Optical frequency division by 3 of 532 nm in periodically poled lithium niobate with a double grating

Optical frequency division by 3 of 532 nm is demonstrated by back-to-back difference-frequency generation in a periodically poled lithium niobate crystal with a double grating. The first grating generates 1596-nm light from 532- and 798-nm inputs, and the second grating mixes the 798-nm input and the 1596-nm output from the first grating to produce a second 1596-nm output. The beat signal between the two 1596-nm outputs is detected and frequency stabilized to yield the 3:1 frequency ratio.     

Growth of the green algae Chlamydomonas reinhardtii under red and blue lasers

Red and blue lasers, holding promise as an electric light source for photosynthetic systems on account of being true monochromatic, high-power, and having high electrical-conversion efficiency, were employed in growing a green alga, Chlamydomonas reinhardtii. The laser treatments tested included: 655-nm Red; 680-nm Red; 655-nm Red+474-nm Blue and 680-nm Red+474-nm Blue. A white cold cathode lamp with spectral output similar to that of white fluorescent lamp served as control. C. reinhardtii successfully grew and divided under the 655 and 680-nm red lasers as well as under the white-light control. Supplementing either red with blue laser, however, resulted in increased algae cell count that significantly exceeded those under both red lasers and the white-light control on average by 241%.     

Asymmetric multiple-quantum-well laser diodes with wide and flat gain

Asymmetric multiple-quantum-well laser diodes with wide and flat gain spectra were designed, fabricated, and analyzed. The active layer was composed of three 10-nm, one 8-nm, and two 6-nm 0.5% compressive strained wells and four 10-nm and one 5-nm 0.4% tensile strained barrier layer. Measured spectra of antireflection-coated ridge waveguide laser diodes with such quantum-well structures have shown that -1-dB spectral gain bandwidth can be as large as 90 nm.     

Acute toxicological impact of nano- and submicro-scaled zinc oxide powder on healthy adult mice

In this work, the acute oral toxicity of 20- and 120-nm ZnO powder at doses of 1-, 2-, 3-, 4-, 5-g/kg body weight was evaluated referred to the OECD guidelines for testing of chemicals. As the results, both 20- and 120-nm ZnO belong to non-toxic chemicals according to the Globally Harmonized Classification System (GHS) for the classification of chemicals. The distribution determination showed that Zn was mainly retained in the bone, kidney and pancreas after 20- and 120-nm ZnO administration. However, the results of blood measurement suggest that the increase in blood viscosity could be induced by low and median dose of 20-nm ZnO but high dose of 120-nm ZnO. The pathological examination showed that the 120-nm ZnO treated mice had dose–effect pathological damages in stomach, liver, heart and spleen, whereas, 20-nm ZnO displayed negative dose–effect damages in liver, spleen and pancreas. Therefore, we conclude that the liver, spleen, heart, pancreas and bone are the target organs for 20- and 120-nm ZnO oral exposure. More attention should be paid on the potential toxicity induced by low dose of 20-nm ZnO oral exposure.     

Modeling erbium–thulium-co-doped fiber amplifier for 1400–1650 nm band

We present numerical models of tri-valence erbium ion and thulium ion-co-doped fiber amplifiers pumped by 800-nm and 980-nm lasers. The rate and power propagation equations of the models are numerically solved to analyze the gain as a function of co-doping concentrations, fiber length and signal wavelength. The results reveal that with 800-nm or 980-nm pump, gain competition exists between 1470- and 1530-nm bands, which may arise from the pump absorption competition and complicated energy transfer between the two types of active ions, and the results further show that the gain spectra may cover 305 nm (1375–1680 nm) for 800-nm pump and 160 nm (1400–1560 nm) for 980-nm pump. The doping concentrations and fiber length may be tuned to reduce the ripple of the gain spectra.     

Excited-state absorption in the range of pumping and laser efficiency of Cr4+:forsterite

The absorption saturation and the laser efficiency of Cr(4+): forsterite were measured with 1064-nm (E || b), 980-nm (E || c), and 780-nm (E || b) pulsed laser pumping. A slope efficiency of 32% was obtained for the 980-nm (E || c) pump wavelength, where the excited-state absorption losses were shown to be negligible.     

Noncritically phase-matched second-harmonic generation in cesium lithium borate

Efficient generation of 236-nm light was demonstrated by use of noncritically phase-matched second-harmonic generation in cesium lithium borate. Noncritical phase matching provided approximately 20x the nonlinear drive for second-harmonic generation than beta-barium borate for 236-nm generation. The 236-nm wavelength is the fourth harmonic of a 946-nm Nd:YAG laser. Phase matching was accomplished at a crystal temperature of -15 degrees C.     

Color-image generation by use of binary-phase holograms

A novel, simple scheme for producing full-color images by use of binary-phase holograms and red (632.8-nm), green (543.5-nm), and blue (488-nm), lasers is reported. The theory and experimental results of the system are also presented.     

Generation of all-solid-state, high-power continuous-wave 213-nm light based on sum-frequency mixing in CsLiB6O10

Achievement of more than 100 mW of pure continuous-wave deep-ultraviolet radiation at 213 nm has been demonstrated in an efficient all-solid-state laser system that uses two Brewster-cut CsLiB6O10 (CLBO) crystals. The first crystal is used for 266-nm generation by external resonant doubling of 532-nm radiation from a frequency-doubled Nd:YVO4 laser. Subsequent sum-frequency mixing is performed in a second CLBO crystal placed in a diode-pumped Nd:YAG laser cavity to mix the single-pass 266-nm output with circulating 1064-nm light.     

Fabrication of silicon webs in the decananometre range

In addition to the high demands on lithography, short-channel effects are problems for miniaturisation of devices. Double-gate MOSFETs are known to improve the short-channel behaviour and are traded in the ITRS roadmap as a part of non-classical CMOS, which can provide a path to scaling MOSFETs below the 65-nm node. For the centre of a special vertical layout a silicon web with 300-nm height and 20-nm width is required. The web lines are made by electron-beam lithography with hydrogen silsesquioxane (HSQ) as negative tone resist. 23-nm wide and 100-nm high lines in HSQ were attained. The transfer of the structures to a substrate by dry etching results in 30-nm-wide and 300-nm-high silicon lines. PACS 81.16.Nd; 81.16.Rf; 85.30.Tv     

Ultra-broadband supercontinuum generated in dispersion-flattened fiber

With 4.28-km dispersion-flattened fiber (DFF), more than 254.9-nm 10-dB bandwidth on the right side of zero-dispersion wavelength and a 190.4-nm wide spectral region with the uniformity of within ±0.5dB are obtained. While on the opposite side, 198.4-nm 10-dB bandwidth and 62.3-nm spectral region with the uniformity of within ±0.5 dB are obtained. More than 88 channels spaced at 2.52 nm on the long wavelength side are generated using Fabry-Perot (F-P) filter. The output supercontinuum (SC)characteristic is also analyzed by spectrum carving.     

Seven-photon ultraviolet upconversion emission of Er3+ induced by 1,540-nm laser excitation

The multi-photon ultraviolet upconversion emission properties and synergistic effect are investigated in BaSr₂Y₆O₁₂:Er³⁺ phosphor. The deep-ultraviolet emissions centered at 274, 297 and 324-nm are observed under the 1,540-nm excitation, which results from a seven-, six- and six-photon upconversion process, respectively. A synergistic effect is found, which shows that the red emission intensity under 351- and 1,540-nm dual excitation is 4.7 % time stronger than the sum of red emission intensities under the 351 and 1,540-nm single excitation. This phenomenon is attributed to the ⁴I_13/2 and ⁴I_11/2 levels of Er³⁺ from non-radiative transition process under the 351-nm excitation are excited again to ⁴F_9/2 level by absorbing 1,540-nm photon in the 351- and 1,540-nm dual-excitation process.     

Effect of graphene/ZnO hybrid transparent electrode on characteristics of GaN light-emitting diodes

In order to reduce the Schottky barrier height and sheet resistance between graphene(Gr) and the p-GaN layers in GaN-based light-emitting diodes(LEDs), conductive transparent thin films with large work function are required to be inserted between Gr and p-GaN layers. In the present work, three kinds of transparent conductive oxide(TCO) zinc oxide(ZnO) films, Al-, Ga-, and In-doped ZnO(AZO, GZO, and IZO), are introduced as a bridge layer between Gr and p-GaN,respectively. The influence of different combinations of Gr/ZnO hybrid transparent conducting layers(TCLs) on the optical and thermal characteristics of the GaN-LED was investigated by the finite element method through COMSOL software. It is found that both the TCL transmittance and the surface temperature of the LED chip reduce with the increase in Gr and ZnO thickness. In order to get the transmittance of the Gr/ZnO hybrid TCL higher than 80%, the appropriate combination of Gr/ZnO compound electrode should be a single layer of Gr with ZnO no thicker than 400 nm(1 L Gr/400-nm ZnO),2 L Gr/300-nm ZnO, 3 L Gr/200-nm ZnO, or 4 L Gr/100-nm ZnO. The LEDs with hybrid TCLs consisting of 1 L Gr/300-nm AZO, 2 L Gr/300-nm GZO, and 2 L Gr/300-nm IZO have good performance, among which the one with 1 L Gr/300-nm GZO has the best thermal property. Typically, the temperature of LEDs with 1 L Gr/300-nm GZO hybrid TCLs will drop by about 7 K compared with that of the LEDs with a TCL without ZnO film.     

Demonstration of long-term reliability of a 266-nm, continuous-wave, frequency-quadrupled solid-state laser using beta-BaB(2)O(4)

We report what we believe to be the first operation of more than 1000 h of a 266-nm (cw) frequency-quadrupled solid-state laser with a 100-mW output. We used beta-BaB(2)O(4)(BBO) crystal grown by the Czochralski method to double the green-light (532-nm) wavelength, using an external resonant cavity. The green light was generated with an intracavity frequency-doubled Nd:YVO(4)laser pumped by a 4-W laser diode. When the incident 532-nm power on the external resonant doubler was 500 mW, we generated 100 mW of cw 266-nm radiation with the BBO crystal. The degradation rate seems to be proportional to the strength of the UV optical electric field. We also obtained a relative intensity noise of -130dB/Hz at frequencies of 2 to 10 MHz for 266-nm laser light.     

784-nm amplified spontaneous emission from Tm3+-doped fluoride glass fiber pumped by an 1120-nm fiber laser

We report 784-nm (1G4 --> 3H5 transition) amplified spontaneous emission (ASE) from Tm3+-doped fluoride (ZrF4-BaF2-LaF3-AlF3-NaF) glass fiber pumped by an 1120-nm fiber laser. To our best knowledge, this is the first report of 784-nm (1G4 --> 3H5 transition) ASE in a Tm3+-doped fluoride fiber laser. Its effects on a 480-nm (1G4 --> 3H6 transition) blue laser were also discussed.     

All solid-state CW orange-red laser at 620 nm

We report for the first time a continuous-wave (CW) orange-red radiation at 620 nm by intracavity sum-frequency generation of 1085-nm Nd:YVO₄ laser and 1444-nm Nd:YAG laser. Using type-II critical phase matching KTP crystal, 620-nm orange-red laser was obtained by 1085- and 1444-nm intra-cavity sum-frequency mixing, and output power of 223 mW was demonstrated. At the output power level of 223 mW, the output power stability is better than 3% and laser beam quality M ² factor is 1.32.     

Direct observation of optically forbidden energy transfer between CuCl quantum cubes via near-field optical spectroscopy

We report, for the first time, evidence of near-field energy transfer among CuCl quantum cubes using an ultrahigh-resolution near-field optical microscopy and spectroscopy in the near UV region at 15 K. The sample was high-density CuCl quantum cubes embedded in a NaCl matrix. Measured spatial distributions of the luminescence intensities from 4.6-nm and 6.3-nm quantum cubes clearly established anticorrelation features. This is thought to be a manifestation of the energy transfer from the lowest state of exciton in 4.6-nm quantum cubes to the first dipole-forbidden excited state of exciton in 6.3-nm quantum cubes, which is attributed to the resonant optical near-field interaction.     

Study on CW Nd:YAG infrared laser at 1319 nm

A continuous wave (CW) Nd:YAG infrared laser at 1319 nm is reported in this paper. The energy level of 1319-nm wave was analyzed. The repression of 1064-nm lasing and enhancement of 1319-nm output power were discussed. Mirror coating and cavity structure were studied and a maximum CW output power of 43 W at 1319 nm was achieved in experiments.     

Structure of Carbon-coated or Silicon-oxide-coated ZnTe,ZnSe and ZnS Nanoparticles Produced by Gas Evaporation Technique

Ultrafine particles of typical chalcogenides have been produced by the advanced gas evaporation method (AGEM) and characterized by transmission electron microscopy. Zinc-blende nanoparticles less than 20-nm in size covered with SiO or carbon layer have been predominately produced. Many growth faults were observed in the zinc-blende particles above 20-nm in size. It has been found that particles less than 10-nm in size have no growth faults.     

355-nm hypersensitization of optical fibers

The intrinsic 244-nm photosensitivity of boron-codoped germanosilicate optical fibers is enhanced by 355-nm hypersensitization. Hypersensitization through standard polymer coating is also demonstrated.