Search

Advances in laser technology over the past 25 years have been impressive, in particular, for the Ytterbium technology where, nowadays, kilowatt-class laser systems are available. This technology also led to the possibility to provide hundreds of kilowatts of laser power by the use of enhancement cavities. We report here on the demonstration of a stable 500 kW average laser power in a high-finesse enhancement cavity. It paves the way toward systems providing laser power in excess of 1 MW and opens the door to a breakthrough in a variety of future applications. [ABSTRACT FROM AUTHOR]

We report on the generation of sub-30 fs pulses from a Kerr-lens mode-locked ytterbium solid-state laser based on a disordered Yb:SrLaAlO4 (Yb:SALLO) crystal as a gain medium. The Yb:SALLO laser, pumped by a spatially single-mode Yb-fiber laser at 979 nm, produces soliton pulses as short as 25 fs at 1090 nm, with an average output power of 149 mW at a pulse repetition rate of ∼80.7 MHz. The power scaling potential of the Kerr-lens mode-locked laser is exploited by achieving watt-level (1.54 W) average output power at 1081 nm for a somewhat longer pulse duration of 34 fs. This result corresponds to an impressive laser efficiency of 49.7% and a peak power of 468 kW. [ABSTRACT FROM AUTHOR]

We report the low temperature thermoelectric properties in the valence fluctuating system Yb3Si5 using high-quality single crystals. The coexistence of the tiny residual resistivity of 0.06 μΩ cm and the considerable Seebeck coefficient of 9 μV K−1 at 7 K leads to a huge Peltier conductivity of 40 A cm−1 K−1 and a power factor of 40 mW m−1 K−2. These pronounced characteristics are possibly attributed to the uncompensated semimetallic state in addition to the valence fluctuation of Yb ions. The large size of Yb3Si5 single crystal, which is typically ϕ 0.5 – 1 mm in diameter and 10 mm in length, enables the realistic application to the cryogenic thermoelectric device. [ABSTRACT FROM AUTHOR]

We report the low temperature thermoelectric properties in the valence fluctuating system Yb3Si5 using high-quality single crystals. The coexistence of the tiny residual resistivity of 0.06 μΩ cm and the considerable Seebeck coefficient of 9 μV K−1 at 7 K leads to a huge Peltier conductivity of 40 A cm−1 K−1 and a power factor of 40 mW m−1 K−2. These pronounced characteristics are possibly attributed to the uncompensated semimetallic state in addition to the valence fluctuation of Yb ions. The large size of Yb3Si5 single crystal, which is typically ϕ 0.5 – 1 mm in diameter and 10 mm in length, enables the realistic application to the cryogenic thermoelectric device. [ABSTRACT FROM AUTHOR]

Exploring the semiconductor materials with suitable gap and chemical stability is the key to developing solar-blind ultraviolet photodetectors with high stability, responsivity, and detectivity. However, available materials are limited currently, hindering the development of solar-blind detectors greatly. Rare earth oxides (Yb2O3) have the bandgap and high-dielectric constants suitable for solar-blind detection, but its potential of being applied to broadband gap semiconductors has not been deeply studied. Therefore, to activate the semiconductor characteristics of Yb2O3, this work builds a p-Gr/i-Yb2O3/n-Si heterojunction solar-blind ultraviolet photodetector by introducing single-layer graphene. Through tests, this device has an absorption cutoff wavelength of 271 nm, which can almost cover the entire solar-blind ultraviolet band, and a high responsivity of 9.78 mA/W under 0 V bias with the rise and fall time as short as 87 and 73 ms, respectively. This work not only prepares a high-performance solar-blind UV photodetector but also presents the potential application of Yb2O3 in the solar-blind ultraviolet light detection. The high-dielectric performance of rare earth oxides makes it expected to be used for the photoelectric chip unit in future integrated circuit. [ABSTRACT FROM AUTHOR]

We reported the realization of a 174Yb+–113Cd+ bi-species Coulomb crystal comprising 174Yb+, a heavier ion, as coolant and verified the potential of applying a coolant ion with a greater mass than the clock ion to sympathetically cooled microwave frequency standard. The two species of massive ions stably trapped in a Paul trap make up this large two-component crystal. The 113Cd+ ions are trapped in the center, which reduces considerably RF heating and excess micro-motion to which the 113Cd+ ions are subjected. Under this scheme, the uncertainty due to the second-order Doppler effect is reduced to 5 × 10 − 16 , which represents an order of magnitude improvement over sympathetic cooled 40Ca+–113Cd+ crystal. The second-order Zeeman frequency shift, which contributes the largest term of the systematic frequency shifts to the microwave ion frequency standard, is estimated to be as low as 7.133 × 10 − 13 corresponding to the low value of the operating magnetic field. The relevant AC Stark shift uncertainty is estimated to be 4 × 10 − 19 . These results demonstrate that using a heavier coolant ion is far superior and confirm the feasibility of a sympathetic-cooled cadmium-ion microwave clock system employing a 174Yb+–113Cd+ bicrystal. [ABSTRACT FROM AUTHOR]

Rare-earth nitride (REN) pnictides are exciting materials due to their localized and strongly correlated 4f-electrons that lead to interesting magnetic properties useful for spintronic devices. Ytterbium nitride (YbN) is a unique rare-earth pnictide as it exhibits antiferromagnetic ground states, unlike most ferromagnetic RENs. Though the magnetic properties of YbN thin films have been studied before, the electronic, thermoelectric, and plasmonic properties of YbN are yet to be investigated. Here, we show coexisting high thermoelectric power factor and short-wavelength infrared plasmon polaritons in epitaxial YbN thin films deposited with the ultrahigh vacuum growth method. YbN thin films deposited on (001) MgO substrates exhibit epitaxial and good quality crystalline growth and exhibit a high thermoelectric power factor of ∼ 1.9 mW/mK2 at 750 K due to high electrical conductivity and a moderately high Seebeck coefficient. High carrier concentration also leads to a positive-to-negative dielectric permittivity transition in YbN at ∼1900–1950 nm, corresponding to the epsilon-near-zero plasmonic resonance. Low-temperature transport measurements revealed that dislocation and acoustic phonon scattering dominate electronic transport. Demonstration of coexisting high thermoelectric power factor and infrared plasmon polaritons marks important progress in designing YbN-based thermoelectric and plasmonic devices for future applications. [ABSTRACT FROM AUTHOR]

We perform the precise measurement of the 6s6p3P2-6s7s3S1 transition frequencies of the neutral ytterbium (Yb) atoms by using the modulation transfer spectroscopy. High-resolution dispersive signals of all isotopes except low-abundance 168Yb (F = 2-F = 1) and 171Yb (F = 5/2-F = 3/2) are obtained. The frequencies of locked laser are measured using an optical comb, and the obtained results are traced to the absolute transition frequency of the 171Yb 1S0-3P0 clock. We measure the isotope shifts relative to 174Yb and evaluate the systematic shifts. The absolute frequency of the 6s6p3P2-6s7s3S1 transition in 174Yb is determined to be 389260605.8 ± 3.2 MHz, which has a huge deviation from the existing data in the studies. Based on the obtained transition frequencies, we calculate the hyperfine constants of the 3P2 and 3S1 states. This research will provide valuable data for the ytterbium-related experiments and improve the reported transition frequencies with higher precision. [ABSTRACT FROM AUTHOR]

While the unique geometrical frustration of pyrochlore Yb2Ti2O7 has attracted attention, the dielectric and other properties of this pyrochlore beyond frustrated magnetism are not well understood. Here, we report on the fascinating low-temperature dielectric relaxation of Yb2-xBaxTi2O7-δ (x = 0–0.20) and demonstrate that this phenomenon is related to structural distortion. A-site Ba substitution, which increases the density of point defects and introduces a different atomic radius, enhances the chemical disorder and structural distortion. As a result, the increases in oxygen vacancies and nonmagnetic Ba2+ and Yb2+ ions dilute the ferromagnetic Yb3+–Yb3+ interactions, as indicated by the decrease in effective magnetic moment. On the other hand, the distorted octahedra facilitate the hopping of Yb ions, and the random distribution of Ba2+ ions at the Yb3+ sites gives rise to additional random fields, leading to significantly increased dielectric relaxation. The room-temperature dielectric constant is improved to ∼170, twice that of pristine Yb2Ti2O7. This work provides a comprehensive view of the structural, magnetic, and dielectric properties of Yb2Ti2O7 and lays the foundation for additional research into pyrochlore compounds. [ABSTRACT FROM AUTHOR]

Graphite is a key material in a variety of cross-cutting applications in energy conversion, energy storage, and nuclear energy. Recently, temporally modulated continuous wave lasers have been shown to produce well-defined ablation features in graphite at relatively high processing speeds. In this work, we analyze in detail the laser ablation dynamics of single-pulse ablation in the sub-millisecond time regime to elucidate the origins of the resulting well-defined ablation craters using a combination of time-resolved emission imaging, diffuse reflection/scattering imaging, and optical emission spectroscopy. These multimodal in situ diagnostics revealed three main contributors to achieve well-defined ablation features: (1) rapid ejection of particles with ∼100 m/s speed, (2) ablation of the graphite in the gaseous form, and (3) absence of bulk liquid motion, which is typically observed in laser processing of metals. Plasma plume formation was sustained throughout the duration of the laser pulse (500 μ s). This work provides insights into the complex physical and chemical mechanisms of sub-millisecond laser–matter interactions, which are critical for parameter space optimization and tailoring of laser machining and drilling processes. [ABSTRACT FROM AUTHOR]

Room-temperature continuous-wave operation of InGaAs/AlGaAs quantum well lasers directly grown on on-axis silicon (001) has been demonstrated. A 420 nm thick GaAs epilayer completely free of antiphase domains was initially grown on the silicon substrate in a metal-organic chemical vapor deposition system and the other epilayers, including four sets of five-period strained-layer superlattices and the laser-structural layers, were successively grown in a molecular beam epitaxy system. The lasers were prepared as broad-stripe Fabry–Pérot ones with a stripe width of 21.5 μm and a cavity length of 1 mm. Typically, the threshold current and the corresponding threshold current density are 186.4 mA and 867 A/cm2, respectively. The lasing wavelength is around 980 nm, and the slope efficiency is 0.097 W/A with a single-facet output power of 22.5 mW at an injection current of 400 mA. This advancement makes the silicon-based monolithic optoelectronic integration relevant to quantum well lasers more promising with an enhanced feasibility. [ABSTRACT FROM AUTHOR]

Biological probes facilitate optical imaging and disease diagnosis and treatment. However, the large absorption and scattering loss in the tissue highly limit the depth during the application. In the present research, an NIR-I bioprobing system, which utilizes the Bessel beam to excite heavily doping nanocrystals, has been developed for deep tissue applications. On the one hand, the capillary mode selection method generates the Bessel excitation beam, lowering the excitation energy loss. On the other hand, a strong energy harvest of NaYbF4:90%Nd nanocrystals enables effective fluorescence and heat generation upon 800 nm excitation. By considering the advantages of Bessel excitation and heavily doping nanocrystals, up to ∼3 cm penetration depth for ex vivo bioimaging and the potential self-monitored photothermal treatment are demonstrated. The resultant bioprobing system allows deep tissue imaging and photothermal therapy, showcasing broad prospects in medical research and clinical applications. [ABSTRACT FROM AUTHOR]

The charge injection mechanism from contact electrodes into two-dimensional (2D) dichalcogenides is an essential topic for exploiting electronics based on 2D channels, but remains not well understood. Here, low-work function metal ytterbium (Yb) was employed as contacts for tungsten disulfide (WS2) to understand the realistic injection mechanism. The contact properties in WS2 with variable temperature (T) and channel thickness (tch) were synergetically characterized. It is found that the Yb/WS2 interfaces exhibit a strong pinning effect between energy levels and a low contact resistance (RC) value down to 5 kΩ μm. Cryogenic electrical measurements reveal that RC exhibits weakly positive dependence on T until 77 K as well as a weakly negative correlation with tch. In contrast to the non-negligible RC values extracted, an unexpectedly low effective thermal injection barrier of 36 meV is estimated, indicating the presence of significant tunneling injection in the subthreshold regime and the inapplicability of the pure thermionic emission model to estimate the height of the injection barrier. [ABSTRACT FROM AUTHOR]

The charge injection mechanism from contact electrodes into two-dimensional (2D) dichalcogenides is an essential topic for exploiting electronics based on 2D channels, but remains not well understood. Here, low-work function metal ytterbium (Yb) was employed as contacts for tungsten disulfide (WS2) to understand the realistic injection mechanism. The contact properties in WS2 with variable temperature (T) and channel thickness (tch) were synergetically characterized. It is found that the Yb/WS2 interfaces exhibit a strong pinning effect between energy levels and a low contact resistance (RC) value down to 5 kΩ μm. Cryogenic electrical measurements reveal that RC exhibits weakly positive dependence on T until 77 K as well as a weakly negative correlation with tch. In contrast to the non-negligible RC values extracted, an unexpectedly low effective thermal injection barrier of 36 meV is estimated, indicating the presence of significant tunneling injection in the subthreshold regime and the inapplicability of the pure thermionic emission model to estimate the height of the injection barrier. [ABSTRACT FROM AUTHOR]

A chiral soliton lattice (CSL) is a topological spin-texture that has potential applications in next-generation spintronic devices. In this work, we performed angle-dependence of magnetization and electron spin resonance (ESR) investigations on the CSL host Yb(Ni1−xCux)3Al9 with x = 0.06 (YNCA). The angle-dependent magnetization reveals a peculiar variable magnetic anisotropy. The maximum magnetization axis is parallel to the ab-plane below the field of ∼35.7 kOe while shifts to the c-axis at higher fields. The microwave responses of the CSL helicoid and ferromagnetic resonance (FMR) of the forced ferromagnetic state (FFM) are observed and appear as two resonance lines on ESR spectra with the highest intensities in the ab-plane. When the external field is rotated from H ⊥ c to H / / c , the resonance field H r 1 corresponding to the CSL helicoid decreases while H r 2 correlated with the FMR increases. Furthermore, the temperature-dependent ESR shows that the CSL persists until 15 K much higher than TC (6.4 K), which suggests a precursor phenomenon. The microwave response in YNCA provides a powerful tool for modulating and researching the CSL. [ABSTRACT FROM AUTHOR]

A chiral soliton lattice (CSL) is a topological spin-texture that has potential applications in next-generation spintronic devices. In this work, we performed angle-dependence of magnetization and electron spin resonance (ESR) investigations on the CSL host Yb(Ni1−xCux)3Al9 with x = 0.06 (YNCA). The angle-dependent magnetization reveals a peculiar variable magnetic anisotropy. The maximum magnetization axis is parallel to the ab-plane below the field of ∼35.7 kOe while shifts to the c-axis at higher fields. The microwave responses of the CSL helicoid and ferromagnetic resonance (FMR) of the forced ferromagnetic state (FFM) are observed and appear as two resonance lines on ESR spectra with the highest intensities in the ab-plane. When the external field is rotated from H ⊥ c to H / / c , the resonance field H r 1 corresponding to the CSL helicoid decreases while H r 2 correlated with the FMR increases. Furthermore, the temperature-dependent ESR shows that the CSL persists until 15 K much higher than TC (6.4 K), which suggests a precursor phenomenon. The microwave response in YNCA provides a powerful tool for modulating and researching the CSL. [ABSTRACT FROM AUTHOR]

The ytterbium oxide (Yb3+) is found to have an extremely low work function of 2.42 eV, which is even lower than that of its metallic form Yb0 (2.64 eV). The stability of oxides makes Yb3+ an ideal electron injection material for both top-emitting and bottom-emitting organic light-emitting diodes (TOLED and BOLED). The device test data indeed show that at 1000 nit luminance, the TOLED has a 94 cd/A current efficiency and 70 lm/W power efficiency, and BOLED has a 76 cd/A and 60 lm/W efficiency, respectively. X-ray and ultraviolet photoemission spectroscopical studies indicate that the Fermi level of the metal oxide is pinned to the lowest unoccupied molecular orbital of the electron transport layer, leading to the formation of a cathode interface with an ultra-low electron injection barrier. [ABSTRACT FROM AUTHOR]

The N-polar orientation of GaN may be an option for the development of longer wavelength visible optoelectronics because of its higher indium uptake. N-polar InGaN LEDs with an inverted p-side down configuration and buried tunnel junctions were grown by metalorganic chemical vapor deposition. Fabricated devices in the wavelength range of 450–509 nm showed record high light output power for N-polar LEDs, up to 0.21 mW on-wafer at 20 A/cm2 with an emission wavelength of 470 nm. These results represent an improvement in performance of more than one order of magnitude over previously reported N-polar LEDs, demonstrating potential for the N-polar orientation in the nitride optoelectronics space. [ABSTRACT FROM AUTHOR]

In this work, we studied single-pulse ablation dynamics of a temporally modulated continuous wave laser–material interaction with Al using in situ multimodal time-resolved diagnostics that describe in detail the associated physical and chemical processes. Time-resolved scattering, emission imaging, and optical emission spectroscopy unveiled a sequence of events spread out across three distinct phases: (i) early phase ablation process, associated with particle generation and liquid Al column formation (<20 μ s), (ii) secondary detonation when sufficient ejected material is accumulated over the surface (20–50 μ s), and (iii) molten liquid Al pool oscillation on the surface, followed by large droplet ejection from the liquid pool (100–500 μ s). Atomic Al and AlO were observed with optical emission spectroscopy at different ratios during the entire lifetime of the event, verifying the formation of oxidized Al vapor upon its interaction with air. Morphological and compositional characterization confirmed surface oxidation and material re-solidification in the form of protrusions produced during the irradiation process. This work provides insights into the complex physical and chemical mechanisms of single-pulse ablation in the sub-millisecond laser pulse regime, which are critically important for parameter optimization in a variety of laser processing, microfabrication, and deposition applications. [ABSTRACT FROM AUTHOR]

In this work, we study THz generation and detection using cadmium telluride (CdTe) crystals pumped by amplified (1.025 μm wavelength) and oscillator (1.045 μm wavelength) ytterbium (Yb) lasers. For each laser, we compare the performances of the CdTe THz emitter and detector to those of GaP crystals. Under optimum conditions, we demonstrate that the former shows 3 and 5 times better performances compared with the latter for detection and generation, respectively. When pumped by an amplified Yb laser, we find that the CdTe crystal is more efficient than the GaP crystal for emission at optical fluences lower than 250 μJ/cm2. Although CdTe has some limitations in comparison with GaP, such as high THz absorption above 1 THz and the appearance of two-photon absorption at relatively low optical intensity, our findings demonstrate the potential of this crystal to be used as the emitter and detector in combination with the Yb laser. [ABSTRACT FROM AUTHOR]

Yttrium aluminum perovskite (YAP) is a host material that can provide a strong emission from a rare-earth dopant and it has a lower phonon energy than yttrium aluminum garnet (YAG). Therefore, YAP is a promising material for optical refrigeration and radiation balanced laser. We measured the photoluminescence (PL) spectra of ytterbium (Yb)-doped YAP and compared them with those of Yb-doped YAG. The estimated ideal laser cooling efficiencies of Yb-doped YAP and Yb-doped YAG were comparable at 300 K. Based on the temperature-dependent anti-Stokes PL, we found that the laser cooling power of Yb-doped YAP at 470 K is 14.3 times higher than that at 200 K. This enhancement at higher temperatures is 3.2 times larger than that observed for Yb-doped YAG. We attributed the higher laser cooling power of Yb-doped YAP to a lower multi-phonon relaxation rate (and/or a higher energy transfer rate) and an antenna effect caused by the energy transfer from Yb ions that are located at the Y-site to Yb ions that are surrounded by an inhomogeneous alloy structure. The calculated small signal gain of (Yb:Y)AP is 3.5 times larger than that of (Yb:Y)AG. The larger small signal gain of (Yb:Y)AP arises from its strong absorbance and small Stark splitting width. [ABSTRACT FROM AUTHOR]

Superconducting single-photon detectors have become a very promising infrared photon counting technology. Utilizing high-Tc superconductors to implement photon counters is significantly more practical due to their much higher operating temperatures. We report photoresponse above 85 K of YB a 2 C u 3 O 7 − δ (YBCO) microwires fabricated using selective epitaxial growth (SEG), demonstrating their high photon detection efficiency. SEG does not require post-deposition treatment of the YBCO layer, thus avoiding material damage and degradation, typically occurring in conventional submicrometer YBCO device fabrication. Our results show excellent superconducting performance with a Tc of up to 89 K and a sharp transition width of Δ T ∼ 2 K , as well as a relatively high critical current density Jc of ∼ 5.7 × 10 5 A / c m 2 at 77 K. The optical response of our YBCO microwires, especially the high responsivity of ∼ 3 × 10 3 mV / (nW / u m 2) , paves the way for infrared single-photon detection using high-Tc superconductors. [ABSTRACT FROM AUTHOR]

We investigated the optical properties of rare-earth ions (Yb3+ and Er3+) implanted into lithium niobate (LN) crystals and observed superluminescent emission from a sheet of Yb ions in the Yb-implanted LN crystal (Yb:LN). Moreover, by directly integrating the Er-implanted LN crystal (Er:LN) with a silicon photonic chip with waveguide and resonator structures, we observed the evanescent coupling of photoluminescent light from the Er ions to the optical modes of the waveguide and microcavity. We measured an optical quality factor of about 104 and observed a modification of the photoluminescent emission from Er3+ ions in the integrated structure. The platform can ultimately enable developing the integrated multifunctional quantum photonic devices. [ABSTRACT FROM AUTHOR]

Bi2Te3-based compounds are the benchmark thermoelectric materials working near room temperature. In this study, we synthesize ytterbium (Yb) doped Bi0.5Sb1.5Te3 bulk materials by high energy ball milling and direct current hot pressing. The Yb-doping increases the carrier concentration and suppresses the intrinsic excitation, thus optimizing the electrical transport properties. In addition, the point defects introduced by adding Yb to the lattice behave as extra phonon scattering centres, yielding a reduction in the lattice thermal conductivity. As a result, for the Yb0.0075Bi0.5Sb1.4925Te3 sample, a high zT of ∼1.3 at 330 K is achieved, and the average zT reaches 0.96 between 303 K and 523 K. [ABSTRACT FROM AUTHOR]

Bi2Te3-based compounds are the benchmark thermoelectric materials working near room temperature. In this study, we synthesize ytterbium (Yb) doped Bi0.5Sb1.5Te3 bulk materials by high energy ball milling and direct current hot pressing. The Yb-doping increases the carrier concentration and suppresses the intrinsic excitation, thus optimizing the electrical transport properties. In addition, the point defects introduced by adding Yb to the lattice behave as extra phonon scattering centres, yielding a reduction in the lattice thermal conductivity. As a result, for the Yb0.0075Bi0.5Sb1.4925Te3 sample, a high zT of ∼1.3 at 330 K is achieved, and the average zT reaches 0.96 between 303 K and 523 K. [ABSTRACT FROM AUTHOR]

Metal silicide-based thermoelectric (TE) materials have attracted attention owing to low toxicity and high chemical stability. Here, we demonstrate that ytterbium silicon-germanium, Yb(Si1−xGex)2−δ, shows a large Seebeck coefficient (S) accompanied by metal-like high electrical conductivity (σ) attributed to the intermediate valence behavior of Yb (Yb2+/Yb3+). We revealed that x = 0.5, i.e., YbSiGe, is the best composition with the highest power factor (S2σ) of 3.6 mW m−1 K−2 at room temperature, which is comparable to those of conventional TE materials, such as Bi2Te3. [ABSTRACT FROM AUTHOR]

The filling fraction limit in filled Skutterudites plays a critical role in thermoelectric properties; however, the exact filling fraction limit for certain fillers is still in debate. In this work, we observed the lattice distortion, where lattice parameters a and b are unequal, in the annealed Yb-filled CoSb3. Microstructure characterization by advanced spherical aberration-corrected (CS-corrected) electron microscopy, energy-dispersive X-ray spectroscopy, and electron energy loss spectroscopy in conjunction with thermoelectric characterization clearly proves that the Yb filling fraction is higher in the annealed sample (with lattice distortion) than in the ball-milled sample (without lattice distortion). Therefore, the results indicate that lattice distortion appears when the Yb filling fraction reaches a certain critical value in CoSb3 Skutterudites. The observed lattice distortion provides an alternative approach to probe the filling fraction in filled Skutterudites. [ABSTRACT FROM AUTHOR]

Cesium lead halide perovskite nanocrystals (CsPbX3, X=Cl, Br, I) have been reported as efficient light-harvesting and light-emitting semiconductor materials, but their nonlinear optical properties have been seldom touched upon. In this paper, we prepare layered CsPbBr3 nanocrystal films and characterize their physical properties. Broadband linear absorption from ∼0.8 to over 2.2 lm and nonlinear optical absorption at the 1-lm wavelength region are measured. The CsPbBr3 saturable absorber (SA), manufactured by drop-casting of colloidal CsPbBr3 liquid solution on a gold mirror, shows modulation depth and saturation intensity of 13.1% and 10.7 MW/cm2, respectively. With this SA, mode-locking operation of a polarization-maintained ytterbium fiber laser produces single pulses with duration of ∼216 ps, maximum average output power of 10.5 mW, and the laser spectrum is centered at ∼1076 nm. This work shows that CsPbBr3 films can be efficient SA candidates for fiber lasers and also have great potential to become broadband linear and nonlinear optical materials for photonics and optoelectronics. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of polycrystalline hexagonal Yb1−xHoxMnO3 (x = 0.1, 0.2, and 0.3) compounds are studied through magnetization measurements. Temperature dependence of Zero Field Cooled magnetic moment measurements shows Néel temperature (TN1) of ~83 K, corresponding to the Mn3+ antiferromagnetic ordering. At low temperatures (TN2 ~ 5 K), all compounds show ferromagnetic ordering due to alignment of the Yb moments and the field induced magnetic transition is observed in the isothermal magnetization measurements. The maximum entropy change |ΔSMmax| and the relative cooling power (RCP) of Yb1−xHoxMnO3 are 3.75 ± 0.78 J/(mol K) and 90.0 ± 27 J/mol for x = 0.3 at ΔH = 100 kOe. Values of both |ΔSMmax| and RCP found to increase with increasing Ho content. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of polycrystalline hexagonal Yb1−xHoxMnO3 (x = 0.1, 0.2, and 0.3) compounds are studied through magnetization measurements. Temperature dependence of Zero Field Cooled magnetic moment measurements shows Néel temperature (TN1) of ~83 K, corresponding to the Mn3+ antiferromagnetic ordering. At low temperatures (TN2 ~ 5 K), all compounds show ferromagnetic ordering due to alignment of the Yb moments and the field induced magnetic transition is observed in the isothermal magnetization measurements. The maximum entropy change |ΔSMmax| and the relative cooling power (RCP) of Yb1−xHoxMnO3 are 3.75 ± 0.78 J/(mol K) and 90.0 ± 27 J/mol for x = 0.3 at ΔH = 100 kOe. Values of both |ΔSMmax| and RCP found to increase with increasing Ho content. [ABSTRACT FROM AUTHOR]

We report dissipative soliton generation from an Yb-doped all-fiber nonlinearity- and dispersionmanaged nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative solitons with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally compressed to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs. [ABSTRACT FROM AUTHOR]

Two-photon excitation is shown to substantially enhance the locality of fiber-based optical interrogation of strongly scattering biotissues. In our experiments, a high-numerical-aperture, large-core-are fiber probe is used to deliver the 200-fs output of a 100-MHz mode-locked ytterbium fiber laser to samples of live mouse brain, induce two-photon fluorescence of nitrogen--vacancy centers in diamond markers in brain sample. Fiber probes with a high numerical aperture and a large core area are shown to enable locality enhancement in fiber-laser--fiber-probe two-photon brain excitation and interrogation without sacrificing the efficiency of fluorescence response collection. [ABSTRACT FROM AUTHOR]

A hollow-core photonic-crystal fiber (PCF) is integrated with a stretched-pulse ytterbium fiber oscillator to enable ultrafast optical waveform shaping, demonstrated through the pulse compression of single-pulse fiber-laser output and tunable ultrashort-pulse pair generation in the regime where the fiber laser delivers a double-pulse output. A hollow PCF with a properly designed dispersion profile is shown to allow the stretched 6.2-ps Yb fiber laser output to be compressed to a pulse width of less than 160 fs, which is only 6% longer than the pulse width supported by the entire 18-nm bandwidth of the fiber laser output. [ABSTRACT FROM AUTHOR]

We investigate the resistive memory switching behaviors of Yb2O3 thin films for different Ti-dopant concentrations. A higher doping concentration of 9.4% of Ti atom into Yb2O3 thin film causes the switching mechanism to change from bipolar to unipolar behavior. This is ascribed to different chemical compositions of the filament through the oxide film. The reset mechanism is associated with the annihilation of oxygen vacancies and other ionic and electronic defects within or near the interface area of oxide film for bipolar switching, while it is believed to be due to rupture of the conducting filament by local Joule heating effect for unipolar resistive switching. Furthermore, the incorporation of Ti atom into the Yb2O3 memory device exhibits improved electrical performances including low set/reset voltages and good endurance and retention characteristics. [ABSTRACT FROM AUTHOR]

A series of shock-recovery experiments on Y2O3:Eu3+ powder were conducted involving the impact of a flyer plate accelerated by a single-stage powder-propellant gun. The recovered samples were characterized by X-ray diffraction (XRD) analysis and photoluminescence (PL) spectroscopy. The XRD and PL results of samples shocked at pressures of 13 GPa indicated that a phase transition from a cubic phase to a monoclinic phase occurred. The recovered samples shocked at 21 and 25 GPa consisted of Y2O3:Eu3+ with the cubic phase and the monoclinic phase. These results indicated that the shock-induced phase transition was the partial completion of the phase transition. [ABSTRACT FROM AUTHOR]

A series of shock-recovery experiments on Y2O3:Eu3+ powder were conducted involving the impact of a flyer plate accelerated by a single-stage powder-propellant gun. The recovered samples were characterized by X-ray diffraction (XRD) analysis and photoluminescence (PL) spectroscopy. The XRD and PL results of samples shocked at pressures of 13 GPa indicated that a phase transition from a cubic phase to a monoclinic phase occurred. The recovered samples shocked at 21 and 25 GPa consisted of Y2O3:Eu3+ with the cubic phase and the monoclinic phase. These results indicated that the shock-induced phase transition was the partial completion of the phase transition. [ABSTRACT FROM AUTHOR]

Poor ohmic contact by Fermi-level pinning to valence band (EV) edge is one of the major challenges for germanium (Ge) n-type metal-oxide-semiconductor field-effect transistor (nMOSFET). Using low work-function rare-earth ytterbium (Yb), good ohmic contact on n-type Ge with alleviated Fermi-level pinning was demonstrated. Such ohmic behavior depends strongly on the germanide formation condition, where much degraded ohmic contact at 600 °C rapid thermal annealing is due to the lower Yb/Ge composition found by energy-dispersive x-ray spectroscopy. The ohmic behavior of Yb-germanide/n-type-Ge has high potential for future high-performance Ge nMOSFET application. [ABSTRACT FROM AUTHOR]

A 20-fold increase over the single path optical absorption is demonstrated with a low loss medium placed in a resonant cavity. This is applied to laser cooling of ytterbium-doped fluorozirconate glass resulting in 90% absorption of the incident pump light. A coupled-cavity scheme to achieve active optical impedance matching is analyzed. [ABSTRACT FROM AUTHOR]

We report all-optical signal gating using ytterbium-doped fiber (YDF) and a pair of thermally expanded core fibers (TECFs). Splicing the YDF with two TECFs at their expanded-core ends, we obtained an interference pattern in the transmission spectrum of the device. When pumped by a laser diode at 980 nm, the interference fringes shift to longer wavelength due mainly to the resonantly enhanced nonlinearity of the YDF. Consequently, signals within the interference pattern can be gated or blocked all optically. Full gating of cw signals at 1564.21 and 1564.54 nm were obtained using a pump power of about 38.44 mW. [ABSTRACT FROM AUTHOR]

We report on the fabrication and the characterization of a design of highly birefringent solid-core photonic bandgap fibers. A form birefringence is obtained by keeping open all interstitial air holes but two diametrically opposite and close to the fiber core. Group birefringence as high as 0.57×10-3 and 0.47×10-3 at 1.1 and 1.55 μm, respectively, are demonstrated in the first bandgap. [ABSTRACT FROM AUTHOR]

A family of Yb-based bulk metallic glasses with excellent glass-forming ability has been fabricated based on the elastic moduli correlations. The YbZnMg(Cu) glasses exhibit very strong liquid characteristic in fragility (m=26±5), while soft mechanical characteristics, such as low bulk elastic modulus (e.g., Young’s modulus is about 26.5 GPa), small Poisson’s ratio (0.276), low Vickers hardness (1.52 GPa) and Debye temperature, and exceptionally low glass transition temperature (Tg∼347 K). The soft bulk metallic glasses with exceptional values of Tg, fragility, Debye temperature, and elastic moduli confirm some found correlations in metallic glasses. [ABSTRACT FROM AUTHOR]

Near single-cycle terahertz pulse generation from lithium niobate crystal by optical rectification of pulses from an Yb:fiber laser/amplifier system was investigated. The pump laser supplied 250 fs duration pulses with 14 μJ energy at up to 1 MHz repetition rate. The terahertz pulse energy and average power exceeded 0.25 nJ and 0.25 mW, respectively. The average power was more than ten times higher than corresponding values achieved by using GaP as the nonlinear crystal under similar pumping conditions. [ABSTRACT FROM AUTHOR]

The thickness dependence was studied for the critical current density (Jc) of YBa2Cu3O7-x(YBCO)+BaSnO3 (BSO) nanocomposite films. These films showed a significantly reduced decline of the Jc with thickness, especially at high magnetic fields. For example, a 2 μm thick YBCO+BSO film had a Jc∼3×105 A/cm2 at 5 T as compared to a typical Jc of 2.4×103 A/cm2 at 5 T for a 300 nm thick YBCO film. The thick YBCO+BSO films maintained high Tc (>88 K) and had a high density (2.5×1011/cm2) of continuous BSO nanocolumns that likely contributed for the observed Jc enhancements. [ABSTRACT FROM AUTHOR]

We report on continuous wave laser oscillation of trivalent ytterbium ions in the frequency converter Yb3+:Sr0.6Ba0.4Nb2O6 ferroelectric laser crystal. Pump induced thermal loading has been used to drive the crystal from its ferroelectric to paraelectric phase. Stable laser radiation at 1070 nm was found in both phases while a bistable laser output is observed through phase transition. In addition, diffuse green (535 nm) radiation was generated by self-frequency doubling of the fundamental laser radiation because of the random distribution of microferroelectric domains existing in the ferroelectric as grown crystal. [ABSTRACT FROM AUTHOR]

Spectral properties of Yb3+/Ni2+ codoped transparent silicate glass ceramics containing LiGa5O8 nanocrystals were investigated. The near-infrared emission intensity of Ni2+ was largely increased with Yb3+ codoping due to Yb3+→Ni2+ energy transfer. The qualitative calculation of the energy transfer constant Cs-a and rate Ps-a showed that the Yb3+→Ni2+ energy transfer was much greater than in the opposite direction. Yb3+/Ni2+ codoped glass ceramics with 0.75 mol % Yb2O3 exhibited a near-infrared emission with full width at half maximum of 290 nm and fluorescent lifetime of 920 μs. The glass ceramics are promising for broadband optical amplification. [ABSTRACT FROM AUTHOR]

Li1.3Al0.3Ti1.7(PO4)3 conductive crystal lines composed of closely compacted fine particles were patterned on the surface of 13.9Li2O–8.9Al2O3–37.6TiO2–38.6P2O5–1NiO (mol %) precursor glass by a continuous wave Yb fiber laser irradiation (λ=1078 nm) using the nickel atom heat processing method. Homogeneous and smooth crystal lines with a uniform width of 30 μm were obtained with a laser power of 1.3 W. The Li+ ion conductivity of the laser patterned glass was about two orders of magnitude higher than that of the glass matrix due to the formation of Li1.3Al0.3Ti1.7(PO4)3 conductive crystalline phase by Yb fiber laser irradiation. [ABSTRACT FROM AUTHOR]