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Abstract In 1917, Einstein considered stimulated photon emission of electron radiation, offering the theoretical foundation for laser, technically achieved in 1960. However, thermal phonons along with heat creation of non-radiative transition, are ineffective, even playing a detrimental role in lasing efficiency. Here, we realize a photon-phonon collaboratively pumped laser enhanced by heat in a counterintuitive way. We observe a laser transition from phonon-free 1064 nm lasing to phonon-pumped 1176 nm lasing in Nd:YVO4 crystal, associated with the phonon-pumped population inversion under high temperatures. Moreover, an additional temperature threshold (Tth) appears besides the photon-pump power threshold (Pth), and a two-dimensional lasing phase diagram is verified with a general relation ruled by Pth = C/Tth (constant C upon loss for a given crystal), similar to Curie’s Law. Our strategy will promote the study of laser physics via dimension extension, searching for highly efficient and low-threshold laser devices via this temperature degree of freedom.

Abstract Since the first invention of the laser in 1960, direct lasing outside the fluorescence spectrum is deemed impossible owing to the “zero-gain” cross-section. However, when electron-phonon coupling meets laser oscillation, an energy modulation by the quantized phonon can tailor the electronic transitions, thus directly creating some unprecedented lasers with extended wavelengths by phonon engineering. Here, we demonstrate a broadband lasing (1000–1280 nm) in a Yb-doped La2CaB10O19 (Yb:LCB) crystal, far beyond its spontaneous fluorescence spectrum. Numerical calculations and in situ Raman verify that such a substantial laser emission is devoted to the multiphonon coupling to lattice vibrations of a dangling “quasi-free-oxygen” site, with the increasing phonon numbers step-by-step (n = 1–6). This new structural motif provides more alternative candidates with strong-coupling laser materials. Moreover, the quantitative relations between phonon density distribution and laser wavelength extension are discussed. These results give rise to the search for on-demand lasers in the darkness and pave a reliable guideline to study those intriguing electron-phonon-photon coupled systems for integrated photonic applications.

Highlights Uniaxial orientation and single-grain penetration of quasi-2D and 3D perovskite films were achieved via a general thermal-pressed (TP) strategy. The TP-perovskite-based self-powered photodetectors (SPPDs) exhibit one of the best results among the 3D and quasi-2D perovskite SPPDs, respectively. These unpackaged TP-based devices exhibit ultrahigh humidity, optical and heat stability.

Electron–phonon‐coupling effect can generate the direct lasing beyond the fluorescence spectrum of the gain medium, but the laser efficiency is still low owing to weak multiphonon‐coupling intensity. Herein, associated with the three‐phonon‐assisted electron transitions beyond 1100 nm, the tunable laser generation from 1125 to 1155 nm and highly efficient continuous‐wave lasers at 1131 and 1140 nm in a ytterbium‐doped YCa4O(BO3)3 crystal are realized, by balancing the intracavity loss and phonon‐determined gain. The maximum output power reaches to 3.95 and 2.06 W at 1131 and 1140 nm, corresponding to a slope efficiency of 52.4% and 39.1%, respectively, which represents the highest efficiency in the solid‐state lasers in this spectral range. More impressively, this phonon‐assisted vibronic laser exhibits a wide‐spectral tunability and a good output power stability. Herein, a practical laser source in the underdeveloped spectral range is provided by the results, and they are helpful for the development of multiphonon‐assisted lasers beyond the inherent fluorescence spectrum.

A widely tunable phase-matched second harmonic generation (221–332 nm) covering almost the entire deep-UV spectral range is experimentally realized by angular engineering strategy of an additional periodic phase.

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor with poor prognosis. Temozolomide (TMZ) is the standard chemotherapy for glioblastoma treatment, but TMZ resistance significantly compromises its efficacy. In the present study, we generated a TMZ-resistant cell line and identified that mitochondrial dysfunction was a novel factor contributing to TMZ resistance though multi-omics analyses and energy metabolism analysis. Furthermore, we found that rotenone treatment induced TMZ resistance to a certain level in glioblastoma cells. Notably, we further demonstrated that elevated Ca2+ levels and JNK–STAT3 pathway activation contributed to TMZ resistance and that inhibiting JNK or STAT3 increases susceptibility to TMZ. Taken together, our results indicate that co-administering TMZ with a JNK or STAT3 inhibitor holds promise as a potentially effective treatment for glioblastoma.

Nonlinear photonic crystals: controlling light from any which way A three-dimensional nonlinear photonic crystal that manipulates light incident from any direction could allow new types of beam shaping for optoelectronic devices. In certain crystals, atoms arrange in mesoscopic structures called supercells, which cause light to interfere in useful ways. Generally, such crystals can only affect light beams that are incident from particular directions, and with certain polarizations. Now, Haohai Yu at Shandong University in Jinan, China, and co-workers have grown crystals of potassium tantalate niobate, with the constituent atoms in a critical ratio that provides a Rubik’s-cube-like structure with supercells 3–10 µm in size. The researchers observed rotating ferroelectric polarization and second harmonic generation in laser beams incident from all three dimensions (x, y, and z directions). They hope that the crystal could provide a useful platform for applications such as terahertz radiation and holography.

The inflammatory response of macrophages is an orderly and complex process under strict regulation accompanied by drastic changes in morphology and functions. It is predicted that proteins will undergo structural changes during these finely regulated processes. However, changes in structural proteome in macrophages during the inflammatory response remain poorly characterized. In the present study, we applied limited proteolysis coupled mass spectrometry (LiP-MS) to identify proteome-wide structural changes in lipopolysaccharide (LPS)-activated macrophages. We identified 386 structure-specific proteolytic fingerprints from 230 proteins. Using the Gene Ontology (GO) biological process enrichment, we discovered that proteins with altered structures were enriched into protein folding-related terms, in which HSP60 was ranked as the most changed protein. We verified the structural changes in HSP60 by using cellular thermal shift assay (CETSA) and native CETSA. Our results showed that the thermal stability of HSP60 was enhanced in activated macrophages and formed an HSP10-less complex. In conclusion, we demonstrate that in situ structural systems biology is an effective method to characterize proteomic structural changes and reveal that the structures of chaperone proteins vary significantly during macrophage activation.

Passive Q-switching is an effective approach for generating pulsed lasers, owing to its compact and additional modulation-free design. However, to compare favorably with active Q-switching and multi-stage amplification, the output energy needs to be enhanced for practical applications. Kramers Ytterbium ion (Yb3+)-doped borate crystals, with their excellent energy storage capacity, have been proven to be high-potential laser gain mediums for achieving pulsed lasers with moderate and high output energy using passive Q-switching technology. In this study, the growth, characterization, and laser generation of one Yb3+-doped borate crystal, the Yb3+:ScBO3 crystal, are systematically reviewed. The continuous-wave and passive Q-switching laser characteristics are presented in detail, and the self-pulsations derived from intrinsic ground-state reabsorption are also demonstrated. The specific characteristics and experiments confirm the potential of the Yb3+:ScBO3 crystal for future pulsed laser applications with moderate or even high energy output.

In recent times, the neodymium-doped gadolinium vanadate (Nd:GdVO4) crystal has attracted significant attention as one of the most valuable functional materials, but its lattice structure can be easily modified in an irradiation environment, which determines its related optical properties and affects the performance of devices based on the Nd:GdVO4 crystal. The near-surface lattice structure change and damage are studied through the displacement per atom (dpa), X-Ray diffraction, hardness and elastic (Young's) modulus, and micro-Raman spectroscopy techniques. We discover that the intensity and peak position of micro-Raman have obvious changes between waveguide and substrate region in Nd:GdVO4 crystal. The related optical properties induced by the structural changes, including the absorption bands and refractive index profiles, are investigated. A new absorption peak was observed after irradiation of the Nd:GdVO4 crystals by C3+ ions. Thus, waveguide optical-coupling techniques identified that the ion- irradiated Nd:GdVO4 crystal can support single-mode or multimode propagation at 633 nm. The fabricated waveguide structures emerge as promising candidate for photonic design and integrated optical devices, which will have a huge application prospect in multimedia and internet.

The self-frequency-doubling (SFD) crystal is a representative of multifunctional crystals. In recent years, SFD crystals and lasers have gained renewed attention based on the progress on SFD crystals and lasers and Nd:RECa4O(BO3)3 (RE = Y or Gd) crystals, with SFD lasers becoming commercial products. Here, we review the advances of SFD crystals and lasers, including the basic selection rules, theoretical analysis and recent progress of some potential SFD crystals and lasers. The Nd:RECa4O(BO3)3 crystals and lasers are highlighted, and their applications are also proposed and discussed, which may provide some inspiration for the further development of the SFD field and multifunctional materials.

Thermal lensing is studied in monoclinic Yb:Ca4YO(BO3)3 (Yb: YCOB) oxoborate crystals cut along the optical indicatrix axes. For all orientations, the thermal lens is positive. In the Z-cut crystal, the sensitivity factors of the thermal lens are MZ-X = 2.4 and MZ-Y = 2.8 m-1/W (for E∥X), and the astigmatism degree is as low as S/M = 14%. The positive thermal lens in Yb:YCOB is related to the large thermal expansion and strong photoelastic effect. Microchip lasers are realized with 3-mm-long X, Y, and Z-cut 15 at.% Yb:YCOB crystals. With a Z-cut crystal, maximum output power of 8.35 W is achieved at ~1040 nm with slope efficiency of 70%. Using various crystal cuts and output coupler transmissions, multiwatt emission in the spectral range of 1033-1091 nm is demonstrated.

The full matrix of electro-elastic constants of sillenite-type crystals Bi12TiO20 (BTO) and Bi12SiO20 (BSO) were determined by the resonance method, with d14 and k14 being on the order of 40–48 pC/N and 31%–36%, respectively. In addition, double-rotated orientation dependence of d33 was investigated, with the maximum values of 25–28 pC/N being achieved in ZXtl45°/54°-cut samples. The electrical resistivity of BSO was found to be two orders higher than that of BTO, being on the order of 7 × 105 Ω cm at 500 °C. The temperature dependence of dielectric and piezoelectric properties were investigated. BSO exhibited a high thermal stability in the temperature range of 25–500 °C, while BTO showed a variation of ~3% in the range of 25–350 °C. The high values of d14 and k14, together with the good thermal stability, make BTO and BSO crystals potential candidates for electromechanical applications in medium temperature range.

We demonstrated the dual-wavelength simultaneously Q-switched Nd: Lu2O3 laser with a topological insulator Bi2Se3 as the Q-switcher. The continuous-wave Nd:Lu2O3 crystal laser with the slope efficiency of 31% was achieved, and the first Nd:Lu2O3 pulsed laser operation was reported, as far as we know. By using the wavelength-insensitive saturable absorption of topological insulators, the dual wavelength of the Nd:Lu2O3 crystal laser can be Q-switched simultaneously without the frequency selection of the saturable absorber, since the emission cross-sections of Nd:Lu2O3 at the wavelengths of 1077 and 1081 nm are comparable. The results indicate that the topological insulator is wavelength-insensitive and should be suitable for the dual-wavelength simultaneously Q-switched laser as a passive Q-switcher. It can be proposed that this work would provide an efficient technology for the dual-wavelength simultaneously Q-switched laser, which has promising applications in many regimes.

Midinfrared (IR) nonlinear optical (NLO) materials with high performance are vital in important technological applications in many civil and military fields. Very recently, langasite family compounds have attracted much attention due to their wide transparency to mid-IR region and ultrahigh laser damage threshold (LDT). In this brief review, three important compounds—LGS, LGN, and LGT—are investigated and analyzed based on available experimental data. The electrooptical (EO) Q-switch and mid-IR OPO applications are summarized in detail. Finally, promising search directions for new metal oxides that have good mid-IR NLO performances are discussed.

A quantitative structure-property relationship (QSPR) model is proposed to explore the relationship between the pKa of various compounds and their structures. Through QSPR studies, the relationship between the structure and properties can be obtained. In this study, a novel chaos-enhanced accelerated particle swarm algorithm (CAPSO) is adopted to screen molecular descriptors and optimize the weights of back propagation artificial neural network (BP ANN). Then, the QSPR model based on CAPSO and BP ANN is proposed and named the CAPSO BP ANN model. The prediction experiment showed that the CAPSO algorithm was a reliable method for screening molecular descriptors. The five molecular descriptors obtained by the CAPSO algorithm could well characterize the molecular structure of each compound in pKa prediction. The experimental results also showed that the CAPSO BP ANN model exhibited good performance in predicting the pKa values of various compounds. The absolute mean relative error, root mean square error, and square correlation coefficient are respectively 0.5364, 0.0632, and 0.9438, indicating the high prediction accuracy. The proposed hybrid intelligent model can be applied in engineering design and the prediction of physical and chemical properties.

In this work, using large-sized single crystals of high optical quality, the optical properties of Ba2TiSi2O8 were systematically investigated, including transmission spectra, refractive indices and nonlinear absorption properties. The crystal exhibits a high transmittance (>84%) over a wide wavelength range from 340 to 2500 nm. The refractive indices in the range from 0.31256 to 1.01398 μm were measured, and Sellmeier’s equations were fitted by the least squares method. The nonlinear absorption properties were studied by using the open-aperture Z-scan technique, with a nonlinear absorption coefficient measured to be on the order of 0.257 cm/GW at the peak power density of 16.4 GW/cm2. Such high transmittance and wide transparency indicate that optical devices using the Ba2TiSi2O8crystal can be applied over a wide wavelength range. Furthermore, the small nonlinear absorption observed in Ba2TiSi2O8 will effectively increase the optical conversion efficiency, decreasing the generation of laser damage of the optical device.

We demonstrate the simultaneous oscillation of different photons with equal orbital angular momentum in solid-state lasers for the first time to our knowledge. Single tunable Hermite-Gaussian (HG0,n) (0 ≤ n ≤ 7) laser modes with dual wavelength were generated using an isotropic cavity. With a mode-converter, the corresponding Laguerre-Gaussian (LG0,n) laser modes were obtained. The oscillating laser modes have two types of photons at the wavelengths of 1077 and 1081 nm and equal orbital angular momentum of nħ per photon. These results identify the possibility of simultaneous oscillation of different photons with equal and controllable orbital angular momentum. It can be proposed that this laser should have promising applications in many fields based on its compact structure, tunable orbital angular momentum, and simultaneous oscillation of different photons with equal orbital angular momentum.

Polycrystalline ZnSe is essential for broadband windows, lenses, and even nonlinear media because its intrinsic transmission covers from visible to mid- and far-infrared regions, and its nonlinear coefficient is larger than that of traditional materials. Its macro- and micro-structures determine its performance and further applications. This study investigates the macro- and micro-structural engineering of large-scale polycrystalline ZnSe, including the structure, morphology, defects and optical properties. The chemical vapor deposition method is used to prepare standard and multispectral ZnSe with sizes of up to 100 mm. As a supplement to a past study, different micro-defects and macro-island-like and coarse columnar structures are observed, and their formation mechanisms are determined. In addition, the influence of micro- and macro-structures on the spectra of the prepared materials is discussed and experimentally identified. More importantly, micro- and macro-structural engineering is used to optimize the preparation technology, thereby increasing the transmission of polycrystalline ZnSe to 75% with the optical bandgap of 2.54 eV, presenting an enhanced transparency compared with the commercialized ZnSe materials (71%). This study should be helpful for understanding the formation mechanism of macro- and micro-structures in polycrystalline materials and for optimizing the preparation technology of optical polycrystalline materials. [ABSTRACT FROM AUTHOR]