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Effect of Uncontrollable Impurities on the Absorption Spectrum of a NaGd(WO4)2 Laser Crystal
摘要： Three NaGd(WO4)2 single crystals were grown by the Czochralski method using charges of different chemical purity. The impurity compositions of the grown crystals were analyzed by inductively coupled plasma mass spectrometry. The optical absorption spectra of the crystals were measured, and the effect of uncontrollable impurities on their optical properties and color was analyzed. The green color encountered in NaGd(WO4)2 crystals in some cases was shown to be due to the uncontrollable impurities of d elements, among which the chromium impurity had the most significant effect.
关键词： optical absorption,impurity purity,color centers,single crystals,zinc tungstate,ytterbium
更新于2025-09-23 15:21:01
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Boosting the Efficiency and Curtailing the Efficiency Roll-off in Green Perovskite Light-Emitting Diodes via Incorporating Ytterbium as Cathode Interface Layer
摘要： Perovskite light-emitting diodes (PeLEDs) exhibit high external quantum efficiencies (EQEs), emerging as a next-generation technology for lighting and display applications. Nevertheless, they suffer from severe efficiency roll-off at high luminance, particularly in case of blue and green emissions, which is one of the major bottlenecks in their industrial applications. Here, we attack this problem using a rare-earth metal, Yb, as cathode interface layer (CIL) for green PeLEDs. By adopting a new device configuration of ITO/TFB/FA-based Quasi-2D Perovskite/TPBi/Yb/Ag, we achieved a peak current efficiency (CE) of 22.3 cd/A with a corresponding EQE of 5.28% and a high maximum luminance of 19,160 cd/m2. Importantly, the maximum CE of 22 cd/A at 2,000 cd/m2 slightly decreased to 16.8 cd/A at 5,000 cd/m2 and maintained a still decent value of 12 cd/A at a very high luminance of 10,000 cd/m2, exhibiting a remarkably low efficiency roll-off. Our Yb-incorporated devices significantly outperformed the PeLEDs containing conventional CILs, including Mg and Liq, in terms of peak efficiency, efficiency roll-off and operational lifetime. We attribute this encouraging performance to barrier-free, efficient electron injection enabled by the low work function of Yb (2.6 eV) which led to a high electron current, nearly approaching the hole current in hole-dominant PeLEDs, as confirmed by the single-carrier device measurements. In addition, we also present Yb-incorporated PeLEDs containing Cs-based Quasi-2D perovskite as the emissive layer which displayed an impressive CE of 51.3 cd/A with a corresponding EQE of 16.4% and a maximum luminance of 14,240 cd/m2, and still demonstrated a reduced efficiency roll-off comparing to that of the Liq-based equivalent. These results unveil the inspiring prospects of Yb as an efficient CIL for PeLEDs towards high efficiency with reduced efficiency roll-off.
关键词： electron injection,ytterbium,quasi-2D,perovskite light-emitting diodes,stability,cathode interface layer,efficiency roll-off
更新于2025-09-23 15:21:01
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Effect of P-to-Rare Earth Atomic Ratio on Energy Transfer in Er-Yb-Doped Optical Fiber
摘要： Erbium (Er)- and Ytterbium (Yb)-doped optical fibers (EYDFs) have been used in various industrial fields as the only technology suitable for >1 W high-power amplifiers in the 1550-nm band. The output power is mainly limited by unwanted 1-μm band amplified spontaneous emissions from excited Yb3+; however, the factors affecting the output performance remain unclear. Here, we quantitatively and systematically reveal that the Phosphorus (P)-to-rare earth atomic ratio in the EYDFs has an optimal value for achieving the best output performance of EYDFs. We experimentally evaluated the quantitative relationship among co-dopants by fabricating preforms, drawing them as fibers, and measuring the amplification characteristics. At an appropriate Er concentration (0.3–0.5 wt %), a pump-to-signal conversion efficiency of 45.4% was obtained when the P/(Yb + Er) atomic ratio was around 25. This study paves the way for energy saving in high-power applications, such as high-speed optical wireless communication and long-distance optical ranging.
关键词： Phosphorus,Atomic ratio,Space communications,Energy-transfer efficiency,Amplified spontaneous emission,Erbium-Ytterbium-doped optical fiber amplifiers
更新于2025-09-23 15:21:01
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Generation of J-shaped pulses in ultra-long Ytterbium doped mode locked fiber laser
摘要： We report, for the first time, generation of J-shaped pulses in figure-eight type ultra-long, all-normal dispersion Ytterbium-doped fiber laser mode locked by the combined effect of nonlinear polarization evolution and nonlinear optical loop mirror. Cavity birefringence based spectral filtering introduced by polarization controllers is used for the formation of J-shaped as well as step-like and flat-top pulses. The shape and duration of generated pulse is found to depend on applied birefringence as well as pump power. J-shaped pulses of 180 ns duration and 332 nJ pulse energy at 201.45 kHz fundamental repetition rate are generated at 200 mW pump power. Experimentally, a strong correlation between spectral and temporal profile of the generated pulse shapes is established where it has been shown that asymmetric spectral filtering is responsible for generation of J-shaped and step-like pulses. Numerically, the spectral transmission of figure-eight type resonator under different cavity birefringence and intra-cavity power is investigated which qualitatively supports the experimental results.
关键词： mode locked lasers,Ytterbium doped fiber lasers,dissipative soliton resonance,pulse shaping
更新于2025-09-23 15:21:01
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Atomic clock performance enabling geodesy below the centimetre level
摘要： The passage of time is tracked by counting oscillations of a frequency reference, such as Earth’s revolutions or swings of a pendulum. By referencing atomic transitions, frequency (and thus time) can be measured more precisely than any other physical quantity, with the current generation of optical atomic clocks reporting fractional performance below the 10?17 level1–5. However, the theory of relativity prescribes that the passage of time is not absolute, but is affected by an observer’s reference frame. Consequently, clock measurements exhibit sensitivity to relative velocity, acceleration and gravity potential. Here we demonstrate local optical clock measurements that surpass the current ability to account for the gravitational distortion of space-time across the surface of Earth. In two independent ytterbium optical lattice clocks, we demonstrate unprecedented values of three fundamental benchmarks of clock performance. In units of the clock frequency, we report systematic uncertainty of 1.4 × 10?18, measurement instability of 3.2 × 10?19 and reproducibility characterized by ten blinded frequency comparisons, yielding a frequency difference of [?7 ± (5)stat ± (8)sys] × 10?19, where ‘stat’ and ‘sys’ indicate statistical and systematic uncertainty, respectively. Although sensitivity to differences in gravity potential could degrade the performance of the clocks as terrestrial standards of time, this same sensitivity can be used as a very sensitive probe of geopotential5–9. Near the surface of Earth, clock comparisons at the 1 × 10?18 level provide a resolution of one centimetre along the direction of gravity, so the performance of these clocks should enable geodesy beyond the state-of-the-art level. These optical clocks could further be used to explore geophysical phenomena10, detect gravitational waves11, test general relativity12 and search for dark matter13–17.
关键词： geodesy,ytterbium,atomic clock,dark matter,geopotential,gravitational waves,relativity,optical lattice clocks
更新于2025-09-23 15:21:01
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Ytterbium laser system for studying parametric amplification of femtosecond pulses with a centre wavelength of a??2 ??m
摘要： A laser system is developed with an optical synchronisation of a femtosecond signal with a pump channel. The signal of a driving ytterbium fibre laser with a 60 MHz repetition rate of stretched femtosecond pulses is amplified in energy from several nanojoules to 0.4 mJ at a pulse repetition rate of 3 kHz in a wide-band amplifier and then is compressed in time to 250 fs. The obtained radiation is used for generating femtosecond laser pulses with a centre wavelength of ~2 mm, pulse energy of above 20 mJ, duration of several field oscillations, and phase stabilisation between the electromagnetic field and envelope. The other pulse of the driving fibre laser provides optical synchronisation and a minimal time delay and is directed to a regenerative Yb : YAG disk amplifier for amplification to an energy of 4 mJ at a pulse repetition rate of 3 kHz and duration of 20 ps. A multipass disk amplifier is developed for further increasing the energy of pump chirped pulses to an energy of 70 mJ at a pulse repetition rate of 10 Hz and duration of 400 ps for studying parametric amplification under sub-nanosecond pumping.
关键词： parametric amplification,Yb :YAG disk amplifier,ytterbium fibre laser,femtosecond pulses,pulse compression
更新于2025-09-23 15:19:57
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Ytterbium-doped fibre femtosecond laser offers robust operation with deep and precise microsurgery of C. elegans neurons
摘要： Laser microsurgery is a powerful tool for neurobiology, used to ablate cells and sever neurites in-vivo. We compare a relatively new laser source to two well-established designs. Rare-earth-doped mode-locked fibre lasers that produce high power pulses recently gained popularity for industrial uses. Such systems are manufactured to high standards of robustness and low maintenance requirements typical of solid-state lasers. We demonstrate that an Ytterbium-doped fibre femtosecond laser is comparable in precision to a Ti:Sapphire femtosecond laser (1–2 micrometres), but with added operational reliability. Due to the lower pulse energy required to ablate, it is more precise than a solid-state nanosecond laser. Due to reduced scattering of near infrared light, it can lesion deeper (more than 100 micrometres) in tissue. These advantages are not specific to the model system ablated for our demonstration, namely neurites in the nematode C. elegans, but are applicable to other systems and transparent tissue where a precise micron-resolution dissection is required.
关键词： Ytterbium-doped fibre femtosecond laser,Laser microsurgery,neuronal regeneration,Ti:Sapphire femtosecond laser,solid-state nanosecond laser,C. elegans
更新于2025-09-23 15:19:57
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Spectroscopic and laser properties of erbium and ytterbium co-doped photo-thermo-refractive glass
摘要： Spectral-luminescent characteristics of erbium ions in photo-thermo-refractive (PTR) glasses doped with different concentrations of ytterbium and erbium oxides were investigated in this work. X-ray diffraction pattern of studied glasses was carried out. Judd-Ofelt parameters of intensity Ωt were obtained and used for deriving emission cross-sections and radiative lifetimes. It was found that the peak emission cross-sections values at a wavelength of 1.53 μm obtained from F-L and McCumber methods are 0.59 × 10?20 cm2 and 0.60 × 10?20 cm2, respectively, which are very similar and compared with those of silicate glasses. A quite high value of quantum yield at the wavelength of 1.53 μm for the sample with 0.1 mol% Er2O3 co-doped with ytterbium oxide has been investigated. Energy transfer efficiency from ytterbium ions to erbium ones was found to be 80% and 86% for erbium- and 1 mol% and 2 mol% Yb2O3-co-doped PTR glass, respectively. Laser properties of 2Yb-01Er PTR glass were carried out. The gain spectrum starts to be positive when the population inversion parameter gets to 0.5. Laser action was demonstrated at room temperature. It was found that the round-trip losses of the Er/Yb-PTR element are 0.28%.
关键词： Ytterbium,DFB laser,PTR glass,Erbium,XRD,Judd-ofelt
更新于2025-09-23 15:19:57
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Six-spectral antireflection coating on zinc sulfide simultaneously effective for the visible, near-IR, and long wavelength IR regions
摘要： In recent years, multi-spectral optical system is steadily growing popularity due to miniaturization and multi-function of optical system. Antire?ection coatings is critical important in multi-spectral device working in the wavelength region of 0.5–10 μm since optics of high refractive index materials are used. A six-spectral antire?ection coating on multispectral zinc sul?de substrate, which is suitable for the wavelength range of 0.5–10 μm, has been designed, fabricated and characterized. The six-spectral antire?ection coating is composed of 29-layer alternative stacking high-index layer of zinc sul?de and low-index coating material of ytterbium ?uoride, which deposits by thermal evaporation. In order to overcome the stress problem in the coating, the maximum layer thickness is restricted about 0.6 μm. This coating conforms to environmental stability standards and shows 94% transmission at 0.532 μm, 97% transmission at 1.064 μm and over 98% transmission at 2.1 μm, 3.9 μm, 4.8 μm and 9.5 μm.
关键词： Ytterbium ?uoride,Zinc sul?de,Durability tests,Antire?ection coating
更新于2025-09-23 15:19:57
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Anion Exchange and the Quantum-Cutting Energy Threshold in Ytterbium-Doped CsPb(Cl1-xBrx)3 Perovskite Nanocrystals
摘要： Colloidal halide perovskite nanocrystals of CsPbCl3 doped with Yb3+ have demonstrated remarkably high sensitized photoluminescence quantum yields (PLQYs), approaching 200%, attributed to a picosecond quantum-cutting process in which one photon absorbed by the nanocrystal generates two photons emitted by the Yb3+ dopants. This quantum-cutting process is thought to involve a charge-neutral defect cluster within the nanocrystal's internal volume. Here, we demonstrate that Yb3+-doped CsPbCl3 nanocrystals can be converted post-synthetically to Yb3+-doped CsPb(Cl1-xBrx)3 nanocrystals without compromising the desired high PLQYs. Nanocrystal energy gaps can be tuned continuously from Eg ~ 3.06 eV (405 nm) in CsPbCl3 down to Eg ~ 2.53 eV (~490 nm) in CsPb(Cl0.25Br0.75)3 while retaining a constant PLQY above 100%. Reducing Eg further causes a rapid drop in PLQY, interpreted as reflecting an energy threshold for quantum cutting at approximately twice the energy of the Yb3+ 2F7/2 → 2F5/2 absorption threshold. These data demonstrate that very high quantum-cutting energy efficiencies can be achieved in Yb3+-doped CsPb(Cl1-xBrx)3 nanocrystals, offering the possibility to circumvent thermalization losses in conventional solar technologies. The presence of water during anion exchange is found to have a deleterious effect on the Yb3+ PLQYs but does not affect the nanocrystal shapes, morphologies, or even reduce the excitonic PLQYs of analogous undoped CsPb(Cl1-xBrx)3 nanocrystals. These results provide valuable information relevant to development and application of these unique materials for spectral-shifting solar energy conversion technologies.
关键词： ytterbium doping,quantum cutting,anion exchange,Perovskite nanocrystals
更新于2025-09-19 17:15:36