High-energy quasi-phase-matched optical parametric oscillation in a periodically poled MgO:LiNbO3 device with a 5 mm x 5 mm aperture

Fabrication of a 5 mm thick periodically poled MgO-doped LiNbO3 device with a 32.1 microm period for mid-infrared generation was demonstrated. The periodic structure was evaluated by measurement of second-harmonic generation with the d31 coefficient. Optical parametric oscillation using this device with an uncoated 5 mm x 5 mm aperture and a 36 mm effective length realized a high-energy output of 77 mJ for both signal (wavelength 1.83 microm) and idler (2.54 microm) waves with a 72% slope efficiency at 110 mJ pumping of a Q-switched Nd:YAG laser with a 12 ns pulse duration.     

Ultralow emittance, multi-MeV proton beams from a laser virtual-cathode plasma accelerator

The laminarity of high-current multi-MeV proton beams produced by irradiating thin metallic foils with ultraintense lasers has been measured. For proton energies >10 MeV, the transverse and longitudinal emittance are, respectively, <0.004 mm mrad and <10(-4) eV s, i.e., at least 100-fold and may be as much as 10(4)-fold better than conventional accelerator beams. The fast acceleration being electrostatic from an initially cold surface, only collisions with the accelerating fast electrons appear to limit the beam laminarity. The ion beam source size is measured to be <15 microm (FWHM) for proton energies >10 MeV.     

用于10Gb/s传输系统的电吸收调制器与分布反馈激光器集成光源

采用超低压(22×１０^２Pa)选择区域生长(selective area growth, SAG)金属有机化学气相沉积(metal-organic chemical vapor deposition, MOCVD)技术成功制备了应变型InGaAsP/InGaAsP电吸收调制器(electroabsorption modulator, EAM)与分布反馈激光器(distribute feedback laser, DFB)单片集成光源的新型光电器件.实验结果表明，采用该技术制备的集成器件表现出了良好的性能：激射阈值为19 mA，出光功率接近7 mW，边模抑制比(side-mode suppression ratio, SMSR)大于40 dB，将该集成器件出射光耦合进普通单模光纤后进行测量，获得了16 dB的消光比，器件3 dB响应带宽达到了10 GHz以上.将该集成器件完全封装后成功进行了10 Gb/s非归零码(non-return zero, NRZ)的传输实验：在误码率为10^-10的传输条件下于普通单模光纤中传输了53.3 km，色散代价小于1.5 dB，动态消光比大于8 dB，且眼图清晰张开. 关键词： 超低压 选择区域生长 集成光电子器件 10 Gb/s     

超低压选择区域生长法制备产生10GHz重复率超短光脉冲的级联电吸收调制器与分布反馈激光器单片集成光源

采用超低压(22×１０^２Pa)选择区域生长(selective area growth, SAG)金属有机化学气相沉积(metal-organic chemical vapor deposition, MOCVD)技术成功制备了InGaAsP/InGaAsP 级联电吸收调制器(electroabsorption modulator, EAM)与分布反馈激光器(distributed feedback laser, DFB)单片集成光源的新型光电器件.实验结果表明，采用该技术制备的器件 关键词： 超低压 选择区域生长 集成光电子器件 超短光脉冲     

Generation of infrared radiation by stimulated Raman scattering in para-hydrogen crystal at 5 K

We report the preliminary results of our experiments with stimulated Raman scattering in para-hydrogen crystal aimed at developing a continuously tunable laboratory laser source of mid-infrared radiation. With laser pulses at 532 nm, a conversion efficiency for the first Stokes beam of as much as 20% in the forward direction was observed through a single-pass, 5-cm-long crystal. Generation of mid-infrared pulses at 4.5 microm was achieved by use of the output of a near-infrared pulsed laser (1.6 microm, 3 ns), and an absorption spectrum of gaseous CD4 molecules was successfully recorded. These results suggest use of the solid para-hydrogen Raman shifter as a promising light source for mid-infrared spectroscopy.     

Simultaneous observation of CO isotopomer absorption by broadband difference-frequency generation using a direct-bonded quasi-phase-matched LiNbO3 waveguide

Rovibration absorption lines both of 12CO and 13CO are observed simultaneously with the output of a 2 microm broadband difference frequency generated in a direct-bonded quasi-phase-matched LiNbO3 waveguide, which is a 50 mm device with a single quasi-phase-matching period that is operated at a constant temperature. The wavelength conversion efficiency and the difference-frequency generation bandwidth reach 100%/W and 100 nm, respectively. The idler output bandwidth in the 2 microm region is obtained by group-velocity matching or phase-mismatch minimization when a 0.94 microm pump laser diode and a 1.55 microm tunable signal source are used.     

Compact soft x-ray microscope using a gas-discharge light source

We report on a soft x-ray microscope using a gas-discharge plasma with pseudo spark-like electrode geometry as a light source. The source produces a radiant intensity of 4 x 10(13) photons/(sr pulse) for the 2.88 nm emission line of helium-like nitrogen. At a demonstrated 1 kHz repetition rate a brilliance of 4.3 x 10(9) photons/(microm2 sr s) is obtained for the 2.88 nm line. Ray-tracing simulations show that, employing an adequate grazing incidence collector, a photon flux of 1 x 10(7) photons/(microm2 s) can be achieved with the current source. The applicability of the presented pinch plasma concept to soft x-ray microscopy is demonstrated in a proof-of-principle experiment.     

Stroboscopic supercontinuum white-light interferometer for MEMS characterization

We used a supercontinuum-based scanning white-light interferometer to characterize the oscillation of a MEMS device. The output of a commercially available supercontinuum light source (FiberWare Ilum II USB) was modulated to achieve stroboscopic operation. By synchronizing the modulation frequency of the source to the sample oscillation, dynamic 3-D profile measurements were recorded. These results were validated against those obtained with a white light LED setup. The measured maximum deflection of a 400×25×4 μm(3) microbridge driven with 0-6.8 V sinusoidal voltage at 10 Hz was 1.42±0.03 μm (supercontinuum), which agreed with the LED measurement. The method shows promise for characterization of high-frequency MEMS devices.     

Closed-loop adaptive optics in the human eye

We have developed a prototype apparatus for real-time closed-loop measurement and correction of aberrations in the human eye. The apparatus uses infrared light to measure the wave-front aberration at 25 Hz with a Hartmann-Shack sensor. Defocus is removed by a motorized optometer, and higher-order aberrations are corrected by a membrane deformable mirror. The device was first tested with an artificial eye. Correction of static aberrations takes approximately five iterations, making the system capable of following aberration changes at 5 Hz. This capability allows one to track most of the aberration dynamics in the eye. Results in living eyes showed effective closed-loop correction of aberrations, with a residual uncorrected wave front of 0.1microm for a 4.3-mm pupil diameter. Retinal images of a point source in different subjects with and without adaptive correction of aberrations were estimated in real time. The results demonstrate real-time closed-loop correction of aberration in the living eye. An application of this device is as electro-optic "spectacles" to improve vision.     

Saturated absorption spectroscopy of acetylene gas inside large-core photonic bandgap fiber

Saturated absorption spectroscopy is performed on the acetylene nu(1) + nu(3) band near 1532 nm inside photonic bandgap fibers of small (approximately 10 microm) and large (approximately 20 microm) core diameters. The observed linewidths are narrower in the 20 microm fiber and vary from 20 to 40 MHz depending on pressure and power. Variations in the background light transmission, attributed by others to surface modes, are significantly reduced in the 20 microm fiber. The optimum signal for use as a frequency reference in a 0.8 m long, 20 microm diameter fiber is found to occur at about 0.5 torr for 30 mW of pump power. The saturation power is found by modeling the propagation and attenuation of light inside the fiber.     

Wavelength-dispersive device based on a Fourier-transform Michelson-type arrayed waveguide grating

We propose a new type of arrayed waveguide grating (AWG) device that operates as a Fourier-transform (FT) spectrometer without the need of scanning elements. The large input aperture size typical of a FT spectrometer eliminates the requirement for a narrow single-mode input waveguide while still achieving high spectral resolution with a markedly increased light-gathering capability (etendue). An example of the device with a resolution of 0.07 nm (approximately 10 GHz) and designed for a silicon-on-insulator platform is presented. The calculated spectra show no noticeable deterioration for aperture widths as large as 40 microm, yielding more than a 50-fold increase in aperture size compared with conventional AWG or echelle grating based devices at the equivalent resolution.     

Diode-bar end-pumped high-power Nd:Y(3)Al(5)O(12) planar waveguide laser

A compact high-power planar waveguide laser end pumped by a diode-bar is reported. The waveguide was fabricated by liquid-phase epitaxy and had an 80-microm-thick, 1.5-at. % Nd:Y(3)Al(5)O(12) core on a Y(3)Al(5)O(12) substrate. A maximum output power of 6.2 W was obtained at 1.064 microm when the device was pumped with a 20-W diode bar operating near 807 nm, giving an overall optical-to-optical conversion efficiency of 31%. The total device length was 5 cm.     

Electrically injected quantum-dot photonic crystal microcavity light sources

The design, fabrication, and characterization of an electrically injected quantum-dot photonic crystal microcavity light source are described. The optical gain in the GaAs/AlGaAs-based device is provided by self-organized InGaAs quantum dots with ground-state room-temperature emission at 1.1 microm. The carriers are injected directly into the photonic crystal microcavity, which contains approximately 50 dots, avoiding surface state recombination in the photonic crystal pattern. The spectral characteristics of a single-defect photonic crystal microcavity show a single 2 nm broad microcavity resonance. The output power is of the order of a few tens of nanowatts.     

Highly efficient single-pass frequency doubling of a continuous-wave distributed feedback laser diode using a PPLN waveguide crystal at 488 nm

A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.     

一种便携式漫反射LED均匀光源的设计与实现

为了满足光电探测仪器校准修正过程中对标准光源的要求,设计了一种采用积分球技术,通过纽扣电池供电的便携式漫反射LED均匀光源。给出了光源的装配图、主要零件3D图及电路图,并对其进行了详细说明。通过Matlab分析光源出光口CCD照片各像素的灰度值,得到出光口?14 mm范围内光强均匀度为95.1%;采用Ocean Optics USB 2000+型光谱仪分析光源出光口光强均匀性及漫反射性,得到沿出光口径方向2个位置光强与中心光强相比,分别下降了2.93%和6.30%的结果。光源出光口平面旋转10°,中心位置光强下降6.30%。测试分析表明:设计的光源具有较好的均匀度和漫反射性,在光电探测仪器校准方面具有一定的应用价值。     

Laser heating of solid matter by light-pressure-driven shocks at ultrarelativistic intensities

The heating of solid targets irradiated by 5 x 10(20) W cm(-2), 0.8 ps, 1.05 microm wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo, and V. A surface layer is heated to approximately 5 keV with an axial temperature gradient of 0.6 microm scale length. Images of Ni Ly(alpha) show the hot region has 100 G bar light pressure compresses the preformed plasma and drives a shock into the solid, heating a thin layer.     

Electron emission from metal surfaces by ultrashort pulses: determination of the carrier-envelope phase

The phase varphi of the field oscillations with respect to the peak of a laser pulse influences the light field evolution as the pulse length becomes comparable to the wave cycle and, hence, affects the interaction of intense few-cycle pulses with matter. We theoretically investigate photoelectron emission induced by an intense, few-cycle laser pulse from a metal surface (jellium) within the framework of time-dependent density functional theory and find a pronounced varphi dependence of the photocurrent. Our results reveal a promising route to measuring varphi of few-cycle light pulses (tau<6 fs at lambda=0.8 microm) at moderate intensity levels (I(p) approximately 10(12) W/cm(2)) using a solid-state device.     

Coupled absorption filters for thermal detectors

A resonant absorption cavity that couples long-wavelength infrared (LWIR) light into a movable plate has been demonstrated for thermal detectors, especially microbolometers. Each device is continuously tunable over 8.7-11.1 microm by using electrostatic actuation with voltages from 0 to 42 V. The width of the resonance is relatively broad, approximately 1.5 microm, to match the large widths of many spectral features in the LWIR. At an actuation voltage of 45 V, the device switches into a broadband mode with an absorption width of 2.83 microm. This latter mode is used to enhance sensitivity in low-light situations in which little spectral information is present.     

Wavelength-agile mid-infrared (5-10 microm) generation using a galvano-controlled KTiOPO4 optical parametric oscillator

A wavelength-agile mid-infrared (IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO) using a galvano-controlled double-crystal KTiOPO4 (KTP) OPO was demonstrated. The mid-IR wavelength was tuned by varying the KTP OPO pump wavelength while the ZGP crystal angle remained fixed. Rapid tuning of the KTP OPO was achieved by changing the crystal angle by using the galvano scanner. Our mid-IR source can jump to a different wavelength without scanning through the intermediate wavelengths while also permitting continuous-wavelength scanning. The mid-IR source can be tuned from approximately 5to10 microm at a phase-matching angle of 51 degrees , while the pump wavelength is controlled in the 1.95-2.2 microm range.     

LiF超薄层引起的OLEDs发光光谱展宽

将LiF插入到发光层Alq₃中,制备了有机电致发光器件(OLED),其器件的结构为:ITO/NPB (45 nm)/Alq₃ (x nm)/LiF (0.3 nm)/Alq₃ /Al(150 nm)。发现器件的电致发光谱(Electroluminescence spectra, EL)有非常明显的展宽现象,这为白光器件的制备提供了一条简单的途径。通过对比LiF在Alq₃中不同厚度处的发光谱,发现在x=10时谱线展宽最显著,器件最大亮度在22 V时达到8 260 cd/m²,最大效率可达 4.83 cd/A,并对其光谱展宽的机理及器件特性进行了分析。