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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Spectral Luminescence Properties of Ho <sup>3+</sup> Ions in Active Media Codoped with Tb <sup>3+</sup> , Pr <sup>3+</sup> and Yb <sup>3+</sup> for Mid-Infrared Laser Development
摘要： Lasers operating in mid-infrared spectral region specifically with 3 m wavelength attract a lot of attention due to their various applications in atmospheric monitoring, medical surgery, remote sensing and scientific research. Such laser can be used as an efficient and high-quality radiation source for optical parametric oscillators and converters to longer IR wavelengths. Laser active media doped with Ho3+ ions are of interest for obtaining the radiation in this spectral range. However the realization of the laser radiation at 5I6 → 5I7 optical transition in Ho3+ ions is a complicated task due to the lack of commercially available laser diodes for efficient pumping of Ho3+ ions. Yb3+ ion is known as an efficient sensitizer for Ho3+ ions in various laser active crystals. The scheme with the excitation transfer from Yb3+ to Ho3+ was realized in Cr:Yb:Ho:YSGG and Cr:Yb:Ho:Eu:YAP lasers with flash lamp pumping [1, 2] and Ho:Yb:GGG and Ho:Yb:YSGG lasers with diode pumping [3]. In addition 5I6 → 5I7 optical transition is known as a “self-terminating” one because the fluorescence lifetime of the lower laser level 5I7 is considerably larger than that of the upper laser level 5I6. Codoping of Ho3+ active media with Tb3+ or Pr3+ ions can accelerate the deactivation process of the lower laser level. The concentration set of CaF2 crystal doped with Ho3+, Yb3+, Tb3+, Pr3+ ions was grown using the Bridgman technique. The number of Gd2O3, Y2O3 single crystal fibers doped with the same ions was successfully obtained by laser-heated pedestal growth method. Absorption spectra of Yb:Ho:Gd2O3 and Yb:Ho:Pr:Gd2O3 crystals showed that Yb3+ doping increased the absorption coefficient within 850-1050nm spectral region and make Yb doped media suitable for efficient pumping by commercially available laser diodes. The fluorescence lifetime of 5I6 and 5I7 manifolds of Ho3+ ions was investigated in CaF2 crystals codoped with Tb3+ and Pr3+ ions. It was found that this codoping resulted in the depopulation of the lower laser level 5I7 in Ho3+ ions and at the same time had little influence on the upper laser level 5I6 (Table 1). The lifetime of the lower laser level reduced from 17.5 ms for Yb:Ho:CaF2 crystal to 0.75 ms for Yb:Ho:Tb:CaF2. Deactivation effect of lower laser level 5I7 in Ho3+ was also observed in Yb3+:Ho3+:Pr3+:Gd2O3 and Yb3+:Ho3+:Tb3+:Gd2O3 single crystal fibers. The lifetime of the lower laser level 5I7 decreased from 8.25 ms to 1.04 ms and to 0.67 ms with a codoping of 0.5 at.% Pr3+ and 0.5 at.% Tb3+ ions, respectively. The use of Yb3+, Tb3+ or Pr3+ codoping with Ho3+ to enhance the laser properties of Ho3+ ions at 5I6→5I7 optical transition at the wavelength of ~2.8-3 μm were investigated in the Gd2O3, Y2O3 single crystal fiber for the first time. Obtained results indicate that single crystal fiber Yb3+:Ho3+:Tb3+:Gd2O3 and CaF2 :Yb3+:Ho3+:Tb3+ crystal is a promising laser medium for developing compact LD-pumped lasers operating at the wavelength of 2.8-3 μm.
关键词： Pr3+ ions,Tb3+ ions,mid-infrared laser,fluorescence lifetime,laser active media,Ho3+ ions,Yb3+ ions
更新于2025-09-11 14:15:04
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Fast repetition rate fs pulsed lasers for advanced PLIM microscopy
摘要： Simultaneous metabolic and oxygen imaging is promising to follow up therapy response, disease development and to determine prognostic factors. FLIM of metabolic coenzymes is now widely accepted to be the most reliable method to determine cellular bioenergetics. Also, oxygen consumption has to be taken into account to understand treatment responses. The phosphorescence lifetime of oxygen sensors is able to indicate local oxygen changes. For phosphorescence lifetime imaging (PLIM) dyes based on ruthenium (II) coordination complexes are useful, in detail TLD1433 which possesses a variety of different triplet states, enables complex photochemistry and redox reactions. PLIM is usually reached by two photon excitation of the drug with a femtosecond (fs) pulsed Ti:Sapphire laser working at 80 MHz repetition rate and (time-correlated single photon counting) (TCSPC) detection electronics. The interesting question was whether it is possible to follow up PLIM using faster repetition rates. Faster repetition rates could be advantageous for the induction of specific photochemical reactions because of similar light doses used normally in standard CW light treatments. For this, a default 2p-FLIM–PLIM system was expanded by adding a second fs pulsed laser ("helixx") which provides 50 fs pulses at a repetition rate of 250 MHz, more than 2.3 W average power and tunable from 720 nm to 920 nm. The laser beam was coupled into the AOM instead of the default 80 MHz laser. We demonstrated successful applications of the 250 MHz laser for PLIM which correlates well with measurements done by excitation with the conventional 80 MHz laser source.
关键词： oxygen consumption,Ru(II) complexes,phosphorescence lifetime microscopy,Multiphoton microscopy,fast repetition rate excitation,short laser pulses
更新于2025-09-11 14:15:04
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Concentration dependent Dy3+ activated LiPbB5O9 phosphor: Structure and luminescence studies for white LED applications
摘要： In this study, distinct concentrations of Dy3t ions (0.04, 0.07, 0.1, 0.4 and 0.7 mol%) doped LiPbB5O9 phosphors were fabricated via solid state reaction technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric studies (TG-DSC) and photoluminescence characterizations were performed to LiPbB5O9:Dy3t phosphors. Photoluminescence excitation and emission spectra were recorded at 576 nm and 349 nm, respectively. The stress, the critical distance (Rc) and energy transfer parameters (Q) between the Dy3t ions were evaluated for all concentrations. To interpret the white light emission ability of the LiPbB5O9:Dy3t phosphor, yellow to blue (Y/B) intensity ratios have been calculated. The decay curves of 4F9/2 level of Dy3t ions were studied. The CIE color co-ordinates and coordinate color temperatures (CCT) were also calculated. From these studies, it is mentioned that LiPbB5O9:0.4Dy3t phosphor is a suitable material for fabrication of WLEDs and laser applications.
关键词： William-Hall analysis,Energy transfer,Lifetime,Photoluminescence,White light
更新于2025-09-11 14:15:04
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Nanoparticulate Metal Oxide Top Electrode Interface Modification Improves the Thermal Stability of Inverted Perovskite Photovoltaics
摘要： Solution processed γ-Fe2O3 nanoparticles via the solvothermal colloidal synthesis in conjunction with ligand-exchange method are used for interface modification of the top electrode in inverted perovskite solar cells. In comparison to more conventional top electrodes such as PC(70)BM/Al and PC(70)BM/AZO/Al, we show that incorporation of a γ-Fe2O3 provides an alternative solution processed top electrode (PC(70)BM/γ-Fe2O3/Al) that not only results in comparable power conversion efficiencies but also improved thermal stability of inverted perovskite photovoltaics. The origin of improved stability of inverted perovskite solar cells incorporating PC(70)BM/ γ-Fe2O3/Al under accelerated heat lifetime conditions is attributed to the acidic surface nature of γ-Fe2O3 and reduced charge trapped density within PC(70)BM/ γ-Fe2O3/Al top electrode interfaces.
关键词： nanoparticulate metal oxides,accelerated lifetime,electrodes,thermal stability,degradation mechanisms,interfaces,inverted perovskites solar cells,impedance spectroscopy,charge traps density
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - The damage mitigation process for Si nanopillar structure using silica nanosphere lithography and metal assisted chemical etching
摘要： This work focuses on mitigating the damage from nanostructure fabrication using silica nanosphere lithography (SNL) and metal assisted chemical etching (MACE). Metal contamination and plasma damage are the two main factors to limit the Si wafer's minority carrier lifetime. Ni/Au and Ti/Au metal layers on bare Si wafer are compared using lifetime recovery test. Ti/Au shows to be more suitable for the MACE process. Samples deposited with Ni/Au and Ti/Au show lifetimes of 7 μs and 1200μs, respectively. The silicon surface is degraded significantly by the RIE plasma during the nanosphere etching process. SiO2 protective layer was added to the process, mitigating significantly the plasma damage on the silicon surface. Lifetime measurements shows an improvement over 1 ms when SiO2 protective layer on planar Si wafer is used. Lifetimes of 353 μs and implied open circuit voltages of 651mV were accomplished on nanopillar structured wafers using SiOx protective layer and Ti/Au.
关键词： lifetime recovery,silica nanosphere lithography,metal assisted chemical etching,Si nanopillar structure,damage mitigation
更新于2025-09-11 14:15:04
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Thermal droop in high-quality InGaN LEDs
摘要： Thermal droop is investigated in high-quality InGaN light-emitting diodes (LEDs). To determine whether it is caused by intrinsic variations in recombination or by transport effects, photoluminescence and electroluminescence measurements are compared. The former does not show signs of pronounced thermal droop, with a near-constant internal quantum efficiency and recombination lifetime, regardless of temperature. In contrast, strong thermal droop is observed in the latter, pointing to transport effects as a leading contributor. Finally, high-efficiency LEDs with near-ideal thermal droop are demonstrated.
关键词： Thermal droop,recombination lifetime,electroluminescence,internal quantum efficiency,transport effects,photoluminescence,InGaN LEDs
更新于2025-09-11 14:15:04
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Fluorescence Lifetime-Based Tumor Contrast Enhancement Using an EGFR Antibody–Labeled Near-Infrared Fluorophore
摘要： Purpose: Imaging techniques for highly specific detection of cancer cells in vivo can have applications ranging from preclinical drug discovery studies to clinical cancer diagnosis and surgical therapy. Although fluorescence imaging using cancer-targeted antibodies has shown promise, nonspecific probe accumulation in tissue results in significant background fluorescence, reducing detection sensitivity using traditional intensity–based continuous-wave (CW) fluorescence imaging. Here we demonstrate that fluorescence lifetime (FLT) imaging can provide significant tumor contrast enhancement over CW intensity in preclinical models of human breast cancer. Experimental Design: Mice bearing MDA-MB-231 tumors were injected with anti-EGFR antibody conjugated to the fluorescent dye IRDye 800CW (anti-EGFR-800). Time domain fluorescence imaging was performed in vivo and in situ up to 48 hours after dye injection. Results: Mice injected with anti-EGFR-800 showed a significantly longer FLT (0.7 ± 0.03 ns) compared with the FLT of nonspecific probe uptake in liver (0.63 ± 0.05 ns), providing a dramatic improvement in sensitivity and specificity compared with CW intensity. IgG antibody–conjugated IRDye 800CW did not show an increased FLT compared with normal tissue, suggesting that the FLT increase of anti-EGFR-800 in tumors was associated with receptor expression. Using serial surgery, we show that FLT allows the detection of smaller residual tumors in the surgical bed than possible using CW intensity. Conclusions: Our data suggest that FLT can significantly enhance tumor contrast using fluorescently labeled antibodies, thereby accelerating the efficient clinical application of these probes for margin assessment in image-guided surgery and for highly specific detection of tumor receptors in vivo.
关键词： near-infrared fluorophore,EGFR,fluorescence lifetime imaging,image-guided surgery,tumor contrast
更新于2025-09-11 14:15:04
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Tuning Spontaneous Emission through Waveguide Cavity Effects in Semiconductor Nanowires
摘要： The ability to tailor waveguide cavities and couple them with quantum emitters has developed a realm of nano-photonics encompassing, for example, highly efficient single photon generation or the control of giant photon nonlinearities. Opening new grounds by pushing the interaction of the waveguide cavity and integrated emitters further into the deep subwavelength regime, however, has been complicated by nonradiative losses due to the increasing importance of surface defects when decreasing cavity dimensions. Here, we show efficient suppression of nonradiative recombination for thin waveguide cavities using core?shell semiconductor nanowires. We experimentally reveal the advantages of such nanowires, which host mobile emitters, that is, free excitons, in a one-dimensional (1D) waveguide, highlighting the resulting potential for tunable, active, nanophotonic devices. In our experiment, controlling the nanowire waveguide diameter tunes the luminescence lifetime of excitons in the nanowires across 2 orders of magnitude up to 80 ns. At the smallest wire diameters, we show that this luminescence lifetime can be manipulated by engineering the dielectric environment of the nanowires. Exploiting this unique handle on the spontaneous emission of mobile emitters, we demonstrate an all-dielectric spatial control of the mobile emitters along the axis of the 1D nanowire waveguide.
关键词： Semiconductor nanowire,free excitons,photonic waveguide cavity,subwavelength nanophotonics,luminescence lifetime,tunable spontaneous emission
更新于2025-09-11 14:15:04
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Solution-Processed Phototransistors Combining Organic Absorber and Charge Transporting Oxide for Visible to Infrared Light Detection
摘要： This report demonstrates high-performance infrared phototransistors that uses a broadband absorbing organic bulk heterojunction (BHJ) layer responsive from the visible to the shortwave infrared, from 500 nm to 1400 nm. The device structure is based on a bilayer transistor channel that decouples charge photogeneration and transport, enabling independent optimization of each process. The organic BHJ layer is improved by incorporating camphor, a highly polarizable additive that increases carrier lifetime. An indium zinc oxide transport layer with high electron mobility is employed for rapid charge transport. As a result, the phototransistors achieve a dynamic range of 127 dB and reach a specific detectivity of 5×1012 Jones under low power illumination of 20 nW/cm2, outperforming commercial germanium photodiodes in the spectral range below 1300 nm. The photodetector metrics are measured with respect to the applied voltage, incident light power, and temporal bandwidth, demonstrating operation at the video-frame rate of 50 Hz. In particular, the frequency and light dependence of the phototransistor characteristics are analyzed to understand the change in photoconductive gain under different working conditions.
关键词： shortwave infrared,phototransistor,indium zinc oxide,bulk heterojunction,carrier lifetime,semiconducting polymer,camphor
更新于2025-09-11 14:15:04
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Luminescence lifetime encoding in time-domain flow cytometry
摘要： Time-resolved flow cytometry represents an alternative to commonly applied spectral or intensity multiplexing in bioanalytics. At present, the vast majority of the reports on this topic focuses on phase-domain techniques and specific applications. In this report, we present a flow cytometry platform with time-resolved detection based on a compact setup and straightforward time-domain measurements utilizing lifetime-encoded beads with lifetimes in the nanosecond range. We provide general assessment of time-domain flow cytometry and discuss the concept of this platform to address achievable resolution limits, data analysis, and requirements on suitable encoding dyes. Experimental data are complemented by numerical calculations on photon count numbers and impact of noise and measurement time on the obtained lifetime values.
关键词： lifetime-encoded beads,multiplexing,Time-resolved flow cytometry,bioanalytics,time-domain measurements
更新于2025-09-11 14:15:04