Broadband light generation at approximately 1300 nm through spectrally recoiled solitons and dispersive waves

We experimentally study the generation of broadband light at approximately 1300 nm from an 810 nm Ti:sapphire femtosecond pump laser. We use two photonic crystal fibers with a second infrared zero-dispersion wavelength (lambda Z2) and compare the efficiency of two schemes: in one fiber lambda Z2=1400 nm and the light at 1300 nm is composed of spectrally recoiled solitons; in the other fiber lambda Z2=1200 nm and the light at 1300 nm is composed of dispersive waves.     

Observation of bright spatial photorefractive solitons in a planar strontium barium niobate waveguide

We have obtained stationary bright spatial solitons in a planar photorefractive strontium barium niobate waveguide for visible light ranging from 514.5 to 780 nm. Even for larger wavelengths (lambda=1047 nm) strong self-focusing of the beam was observed; however, input power had to be some orders of magnitude higher than for visible light for self-focusing to occur. Furthermore, we found transient self-trapping of red light (lambda=632.8 nm) that corresponds to the formation of bright quasi-steady-state solitons.     

Solid state solvation in amorphous organic thin films

The photoluminescence (PL) of the red laser dye DCM2, doped into blended thin films of polystyrene (PS) and the polar small molecule camphoric anhydride (CA), redshifts as the CA concentration increases. The DCM2 PL peaks at 2.20 eV (lambda=563 nm) for pure PS films and shifts to 2.05 eV (lambda=605 nm) for films with 24.5% CA (by mass). The capacitively measured electronic permittivity also increases from epsilon=2.4 to epsilon=5.6 with CA concentration. These results are consistent with the theory of solvatochromism developed for organic molecules in liquid solvents. To our knowledge, this work is the first application of a quantitative theory of solvation to organic molecules in amorphous thin films with continuously controllable permittivity, and demonstrates that "solid state solvation" can be used to predictably tune exciton energies in organic thin film structures.     

High-speed wave-mixing laser Doppler imaging in vivo

An interferometric method for parallel optical spectroscopy in the kilohertz range is reported, as well as its experimental validation in the context of high-speed laser Doppler imaging in vivo. The interferometric approach enables imaging in the low light conditions of a 2 kHz frame rate recording with a complementary metal-oxide semiconductor camera. Observation of mice craniums with near-infrared (lambda=785 nm) laser light in reflection configuration is reported. Doppler spectral images allegedly sensitive to blood flow are sequentially measured at several optical frequency detunings, to shift the spectral range of analysis in the radio-frequency spectrum.     

Integrated optical Ti:Er:LiNbO3 distributed Bragg reflector laser with a fixed photorefractive grating

For the first time to the authors' knowledge, an integrated optical distributed Bragg reflector laser with a fixed photorefractive grating in LiNbO(3) is demonstrated. Sample preparation, grating fabrication, and laser characteristics are reported. The device is pumped by a fiber pigtailed laser diode (lambda(p) approximately 1480 nm) through the Bragg grating in a double-pass configuration, yielding an emission in the backward direction at lambda=1531.7nm . The laser threshold is 40 mW; as much as 5 mW of output power has been obtained at 110 mW of launched pump power in cw operation.     

Ultracold atom-atom collisions in a nonresonant laser field

Using a recently developed approach for treating the three-dimensional anisotropic scattering we find considerable influence of a nonresonant laser field with intensity I> or =10(5) W/cm(2) on the Cs-Cs ultracold collisions. Strong dependence on the laser wavelength lambda(L) is shown at the optical region as lambda(L) becomes shorter than the critical value lambda(0) approximately 3000 nm (of the atomic de Broglie wave lambda) defining the region lambda(0)< or =lambda of the s-wave domination in the absence of the external field. Dependence on the laser polarization is also essential. The found effect can be applicable for controlling atom-atom interactions at ultralow temperatures.     

Distributed feedback-distributed Bragg reflector coupled cavity laser with a Ti:(Fe:)Er:LiNbO3 waveguide

A thermally fixed photorefractive Bragg grating is written in a single-mode Ti:Fe:Er:LiNbO3 channel waveguide and used to develop a distributed feedback-distributed Bragg reflector coupled cavity laser with a second broadband dielectric cavity mirror. The optically pumped (lambda(p) = 1480 nm, P = 130 mW) laser emits in single-frequency operation as much as 8 mW at lambda = 1557.2 nm with a slope efficiency of approximately 22%. The laser wavelength can be thermo-optically and electro-optically tuned over 100 pm.     

Ultraviolet-light generation in nitrogen-doped silica fiber

Nonlinear light transformations were observed in a nitrogen-doped silica fiber pumped with a Nd:YAG laser (lambda=1.06 microm) . Light generation in the spectral range 355-430nm was obtained with an efficiency of up to 2x10(-4) . The UV light was found to be the result of third-harmonic generation, stimulated Raman scattering of the third harmonic, and third-harmonic generation from the Stokes components of the pump light. Lasing based on the color centers of nitrogen-doped silica was observed in the range 380-430nm.     

Infrared holographic recording in LiNbO3:Cu

Holograms may be recorded in photorefractive LiNbO₃:Cu with pulsed infrared light (wavelength =1064 nm, Q-switched Nd:YAG laser), if the crystals are previously or simultaneously illuminated with a green (=532 nm) light pulse. We study refractive index changes and time constants of as-grown and thermally treated crystals with different copper concentrations. A model explaining this effect is discussed.     

Non-thermal laser-induced desorption of metal atoms with bimodal kinetic energy distribution

Laser-induced desorption of metal atoms at low rate has been studied for pulsed excitation with wavelengths of = 266, 355, 532 and 1064 nm. For this purpose sodium adsorbed on quartz served as a model system. The detached Na atoms were photo-ionized with the light of a second laser operating at = 193 nm and their kinetic energy distribution was determined by time-of-flight measurements. For = 1064 nm a distribution typical of thermal bond breaking is observed. If desorption, however, is stimulated with light of = 266 or 532 nm, the kinetic energy distribution is non-thermal with a single maximum atE _kin = 0.16 ± 0.02 eV. For = 355 nm the non-thermal distribution is even bimodal with maxima appearing atE _kin = 0.16 ± 0.02 and 0.33 ± 0.02 eV. These values of the kinetic energies actually remain constant under variation of all experimental parameters. They appear to reflect the electronic and geometric properties of different binding sites from which the atoms are detached and thus constitute fingerprints of the metal surface. The non-thermal desorption mechanism is discussed in the framework of the Menzel-Gomer-Redhead scenario. The transition from non-thermal to thermal desorption at large fluentes of the laser light could also be identified.     

An integrated organic photoconductive detector for optoelectronics

In the system (poly-(N-vinyl carbazole) (PVK): trinitrofluorenone (TNF) a photoconductive complex is formed. Thin metal films are sputtered on BK7 glass substrates, forming two electrodes with 1 mm separation. The photoconductive complex is deposited from a solution in chlorobenzene/tetrahydrofurane on the glass substrate between the electrodes, forming a photoconductive detector. Photoconductivity of these planar detectors is studied using He-Ne laser light (=633 nm) as a function of electric field and for different TNF concentrations. An increase of photosensitivity is found for high TNF concentrations.Time resolution of the photoconductive PVK:TNF detector is investigated using a ruby pulse laser (=694 nm). The possible use of such detectors in combination with other polymer lightguides is demonstrated. Compared to most polymer waveguide materials PVK exhibits a rather high refractive index ofn=1.7. Thus the coupling of light into the photoconductive film is achieved directly. The planar structure allows further integration of polymeric components for optoelectronics.     

激光等离子体软X光源8—20nm光谱辐射研究

研制了了一种脉冲重复频率为１０Ｈｚ的激光等离子软Ｘ射线源；傅波长０．５３μｍ和波长１．０６μｍ的激光脉冲，聚焦在不同的金属靶上，使之离子化。     

Organic Materials for Optical Technologies

Photophysical processes in pyrane substitutes excited by high-power laser radiation are investigated. It is demonstrated that the examined molecules offer promise as active media of tunable lasers (including solid-state lasers), optical radiation limiters with = 532 nm, and emitting layers of organic light diodes.     

High-power continuous-wave upconversion fiber laser at room temperature

We report cw laser emission of a Pr, Yb-doped ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF fiber in the red spectral region. Laser emission was achieved on the transition P(0)(3)?F(2)(3)(lambda(L)=635 nm) with a Ti:sapphire pump laser tuned to lambda(p)=850 nm . A maximum output power of P(out)=675 mW was obtained at an incident pump power of P(in)=3.37 W . The output power was increased to P(out)=1020 mW when pumping with P(in)=5.51 W was provided by two Ti:sapphire lasers. A photon avalanche process was found to contribute strongly to the population of the upper laser level.     

Orange,red and deep-red flashlamp-pumped Pr3+:LiYF4 laser with improved output energy and efficiency

Three laser transitions (607.2 nm, 639.5 nm, 720.9 nm) in a flashlamp-pumped Pr³⁺:LiYF₄ laser at room temperature are investigated. Cerium ions (Ce³⁺) doped into the fused-quartz envelope of the flashlamp efficiently transfer strong UV radiation from pumping light into the absorption region of Pr³⁺ ions ( = 420–480 nm), so that the slope efficiency of all three laser emissions could be increased by almost 100% compared to excitation with a pure quartz flashlamp. At a pump energy of 30 J the output energy of these three laser emissions reached 4.7 mJ, 87 mJ and 30 mJ.     

Demonstration of fiber-laser-produced plasma source and application to efficient extreme UV light generation

Efficient generation of extreme UV (EUV) light at lambda = 13.5 nm from a bulk Sn target has been demonstrated by using a fiber laser. The conversion efficiency from the 1064 nm IR to the EUV was measured to be around 0.9% into 2pi steradians within a 2% bandwidth. To the best of our knowledge, this is the first time an all-fiber system was used to generate EUV or soft x rays.     

Far-field generation of localized light fields using absorbance modulation

In this Letter, we report the confinement of a uniform beam of light (lambda(1) = 400 nm) at the nodes of a standing wave (lambda(2) = 532 nm) via absorbance modulation. In the present implementation of absorbance modulation, a thin polymer film containing a photochromic azobenzene side chain is exposed to a standing wave at lambda(2) and a uniform beam at lambda(1), resulting in alternate regions of high and low absorbance. Light at lambda(1) is localized around the low-absorbance regions. Using photoresist exposures, we mapped out the localized light intensity distribution, which agrees well with our theoretical model. Since the width of this distribution is primarily determined by the ratio of the intensities at the two wavelengths, this technique opens up the possibility of localizing light fields below the diffraction limit using far-field optics.     

880nm半导体激光主动照明光纤耦合模块

为降低半导体激光主动照明红曝,选择波长880 nm大功率半导体激光器作为新型激光主动照明成像系统光源。根据光纤耦合过程光参数积不变原理,研制出波长880 nm大功率半导体激光器阵列单光纤耦合模块,利用光纤匀光作用使激光光束匀化整圆后用于激光主动照明。首次在波长880 nm大功率半导体激光器上采用阶梯反射镜光束整形方法,使激光光参数积与光纤匹配,激光高效耦合进入纤芯400μm、数值孔径0.22的光纤。室温条件下光纤耦合模块连续输出功率44.9 W,电光转化效率35%,波长880 nm大功率半导体激光器阵列光纤耦合模块,不仅其红曝小而且对应CMOS图像传感器光谱响应度较高,系统成像质量好。     

Quasinondestructive holographic recording in photochromic LiNbO3

We have observed quasinondestructive holographic storage with a continuous-wave laser at lambda = 532 nm in near-stoichiometric LiNbO3 doped with Tb and Fe. This crystal showed an exceptionally long grating decay time and also exhibited a fast color change upon exposure to ultraviolet (UV) light. It was demonstrated that the grating recorded from the UV-exposed, colored state can be continuously read out over 9 h at a reading intensity as high as 8 mW/cm(2). In addition, the written grating could be easily erased with UV illumination which returned the crystal back to the original colored state.     

Optically produced arrays of planar nanostructures inside fused silica

Linearly polarized femtosecond light pulses, focused inside fused silica to an intensity that leads to multiphoton ionization, produce arrayed planes of modified material having their normal parallel to the laser polarization. The planes are < or = 10 nm thick and are spaced at approximately lambda/2 in the medium for free space wavelengths of both 800 and 400 nm. By slowly scanning the sample under a fixed laser focus, order is maintained over macroscopic distances for all angles between the polarization and scan direction. With the laser polarization parallel to the scan direction we produce long-range Bragg-like gratings. We discuss how local field enhancement influences dielectric ionization, describe how this leads to nanoplane growth, why the planes are arrayed, and how long-range order is maintained.