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A good quality single crystal of Tm3+ doped YPO4 crystal was grown utilizing the flux method using a lead or molybdenum free flux. The spectroscopic properties of the crystal were investigated. The absorption cross-section of Tm3+:YPO4 at 791 nm is as large as 3.09 × 10−20 cm2. The intensity parameters Ω2,4,6, radiative transition rates, branching ratios and radiative lifetime were calculated by using the Judd–Ofelt theory. The strong experimental emission cross-section has an astounding value of 6.71 × 10−20 cm2 and is located at 1802 nm. All the results indicate that the Tm3+:YPO4 crystal is a potential laser medium crystal. [ABSTRACT FROM AUTHOR]

MXenes, a family of two-dimensional nanomaterials that have emerged in recent years, have attracted much attention in the field of optoelectronics due to their unique physicochemical properties and abundant elemental composition. Nevertheless, research studies on the broadband nonlinear optical properties of MXenes are rarely reported, especially in the deep ultraviolet region. Herein, we investigated the broadband nonlinear absorption properties (deep ultraviolet to near-infrared waveband) of Ti3C2 and Ti3AlC2 nanosheets by picosecond Z-scan. To the best of our knowledge, this is the first time that two-dimensional materials exhibit efficient optical limiting properties at deep ultraviolet wavelengths as short as 266 nm. Our results reveal the great potential of Ti3C2 and Ti3AlC2 nanosheets for laser protection, optical sensors, and device protection in the deep ultraviolet band, which are anticipated to be beneficial for the further design of MXene-based optical limiting devices. [ABSTRACT FROM AUTHOR]

A new Sm-doped calcium oxyborate crystal, SmxGd1−xCa4O(BO3)3 (Sm:GdCOB), was grown by the Czochralski (Cz) method. The cell parameters were determined to be a = 8.0910 Å, b = 16.0090 Å, c = 3.5571 Å, β = 101.267°, and Z = 2 with the Cm space group. The density was determined to be 3.72 g cm−3 by the Archimedes method. The thermal properties, including thermal expansion coefficient, the thermogravimetric and differential thermal analysis (TG-DTA) as well as specific heat were investigated systematically. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay lifetimes of the Sm:GdCOB crystal were measured at room temperature. Based on the J–O theory, various spectra parameters, such as polarized absorption cross-section, intensity parameters, transition probabilities, radiative lifetime, and branching ratios were obtained, and the polarized stimulated emission cross-sections were determined. For the Sm:GdCOB crystal, excellent physical properties, such as rapid growth with large size, high specific heat (0.585 J g−1 K−1, RT), large quantum yield (76%), and strong emission around 600 nm predict potential application as a reddish-orange laser medium. In addition, the Sm:GdCOB crystal exhibits a distinct saturable absorption characteristic at 1064 nm, indicating that it can be used as a pulse modulation material in the solid-state laser. [ABSTRACT FROM AUTHOR]

Disordered crystals have garnered increasing attention as new laser materials because of their broad emission bandwidths. This paper reports a novel Yb-doped strontium yttrium phosphate (Yb:YSr3(PO4)3) crystal with a disordered structure, as well as its crystal growth, structure, spectral properties, and laser performance. The crystal structure (cubic, 4¯3m point group) was refined using the Rietveld method. The absorption cross-section and fluorescence lifetime were determined to be 1.31 × 10−20 cm2 at 976 nm and 1267 μs, respectively. The stimulated emission cross-section was 1.04 × 10−20 cm2 at 1013 nm, with an emission bandwidth of 55 nm. In addition, continuous-wave laser operation was realized using the Yb:YSr3(PO4)3 crystal with different output coupler transmissions, where the obtained maximum output power and slope efficiency were 1.3 W and 61%, respectively. A dual-wavelength regime with wavelengths centered at 1039 nm and 1047 nm (Δν = 2.2 THz) was achieved under certain conditions; thus, this crystal is expected to be employed for developing terahertz sources. In addition, the laser can operate at multiple wavelengths, ranging from 1023 to 1050 nm. The results indicate that the Yb:YSr3(PO4)3 crystal with a disordered structure may be a promising multi-wavelength laser crystal. [ABSTRACT FROM AUTHOR]

Large size HoCa4O(BO3)3 (HoCOB) crystal was successfully grown by the Czochralski (Cz) method. Through single-crystal X-ray diffraction the cell parameters were determined to be a = 8.090(3) Å, b = 16.018(7) Å, c = 3.5317(14) Å, β = 101.28°(4) and Z = 2 with the space group Cm. The Archimedes method was used to measure the density which was 3.85 g cm−3. In the transmittance spectrum of HoCOB, there are strong absorption peaks from 200 to 680 nm and 1800 to 2200 nm, corresponding to the Stokes levels between 13 219 and 49 335 cm−1. The thermal and the piezoelectric properties were investigated under different temperatures. At 300 K around, the thermal expansion coefficient, thermal conductivity, specific heat, and relative dielectric constant on the b axis direction (i.e. the unique two-fold axis direction) were 5.35 × 10−6 K−1, 2.18 W m−1 K−1, 0.58 g−1 K−1, and 12.5, respectively. [ABSTRACT FROM AUTHOR]

In current inertial confinement fusion (ICF) facilities, potassium dihydrogen phosphate (KH 2 PO 4 , KDP) type crystals are the only nonlinear optical (NLO) materials that can satisfy the aperture requirement of the ICF laser driver. Ammonium dihydrogen phosphate (NH 4 H 2 PO 4 , ADP) crystal is a typical isomer of KDP crystal, with a large nonlinear optical coefficient, high ultraviolet transmittance, and large growth sizes, which is an important deep ultraviolet (UV) NLO material. In this paper, we investigated the effect of ADP temperature on its fourth-harmonic-generation (FHG) performance. When the temperature of the ADP crystal was elevated to 48.9 °C, the 90° phase-matched FHG of the 1064 nm laser was realized. Compared with the 79° phase-matched FHG at room temperature (23.0 °C), the output energy at 266 nm, conversion efficiency, angular acceptance, and laser-induced damage threshold (LIDT) increased 113%, 71%, 623%, 19.6%, respectively. It shows that elevating ADP temperature is an efficient method to improve its deep UV frequency conversion properties, which may also be available to other NLO crystals. This discovery provides a very valuable technology for the future development of UV, deep UV lasers in ICF facilities.

In this Letter, the spontaneous Raman spectra of a novel, to the best of our knowledge, crystal α-BaTeW 2 O 9 (α-BTW) are characterized and analyzed. The relative Raman gain coefficient of the α-BTW crystal is calculated to be 0.84 times that of YVO 4 . With a 35-mm-long crystal, the first-order Raman laser of α-BTW operating at 1178 nm is realized. The simple external resonator setup is employed in the first-order Raman laser of α-BTW. The pump source is a lamp-pumped electric-optical Q switched Nd:YAG laser amplifier system operating at 1064 nm with a pulse width of 10 ns. The Raman laser exhibits a threshold of 14.7 MW/cm 2 . In our experiments, a maximum pulse energy of 21.5 mJ is obtained with an optical-to-optical conversion efficiency and slope efficiency of 43.6%, 57.9%, respectively. Due to its high laser damage threshold, relative high Raman gain coefficient, and excellent thermal properties, the α-BTW crystal is a potential Raman material.

Disordered crystals have attracted immense attention for the generation of ultrashort laser pulses due to their good thermomechanical characteristics and wide emission bandwidths. In this work, a Gd-based orthophosphate crystal, GdSr 3 (PO 4 ) 3 , (GSP), and a Nd 3+ -doped GdSr 3 (PO 4 ) 3 crystal, (Nd:GSP), were obtained by the Czochralski method. The crystal structure, optical properties, electronic band structure, laser damage threshold, and hardness of the GSP crystal were comprehensively investigated. It exhibited a disordered structure due to the random distribution of Sr and Gd atoms in the same Wyckoff site, which caused inhomogeneous spectral broadening. Additionally, it exhibited a short UV absorption cutoff edge (<200 nm), a large band gap (5.81 eV), and a high laser damage threshold (∼1850 MW/cm 2 ). The spectral properties and Judd-Ofelt calculations of the Nd:GSP crystals were analyzed. A wide absorption band at 803 nm, with a full width at half-maximum value of 20 nm, makes the Nd:GSP crystal suitable for the efficient pumping of AlGaAs laser diodes. Sub-100-fs pulses could be supported by its 25 nm emission bandwidth. Hence, the GSP crystal could be a promising disordered crystal laser matrix.