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1.
The absorption of the tunable narrow-band laser radiation with λ = 276.9 nm at the 62 P 1/2 → 62 D 3/2 transition in the atomic thallium beam is experimentally studied. The isotopic selectivity and efficiency of the excitation of the 62 D 3/2 state is investigated. The splittings between the 203Tl and 205Tl isotopes were found to be Δv = 0.98 and 1.25 GHz for the transitions with the nuclear momenta F = 1 → F = 1, 2 and F = 0 → F = 1, respectively, which is sufficient for a relatively high isotopic selectivity of the 62 D 3/2 state excitation with the subsequent ionization for the laser separation of the thallium isotopes. The effects that lead to the broadening of the resonance and a decrease in the selectivity are analyzed. The main contribution is related to the field broadening by the laser radiation, which limits the mean laser power density.  相似文献   

2.
We have demonstrated the continuous wave laser operation of Yb3+:YVO4. For Ti:Al2O3 laser pumping at 985 nm, a maximum slope efficiency of 41.1% and a threshold pump power of 76 mW were obtained. The maximum output power was 433 mW at a laser wavelength of 1037 nm.Using a cw diode laser around 974 nm as a pump source, a slope efficiency of 10.9% and a maximum output power of 152 mW were achieved at a laser wavelength of 1039 nm. The laser threshold pump power was 608 mW with respect to the absorbed pump power. The effective emission cross-sections for the 2F5/22F7/2 transition were determined using the Füchtbauer–Ladenburg equation. The maxima of the effective absorption and emission cross-sections were found at 984.5 nm (6.74×10-20 cm2) in -po larization and 985.5 nm (4.28×10-20 cm2) also in -p olarization. The upper laser level lifetime was measured with suppression of radiation trapping and is around 318 s. PACS 42.55.Rz; 42.55.Xi; 42.70.Hj  相似文献   

3.
C.P. Singh  Sukhdev Roy   《Optik》2002,113(9):373-381
We present a detailed and accurate analysis of low power spatial light modulation characteristics of bacteriorhodopsin (bR) based on nonlinear intensity induced absorption. Amplitude modulation of probe laser read beam transmissions at 410 nm and 640 nm, corresponding to the peak absorption of MII and O states of D96N bR and WT bR respectively, by the modulation laser write beam intensity-induced population changes at 570 nm has been analyzed, considering all intermediate states with both forward and backward transitions in the respective bR photocycles, using the rate equation approach. The SLM characteristics are shown to be sensitive to the normalized small signal absorption coefficient β, rate constants of MII and O intermediate states and the absorption cross-section of the initial B state at the probe wavelength (σBp). There exists an optimum value of β for which maximum percentage modulation can be achieved. It is shown that for extended MII state lifetime of 250 s in D96N bR and O state lifetime of 2.2 s in WT bR, with σBp= 0, 100% modulation of read beam transmissions can be achieved, leading to high dynamic range and sensitivity for low laser write beam intensities of 50 μW/cm2 and 4 mW/cm2 at 570 nm, respectively.  相似文献   

4.
This paper describes trapping and laser cooling of a Ca+ ion in an rf quadrupole ion trap. A single Ca+ ion is laser cooled to below 130 mK and quantum jumps are observed by exciting the ion into the metastable D 5/2 state via the P 3/2 state. The lifetime of the metastable D 5/2 state is estimated from the distribution of the dark periods of the quantum-jump signal. Collision-induced jumps between the metastable D 3/2 state and the D 5/2 state in a background gas are also directly observed.  相似文献   

5.
We present the first sequential laser excitation of atom-doped helium nanodroplets. Rubidium atoms on the surface of helium nanodroplets are selectively excited with a continuous wave laser to the 52P1/2 state so as not to desorb from the nanodroplets. From there they are excited by a laser pulse to the 52D state; a laser-induced fluorescence (LIF) spectrum is recorded by monitoring the 62P ?\rightarrow 52S1/2 emission. The LIF spectrum differs from that of the two-photon one-color direct excitation spectrum 52D ?\leftarrow 52S1/2, indicating that the system does relax vibrationally during the lifetime of the 52P1/2 state. To model the LIF spectra we use calculated energy levels of the Rb atom as a function of its distance R from the center of the helium nanodroplet. The Franck-Condon factors of the resulting potential energy curves agree with the experimental spectra. In the future the 52P1/2 state can be used as a springboard to reach high-lying 2S and 2D states, and possibly create an artificial super-atom.  相似文献   

6.
Population kinetics of the upper4I11/2 and lower4I13/2 laser states of the Er3+ ion were studied experimentally and theoretically in (Er)BaY2F8, (Er)YLF, (Er)YSGG, (Er)CaF2 and (Er)YALO. Fluorescence from these states to the4I15/2 ground state was excited through upconversion simultaneously with the4I11/24I13/2 lasing using 1.53 µm radiation from an erbium : glass laser for optical pumping. Lifetimes of both states are altered during lasing by co-operative energy transfer processes: the lifetime of the lower state τ1 is shortened and that of the upper state τ2 increased with the resultant ratio τ21>1. After lasing the lifetime ratio returns to the ‘normal’ value τ21 <1; that is, one obtained under weak ultraviolet excitation. Kinetic rate equations for the population density functions for both laser states were set up and solved by approximation in three time domains. It was assumed that only one co-operative energy transfer process operates in the laser crystals and determines the population inversion kinetics. Consistency relationships for comparison of the theoretical results with the experiment were developed. Only (Er)BaY2F8 spectral features showed close agreement with theory, resulting in a high score of 94% for the overall correlation in the consistency test, whereas all other crystals scored <50%. As a result of this high correlation, a close match between theoretical and experimental population decay curves was shown for (Er)BaY2F8. Most probably, more than one energy transfer process shapes the decay curves and determines the population inversion kinetics for the other laser crystals. (Er)YALO showed little lifetime change for the laser states, apparently due to inefficient co-operative energy transfer processes. As a result it probably lased in a self-terminating short-pulse mode.  相似文献   

7.
We study experimentally and theoretically D 1 lines of 85Rb and 87Rb atoms and show that using atomic-velocity-selective optical resonances which are formed in the transmission spectrum of an atomic rubidium-filled submicron cell at single pass of linearly polarized laser radiation, it is possible to measure weak magnetic fields beginning with 5 G. Having in mind the results obtained earlier with use of also submicron cell with 87Rb (D 1 line) and circularly polarized laser radiation, the entire range of measurable magnetic fields (both homogeneous and inhomogeneous) becomes 5–5000 G.  相似文献   

8.
For laser collimation of neutral F atoms, a resonance transition cycle between the metastable and the upper excited states (3s4 P 5/2?3p4 D 0 7/2) can be used as a two-level closed system. We have determined the lifetime of the metastable state (3s4 P 5/2) in F atoms by measuring the decay curve of the fluorescence intensity as a function of distance from the plasma source. Combining the measured velocity of F radicals from the Doppler shift of the fluorescence peak, we have obtained the lifetime of the F metastable state as 3.7±0.5 μs. With this short metastable lifetime of F radicals, the simple Doppler cooling method using spontaneous light force is not practical for laser collimation of F radicals. Use of stimulated light force may be necessary to collimate F radical beams in a short distance. Received: 4 July 2000 / Published online: 13 September 2000  相似文献   

9.
A pulsed tunable dye laser was used for a high resolution experimental study of mercury fluorescence from the 63P1 state. The output of the dye laser was frequency doubled into the 253.7 nm region using a potassium penta-borate crystal. Exponential decays were observed for each of the five individual components of the hyperfine structure separately and the effects of the trapping of resonance radiation on the observed lifetime of the 63P1 state of mercury were investigated for each resolvable component. Within experimental error, the natural radiative lifetime of the 63P1 state was found to be independent of the hyperfine component irradiated and a value of 122±2 nsec was obtained, consistent with results found by other methods.  相似文献   

10.
A time-resolved experiment on the A2Π state of gaseous calcium hydride has been performed by applying laser spectroscopic methods. The following zero-pressure lifetime was obtained for the CaH A2Π state: τυ´=0 = 33.2 (±3.2) ns and τυ´=1 = 33.7 (±5.2) ns. The lifetime was found to be the same for the A2Π½ and A2Π3/2 states.  相似文献   

11.
N. Pavel 《Laser Physics》2010,20(1):215-221
Continuous-wave (CW) simultaneous laser emission on the 0.9-μm 4 F 3/24 I 9/2 transition and the 4 F 3/24 I 11/2 transition at 1.06 μm is obtained in Nd-based laser crystals of thin-disk geometry and using a multi-pass pumping scheme. A Nd:Y3Al5O12 (Nd:YAG) thin disk emitted simultaneous laser radiation at 946 and 1064 nm with 5.1 W output power, and Nd:YVO4 and Nd:GdVO4 thin-disk lasers with more than 3 W output power at 0.91 and 1.06 μm were realized. The ratio between the output power at one of the wavelengths and the total output power could be varied by the laser resonator design. An intracavity frequency-doubled Nd:YVO4 thin-disk laser with alternate green at 532 nm and “deep-blue” at 457 nm generation of high average output powers is demonstrated.  相似文献   

12.
The terahertz (THz) frequency radiation production as a result of nonlinear interaction of high intense laser beam with low density ripple in a magnetized plasma has been studied. If the appropriate phase matching conditions are satisfied and the frequency of the ripple is appropriate then this difference frequency can be brought in the THz range. Self focusing (filamentation) of a circularly polarized beam propagating along the direction of static magnetic field in plasma is first investigated within extended‐paraxial ray approximation. The beam gets focused when the initial power of the laser beam is greater than its critical power. Resulting localized beam couples with the pre‐existing density ripple to produce a nonlinear current driving the THz radiation. By changing the strength of the magnetic field, one can enhance or suppress the THz emission. The expressions for the laser beam width parameter, the electric field vector of the THz wave have been obtained. For typical laser beam and plasma parameters with the incident laser intensity ≈ 1014 W/cm2, laser beam radius (r0) = 50 μm, laser frequency (ω0) = 1.8848 × 1014rad/s, electron plasma (low density rippled) wave frequency (ω0) = 1.2848 × 1014 rad/s, plasma density (n0) = 5.025 × 1017cm–3, normalized ripple density amplitude (μ)=0.1, the produced THz emission can be at the level of Giga watt (GW) in power (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
The subject of investigation is the kinetic mechanisms intensifying chain reactions that proceed in a hydrogen-air mixture when O2 molecules dissociate under the action of laser radiation with wavelength λ I = 193.3 nm and are excited into the b 1Σ g + electron state by radiation with λ I = 762.346 nm. The efficiencies of both methods to initiate ignition are compared. Numerical simulation shows that the ignition temperature for the laser-induced excitation of O2 molecules into theb 1Σ g + state is lower than for the dissociation of O2 molecules by UV laser radiation, with the energy supplied to the mixture being the same. However, both photochemical methods are much more efficient than mere heating of the mixture by laser radiation or another source of heat.  相似文献   

14.
We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.  相似文献   

15.
The variation of parameters of Si-based MOS-transistors affected by combined infrared and X- ray photons processing were presented. It was found that X-ray irradiated transistor under incoherent infrared radiation is characterized by lowering of radiation sensitivity. As positive charge and its radiation-induced rate of generation in undergate SiO2 insulator decreases, we observe a reduction of both ΔUNo and voltage threshold Uth transistor components. Under pulsed laser processing (λ?=?1.06?µm, τ?=?10?3s) of the X-rays irradiated transistor the energy density of laser beam corresponding to the minimum threshold voltage was established. It was shown that the combined treatment can be effectively used to control the transistor parameters. The model describing the radiation changes of parameters in Si-SiO2 structure was proposed. The effect of Na+, K+ and H+ ions in undergate insulator on variation of charge state and interface reconstruction under laser irradiation were predicted by proposed model.  相似文献   

16.
Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra (400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear materials of GaSe x S1 − x (0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3 ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10−4−1 × 10−4 W/cm2) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10−4−1.5 × 10−4 W/cm2) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10−4–4.6 × 10−4 W/cm2) at 1360 nm. Threshold damage density is more than 10 MW/cm2 at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators.  相似文献   

17.
Stimulated Brillouin scattering (STBS) and phase conjugation of CO2 laser radiation have been demonstrated experimentally for the first time in compressed xenon (59 atm at 21°C) located inside the low-Q cavity of this laser. The nonlinear medium was exposed to the action of counterpropagating focused multimode radiation beams. The difference between the frequencies of the longitudinal cavity modes was set at the frequency of the acoustic wave (v s=32.2±0.3 MHz) excited as a result of STBS by 9.584 μm radiation. The duration of the radiation pulse τ L was close to the acoustic phonon lifetime (τ L<τ ph≈3× 10−6s). The excitation of STBS was manifested experimentally as the locking of longitudinal modes, an increase in power and energy, and also an increase in the duration of the lasing pulse and a reduction in the divergence to the diffraction limit. Zh. éksp. Teor. Fiz. 116, 1941–1946 (December 1999)  相似文献   

18.
The amplitude, time, spectral, and energetic characteristics of a volume (diffuse) discharge at an elevated pressure (up to 5 atm) in a gap with an inhomogeneous electric field without an additional preionization source are studied. The concentration and temperature of electrons in the discharge plasma are mea-sured by spectral methods. The effective lifetime of the C 3Π u state of the nitrogen molecule at the trailing edge of the radiation pulse is shown to be determined by radiative and collisional quenchings. For transitions of the second positive system of nitrogen, a plasma discharge radiation power into the complete solid angle is obtained to be ~120 kW, with a specific radiation power of up to ~50 kW/cm3.  相似文献   

19.
Single tracks and pairs of tracks are written in the volume of Pr-doped LiYF4-crystals using tightly focused femtosecond laser radiation (λ=1045 nm, τ p=400–500 fs, f=0.1–1 MHz). Waveguiding between the tracks is demonstrated and optimized by varying the distance between the tracks and the laser writing conditions. The stress-induced guiding mechanism is explained based on TEM, interference microscopy, near-field and far-field measurements. It is shown that the single-crystalline material is getting poly-crystalline under femtosecond laser irradiation. By measuring the lifetime of the 3P13H5 transition and the emission spectrum at excitation with λ=444 nm, no influence on these properties of the guided light is observed. This possibly enables the realization of a channel waveguide laser in the visible spectral range.  相似文献   

20.
By photodissociation ZnI2 with 193 nm (ArF) laser radiation, the rate constants for quenching of the upper and lower energy levels of the ZnI (B → X) laser by ZnI2 have been measured to be (1.7 ± 0.2) × 10-9 and (1.4 ± 0.4) × 10-9 cm3 s-1, respectively. Although the former rate constant was found to be laser intensity-dependent for I ? 105 W cm-2, the ZnI(B) state radiative lifetime was determined to be 26 ± 4 ns. Also, the small signal gain coefficient, g0, of this molecular laser has a peak value of ? 15% cm-1 at λ ? 602 nm and exceeds 5% cm-1 for 591 nm ≤ λ ≤ 608 nm for a potential tuning range of at least 170 Å.  相似文献   

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