Optics Express

Published by Optica Publishing Group

Online ISSN: 1094-4087


Surface phonon polariton characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure
ArticleFull-text available

May 2010


381 Reads






Surface phonon polariton (SPP) characteristics of In(0.04)Al(0.06)Ga(0.90)N/AlN/Al(2)O(3) heterostructure are investigated by means of p-polarized infrared (IR) attenuated total reflection spectroscopy. Two absorption dips corresponding to In(0.04)Al(0.06)Ga(0.90)N SPP modes are observed. In addition, two prominent dips and one relatively weak and broad dip corresponding to the Al(2)O(3) SPP mode, In(0.04)Al(0.06)Ga(0.90)N/Al(2)O(3) interface mode, and Al(2)O(3) bulk polariton mode, respectively, are clearly seen. No surface mode feature originating from the AlN layer is observed because it is too thin. Overall, the observations are in good agreement with the theoretical predictions.

Fig. 1. (a) Cross-sectional schematic of the reference device structure (b) cross-sectional schematic of the improved device structure (c) an optical microscopy image of a fabricated device 
Fig. 2. Omega /Two-Theta XRD rocking curves of InGaN solar cell with and without ultra-thin inserting layer. 
Fig. 3. Reciprocal space map around the asymmetric (105) reflection of InGaN/GaN solar cell sample A (a) and sample B (b). 
Fig. 4. Normalized EQE spectra from devices with and without ultra-thin inserting layer Table 1. The summary of the photovoltaic property of the two samples Sample J SC (mA/cm2) V OC (V) Max-EQE (%) 
Fig. 5. Illuminated J-V curves from devices with and without ultra-thin inserting layer under 1sun AM1.5G equivalent illumination. 


Enhanced performance of InGaN/GaN based solar cells with an In(0.05)Ga(0.95)N ultra-thin inserting layer between GaN barrier and In(0.2)Ga(0.8)N well

March 2013


832 Reads

The effect of ultra-thin inserting layer (UIL) on the photovoltaic performances of InGaN/GaN solar cells is investigated. With UIL implemented, the open-circuit voltage was increased from 1.4 V to 1.7 V, short-circuit current density was increased by 65% and external quantum efficiency was increased by 59%, compared to its counterparts at room temperature under 1-sun AM1.5G illumination. The improvements in electrical and photovoltaic properties are mainly attributed to the UIL which can boost the crystal quality and alleviate strain. Moreover, it can act as a transition layer for higher indium incorporation and an effective light sub-absorption layer in multiple quantum wells.

Electro-optic phase modulation in ridge waveguides of epitaxial K(0.95)Na(0.05)Ta(0.71)Nb(0.29)O(3) thin films

July 2007


85 Reads

Electro-optic modulation at lambda=1.5 mum has been demonstrated for the first time to the best of our knowledge in a ridge waveguide phase modulator produced in cubic potassium sodium tantalate niobate thin films epitaxially grown on potassium tantalate substrates exploiting the large quadratic electro-optic Kerr coefficient of R11 = 8.2x10(-17) m(2)/V(2). The relative permittivity, Kerr coefficient, and refractive index have been evaluated for the thin film crystal and are compared to the values measured in bulk crystals. The half-wave voltage times length figure of merit of the modulator has been measured to be Vpil=38 Vcm at room temperature.

Tunable luminescence Y₃Al₅O₁₂:0.06Ce³⁺, xMn²⁺ phosphors with different charge compensators for warm white light emitting diodes

September 2012


63 Reads

Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:0.06Ce<sup>3+</sup>, xMn<sup>2+</sup> (YAG:0.06Ce,xMn) phosphors have been synthesized and the effect of different charge compensators on the color adjustment has been investigated for the first time. The luminescence properties of Mn<sup>2+</sup> singly doped and co-doped with Ce<sup>3+</sup> into YAG host have been discussed. It is observed that in singly doped sample, Mn<sup>2+</sup> ions not only occupy two kinds of Al<sup>3+</sup> sites to generate a yellow and a deep red emission bands, but also occupy Y<sup>3+</sup> sites to obtain a green emission band in YAG host. Considering Mn<sup>2+</sup> substitution for Al<sup>3+</sup>, quadrivalence ions including Zr<sup>4+</sup>, Ge<sup>4+</sup> and Si<sup>4+</sup> ions are introduced to balance the charge difference. The results show that Si<sup>4+</sup> as charge compensator exhibits the best tunable effect on controlling the Mn<sup>2+</sup> emissions in YAG:0.06Ce, xMn. In Si<sup>4+</sup>-Mn<sup>2+</sup> co-doped samples, the emission color can be tuned from greenish-yellow to red with increasing the content of Mn<sup>2+</sup>. The Commission International de L'Eclairage (CIE) chromaticity coordinates are also investigated.

Tunable emission from blue to white light in single-phase Na<sub>0.34</sub>Ca<sub>(0.66-</sub>x<sub>-</sub>y<sub>)</sub>Al<sub>1.66</sub>Si<sub>2.34</sub>O<sub>8</sub>: xEu<sup>2+</sup>,yMn<sup>2+</sup> (x = 0.07) phosphor for white-light UV LEDs.

February 2013


115 Reads

A series of single-phased emission-tunable Na<sub>0.34</sub>Ca<sub>0.66</sub>Al<sub>1.66</sub>Si<sub>2.34</sub>O<sub>8</sub>:Eu<sup>2+</sup>,Mn<sup>2+</sup> phosphors were successfully synthesized by a wet-chemical synthesis method. Photoluminescence excitation (PLE) spectra indicate that the phosphor can be efficiently excited by UV radiation from 250 to 420 nm. Also, NCASO:Eu<sup>2+</sup>,Mn<sup>2+</sup> phosphor exhibit a broad blue emission band at 440 nm and an orange emission band at 570 nm, which originate from Eu<sup>2+</sup> and Mn<sup>2+</sup> ions, respectively. Therefore, overall emission color can be tuned from blue to white by increasing the concentration of Mn<sup>2+</sup> ions in the host lattice utilizing energy transfer from Eu<sup>2+</sup> to Mn<sup>2+</sup> ions. This energy transfer phenomenon was demonstrated to be a resonant type through dipole-dipole interaction determined with the help of PL spectra, decay time measurement, and energy transfer efficiency of the phosphor. These results indicate that NCASO:Eu<sup>2+</sup>,Mn<sup>2+</sup> can be a promising single-phased white-emitting phosphor for white-light UV LEDs.

Absorption coefficients of selected explosives and related compounds in the range of 0.1-2.8 THz

October 2007


113 Reads

We have investigated the absorption spectra of seventeen explosives and related compounds (ERCs) by using terahertz time-domain spectroscopy in the 0.1-2.8 THz region. Most of these substances show characteristic absorption features in this frequency range. The measured absorption coefficients of these ERCs form a database, which is of great importance for biochemical, defense and security related applications.

Planar waveguides with less than 0.1 dB/m propagation loss fabricated with wafer bonding

November 2011


1,552 Reads

We demonstrate a wafer-bonded silica-on-silicon planar waveguide platform with record low total propagation loss of (0.045 ± 0.04) dB/m near the free space wavelength of 1580 nm. Using coherent optical frequency domain reflectometry, we characterize the group index, fiber-to-chip coupling loss, critical bend radius, and propagation loss of these waveguides.

Passive mode-locking performance of mixed Nd:La<sub>0.11</sub>Y<sub>0.89</sub>VO<sub>4</sub> crystal.

March 2014


23 Reads

Passive mode locking of a diode pumped Nd:La<sub>0.11</sub>Y<sub>0.89</sub>VO<sub>4</sub> mixed crystal laser with a semiconductor saturable absorber mirror (SESAM) was experimentally investigated for the first time to our knowledge. Stable CW mode-locking has been achieved on both a-cut and c-cut mixed crystals. In case of the a-cut crystal, when a 2% output coupler (OC) was used, the shortest pulse obtained was 4.5 ps and the highest output power was 0.94 W, while when a 6% OC was used, the shortest pulse obtained was 6.8 ps and the highest output power was 5.16 W. In the latter case the optical conversion efficiency is 38% and the slope efficiency is 40.3%, respectively; with the c-cut crystal the shortest pulse achieved was 5.5 ps. Moreover, simultaneous mode locking at two close wavelengths of 1064.3 nm and 1066.2 nm was observed on the c-cut crystal. The mode locked pulse beating generated temporal interference fringe of 0.5 THz repetition rate.

Fig. 1. Concept of IEM algorithm. The decay of a molecule is discretized in time and for each time slot the corresponding photon count is measured, approaching for large values of M the decay function f ( t ). 
Fig. 6. Number of bits required to store N c for (a) fixed accuracy mode and (b) fixed total count mode. 
Fig. 7. Schematic and photo of the experimental setup. A standard Nikon B2-A filter cube was used for the fluorescence imaging.
Fig. 9. (Media 1) Interface between two streams (100 μ M Rhodamine B from top inlet and 20 μ M Rhodamine 6G in water from the bottom inlet) changes as the flow rate is varied in a T- mixer (dimensions: W400 μ m × H200 μ m). Media at 5 times the actual speed (104s in real time): Initially the flow had been stopped, the flow was then re-started at time 5s, leading to a sharp interface between 2 well distinguished streams, but start to mix again after the flow has been stopped at time 45s. 
Real-time fluorescence lifetime imaging system with a 32 x 32 0.13microm CMOS low dark-count single-photon avalanche diode array

May 2010


352 Reads

A compact real-time fluorescence lifetime imaging microscopy (FLIM) system based on an array of low dark count 0.13microm CMOS single-photon avalanche diodes (SPADs) is demonstrated. Fast background-insensitive fluorescence lifetime determination is achieved by use of a recently proposed algorithm called 'Integration for Extraction Method' (IEM) [J. Opt. Soc. Am. A 25, 1190 (2008)]. Here, IEM is modified for a wider resolvability range and implemented on the FPGA of the new SPAD array imager. We experimentally demonstrate that the dynamic range and accuracy of calculated lifetimes of this new camera is suitable for widefield FLIM applications by imaging a variety of test samples, including various standard fluorophores covering a lifetime range from 1.6ns to 16ns, microfluidic mixing of fluorophore solutions, and living fungal spores of Neurospora Crassa. The calculated lifetimes are in a good agreement with literature values. Real-time fluorescence lifetime imaging is also achieved, by performing parallel 32 x 16 lifetime calculations, realizing a compact and low-cost FLIM camera and promising for bigger detector arrays.

PAM-4 Signaling over VCSELs with 0.13microm CMOS Chip Technology

January 2007


44 Reads

We present results for VCSEL based links operating PAM-4 signaling using a commercial 0.13microm CMOS technology. We perform a complete link analysis of the Bit Error Rate, Q factor, random and deterministic jitter by measuring waterfall curves versus margins in time and amplitude. We demonstrate that VCSEL based PAM-4 can match or even improve performance over binary signaling under conditions of a bandwidth limited, 100meter multi-mode optical link at 5Gbps. We present the first sensitivity measurements for optical PAM-4 and compare it with binary signaling. Measured benefits are reconciled with information theory predictions.

Fig. 1. This figure is a revised version of Fig. 10 of [4 ]. “Spectral plots of the nea r-millimeter attenuation by the atmospheric H 2 O at sea level. H 2 O density = 5.9 g/m 3 . Curve A represents 
Fig. 2. Atmospheric attenuation at sea level for different conditions of temperature, relative humidity (RH), fog, dust and rain. (STD: 20 °C, RH 44%), (Hu 35 °C, RH 90%), (Winter:  10 °C, RH 30%), (Fog, Dust, and Rain: 20 °C, RH 44%). Revised figure taken from Ref. 2. Six water windows (circled numbers) and 5 weak water lines (broad arrows) are marked for comparison with the THz-TDS measurements. 
Fig. 3. Enclosed THz-TDS system for atmospheric measurements. 
Fig. 4. (a). Measured THz reference pulse (lower trace) and measured THz sample pulse (upper trace). For clarity the THz sample pulse was shifted upwards by 500 pa. (b). Corresponding amplitude spectrum (upper curve) for the THz reference pulse and the amplitude spectrum for the sample pulse. 
Fig. 5. The amplitude transmission through 6.18 m of atmosphere at 21 °C with RH 51%. The “real data points” are indicated by the larger open circles separated from each other by 6.1 GHz, and the interpolated points obtained from the zero-padding are separated from each other by 0.61 GHz and define the solid line. 10 water windows (circled numbers) and 8 weak water lines are marked to compare with previous predictions and measurements. 
Measurement of the transmission of the atmosphere from 0.2 to 2 THz

April 2011


1,980 Reads

The attenuation of electromagnetic wave propagation in the clear atmosphere from low frequencies up to 2 THz is mainly caused by water vapor. Although there have been many numerical simulations and excellent early sub-mm and far-infrared measurements of this attenuation, there has remained controversy about the background absorption in the most promising windows of transparency below 1 THz. Here, we report an accurate terahertz time-domain spectroscopy (THz-TDS) characterization of water vapor from 0.2 to 2 THz. Our results agree with the previous predicted and measured attenuations for the weak water lines, but show more attenuation for the relatively transparent windows between these lines.

Fig. 1. Schematic diagram of the system. : T. F. P., thinfilm polarizers; T. F. P. E. , thinfilm polarizer etalon; P. C. , Pockels cell; TiS, Ti:sapphires; CC1, concave mirror with a radius of curvature of 0.2 m; CC2, concave mirror with a radius of curvature of 0.3 m; F. R. , Faraday rotator; F. I. , Faraday isolator; CC3, concave mirrors with radii of curvature of 0.5 m; FM, flat mirrors; Pumping1, Second Harmonic of LD-pumped YAG laser with a power of 56 W; Pumping2, Second Harmonic of LD-pumped YAG laser with a power of 83 W; B. S. beam splitter with 30-% reflection. 
Fig. 4. Average power of the amplified beam at each pass of 4-pass and single-pass amplifiers. 
Fig. 5. Calculated and measured intensity profiles and phases of the compressed pulse. The measured traces were retrieved from SHG FROG, and the calculated ones were derived from the measured spectrum and calculated phase by ray tracing. R. En. , retrieved envelope (open circles); C. En. , calculated envelope (solid curve); R. Ph. , retrieved phase (open squares); C. Ph. , calculated phase (dashed curve). 
All-solid-state 5-kHz 0.2-TW Ti: Sapphire laser system

January 2000


129 Reads

An all solid state Ti:Sapphire amplifier system was developed consisting of a regenerative and multipass amplifiers with a peak power of 0.2 TW and a pulse width of 22 fs at 5 KHz. The pumping sources for the amplifiers are two diode pumped, Q-switched YAG lasers. The system consists of a mode locked oscillator, an Offner type stretcher, a regenerative amplifier, a four pass amplifier, a one pass amplifier and a compressor. A22.2 W average power is the highest ever obtained at any repetition rate in ultrashort pulse amplifiers.

Fig. 1. Schematic overview of the ZGP-based MOPA. PBS: polarizer, λ /2: half-wave plate @ 2.05 µm, CaF 2 : CaF 2 wedge. The number of ZGP crystals in the OPA were 1-3 in the experiments. 
Mid-infrared source with 0.2 J pulse energy based on nonlinear conversion of Q-switched pulses in ZnGeP2

April 2014


212 Reads

Mid-infrared (3-5 μm) pulses with high energy are produced using nonlinear conversion in a ZnGeP<sub>2</sub>-based master oscillator-power amplifier, pumped by a Q-switched cryogenic Ho:YLF oscillator. The master oscillator is based on an optical parametric oscillator with a V-shaped 3-mirror ring resonator, and the power amplifier is based on optical parametric amplification in large-aperture ZnGeP<sub>2</sub> crystals. Pulses with up to 212 mJ energy at 1 Hz repetition rate are obtained, with FWHM duration 15 ns and beam quality M<sup>2</sup> = 3.

Passively Q-switched Nd:Sc<sub>0.2</sub>Y<sub>0.8</sub>SiO<sub>5</sub> dual-wavelength laser with the orthogonally polarized output.

September 2012


21 Reads

We have demonstrated a laser-diode pumped continuous-wave (CW) and passively Q-switched laser with a Nd:Sc<sub>0.2</sub>Y<sub>0.8</sub>SiO<sub>5</sub> (Nd:SYSO) crystal for the first time. In the CW operation, the laser was found to oscillate in tri-wavelength regime at 1074.8 nm, 1076.6 nm and 1078.2 nm, respectively. The maximum CW output power of 1.96 W was obtained, giving an optical-to-optical conversion efficiency of 35% and a slope efficiency of 39%. Using either Cr<sup>4+</sup>:YAG or V<sup>3+</sup>:YAG crystal as saturable absorber, stable passively Q-switched laser was obtained at dual-wavelength of 1074.8 nm and 1078.2 nm with orthogonal-polarization. The maximum average output power, pulse repetition rate, and shortest pulse width were 1.03 W, 50 kHz, and 24 ns, respectively. The passively Q-switched dual-wavelength laser could be potentially used as a source for generation of terahertz radiation.

Hybrid diamond-silicon angular-dispersive x-ray monochromator with 0.25-meV energy bandwidth and high spectral efficiency

December 2013


173 Reads

We report on the design, implementation, and performance of an x-ray monochromator with ultra-high energy resolution (ΔE/E ≃ 2.7 × 10<sup>-8</sup>) and high spectral efficiency using x rays with photon energies E ≃ 9.13 keV. The operating principle of the monochromator is based on the phenomenon of angular dispersion in Bragg back-diffraction. The optical scheme of the monochromator is a modification of a scheme reported earlier [Shvyd'ko et al., Phys. Rev. A 84, 053823 (2011)], where a collimator/wavelength selector Si crystal was replaced with a 100-μm-thick type IIa diamond crystal. This modification provides a very-small-energy bandwidth ΔE ≃ 0.25 meV, a 3-fold increase in the aperture of the accepted beam, a reduction in the cumulative angular dispersion rate of x rays emanating from the monochromator for better focusing on a sample, a sufficient angular acceptance matching the angular divergence of an undulator source (≈ 10 μrad), and an improved throughput due to low x-ray absorption in the thin diamond crystal. The measured spectral efficiency of the monochromator was ≈ 65% with an aperture of 0.3 × 1 mm<sup>2</sup>. The performance parameters of the monochromator are suitable for inelastic x-ray spectroscopy with an absolute energy resolution ΔE < 1 meV.

High speed carrier-depletion modulators with 1.4 V-cm V(pi)L integrated on 0.25 microm silicon-on-insulator waveguides

April 2010


299 Reads

We demonstrate a very efficient high speed silicon modulator with an ultralow pi-phase-shift voltage-length product V(pi)L = 1.4V-cm. The device is based on a Mach-Zehnder interferometer (MZI) fabricated using 0.25microm thick silicon-on-insulator (SOI) waveguide with offset lateral PN junctions. Optimal carrier-depletion induced index change has been achieved through the optimization of the overlap region of carriers and photons. The 3dB bandwidth of a typical 1mm long device was measured to be more than 12GHz. An eye-diagram taken at a transmission rate of 12.5Gb/s confirms the high speed capability of the device.

Energy-efficient 0.26-Tb/s coherent-optical OFDM transmission using photonic-integrated all-optical discrete Fourier transform

January 2012


235 Reads

We propose a novel energy-efficient coherent-optical OFDM transmission scheme based on hybrid optical-electronic signal processing. We demonstrate transmission of a 0.26-Tb/s OFDM superchannel, consisting of 13 x 20-Gb/s polarization-multiplexed QPSK subcarrier channels, over 400-km standard single-mode fiber (SSMF) with BER less than 6.3x10(-4) using all-optical Fourier transform processing and electronic 7-tap blind digital equalization per subchannel. We further explore long-haul transmission over up to 960 km SSMF and show that the electronic signal processing is capable of compensating chromatic dispersion up to 16,000 ps/nm using only 15 taps per subchannel, even in the presence of strong inter-carrier interference.

Broadband laser tunability of Nd3+ ions in 0.8CaSiO(3)-0.2Ca(3)(PO4)(2) eutectic glass

March 2009


60 Reads

Site-selective spectroscopy and stimulated emission experiments performed in the (4)F(3/2)-->(4)I(11/2) laser transition of Nd(3+)-doped 0.8CaSiO(3-) 0.2Ca(3)(PO(4))(2) eutectic glass are presented. The spectral features of the excitation spectra and those of spontaneous and stimulated emissions reveal the existence of a very complex crystal field site distribution for Nd(3+) ions. As a consequence, the stimulated emission of Nd(3+) in this glass shows a tunability of about 10 nm as a function of excitation wavelength.

Efficient Nd3+-> Yb3+ energy transfer in 0.8CaSiO(3)-0.2Ca(3)(PO4)(2) eutectic glass

June 2010


82 Reads

In this work we report the study of energy transfer between Nd(3+) and Yb(3+) ions in glasses with the 0.8CaSiO(3)-0.2Ca(3)(PO(4))(2) eutectic composition at room temperature by using steady-state and time-resolved laser spectroscopy. The Nd(3+)?Yb(3+) transfer efficiency obtained from the Nd(3+) lifetimes in the single doped and codoped samples reaches 73% for the highest Nd(3+) concentration. The donor decay curves obtained under pulsed excitation have been used to establish the multipolar nature of the Nd(3+)-->Yb(3+) transfer process and the energy transfer microparameter. The nonradiative energy transfer is consistent with an electric dipole-dipole interaction mechanism assisted by energy migration among donors. Back transfer from Yb(3+) to Nd(3+) is also observed.

Fig. 1. Cross-section (a) and longitudinal-section (b) of a sample grown at 100 mm/h with a diameter of 2.5 mm and doped with 1 wt% of Nd 2 O 3 . Longitudinal-section micrographs of 
Fig. 2. Cross-section micrograph of a sample grown at 50 mm/h doped with 1 wt% of Nd 2 O 3 . 
Fig. 4. Excitation spectra obtained at different emission wavelengths for the glass-ceramic samples grown at 50 mm/h (a) and 500 mm/h (b) and for the glass sample (c). 
Fig. 5. Steady-state emission spectra of the 4 F 3/2 → 4 I 11/2 transition obtained under excitation at 
Fig. 6. Experimental decays of the 4 F 3/2 level obtained under excitation at 802.2 nm at three emission wavelengths for the sample grown at 50 mm/h. 
Site-selective laser spectroscopy of Nd3+ ions in 0.8CaSiO(3)-0.2Ca(3)(PO4)(2) biocompatible eutectic glass-ceramics

May 2012


74 Reads

In this work we report the influence of the crystallization stage of the host matrix on the spectroscopic properties of Nd3+ ions in biocompatible glass-ceramic eutectic rods of composition 0.8CaSiO3-0.2Ca3(PO4)2 doped with 1 and 2 wt% of Nd2O3. The samples were obtained by the laser floating zone technique at different growth rates between 50 and 500 mm/h. The microstructural analysis shows that a growth rate increase or a rod diameter decrease leads the system to a structural arrangement from three (two crystalline and one amorphous) to two phases (one crystalline and one amorphous). Electron backscattering diffraction analysis shows the presence of Ca2SiO4 and apatite-like crystalline phases. Site-selective laser spectroscopy in the (4)I(9/2)→(4)F(3/2)/(4)F(5/2) transitions confirms that Nd(3+) ions are incorporated in crystalline and amorphous phases in these glass-ceramic samples. In particular, the presence of Ca(2)SiO(4) crystalline phase in the samples grown at low rates, which has an excellent in vitro bioactivity, can be unambiguously identified from the excitation spectra and lifetime measurements of the (4)F(3/2) state of Nd(3+) ions.

0.3% Energy stability, 100-millijoule-class, Ti:sapphire chirped-pulse eight-pass amplification system

October 2008


31 Reads

Highly stable operation of a two-stage multipass Ti:sapphire amplifier (a four-pass pre-amplifier and a four-pass power amplifier) for a 100-mJ-class chirped-pulse amplification system has been demonstrated by passive stabilization. By optimizing the ratio of pump energies to the two amplifiers and the optical losses artificially inserted into the second power amplifier, a root-mean-square fluctuation in pulse energy of 0.3% was achieved, which was 5 times lower than that of the pump laser. This is the lowest pulse-to-pulse fluctuation, to the best of our knowledge, obtained by the 100-mJ-class Ti:sapphire amplifiers.

White-emissive tandem-type hybrid organic/polymer diodes with (0.33,0.33) chromaticity coordinates

November 2009


37 Reads

This study reports fabrication of white-emissive, tandem-type, hybrid organic/polymer light-emitting diodes (O/PLED). The tandem devices are made by stacking a blue-emissive OLED on a yellow-emissive phenyl-substituted poly(para-phenylene vinylene) copolymer-based PLED and applying an organic oxide/Al/molybdenum oxide (MoO(3)) complex structure as a connecting structure or charge-generation layer (CGL). The organic oxide/Al/MoO(3) CGL functions as an effective junction interface for the transport and injection of opposite charge carriers through the stacked configuration. The electroluminescence (EL) spectra of the tandem-type devices can be tuned by varying the intensity of the emission in each emissive component to yield the visible-range spectra from 400 to 750 nm, with Commission Internationale de l'Eclairage chromaticity coordinates of (0.33, 0.33) and a high color rendering capacity as used for illumination. The EL spectra also exhibit good color stability under various bias conditions. The tandem-type device of emission with chromaticity coordinates, (0.30, 0.31), has maximum brightness and luminous efficiency over 25,000 cd/m(2) and approximately 4.2 cd/A, respectively.

A 0.4-mm-diameter probe for nonlinear optical imaging

July 2009


62 Reads

A miniaturized probe that possesses a diameter of 0.4 mm is developed for two-photon-excited fluorescence imaging. The miniaturized probe was manufactured by the collapse of air holes and the formation of a lens on the tip of a double-clad photonic crystal fiber (DCPCF) using electric arc discharging from a conventional fusion splicer. As a result, a femtosecond pulsed laser beam delivered by the DCPCF can be directly focused on a sample for two-photon fluorescence imaging. The numerical aperture of the lensed DCPCF is 0.12. The corresponding focal spot size is 6 microm, which is close to the diffraction limit. This 0.4-mm-diamter probe can provide clear two-photon-excited fluorescence images of 10-microm-diameter fluorescent microspheres.

SHG phase matching in GaSe and mixed GaSe1(1-x)S(x), x < or =0.412, crystals at room temperature

July 2008


38 Reads

The optical properties of p-type GaSe and mixed GaSe(1-x)S(x), x=0.04, 0.023, 0.090, 0.133, 0.175, 0.216, 0.256, 0.362, 0.369, and 0.412, crystals were studied to reveal the potentials for phase matching and frequency conversion. Comparative experiment on Er3+:YSGG and CO2 laser SHG at identical experimental conditions is carried out at room temperature. Any change in polytype structure of GaSe1(1-x)S(x) was not found.

84 dB amplification, 0.46 J in a 10 Hz output diode-pumped Nd:YLF ring amplifier with phase-conjugated wavefront corrector

June 2010


49 Reads

A diode-pumped joule class in a 10 Hz output Nd:YLF ring amplifier has been developed. A phase conjugate plate was developed as a wavefront corrector for the residual wavefront distortion of an Nd:YLF rod. We have demonstrated a 0.46 J output of 10 ns pulse duration at 10 Hz repetition rate with 1.5 nJ of input energy. The effective gain of the ring amplifier system was 84.8 dB. To our knowledge, this is the highest magnification with joule-level output energy in a single-stage amplifier system that has ever been built. As a preamplifier system, this system contributed a demonstration of 21.3 J in a 10 Hz output diode-pumped Nd:glass zigzag slab laser system with a stimulated Brillouin scattering- phase conjugation mirror. We describe a robust and effective method of wavefront correction for high-energy laser systems.

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