Energy loading effects in the scaling of atomic xenon lasers

The intrinsic power efficiency of the atomic xenon (5d→6p) infrared (1.73-3.65-μm) laser is sensitive to the rate of pumping due to electron collision mixing of the laser levels. Long-duration pumping at moderate power deposition may therefore result in higher energy efficiencies than pumping at higher powers. The consequences of high energy deposition (hundreds of joules per atmosphere) during long pumping pulses (hundreds of microseconds) on the intrinsic power and energy efficiency and optimum power deposition of the atomic xenon laser are examined. The dominant effect of high energy loading, gas heating, causes an increase in the electron collision mixing of the laser levels. The optimum power deposition for a given gas density therefore shifts to lower values with increasing gas temperature     

High-power pulsed xenon ion lasers

Output and threshold characteristics of small-bore pulsed xenon ion lasers are presented in detail as a function of current and gas pressure for ranges of these parameters that are consistent with high optical power output in the green-blue spectral region. It has been found that six wavelengths characteristic of xenon exhibit peak output powers greater than 100 watts, from a 5-foot laser tube over a limited (8-24 mtorr) range of xenon tube pressure. Laser action has also been obtained at high peak powers for longer current pulse (5-50 mus) operation of the tube. In addition, observation of three new laser wavelengths 5340, 5501, and 5590 Å is reported. These lines are only observed at very low tube pressures and very high peak currents.     

Time-resolved spectral output of pulsed GaAs lasers

When pulse operated, all injection lasers show a laser line shift which is linear with time during the pulse length. This is evident for time-resolved spectra obtained by a scanning technique. The data present time-resolved spectra for pulse-operated gallium arsenide laser diodes. At high peak current values, joule heating results and the time-resolved laser spectra are seen to shift to longer wavelengths. A line-shift coefficient is defined for which the units are angstroms per (ampere)²per microsecond. For high peak current and long pulse length, the laser lines may shift one hundred angstroms or more.     

Sustainer enhancement of the VUV fluorescence in high-pressure xenon

A low-energy (20-60 kV), high-repetition-rate (∼60-Hz) electron-beam system is used to excite xenon at pressures up to 600 psi. The salient features of the temporal and spatial measurements of the VUV fluorescence, corresponding to the¹Σg+-^3,1Sigma_{u}+transitions in xenon, are presented. Experimentally, it is found that in a regime where more than 20 percent of the electron-beam energy incident on the gas is converted to VUV fluorescence, the maximum incremental efficiency due to the addition of a sustainer discharge is about 7 percent. A kinetic model is described which attributes the low sustainer efficiencies to electron interactions with the excited state populations.     

小型激光器用泵浦源——微型氙闪光灯

介绍了一种外径只有3mm大小的激光器泵浦源——微型氙闪光灯。     

Optically pumped continuously tunable high-pressure molecular lasers

Recent developments in the optical pumping of high-pressure molecular lasers, particularly continuously tunable high- pressure molecular lasers, are described. Included are some experimental results on optically pumped pure CO2lasers, optically pumped ultrahigh-pressure CO2-He lasers, and optically pumped N2O/CO2transfer lasers. Recent efforts to use the output from these devices for high-resolution infrared spectroscopy are also described.     

Optically pumped atomic thulium lasers

A thulium vapor column is irradiated with the fourth harmonic of a Nd:YAG laser at 266 nm. The near coincidence with a dipole allowed transition from ground state results in efficient optical pumping yielding 87 simultaneous superfluorescent laser transitions from 300 to 900 nm. Many of the emissions are due to inversions to the ground state of both neutral and singly ionized Tm atoms.     

Effects of helium addition to Ar-Xe mixtures in high-pressureatomic-transition xenon lasers

The output energy and spectral distribution of the atomic-transition xenon laser have been investigated with ternary mixtures based on Ar-Xe to explore kinetic issues and to enhance particular lines of the xenon laser pumped by an e-beam and e-beam sustained discharge. Addition of helium into the Ar-Xe mixtures increased the 2.03 μm line energy by a factor of 3-5 while suppressing the 1.73-μm line even during single-line oscillation. The maximum output energy obtained at 2.03 μm was 1.2 J/L and the intrinsic efficiency was ~1%. Effects of neon or krypton addition have also been studied with e-beam sustained discharge pumping     

Effect of xenon on the gas temperature in carbon monoxide lasers

By experimentally measuring the gas temperature of a discharge in CO-He-(Xe) laser gas mixtures it is established that the advantageous effect of the addition of xenon in > 10 percent efficient room temperature lasers is not a gas temperature effect.     

用HCD灯作金属原子蒸气源的激光光谱研究

利用Ne-Cu HCD灯研究了金属原子蒸气源的光电流光谱和激光荧光光谱,发现了Cu 4p~2P_(3/2)能级的表观寿命随灯电流增加而增大。认为这一现象起因于“共振俘获”效应。     

Observations of xenon gas-treated barley cells in solution by atomic force microscopy

Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution.     

中国科学院举办激光器与光谱仪器展览会

本文简单介绍了中国科学院技术科学部在北京举办的激光器与光谱仪器展览会,并对其中的某些展品作了扼要介绍.     

Time-resolved study of silicon surface recombination

The technique of two-photon time- and angle-resolved photoemission spectroscopy was used to observe the dynamics of surface-state populations directly as photoexcited bulk carriers recombine on a semiconductor surface with a well-known electronic structure. The surface chosen for this study is the clean, cleaved Si(111)2×1 surface. These observations were used to construct a detailed and comprehensive model for electron-hole recombination on this surface which incorporates and is consistent with all previously obtained data on its electronic structure and dynamics. Transient surface charging effects which occur as the surface-state populations evolve were found to influence strongly the flow of bulk carriers toward the surface and were included in the model self-consistently     

掺杂石英玻璃管脉冲氙灯及滤光套管在激光器中的应用

采用合适厚度,掺杂合适浓度的铈、铕等稀土元素的石英玻璃管制作的脉冲氙灯和滤光套管,其3500埃以下的紫外辐射基本消除,因而在固体激光器中能替代滤光溶液和黄色玻璃滤光套管,防止工作物质着色.比较了不同滤光材料的滤光特性及其在重复频率钇铝石榴石激光器中的激光效率.在Nd:YAG及钕玻璃激光器中,使用掺杂石英玻璃后,可使激光器效率提高25～100%.     

Monitoring of CdTe atomic layer epitaxy using in-situ spectroscopic ellipsometry

Atomic layer epitaxy or ALE has proven to be useful for the growth of epitaxial layers of high uniformity, good quality, and well-controlled thickness. In this study, we have carried out in-situ monitoring during the atmospheric pressure ALE of CdTe on GaAs (100) substrates using spectroscopic ellipsometry (SE). The susceptor temperature, reactant partial pressures, as well as the flow and flush duration for each precursor are crucial process variables for ALE growth. Growth was carried out for 20–25 cycles under different sets of these process conditions during the experiment and in-situ SE was used to verify the presence of layer-by-layer growth, which enabled the quick determination of the process window. We observed ALE growth of CdTe at 300°C, supporting the explanation that the growth of CdTe occurs via a surface catalyzed decomposition of the Te precursor di-isopropyltelluride (DIPTe). Investigation of ALE mode growth behavior for different susceptor temperatures and DIPTe flush times indicated that the growth was limited by competition between desorption and reaction of the adsorbed DIPTe species on the Cd terminated surface.     

He—Ne激光器激光增益与增益饱和性质的空间分布特性研究

用二维ＯＭＡ系统对Ｈｅ－Ｎｅ激光管的侧光辐射进行了空间分辨光谱测量，得到了Ｈｅ－Ｎｅ激光器可见激光辐射的小讯号增益及增益饱和的空间分布，研究了增益饱和性质，推算了活体积的大小和饱和光强等参量。     

Single-mode vertical-cavity surface emitting lasers for 87Rb-based chip-scale atomic clock

The results of numerical simulation and study of lasing characteristics of semiconductor verticalcavity surface-emitting lasers based on Al _x Ga_{1 ? x} As alloys are presented. Lasers exhibit stable single-mode lasing at a wavelength of 795 nm at low operating currents ～1.5 mA and an output power of 350 μW, which offers prospects of their applications in next-generation chip-scale atomic clocks     

Impact of electron collision mixing on the delay times of anelectron beam excited atomic xenon laser

The atomic xenon (5d→6p) infrared laser has been experimentally and theoretically investigated using a short-pulse (30-ns), high-power (1-10-MW/cm³) coaxial electron beam excitation source. In most cases, laser oscillation is not observed during the e-beam current pulse. Laser pulses of hundreds of nanoseconds duration are subsequently obtained, however, with oscillation beginning 60-800 ns after the current pulse terminates. Results from a computer model for the xenon laser reproduce the experimental values and show that oscillation begins when the fractional electron density decays below a critical value of ≈0.2-0.8×10 ⁶. These results lend credence to the proposal that electron collision mixing of the laser levels limits the maximum value of specific power deposition that can be used to excite the atomic xenon laser efficiently on a quasi-CW basis     

Comparison of the performance of krypton and xenon filled flashtubes for pumping Nd3+doped YAG lasers

It has been shown experimentally that xenon filled flashtubes are more efficient for pumping Nd³⁺doped YAG lasers than krypton flashtubes in spite of the higher output of the krypton flashtube at 0.810 microns.     

Blue-green atomic photodissociation lasers in group IIb: Zn, Cd, and Hg

Four new laser lines, two in atomic Zn at 481.1 and 472.2 nm and two in atomic Cd at 508.6 and 480.0 nm, are reported. The analog laser lines in Hg at 546.1 and 435.8 nm are studied further. These lines correspond to the transitionsn^{3}S_{1} rightarrow (n-1)^{3}P_{2}andn^{3}S_{1} rightarrow (n-1)^{3}P_{1}of the triplet system of the metals. The medium in the three cases is MI2(M= Zn, Cd, or Hg) vapor at about 1 mbar and the pump is a KrF laser at 248 nm. The blue-green superfluorescent pulse power is in the kilowatt range, with a pulse duration of about 1 ns. The pumping process must involve more than one photon. A sequential three-photon pumping process is proposed for the three cases.