Diode-side-pumped Nd:GGG laser at 1,105?nm and frequency-doubled laser at 552?nm

A high-power diode-side-pumped 1,105?nm Nd:GGG laser and a laser at 552?nm based on intracavity frequency doubling of 1,105?nm laser are demonstrated for the first time. A 26.8-W 1,105?nm laser continuous wave output was achieved under the incident pump power of 170?W. A LiB₃O₅ crystal is used for second harmonic generation of 1,105?nm laser. When the pump power was 170?W, the average output power at 552?nm of 7.3?W was obtained, corresponding to the optical conversion efficiency of 4.3?%. And the minimum pulse width is 181?ns with the pulse repetition rate of 10?kHz. The M ² factors are measured to be 19.8 and 17.6 in the horizontal and vertical directions, respectively.     

Spectral structure of 510.6 and 578.2 nm lines in?a?CuBr?vapor?laser

Considering the hyperfine structure and the isotopic splitting of copper active atomic levels, the temporal behavior of the spectral structure of amplified spontaneous emission at 510.6 nm line was calculated. The spectral line shapes of 510.6 and 578.2 nm laser lines were measured and compared with the calculated results at different experimental configurations, i.e., without cavity mirrors, with the back mirror, and with cavity mirrors. The results of the 578.2 nm line revealed that the mode competition was involved in the formation of laser oscillation.     

Intermittent oscillation of 1064 nm and 1342 nm obtained in?a?diode-pumped doubly passively Q-switched Nd:YVO4 laser

The intermittent oscillation of 1064 nm and 1342 nm was demonstrated in a diode-pumped doubly passively Q-switched Nd:YVO₄/Cr⁴⁺:YAG/V³⁺:YAG laser for the first time to our best knowledge. By exploiting a three-mirror configuration and choosing appropriate reflectivity values for the two wavelengths on the output couplers, the dual-wavelength pulsed operation was obtained. The maximum dual-wavelength average output power was 428 mW, corresponding to an optical-to-optical conversion efficiency of 8.5%. The corresponding physical explanations for the intermittent oscillation as well as the related phenomena are also given in this paper.     

Absolute frequency measurements of wavelength standards 532 nm, 543 nm, 633 nm and 1540 nm

This paper describes the results of absolute frequency measurements of primary wavelength standards 633 nm, 543 nm, 532 nm, (iodine stabilized) and 1540 nm (acetylene stabilized) in CMI. The values obtained with Menlo Systems femtosecond frequency comb in CMI are compared with previous measurements of the same standards in BIPM, BEV and MPQ. Measured sub-Doppler linewidths and relative intensities of several hyperfine spectral components of iodine molecule are also presented.     

Diode-end-pumped Tm:GdVO4 laser operating at 1818 and?1915?nm

High power operation at 1818 and 1915 nm has been demonstrated from a Tm:GdVO₄ laser operating in quasi-continuous-wave mode with a maximum measured power of 8.7 W and a laser output energy of 175 mJ was observed in a 20 ms pulse at 1.9 μm. The operation at 1818 nm is the shortest wavelength achieved at multi-watt power levels for a Tm-doped solid-state laser without intra-cavity tuning elements. It has been shown that by careful analysis of the emission spectra, the Tm:GdVO₄ laser can be tuned over a 100 nm wavelength range simply by appropriate selection of the reflectivity of the output coupler.     

Time-resolved hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm

Spectra of low energy, high current pinch discharges in pure hydrogen, oxygen, nitrogen, and helium were recorded in the EUV region, and continuum radiation was only observed from hydrogen [www.blacklightpower.com/pdf/GEN3_Harvard.pdf; Int. J. Hydrogen Energy 35, 8446 (2010); Cent. Eur. J. Phys. 8, 318 (2010)]. The continuum radiation bands at 10.1 and 22.8 nm and going to longer wavelengths for theoretically predicted transitions of hydrogen to lower-energy, so called “hydrino” states, was observed first at blacklight power, Inc. (BLP) and reproduced at the Harvard center for astrophysics (CfA). Considering the low energy of 5.2 J per pulse, the observed radiation in the energy range of about 120 eV to 40 eV and reference experiments, no conventional explanation was found to be plausible, including electrode metal emission, Bremsstrahlung radiation, ion recombination, molecular or molecular ion band radiation, and instrument artifacts involving radicals and energetic ions reacting at the CCD and H₂ re-radiation at the detector chamber. To further study these continuum bands assigned to hydrinos, time resolved spectra were performed that showed a unique delay of the continuum radiation of about 0.1 μs and a duration of < 2   μs following the high-voltage pulse consistent with the mechanism of recombination to form the optimal high-density atomic hydrogen in the pinch that permits the H–H interactions to cause the hydrino transitions and corresponding emission.     

Laser diode-array pumped Nd:YAlO_3 CW laser at 1079.5nm and 1341.4nm

Two key problems,spectral matching and spatial overlap between pumpingbeam and the laser mode in the active material,of diode-laser-arrays(LD)end-pumped solid-state laser have been discussed.Initial experimental results were given for LD end-pumpedTEM_(00) CW Nd:YAlO_3 laser at the wavelength of 1079.5nm and 1341.4nm.The outputpower at 1079.5nm is 24.4mW with 14.5％ slope efficiency,and the output power is 1.2mW at 1341.4nm.     

Compact Diode-Pumped Continuous-Wave Nd：LuVO4 Lasers Operated at 916 nm and 458 nm

We report the compact diode-pumped continuous-wave （CW） Nd：LuV04 lasers operated at 916nm and 458nm for the first time. The maximum output power of 780mW at 916nm laser is obtained with a slope efficiency of 9.3%. We generate 50roW of 458nm blue laser employing a type-Ⅰ critical phase-matched LBO crystal.     

Characteristics of THz Emission from GaAs Crystal Excited by 400 nm and 800 nm Optical Pulses

THz emission spectroscopy is used to study the generation mechanism dependent behaviour of terahertz (THz) electromagnetic waves from the GaAs crystal under excitation by 40Ohm and 800hm femtosecond (fs) pulses, respectively. The wavelength dependence of the emission spectrum under two types of THz generation mechanis msis analysed. Under the optical rectification mechanism, a slight enhancement of the spectral amplitude in the high-frequency regime is observed in a GaAs(l10) crystal by the excitation of a 400-nm optical pulse compared with that of 800nm. Whereas an obvious red shift of the amplitude spectrum occurs in the GaAs(100) sample under the transient photoconduction mechanism. These phenomena are explained in detail by the duration of the optical pump pulse and the band structure of GaAs, respectively.     

Multiphoton ionization and dissociation of CH_3I at 266 and 355 nm

The mechanisms of multiphoton ionization(MPI)and dissociation of CH_3I have been studied using time- of-flight(TOF)mass spectrometer at 266 and 355 nm.MPI mass spectrum at 266 nm consists mostly of fragment ions.This is consistent with a neutral-fragment photoionization mechanism in which rapid one-photon dissociation occurs from the repulsive potential energy surface followed by MPI of neutral photofragments.The observation of parent ions at 355-nm excitation is indicative of parent-ionic ladder mechanism in which the parent ions are produced directly by two-photon excitation resonantly excited to Rydberg C state and then ionized through additional one-photon absorption to produce CH_3I~ .Fragment ions are produced by dissociation of CH_3I~ .     

Single-frequency linearly-polarized 1083?nm all fiber nanosecond laser

Single-frequency linearly-polarized 1083?nm all fiber nanosecond master-oscillator power amplifier laser system is demonstrated. A ring laser, whose key components are one saturable absorber and two polarization controllers, delivers a single-frequency continuous wave laser. Using an electro-optic modulator as the modulator, the pulse laser seed is obtained by modulating the CW laser. By amplifying the pulse seed to the average power of 61.6?W in three stages, a single-frequency linearly-polarized laser with pulse duration of 16?ns, repetition rate of 10?MHz and pulse energy of 6.16???J is obtained. No nonlinear effect is observed in our experiment. Higher output power can be obtained by increasing LDs of the main amplifier.     

Comparison of 905 nm and 1550 nm semiconductor laser rangefinders’ performance deterioration due to adverse environmental conditions

Laser rangefinder performance (i.e., maximum range) is strongly affected by environment due to visibility-dependent laser attenuation in the atmosphere and target reflectivity variations induced by surface condition changes (dry vs. wet). Both factors have their unique spectral features which means that rangefinders operating at different wavelengths are affected by specific environmental changes in a different way. Current state of the art TOF (time of flight) semiconductor laser rangefinders are based mainly on two wavelengths: 905 nm and 1550 nm, which results from atmospheric transmission windows and availability of high power pulsed sources. The paper discusses the scope of maximum range degradation of hypothetical 0.9 μm and 1.5 μm rangefinders due to selected water-related environmental effects. Atmospheric extinction spectra were adapted from Standard Atmosphere Model and reflectance fingerprints of various materials have been measured. It is not the aim of the paper to determine in general which wavelength is superior for laser range finding, since a number of criteria could be considered, but to verify their susceptibility to adverse environmental conditions.     

High-gain Al2O3:Nd3+ channel waveguide amplifiers at 880 nm, 1060 nm, and 1330 nm

Neodymium-doped aluminum oxide films with a range of Nd³⁺ concentrations are deposited on silicon wafers by reactive co-sputtering, and single-mode channel waveguides with various lengths are fabricated by reactive ion etching. Photoluminescence at 880, 1060, and 1330 nm from the Nd³⁺ ions with a lifetime of 325 μs is observed. Internal net gain at 845–945 nm, 1064, and 1330 nm is experimentally and theoretically investigated under continuous-wave excitation at 802 nm. Net optical gain of 6.3 dB/cm at 1064 nm and 1.93 dB/cm at 1330 nm is obtained in a 1.4-cm-long waveguide with a Nd³⁺ concentration of 1.68×10²⁰ cm^?3 when launching 45 mW of pump power. In longer waveguides a maximum gain of 14.4 dB and 5.1 dB is obtained at these wavelengths, respectively. Net optical gain is also observed in the range 865–930 nm and a peak gain of 1.57 dB/cm in a short and 3.0 dB in a 4.1-cm-long waveguide is obtained at 880 nm with a Nd³⁺ concentration of 0.65×10²⁰ cm^?3. By use of a rate-equation model, the gain on these three transitions is calculated, and the macroscopic parameter of energy-transfer upconversion as a function of Nd³⁺ concentration is derived. The high internal net gain indicates that Al₂O₃:Nd³⁺ channel waveguide amplifiers are suitable for providing gain in many integrated optical devices.     

The absorption spectrum of diatomic calcium between 120 and 20 nm

The vacuum ultraviolet absorption spectrum of Ca₂ has been extended down to 20?nm by using the same techniques as those described by Nzohabonayo et al. [2003, Molec. Phys., 101, 2917]. All the new states observed are Rydberg states giving three new ionization limits at 13.76?eV, 17.99?eV and a third one higher than 33?eV.     

520nm泵浦780nm+1560nm双共振光学参量振荡器

我们在实验中演示了520nm单频绿光泵浦的基于周期极化磷酸钛氧钾(PPKTP)晶体的780nm+1560nm双共振光参量振荡器,高效制备780nm+1 560nm连续可调谐双色下转换光场。该参量振荡器可输出93.3 mW的1 560nm单频激光和44.6mW的780nm单频激光。通过改变PPKTP晶体的温度所得到的波长粗调范围为:信号光1 529.81nm~1 573.83nm(~44nm),闲置光788.26nm~777.20nm(~11nm);通过连续调谐520nm泵浦激光频率初步得到的闲置光在780.24nm(铷原子D2线)处频率连续调谐范围约1.6GHz。     

Optical and structural characterization of iron oxide and cobalt oxide thin films at 800 nm

We report on optical and structural properties of α-Fe₂O₃ and Co₃O₄ thin films, grown by direct oxidation of pure metal films deposited on soda-lime glass. Structural characteristics and morphology of the films were investigated by X-ray diffraction, atomic force microscopy, and scanning electron microscopy. Linear optical absorption, and linear refraction as well as nonlinear optical properties were investigated. The third-order optical susceptibilities were measured applying the Thermally managed Z-scan technique using a Ti: sapphire laser (150 fs; 800 nm). The results obtained for the Co₃O₄ film were \( \text{Re} \chi^{\left( 3 \right)} \) = ?(5.7 ± 2.4) ×10^?9 esu and \( \text{Im} \chi^{(3)} \) = ?(1.8 ± 0.2) ×10^?8 esu while for the α-Fe₂O₃ film we determined \( \text{Re} \chi^{(3)} \) = +(6.6 ± 2.4) ×10^?10 esu and \( \text{Im} \chi^{(3)} \) = +(2.2 ± 0.4) ×10^?10 esu.     

Shape Invariant and Rodrigues Solution of?the?Dirac-shifted Oscillator and?Dirac-Morse Potentials

We show that the Dirac equation for a charged spinor in spherically symmetric electromagnetic potentials as Dirac-shifted oscillator and Dirac-Morse potentials have the conditions of shape invariant symmetry in non-relativistic quantum mechanics. The relativistic spectra of the bound states and spinor wavefunctions can be obtained by the Rodrigues polynomials of one associated differential equation.     

Linewidth studies on Cd+ 636.0 nm and 537.8 nm lines excited in a He-Cd hollow cathode discharge

Hollow cathode (HC) lasers usually operate in a single axial mode without any optical selection. This is attributed to the large homogeneous linewidth of the gain curve due to the relatively high filling pressure of these lasers. Collisional and Doppler broadening (Δν_C and Δν_D) of the Cd⁺ 636 nm and Cd⁺ 538 nm lines (laser transitions of the HeCd⁺ laser) excited in a HC discharge tube were determined using a Fabry–Perot interferometer technique. It was found that in the pressure range 7–25 mbar Δν_D was nearly constant, while, as expected, Δν_C increased linearly with pressure. The broadening constants were α(636 nm)= (47±2) MHz/mbarand α(538 nm)=(11.8±0.5) MHz/mbar. The first constant is large enough to explain single-mode operation of the red HeCd⁺ laser; but in the case of the green laser, the exact reason for the single-mode operation remained unclear. Received: 23 November 2000 / Revised version: 30 March 2001 / Published online: 7 June 2001     

Diode-end-Pumped Nd:YAG Ceramic and Crystal Operation at 1,123 nm

We present a high-power diode-end-pumped continuous-wave Nd:YAG laser operating at 1,123 nm. Laser operation was carried out and compared using high optical quality Nd:YAG ceramics fabricated in-house and commercial Nd:YAG single crystals. At the absorbed diode pump powers of 23.2 and 28.0 W, output powers of 10.7 and 12.5 W at 1,123 nm were achieved for the employed ceramics and crystals as the laser material, which correspond to conversion efficiencies of 46.1% and 44.6%. For high-power lasers, the Nd:YAG ceramic has the advantage of a higher destructive threshold than that of commercial crystals.     

Two-photon absorption and two-photon induced absorption of liquid toluene at 347.15 nm

Pump pulse transmission and time-delayed probe pulse transmission measurements through liquid toluene were performed with linear and circular polarized second harmonic pulses of a mode-locked ruby laser system. Two-photon absorption and two-photon induced absorption are observed. The induced absorption anisotropy is investigated. A theory of two-photon absorption in isotropic media is presented. The two-photon absorption cross-section components, the effective excited-state absorption cross-section, the absorption anisotropy relaxation time and the excited singlet-state relaxation time are determined.