter) depressed-index cladding (type III) geometry are fabricated in monoclinic Tm:MgWO by femtosecond (fs) laser writing at a repetition rate of 1 kHz. The WGs are characterized by confocal laser microscopy and -Raman spectroscopy. A Tm:MgWO WG laser generates 320 mW at ∼2.

Spectroscopy and high-power laser operation of a monoclinic Yb:MgWO crystal.

Monoclinic (wolframite-type) monotungstate crystals are promising for rare-earth doping. We report polarized room- and low-temperature spectroscopy and efficient high-power laser operation of such a ${{\rm Yb}^{3 + }}{:}\,{{\rm MgWO}_4}$Yb:MgWO crystal featuring high stimulated emission cross section (${\sigma _{\rm SE}}\; = \;{6}.{2}\; \times \;{{10}^{ - 20}}\;{{\rm cm}^2}$σ=6.

KSrPO: a deep-UV transparent cyclophosphate as a nonlinear optical crystal.

Benefiting from high transmittance of PO4 tetrahedra in the deep-ultraviolet (deep-UV) region, phosphates have been investigated as deep-UV nonlinear optical (NLO) candidates for years. So far, reported deep-UV NLO phosphates are orthophosphates and polyphosphates while cyclophosphates, important members of the phosphates family, have usually been neglected for use as deep-UV NLO crystals. Here, we first report a novel cyclotetraphosphate K2SrP4O12 (KSPO) as a deep-UV transparent NLO crystal.

Polarization switching realized in the continuous-wave and acousto-optic Q-switched pulse Er:Yb:LaMgBO lasers at 1556 and 1568 nm.

By using the natural birefringence of crystalline quartz, the switching of a 1568 nm laser with polarization parallel to the Z optical indicatrix axis to a 1556 nm laser with polarization parallel to the Y optical indicatrix axis was observed in both continuous-wave and acousto-optic Q-switched pulse lasers based on an X-cut Er:Yb:LaMgBO crystal, when the alignment of the output mirror in a 976 nm diode-end-pumped plano-concave resonator was precisely tilted. For the continuous-wave regime, a 1568 nm laser with a maximum output power of 500 mW and slope efficiency of 16%, as well as a 1556 nm laser with a maximum output power of 400 mW and slope efficiency of 13.5% were realized, respectively.

Thermal, Spectral and Laser Properties of Er:Yb:GdMgB₅O: A New Crystal for 1.5 μm Lasers.

A novel laser crystal of Er:Yb:GdMgB₅O with dimension of 26 × 16 × 12 mm³ was grown successfully from K₂Mo₃O flux by the top seeded solution growth method. The thermal diffusivity and specific heat capacity were measured to calculate the thermal conductivity of the crystal. The absorption and fluorescence properties of the crystal at room temperature were investigated in detail.

Efficient continuous-wave diode-pumped Er:Yb:LaMgBO laser with sapphire cooling at 1.57 μm.

Efficient 1.57 μm continuous-wave laser was demonstrated in an X-cut, 2.0 mm-thick Er:Yb:LaMgBO crystal with sapphire cooling end-pumped by a 976 nm laser diode.

Sub-100 fs Tm:MgWO laser at 2017 nm mode locked by a graphene saturable absorber.

We present the first sub-100 fs bulk solid-state laser in the 2-μm spectral range employing the monoclinic Tm-dopedMgWO crystal as an active medium. By applying a graphene-based saturable absorber and chirped mirrors for dispersion management, stable self-starting mode-locked operation at 2017 nm was achieved. Nearly Fourier-limited pulses as short as 86 fs featuring a bandwidth of 53 nm were generated at a repetition rate of 76 MHz.

Continuous-wave and SESAM mode-locked femtosecond operation of a Yb:MgWO laser.

We present a detailed continuous-wave regime characterization and, for the first time to the best of our knowledge, SESAM mode-locked femtosecond operation with a monoclinic, Yb-doped, MgWO crystal. Pumping with a low-power, single-mode fiber-coupled laser diode emitting at 976 nm, we demonstrate threshold for continuous-wave (cw) operation as low as 50 mW (absorbed pump power) and slope efficiency up to ~60% (with respect to the absorbed pump power) for two of the principal emission polarizations. The output wavelength in the cw regime is continuously tunable over a ∼50 nm broad range.

Monoclinic Tm:MgWO: a promising crystal for continuous-wave and passively Q-switched lasers at ∼2 μm.

Monoclinic thulium-doped magnesium monotungstate, Tm:MgWO, is promising for efficient power-scalable continuous-wave (CW) and passively Q-switched lasers at >2  μm. Under diode pumping at 802 nm, a compact CW laser based on Z-cut Tm:MgWO generated 3.09 W at 2022-2034 nm with a slope efficiency of 50% which represents the highest output power ever achieved with this type of laser host.

Crystal growth, optical spectroscopy and laser action of Tm-doped monoclinic magnesium tungstate.

We report on the crystal growth, spectroscopic investigation and laser performance of Tm-doped monoclinic magnesium tungstate (Tm:MgWO), for the first time, to the best of our knowledge. A high-quality crystal has been grown by the top seeded solution growth method. The relevant spectroscopic properties are characterized in terms of absorption, luminescence and Raman spectroscopy.

Efficient orthogonally polarized dual-wavelength Nd:LaMgB₅O₁₀ laser.

We reported an efficient, continuous-wave, diode-pumped, orthogonally polarized dual-wavelength laser working at 1051.8 and 1081.4 nm in a new neodymium-doped borate crystal, Nd:LaMgB5O10, which was grown by the top-seeded solution growth method.

Growth and spectral assessment of Yb(3+)-doped KBaGd(MoO4)3 crystal: a candidate for ultrashort pulse and tunable lasers.

In order to explore new more powerful ultrashort pulse laser and tunable laser for diode-pumping, this paper reports the growth and spectral assessment of Yb(3+)-doped KBaGd(MoO(4))(3) crystal. An Yb(3+):KBaGd(MoO(4))(3) crystal with dimensions of 50×40×9 mm(3) was grown by the TSSG method from the K(2)Mo(2)O(7) flux. The investigated spectral properties indicated that Yb(3+):KBaGd(MoO(4))(3) crystal exhibits broad absorption and emission bands, except the large emission and gain cross-sections.