RESUMEN
Cr4+-activated phosphors are important candidate materials for NIR-II light sources, but providing a suitable lattice coordination environment for Cr4+ and achieving long wavelength broadband emission remains a challenge. In this work, a series of Cr4+-activated ABO2 (A = Li, Na; B = Al, Ga) phosphors were successfully prepared. Due to the presence of only tetrahedral coordination structures available for Cr4+ to occupy in the matrix crystal ABO2, the valence state and luminescence stability of Cr4+ are effectively guaranteed. Through the cation substitution design of A-site (Na â Li) and B-site (Ga â Al), the [BO4] tetrahedron is distorted and expanded, which degrades the symmetry of the Cr4+ coordination crystal field. Consequently, the central wavelength of the Cr4+ emission peak is tuned from 1280 to 1430 nm, and the fwhm is significantly extended from 257 to 355 nm. Thebroadband NIR-II light sources constructed with LiAlO2: 0.03Cr4+ and NaGaO2: 0.03Cr4+ phosphors verify their important potential applications in nondestructive testing and biological imaging.
RESUMEN
As a key material for phosphor-converted light-emitting diodes (pc-LEDs) applications, broadband near-infrared (NIR) phosphors currently face poor thermal stability issues. In this work, we synthesized a broadband near-infrared phosphor YGa3(BO3)4: Cr3+ (YGBO: Cr3+) with a high thermal stability. The YGBO: Cr3+ sample exhibits a broadband near-infrared emission centered at 770 nm with a full width at half-maximum (fwhm) of 2130 cm-1 under blue light excitation. Benefiting from the borate host crystal's strong structural rigidity, wide optical band gap, and weak electron-phonon coupling strength, YGBO: Cr3+ demonstrates strong luminescence thermal stability, and the corresponding luminescence intensity can maintain 80% at 150 °C compared to room temperature. Furthermore, we fabricated a pc-LED device using a blue light chip and YGBO: Cr3+ phosphor, and confirmed its application potential as a near-infrared light source in the spectral analysis of fruit freshness.
RESUMEN
At present, most fluorescent materials that can be used for optical temperature measurement exhibit poor thermochromic performance, which limits their applications. In this study, the phosphor Ba3In(PO4)3:Er/Yb was synthesized with a high doping concentration of Yb3+, and it emitted composition- and temperature-induced wide color gamut up-conversion luminescence from red to green. Four modes of fluorescence thermometry can be realized in the temperature range of 303-603 K, which is based on the ratio of fluorescence intensity between thermally coupled energy levels and non-thermally coupled energy levels, color coordinate shift, and fluorescence decay lifetime, respectively. The highest Sr value obtained was 0.977% K-1. Taking advantage of the fact that temperature can significantly change the luminous color of the phosphor Ba3In(PO4)3:0.02Er3+/0.05Yb3+, we demonstrated 'temperature mapping' on a smooth metal surface with multiple optical encryptions. These results indicate that the Ba3In(PO4)3:Er/Yb phosphor is an excellent fluorescent material for thermal imaging and has great application potential in temperature visualization measurement and optical encryption.
RESUMEN
The laser properties of Nd:YPO4 crystal were demonstrated for the first time. For a 1.2 at.% doped Nd:YPO4 crystal, the absorption cross-section at 803 nm, stimulated emission cross-section at 1063 nm, and fluorescence lifetime was measured to be 8.1 × 10-20 cm2, 1.6 × 10-19 cm2, 156 µs, respectively. With an as-grown 0.6 mm thin slice which was unpolished and uncoated, efficient diode-pumped continue-wave (CW) laser operations were realized at 1.06 and 1.3 µm wavebands. The 1063 nm output power reached 2.16 W when the absorbed pump power was 4.07 W, corresponding to an optical-to-optical efficiency of 53%, and a slope efficiency of 56.4%. The 1.3 µm laser output exhibited the simultaneous operations of dual-wavelengths, i.e. 1338 and 1347 nm. The maximum output power was 800 mW at an absorbed pump power of 3.08 W, giving an optical-to-optical efficiency of 26% and a slope efficiency of 28.2%.
RESUMEN
We report on a miniature Yb:LuPO4 crystal laser at 1.01 µm that is passively Q-switched with a sapphire-based few-layer WS2 saturable absorber, and that can be operated under very high output couplings (≥80%). With 12.6 W of pump power absorbed, an average output power of 4.35 W is generated at a repetition rate of 1.33 MHz with a slope efficiency of 47%. The maximum pulse energy and highest peak power achieved are 3.41 µJ and 110 W, respectively; while the shortest pulse duration obtained is 28.6 ns. To the best of our knowledge, these results represent the highest output power and shortest pulse duration ever achieved in the 1 µm region from solid-state lasers passively Q-switched by using two-dimensional saturable absorbers.
RESUMEN
We demonstrate a Yb:LuPO4 miniature crystal laser that is formed with a 5 mm long plane-parallel resonator, and is passively Q-switched by a few-layer MoS2 saturable absorber. With 6.53 W of pump power absorbed, an average output power of 2.06 W at 1020.8 nm is generated at a pulse repetition rate of 429 kHz with a slope efficiency of 50%; the resulting pulse energy, duration, and peak power are respectively 4.8 µJ, 83 ns, and 57.8 W. While operating at 1010.5 nm, the laser is capable of producing an average output power of 1.53 W at a repetition rate of 870 kHz, with pulse duration being shortened to 61 ns. These results represent a significant progress in the development of Yb- or Nd-ion lasers passively Q-switched by two-dimensional MoS2.
RESUMEN
The efficient organic nonlinear optical material 4-hydroxy benzaldehyde-N-methyl 4-stilbazolium tosylate (HBST) was grown from methanol by slope nucleation method combined with slow cooling (SNM-SC) for the first time. The optimum growth conditions based on the cooling rate was further investigated. The single crystal X-ray diffraction (XRD) revealed that the chromophores of HBST crystal make an angle of about 33° with respect to the a-axis, which is close to the optimum of Terahertz (THz)-wave generation and electro-optics applications. NMR and FT-IR spectral studies have been performed to ascertain various functional groups present in the sample. Futhermore, the thermal stability and decomposition stages were analyzed through TG-DTA and DSC techniques. The dielectric constant and dielectric loss of HBST crystal have been studied. Critical optical properties like the absorption coefficient, refractive index, cut-off wavelength and band gap energy were calculated. Photoluminescence (PL) exication studies indicated green emission occured at 507nm. All the results of HBST crystal make it a promising candidate in the fields of optoelectronic and the generation of THz.
RESUMEN
For the first time, and to the best of our knowledge, we report a continuous-wave (cw) laser operation of Yb:LuPO4 crystal, demonstrated at room temperature in a compact plano-concave resonator end pumped by a diode laser. 1.61 W of cw output power around 1039 nm were generated with 2.40 W of pump power at 976 nm absorbed in a 0.3 mm thick crystal, leading to an optical-to-optical efficiency of 67%, whereas the slope efficiency was 75%. Polarized absorption and emission cross-section spectra are also presented and discussed in detail.
