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The sesquioxide Lu2O3 possesses superior physical and chemical properties and emerges as a promising host material for high-power laser applications. However, Lu2O3 has an extremely high melting point, making it difficult to prepare large-size and high-quality crystals. In this paper, we report the growth of a Yb:Lu2O3 crystal with dimensions of Φ50.7 × 43.0 mm3 using the temperature gradient technique (TGT) combined with the directional solidification technique. The full width at half maximum (FWHM) of the high-resolution X-ray rocking curve of the crystal was determined to be 58.76 arcsec. Additionally, the optical homogeneity root mean square (RMS) was 10−5. The thermal properties, spectroscopic characterization, and continuous wave (CW) laser operation of Yb:Lu2O3 crystal were systematically studied. The results demonstrate the efficacy of the TGT as a novel approach for growing large-sized Lu2O3 crystals of exceptional quality. [ABSTRACT FROM AUTHOR]

The development of nonlinear optical (NLO) devices is limited to the mid‐infrared range due to the lack of broadband NLO response. As an indirect band gap semiconductor, BiOCl has a band gap of ≈3.3 eV. The special anisotropic lamellar structure makes it exhibit excellent electrical and optical properties; however, its NLO saturable absorption effect is rarely reported. In this study, the NLO response, optical properties, and applications of BiOCl crystals grown by chemical vapor phase transport method are studied in detail. The transmission spectrum indicates the BiOCl crystal has a broadband transparent region (0.4–11 µm). The saturable absorption of BiOCl is characterized by the Z‐scan method with 532 and 1030 nm pulsed lasers. With BiOCl as the saturable absorber (SA), watt‐level passively Q‐switched pulsed laser based on Yb:LuAG single crystal fiber (SCF) is realized. This is the first report of BiOCl as SA for passively Q‐switched all‐solid‐state pulsed laser, and the obtained average power is the highest value of passively Q‐switched SCF pulsed lasers reported so far. The high transmittance, high laser damage threshold, wideband NLO response, and environmental stability of BiOCl indicate that BiOCl crystal is a potential candidate for NLO applications. [ABSTRACT FROM AUTHOR]

A high-quality Er3+-doped (Gd1−xLux)3Ga5O12 (Er: LGGG) laser crystal with a size of Φ 36 × 45 mm3 was successfully grown by the Czochralski (Cz) method for the first time. The effective segregation coefficient of Er3+ was determined to be 0.97, close to 1, and, thus, the uniform high-quality Er: LGGG crystal can be grown. In addition, the thermal and spectroscopic properties of Er: LGGG were investigated. Based on the measured characteristics, the Er: LGGG crystal has a huge potential for use in the 3.0 µm mid-infrared laser because of its outstanding optical quality, extraordinary thermal conductivity and stable structure. [ABSTRACT FROM AUTHOR]

The sesquioxide Lu2O3 single crystal has enormous potential applications as host material for solid-state lasers operating at high average powers, and its development is limited by the lack of large sized single crystals with high quality. Compared with the traditional Czochralski (Cz) method, the edge-defined film-fed growth (EFG) method, employing a die or a shaper, doesn't make the grown crystal come into contact with the melt in crucible directly during the growth process. Therefore, the growth interface is stable and the serious bottleneck problems of a "w"-shaped isotherm in the Czochralski method could be avoided effectively. Herein, the EFG method may be a promising technique to obtain ultra-high temperature sesquioxide single crystals with a large size, and more importantly, high quality. Accordingly, the sesquioxide Lu2O3 single crystal has been grown controllably with an oriented seed by the EFG method for the first time and the EFG method is promoted to an extremely high temperature of 2450 °C. The dimensions of the grown crystal are Φ 25 × 30 mm3, and the difficulties encountered during the crystal growth have been discussed in detail. Furthermore, the quality of the crystal has been evaluated. The optical properties of the grown crystal have been investigated. [ABSTRACT FROM AUTHOR]

A novel disordered structure crystal has drawn intense interest as a promising ultrafast laser crystal host for its broad absorption and emission bands. Herein, a novel disordered crystal of Nd3+-doped CaYAl3O7 (CYAM) was successfully grown using the Czochralski method for the first time. The effective segregation coefficient of Nd3+ ions in CaYAl3O7 was calculated to be 0.76. To better understand the intrinsic optical properties, the transmission spectra and refractive index of pure CaYAl3O7 were measured. A systematic investigation of the crystal structure characteristics, fluorescence lifetime, and polarized absorption and emission cross-sections of the Nd:CYAM crystal at RT was reported. The maximal absorption cross-sections are 3.51 and 5.34 × 10−20 cm2 for π-polarization and σ-polarization, with a FWHM of 18 nm. The emission cross-sections of π- and σ-polarization are 5.97 and 4.55 × 10−20 cm2 with FWHM values of 14 and 14.4 nm, respectively. The results show that the Nd:CYAM crystal has broad, strong absorption and emission cross-sections. In particular, effective continuous-wave laser operation was realized with this crystal in the a-cut sample for the first time. A maximum output power of 714 mW was achieved, corresponding to an optical-to-optical conversion efficiency of 7.14% and a slope efficiency of 8.6%. Collectively, these results show that the Nd:CaYAl3O7 crystal is a promising disordered laser host. [ABSTRACT FROM AUTHOR]

Highly efficient continuous-wave (CW) and passively Q-switching Er:YSGG lasers at around $2.8~\mu \text{m}$ were demonstrated. In the CW regime, a maximum output power was 514 mW with the dual-wavelength of 2795 and 2825 nm. The slope efficiency and optical-optical conversion efficiency were as high as 31% and 23%, respectively. Adopting black phosphorus as saturable absorber, a maximum output power of the passively Q-switched Er:YSGG laser was 240 mW, with a corresponding slope efficiency up to 15.8%. The shortest pulse duration was 293 ns, and the repetition rate was 109.1 kHz. The results indicated that Er:YSGG crystal would be a promising mid-infrared gain medium for high-efficiency laser operation. [ABSTRACT FROM AUTHOR]

A diode-pumped passively mode-locked Yb 3+ :Gd 3 Al 0.5 Ga 4.5 O 12 (Yb:GAGG) laser has been investigated by using a semiconductor saturable absorber mirror (SESAM) for the first time. Pulses with duration of 1.6 ps were produced at the central wavelength of 1027.8 nm. At the absorbed pump power of 8.4 W, the maximum average output power of 1.02 W was obtained with the repetition rate of 45 MHz. The corresponding single pulse energy and the peak power were calculated to be 22.7 nJ and 14.2 kW, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report the growth and characterization of Nd:(Lu x Gd1− x )3Ga5O12 crystal for the first time. The polycrystalline materials were synthesized by conventional solid-state reaction. Single crystal with good optical quality was successfully obtained and the dimensions of the as-grown crystal were Ø21×30mm3. X-ray powder diffraction studies confirm that the Nd:(Lu x Gd1− x )3Ga5O12 crystal is isostructural with Gd3Ga5O12 with unit cell parameter of 1.2361nm which is less than that of Gd3Ga5O12 crystal (1.2376nm). The absorption and emission spectra of the crystal at room temperature have also been studied. Continuous-wave (CW) laser performance at 1.06μm has been demonstrated on the crystal. [Copyright &y& Elsevier]

Single-crystal fibers (SCFs) have a great application potential in high-power lasers due to their excellent performance. In this work, high-quality and crack-free Yb3+:Lu3Al5O12 (Yb:LuAG) SCFs were successfully fabricated by the micro-pulling-down (μ-PD) technology. Based on the laser micrometer and the X-ray Laue diffraction results, these Yb:LuAG SCFs have a less than 5% diameter fluctuation and good crystallinity along the axial direction. More importantly, the distribution of Yb ions is proved to be uniform by electron probe microanalysis (EPMA) and the scanning electron microscope (SEM). In the laser experiment, the continuous-wave (CW) output power using a 1 mm diameter Yb:LuAG single-crystal fiber is determined to be 1.96 W, at the central wavelength of 1047 nm, corresponding to a slope efficiency of 13.55%. Meanwhile, by applying a 3 mm diameter Yb:LuAG SCF, we obtain a 4.7 W CW laser output at 1049 nm with the slope efficiency of 22.17%. The beam quality factor M2 is less than 1.1 in both conditions, indicating a good optical quality of the grown fiber. Our results show that the Yb:LuAG SCF is a potential solid-state laser gain medium for 1 μm high-power lasers. [ABSTRACT FROM AUTHOR]

• A large sized Tm, Ho:GGAG disordered crystal was successfully grown by Czochralski method. • The thermal and spectra properties and lifetime were systematically investigated. • The crystal has wide absorption and emission bandwidth with large absorption and emission cross-sections. • Diode-pumped continuous-wave laser was demonstrated in Tm, Ho: GGAG crystal. In this work, crystal growth, thermal properties, spectroscopic characterization, energy-transfer (ET) schemes and continuous wave (CW) laser operation of Tm, Ho: Gd 3 Ga 3 Al 2 O 12 (GGAG) disordered crystal were systematically studied. The thermal conductivity was calculated to be 8.53 Wm-1K−1 at 25 °C. The optical properties including absorption and emission spectra were investigated in detail. The crystal exhibits broad absorption band at 784 nm and the full width at half maximum (FWHM) and absorption coefficient are about 36 nm and 2.20 cm−1, respectively. The maximum stimulated emission cross-section for the 5I 7 5I 8 transition of Ho3+ ions at 2.07 μm is calculated to be 4.94 × 10−19 cm2 and the emission bandwidth is about 56 nm. Continuous wave laser performance of a 〈1 1 1〉 oriented Tm, Ho: GGAG crystal sample was demonstrated, and a maximum output power of 218 mW was achieved at 2112 nm. The results indicate that the Tm, Ho: GGAG crystal is promising for broadly tunable, ultrashort pulse lasers at ∼ 2 μm. [ABSTRACT FROM AUTHOR]

Nd:Gd 3 AlGa 4 O 12 laser crystal has been successfully grown by the Czochralski method. The absorption and fluorescence spectra of Nd:Gd 3 AlGa 4 O 12 crystal at room temperature was investigated. Continuous-wave (CW) and passively Q-switched laser at 1106 nm were demonstrated. The minimum pulse width of 26.2 ns with the pulse repetition rate of 9 kHz was obtained, which is the shortest pulse width of 1106 nm Nd:Gd 3 AlGa 4 O 12 laser to our knowledge. • A new Nd:Gd 3 AlGa 4 O 12 crystal laser crystal has been successfully grown by the Czochralski method. • The fluorescence spectrum of Nd:Gd 3 AlGa 4 O 12 crystal was studied, and the FWHM of 1106 nm is measured to be 10 nm. • The maximum output power of Q-switched laser was 117 mW and the shortest pulse width was 26.2 ns. [ABSTRACT FROM AUTHOR]

Er3+ doped laser crystals emitting at ∼3 µm mid-infrared (MIR) waveband have been intensively studied for their essential roles in surgery, military and other fields. In this work, Er: LuYAG and Er/Eu: LuYAG single crystal fibers (SCFs) were successfully grown by micro-pulling-down method for the first time. The as-grown SCFs demonstrated high crystalline quality and excellent transmittance. The distribution of the doping ions was proven to be uniform by XRF and EPMA measurements. The effect of Eu3+ deactivator on the spectroscopic properties was systematically investigated and the spectra parameters were calculated using Judd-Ofelt (J-O) theory. The luminescence decay curves illustrated that the co-doping of Eu3+ reduced the fluorescence lifetime of 4I 11/2 upper level and 4I 13/2 lower level simultaneously, making the lifetime ratio τ(4I 11/2)/τ(4I 13/2) in Er/Eu:LuYAG SCF greater than 1, so that the necessary population inversion can be maintained. It can be speculated that the co-doping of Eu3+ deactivator can effectively suppress the self-terminating bottleneck problem, which is beneficial to realize the ∼3 µm MIR laser output. [Display omitted] • Er: LuYAG and Er/Eu: LuYAG single crystal fibers are successfully grown by the micro-pulling-down method. • The co-doping of Eu3+ weakens the deleterious ∼1.5 µm near-infrared emission markedly while has slight effect on the ∼3 µm mid-infrared emission. • The incorporation of Eu3+ enables the fluorescence lifetime of 4I 11/2 upper level longer than the 4I 13/2 lower level. [ABSTRACT FROM AUTHOR]

• Yb:CTGS crystal was successfully grown by Cz method for the first time. • The thermal properties of Yb:CTGS were systematically studied. • Yb:CTGS possesses a nearly isotropy in thermal expansion (25–540 °C). The catangasite Ca 3 TaGa 3 Si 2 O 14 (CTGS) single crystal is considered to be a promising self-frequency-doubling material for visible lasers. In this work, a CTGS single crystal with Yb-doping was successfully grown by the Czochralski method for the first time. The as-grown crystal showed yellowish coloration. The temperature dependent thermal properties, such as thermal expansion, specific heat, thermal diffusivity and thermal conductivity, were systematically investigated. The anisotropy of thermal expansion is rather small. Furthermore, its thermal conductivity is comparable to those well-known self-frequency-doubling laser crystals. In laser operation, a maximum continuous wave output power of 4.2 W at the wavelength of 1047 nm was obtained under the output coupler of 5%. These characteristics are very beneficial to laser applications. [ABSTRACT FROM AUTHOR]

Abstract: Laser operation near 1.06μm by a diode-pumped Nd:Gd3Al x Ga(5− x ) O12 (x =0.94) (Nd:GAGG) disordered crystal has been investigated. Free-running oscillation, with a slope efficiency as high as 55% and 256mW output power, was achieved with 500mW absorbed power using a 1-W laser diode for pumping. Stable passive mode-locking with dual-wavelength operation was obtained with a semiconductor saturable absorber mirror (SAM) and a single-prism, dispersion-compensated cavity. The two-color mode-locking regime is well described by Fourier-limited synchronized pulses with duration ≈3.7 and 5.9ps and output power ≈65mW, with wavelength separation of 1.3nm around 1062nm. [Copyright &y& Elsevier]