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Annealing of proton-exchanged planar optical waveguides in z-cut LiNbO3 fabricated using stearic acid has been studied systematically. The effects of annealing on waveguide propagation loss, surface index change, and waveguide depth were measured as a function of annealing time, and were found to follow a power-law relationship. [ABSTRACT FROM AUTHOR]

In this letter, we present the dc characteristics, stability, and low-frequency noise (LFN) measurements, for n-type indium arsenide nanowire (NW) parallel-array thin-film transistors (TFTs) with a global back gate. These devices perform with mobilities ranging from 200-1200 cm2V-1s-1 and produce a threshold voltage shift less than 0.25 V after 10 000 s of stress. The resulting LFN measurements indicate that the 1/f noise can be modeled by the number fluctuation model, at low drain currents, which can provide an essential guideline for the device design considerations of NW TFTs. [ABSTRACT FROM AUTHOR]

We report near-stoichiometric (NS) Ti:Mg:LiNbO3 strip waveguides fabricated starting from a Z-cut pure congruent LiNbO3 substrate in sequence by Tiand MgO-diffusion and post vapor transport equilibration. These waveguides with an initial Ti-strip width of 4-8 μ.m well support transverse magnetic mode, are single-mode at 0.98and 1.5-μ.m wavelengths, have a smooth surface and a loss as low as 0.1 dB/cm at 1.5 μm. The waveguides are NS and optical-damage-resistant, and have a homogeneous Mg concentration of 1.7 ± 0.3 mol% in the guiding layer. Such a waveguide is promising for nonlinear integrated optics. [ABSTRACT FROM PUBLISHER]

Near-stoichiometric planar and strip LiNbO3 optical waveguides were demonstrated using vapor transport equilibrium process and co-diffusion of titanium metal. Optical confinement is better in z-cut substrates than in x-cut substrates, and the waveguides were characterized optically. Spectral measurements, such as OH- absorption, optical absorption near the fundamental edge, and Raman scattering, were carried out to examine the Li-composition and crystalline phase inside and outside the guiding layer. The results have shown that the vapor transport equilibration process has brought these waveguides toward stoichiometric composition, the Li content inside and outside the waveguide layer is essentially identical, and the LiNbO3 phase is still retained within the waveguide layer. [ABSTRACT FROM AUTHOR]

Sm[sup 3+]-doped cadmium–aluminum–silicate glasses (CdO–Al[sub 2]O[sub 3]–SiO[sub 2]) have been fabricated and characterized optically. Intense visible lights and near-infrared emissions were observed under ultraviolet light and 488 nm laser excitation. The density, refractive index, optical absorption, Judd–Ofelt parameters, and spontaneous transition probabilities have been measured and calculated. Intense fluorescences at 1.2 and 1.29 μm wavelengths were observed, indicating that the glasses are promising materials for laser and optical amplifier applications operating in the 1.2–1.3 μm low-loss window of telecommunication fiber. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Efficient infrared emissions at ~ 1.2 and ~ 2.0 µm were recorded in Ho3+-single-doped and Ho3+/Yb3+-co-doped aluminum germanate glasses (NMAG), respectively. The maximum stimulated emission cross-sections for the ~ 1.2- and ~ 2.0 µm emissions were derived to be 2.3 × 10−21 and 5.8 × 10−21 cm2, respectively; then the gain cross-sections were further evaluated and the effective gains have been anticipated. In addition, the channel waveguide fabricated by K+-Na+ ion-exchanged method exhibited a complete single mode at 1.55 µm and the field diameters were identified to be horizontally 10.6 µm and vertically 6.7 µm. Effective amplified spontaneous emission at ~ 2.0 µm was recorded under 980 nm laser pumping. Broad bandwidth, large emission cross-section and perfect thermal ion-exchangeability indicate that Ho3+- and Yb3+-doped NMAG glasses are promising for the development of optical amplifier, tunable laser and light source operating at ~ 1.2 and ~ 2.0 µm.Graphical abstract: [ABSTRACT FROM AUTHOR]

Comments on the article of Jeongan Kang and colleagues about the emission characteristics of erbium-doped stoichiometric lithium niobate crystals. Preparation of the crystals by top-seeded solution growth method; Effects of vapor transport equilibration technique; Radiation trapping effect.

Frequency upconversion of Er[sup 3+] in alkali bismuth gallate glasses have been investigated. The upconversion mechanisms are discussed, and the dominant mechanisms are excited state absorption for the [sup 2]H[sub 11/2]→[sup 4]I[sub 15/2] and [sup 4]S[sub 3/2]→[sup 4]I[sub 15/2] transitions, and energy transfer upconversion for the [sup 4]F[sub 9/2]→[sup 4]I[sub 15/2] transition. Intense green (around 525-550 nm) and red (around 660 nm) emission bands were observed under 800 nm excitation. At a pump intensity of 15.6 W/cm2, frequency upconversion efficiencies of 2.1x10[sup -2] and 4.8x10[sup -3] were obtained for the green and red emissions, respectively. The results are the highest among doped oxide glasses, and are comparable to those reported for Er[sup 3+]/Yb[sup 3+] codoped fluoride glasses. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Sm3+ doped germanotellurite glasses (NZPGT) with maximum phonon energy of 793cm−1 have been prepared and characterized. Judd-Ofelt parameters Ωt (t=2, 4, 6) have been calculated to be 3.52×10−20, 4.70×10−20 and 1.90×10−20cm2, respectively. Large value of Ω2 indicates a high asymmetry and covalent environment around Sm3+ in the glass system. The maximum stimulated emission cross-section of the dominant transition 4G5/2→6H9/2 peaking at 645.0nm was derived to be 10.00×10−22cm2, predicting that the red fluorescence emission can be efficiently extracted from the optical glasses. The internal quantum efficiency and external quantum yield of 0.4wt% Sm2O3 doped NZPGT glasses were deduced to be 82.5% and 6.0%, respectively. The results demonstrate that Sm3+ doped NZPGT glasses are a potential candidate for developing tunable visible lasers, compact light sources and solid-state display devices. [ABSTRACT FROM AUTHOR]

Two simple methods for estimating the potential modulation bandwidth of TO packaging technique are presented. The first method is based upon the comparison of the measured frequency responses of the laser diodes and the TO laser modules, and the second is from the equivalent circuit for the test fixture, the TO header, the submount and the bonding wire. It is shown that the TO packaging techniques used in the experiments can potentially achieve a frequency bandwidth of over 10.5 GHz, and the two proposed methods give similar results. [ABSTRACT FROM AUTHOR]

Sr 2 (La 1- x Er x )F 7 /polyacrylonitrile composite fibers with special pliability and excellent crystal dispersibility have been fabricated, which provide smaller size and appropriate temperature sensitivity. Up-conversion emission shows quadratic dependence of the photoluminescence intensity on pump power, confirming the participation of two photons during the excitation processes. The composite fibers, combining main and auxiliary sensing derived from green and red emissions, give fibers the ability to obtain accurate results and better reproducibility. Among them, assigning the green emission as the main indicator of non-contact temperature sensing, the absolute and relative sensitivities are 0.514% K -1 and 0.654% K -1 at 373 K, respectively. Furthermore, the ratio of green and red emission serves as an auxiliary monitoring parameter to calibrate the deviation, where the absolute and relative sensitivities reach 7.208% K -1 and 0.901% K -1 at 373 K. In general, composite fibers with excellent dual-ratiometric temperature sensing are expected to be applied in biological probes, miniature devices and accurate temperature sensors.

C e 3+ doped M , Y) glass ceramics (GCs) have been proved to be shapeable phosphors for white lighting driven by a 453 nm laser. Quantitative characterization reflects that the net emission powers of 4 wt% LuAG-doped GC and 4 wt% YAG-doped GC are 59.99 mW and 66.22 mW at the pump power of 117.63 mW, and the quantum yields reach up to 71.1% and 78.0%, respectively. Miniaturization of devices can be achieved for LuAG/YAG-GCs by optimizing sample size and phosphor concentration with maintaining fluorescence intensity of the samples. Presupposed color coordinate trace reveals that the high-brightness white fluorescence can be realized when the appropriate intensity ratio is determined between residual laser and sample emission. The tunable white fluorescence and the efficient radiation releasing illustrate that LuAG/YAG-GCs are potential candidates for application in solid-state laser illumination.3 A l 5 O 12 (MAG, M = L u , Y) glass ceramics (GCs) have been proved to be shapeable phosphors for white lighting driven by a 453 nm laser. Quantitative characterization reflects that the net emission powers of 4 wt% LuAG-doped GC and 4 wt% YAG-doped GC are 59.99 mW and 66.22 mW at the pump power of 117.63 mW, and the quantum yields reach up to 71.1% and 78.0%, respectively. Miniaturization of devices can be achieved for LuAG/YAG-GCs by optimizing sample size and phosphor concentration with maintaining fluorescence intensity of the samples. Presupposed color coordinate trace reveals that the high-brightness white fluorescence can be realized when the appropriate intensity ratio is determined between residual laser and sample emission. The tunable white fluorescence and the efficient radiation releasing illustrate that LuAG/YAG-GCs are potential candidates for application in solid-state laser illumination.

Multi-photon-excited thermal-correlated green and red upconversion (UC) emissions have been quantified in H o 3+ / Y b 3+ co-doped fluotellurite (BZLFT) glass phosphor under the 978 nm laser excitation. The temperature dependence of the fluorescence intensity ratio (FIR) originated from UC emissions bands centered at 550 nm and 661 nm has been verified in the range of 303-543 K. The net emission photon numbers of 5 F 4 + 5 S 2 → 5 I 8 and 5 F 5 → 5 I 8 transition emissions are up to 40.08×10 12 and 68.51×10 12 c p s in the 0.4 w t . % H o 2 O 3 -0.4 w t . % Y b 2 O 3 co-doped BZLFT case under the 6.95 W / m m 2 laser power density. Furthermore, the quantum yield (QY) and luminous flux are determined to be dependent on pumping power. When the excitation power increases 874 mW, the QY values for 550 nm and 661 nm emissions are as high as 0.94×10 -5 and 1.60×10 -5 . In addition, the high photon producing efficiency is conducive to ensuring high feedback to thermosensitive performance. The temperature thermal sensor can be manipulated steadily in medium temperature range, and the relative sensitivity reaches 0.4 % K -1 at 303 K, which is 1 order of magnitude larger than those in several rare-earth-doped materials. Efficient photon conversion ability and high temperature sensitivity indicate that the rare-earth-ion-doped fluotellurite material has a prospective application in the construction of optical temperature sensors based on the FIR technique allowing for self-referenced temperature determination.

Adaptive fluoride ceramic with glass forming layer (GC ZBL -Er) used in laser anti-escaping has been prepared by one-step synthesis, and the thickness of glass layer is identified as ~0.41 mm. Blue, green and red emissions of Er 3+ /Yb 3+ codoped fluoride ceramic (C ZBL -Er) and glass layer (G ZBL -Er) have been investigated under ~980 nm laser pumping. With the forming of thin glass layer on ceramic surface, the absorption intensities on diffuse reflection of GC ZBL -Er at 974 nm and 1.53 μm increase by 48% and 53% than those of C ZBL -Er. Excited by a 979 nm laser, the presence of the glass layer increases the absolute absorption rate in spectral power from 75% in C ZBL -Er to 83% in GC ZBL -Er, which is consistent with the improvement in the absorbed photon number. In addition, the quantum yield of GC ZBL -Er complex is raised by 28.4% compared to the case of ceramic substrate by photon quantification. Intense absorption-conversion ability and efficient macroscopical anti-escaping effect confirm the superiority of ingenious structure in the fluoride ceramics with glass forming layer, which provides a new approach for developing the absorption-conversion materials of anti-NIR laser detection.

Intense multi-peak red fluorescence and effective near-infrared (NIR) ultra-broadband emission have been observed in Pr 3+ doped ion-exchangeable aluminum germanate (NMAG) glasses. The maximum emission cross section for P 0 3→F 2 3 red emission is up to 100.58×10 -21   cm 2 , and the NIR emission corresponding to D 2 1→G 4 1 transition possesses a full-width at half-maximum (FWHM) of 210 nm. Although the obvious cross-relaxation (CR) process at high concentration causes a decrease of the quantum efficiency, the CR broadens the spectral FWHM effectively from another perspective. The admirable red fluorescence trace and the NIR single-mode transmission confirm that Pr 3+ doped NMAG glass planar waveguides can support the generation of visible fluorescence and the amplification of infrared signal. For a waveguide channel ion-exchanged in molten KNO 3 for 2 h, the single-mode field diameters at 1.55 μm are identified to be 10.4 μm in the horizontal direction and 6.5 μm in the vertical direction, implying an acceptable overlap with a standard single-mode fiber. Effective red fluorescence and broad NIR emission demonstrate that Pr 3+ doped NMAG glasses are a promising substrate in developing irradiative luminescence sources and ultra-broadband waveguide amplifiers, especially operating at the entire S-, C-, and L- bands.

Photon conversion is exhibited in a borate (LKZBSB) glass system containing Eu(3+), and the enhanced characteristic emissions of Eu(3+) with the codoping of Ce(3+) have been verified. A large Judd-Ofelt intensity parameter Ω2 of Eu(3+) indicates a high asymmetrical and strong covalent environment around rare-earth (RE) ions in LKZBSB glasses and spontaneous emission probability and a maximum emission cross section of the dominant 5D0→7F2 transition were derived to be 370  s(-1) and 1.28×10(-21)  cm2, respectively, revealing the potential UV→visible photon-conversion capacity of Eu(3+). Absolutely quantitative evaluation illustrates that Eu(3+) is a favorable photon-conversion center to achieve high photon-conversion efficiency. The addition of Ce(3+) is beneficial to realizing effective red emission of Eu(3+), which possesses commercial value by decreasing the dopant of expensive europium compounds. As an expectation, this photon-conversion LKZBSB glass system can promote the development of a photon downconversion layer for solar cells, which are particularly used in outer space with intense UV radiation.

Ho(3+)-doped and Ho(3+)/Yb(3+)-codoped multicomponent germanium tellurite (MGT) glasses with multifarious emission channels in the near-infrared wavelength region have been fabricated and characterized. Judd-Ofelt intensity parameters of Ho(3+)-doped MGT glasses are solved to be Ω2=5.32×10(-20)  cm(2), Ω(4)=2.73×10(-20)  cm(2), and Ω(6)=1.12×10(-20)  cm(2), indicating a higher asymmetric and stronger covalent environment around Ho(3+) ions in MGT glasses. Efficient infrared fluorescences have been observed in MGT glasses, and spontaneous emission probabilities are derived to be 230.4, 79.9, and 138.3  s(-1) for the (5)I(6)→(5)I(8), ((5)F(4),(5)S(2))→(5)I(5), and (5)I(7)→(5)I(8) radiative transitions, respectively. In Ho(3+)/Yb(3+)-codoped MGT glasses, the maximum stimulated emission cross-section of 2.0 μm emission is calculated to be 4.93×10(-21)  cm(2), and the corresponding gain cross-section is derived to be 3.62×10(-21)  cm(2) when the excited state population fraction P reaches 0.8. Multifarious infrared emissions show that Ho(3+) in MGT glasses is a good candidate for optical amplifiers and optoelectronic devices.

Pr3+-doped medium-low phonon energy heavy metal germanium tellurite (NZPGT) glasses have been fabricated and the intense multi-peak red fluorescence emissions of Pr3+ are exhibited. Judd-Ofelt parameters Ω2 = 3.14 × 10(-20)cm(2), Ω4 = 10.67 × 10(-20)cm(2) and Ω6 = 3.95 × 10(-20)cm(2) indicate a high asymmetrical and covalent environment in the optical glasses. The spontaneous emission probabilities A(ij) corresponding to the 1D2→3H4, 3P0→3H6, and 3P0→3F2 transitions are derived to be 1859.6, 6270.1 and 17276.3s(-1), respectively, and the relevant stimulated emission cross-sections σ(em) are 5.20 × 10(-21), 14.14 × 10(-21) and 126.77 × 10(-21)cm(2), confirming that the effectiveness of the red luminescence in Pr3+-doped NZPGT glasses. Under the commercial blue LED excitation, the radiant flux and the quantum yield for the red fluorescence of Pr3+ are solved to be 219μW and 11.80%, respectively. 85.24% photons of the fluorescence in the visible region are demonstrated to be located in 600-720nm wavelength range, which matches the excitation band of the most photosensitizers (PS), holding great promise for photodynamic therapy (PDT) treatment and clinical trials.

In Sm(3+)-doped K(+)-Na(+) ion-exchanged aluminum germanate (NMAG) glass channel waveguide, a clear and compact red amplified spontaneous emission (ASE) trace is observed under the excitation of a 488nm Ar(+) laser. 78% photons of ASE fluorescence in visible region are demonstrated to be located in 600-730nm wavelength range. High-directivity and high-brightness ASE fluorescence of Sm(3+)-doped NMAG glass channel waveguide, which matches the excitation band of most photosensitizers (PS) currently used in photodynamic therapy (PDT) or clinical trials, has promising potential application as an excitation light source for PDT treatment.

Plasmonic or metamaterial nanostructures are usually fabricated on rigid substrate i.e. glass, silicon. Optical functionality of such kinds of nanostructures is limited by the planar surface and thus sensitive to the incident angle of light. In this work, we demonstrated that a tri-layer flexible metamaterials working at near infrared (NIR) regime can be fabricated on transparent PET substrate using flip chip transfer (FCT) technique. FCT technique is solution-free and can also be applied to fabricate other functional nanostructures device on flexible substrate. We demonstrated NIR metamaterial device can be transformed into various shapes by bending the PET substrate.

In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers.

This paper presents the synthesis of CuO nanowires using a localized thermal heating method in ambient air. It employs local heat sources defined in micro-resistive heaters fabricated by a standard polysilicon-based surface micromachining process instead of a global furnace heating. Since the synthesis is performed globally at room temperature, the presented process is compatible with standard CMOS. The synthesized CuO nanowires are characterized by scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. It is found that this approach provides a simple method to locally synthesize suspended CuO nanowires on polysilicon microbridges on silicon substrates, thus allowing for integration of CuO nanowires into silicon-based devices. It provides a significant step towards the process integration of CuO nanowires with MEMS to realize functional devices.

Efficient 2.0 microm infrared and visible upconversion emissions have been observed in Ho3+/Yb3+ co-doped mixed-alkali bismuth gallate (LKBBG) glasses having a maximum-phonon energy of 673 cm(-1). The Judd-Ofelt parameters Omega2, Omega4 and Omega6 of Ho3+ indicate that there is a high asymmetry and strong covalent environment in LKBBG glasses. The large absorption and emission cross-sections of Yb3+ confirm that it is a suitable sensitizer for capturing and transferring pump energy to Ho3+. The emission cross-section profile for the 5I7-->5I8 transition is derived using the reciprocity method and the peak value is 5.54 x 10(-21)cm2, which is much larger than the value in fluorozircoaluminate glasses. LKBBG glasses exhibit low maximum-phonon energy and large refractive index, and it is possible to achieve an effective 1.66 microm U-band emission of Ho3+ under 900 nm laser radiation.