Infrared laser emission in two-photon pumped sodium vapour

We report infrared laser emission in the region of 3 to 5 μm from sodium vapour optically pumped by a pulsed dye laser with wavelengths ranging from 585 to 610nm. Twophoton excitation processes are believed to be responsible for the primary excitation. Both molecular transitions (4 to 5 μm) between high lying states, and atomic transitions (5² S _1/2−4² P _3/2,1/2 at 3.41 μm) have been identified.     

On spin relaxation of optically pumped cesium vapour

〈S_Z〉 relaxation of cesium is measured in the presence of foreign gases, using the detecting beam method. From the results obtained in the low-pressure regions calculations for the diffusion coefficient, D₀, for cesium in Ne and Ar yield values of 0.113 cm²/sec and 0.145 cm²/sec at 760 torr and 0°C, respectively. A comparison of our D₀ values with those published previously is made.     

Detection of quadrupole relaxation in an optically pumped cesium vapour

Summary The relaxation of quadrupole orientation induced by means of optical pumping in a cesium vapour is experimentally studied, and the results are compared to the theoretical predictions. The optical detection process of this type of orientation is also discussed as a function of the polarization and spectral profile of the detection light.

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Riassunto Si studia sperimentalmente il rilassamento dell'orientamento quadrupolare indotto mediante pompaggio ottico in un vapore di cesio e i risultati sono confrontati con le previsioni teoriche. Si discute anche il processo ottico di determinazione di questo tipo di orientamento in funzione della polarizzazione e del profilo spettrale della luce di rilevamento.

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Резюме Экспериментально исследуется релаксация квадрупольной ориентации, индуцированной с помощью оптической накачки в парах цезия. Полученные результаты сравниваются с теоретическими предсказаниями. Также обсуждается процесс оптического детектирования этого типа ориентации в зависимости от поляризации и спектрального профиля детектируемого света.

     

Ionization of sodium vapour by intense laser light tuned to 3S → 3P transition

The efficient production of plasma was observed in a sodium cell irradiated by intense laser light tuned to the 3S → 3P transition. This phenomenon was explained as the result of avalanche ionization by superelastically heated electrons. The electron temperatures and densities were measured.     

Transverse spatial coherence of a transient nickellike silver soft-x-ray laser pumped by a single picosecond laser pulse

The degree of spatial coherence in the direction perpendicular to the target surface is reported for a transient nickellike silver x-ray laser at 13.9 nm. An x-ray laser plasma column was produced by irradiating a slab silver target with a single shaped picosecond laser pulse with energy less than 3 J. Young's double-slit method was applied to measure the fringe visibility as a function of the slit separation for different target lengths. The diameter of the equivalent incoherent source and the coherence radius of the output radiation were determined as well.     

Transverse modes of a diode-laser pumped monolithic unidirectional non-planar ring laser

Diode-laser pumped monolithic single-frequency non-planar ring laser has the advantages of compactness, reliability and high efficiency. But when the pump power is high enough, the thermal effect will be serious and the high-order transverse modes will appear. Therefore the single-mode output power is limited. In this paper, the mechanism of generating the high-order transverse modes in the monolithic unidirectional non-planar ring cavity is analyzed using ray tracing method. The calculated results are in agreement with the experiments.     

Conical four-wave mixing in sodium vapour excited by femtosecond laser pulses

Broadband (sometimes exceeding 1500 cm^-1) red-shifted (with respect to the sodium 3S–3P transition frequency) conical emission has been observed with the pump wavelength tuned in the range between 540 and 589 nm. Such broadband emission was attributed to the generation and amplification of light at the Rabi sideband frequencies in the field of intense femtosecond laser pulses. It has been shown that the cone angle of the emitted radiation is determined by the process of four-wave mixing under the conditions of longitudinal (Cherenkov-type) phase matching. PACS 42.65.Ky; 42.65.Re; 42.50.Hz     

Transverse relaxation of cesium vapour in a “strong” resonance radio frequency field

The fast adiabatic passage method was used to conduct measurements of the transverse relaxation times within hyperfine states of the ground state of cesium. The results of the experiment confirm the relations presented by Bouchiat for “weak” fields in spite of the fact that the field used, H₀ = 0.40 Oe is not a “weak” field. This apparent controversy is easily removed when one considers that in the presence of a rf field, atoms “see” an effective field which turns out to be a “weak” field.     

Transverse relaxation determination based on light polarization modulation for spin-exchange relaxation free atomic magnetometer

A transverse relaxation determination of spin-exchange relaxation free(SERF) magnetometer based on polarization modulation technique is proposed. Compared with the radio-frequency(RF) excitation and light intensity excitation methods used in SERF magnetometer, the light polarization modulation method has a high stability in low-frequency range,which indicates a more accurate transverse relaxation measurement.     

Free-running emerald laser pumped by laser diode

Free-running emerald laser pumped by 660-nm laser diode (LD) was reported. Free-running output powerof 24 mW has been obtained with overall efficiency of 1.4% and slope efficiency of 11.9% when the LD incident power was 2.56 W. The laser threshold value of emerald crystal was estimated to be 0.7 W.     

Time-resolved studies of emission excited in sodium vapour by 330 nm laser pulses

Received: 21 June 1996/Accepted: 4 November 1996     

Comparative laser performances of pyrromethene 567 and rhodamine 6G dyes in copper vapour laser pumped dye lasers

Narrowband laser performances and photochemical stability of alcoholic solutions of pyrromethene 567 and rhodamine 6G dyes, under high-repetition rate copper vapour laser (at 510 nm), as well as, high-peak intensity Nd:YAG laser (at 532 nm) excitation have been investigated. We have observed that pyrromethene 567 dye solutions offer higher efficiency, wider tuning range, but lower photochemical stability and higher lasing threshold than that of rhodamine 6G dye solutions. An addition of about 100 mM DABCO, as a singlet oxygen quencher, in pyrromethene 567 dye solutions improved its photochemical stability close to that of rhodamine 6G. The observation of higher slope efficiency, in spite of higher threshold pump energy for pyrromethene 567 dye than that of rhodamine 6G dye solutions, was explained by a predictive model on gain characteristics of both dye solutions as a function of pump energy. PACS 42.55.Mv; 42.55.Rz; 42.70.Hj; 42.70.Jk     

Optical parametric oscillator pumped by relaxation oscillation pulses of a mechanically Q-switched Nd:YAG laser

We report the generation of mid-infrared pulsed radiation between 2.2 and 3 μm range using a singly-resonant optical parametric oscillator (SR-OPO) based on a 40-mm-long crystal of periodically-poled LiNbO₃ (PPLN) pumped by mechanically Q-switched pulses from a Nd:YAG laser, obtained by chopping the beam inside the laser resonator over a 1–10 kHz duty cycle. An appreciable reduction in pulse width as well as the number of relaxation oscillation pulses of the Nd:YAG pump laser is observed when the frequency of the Q-switch chopper is increased up to 10 kHz. Sub-nanosecond relaxation oscillation pulses of about 170–210 ns duration are generated under the width of the idler envelope varying from 4.6 to 8.55 μs. The same behavior is observed for the signal wave. A maximum extraction efficiency of 22 % is obtained for the idler, corresponding to 785 mW of output power at 10 kHz. The tuning of the signal and idler beams were performed by temperature variation of the PPLN crystal within 100–200 °C range.     

A free-electron laser pumped by the soliton laser

We propose a scheme for building a free-electron laser in the soft X-ray region pumped by the soliton laser. Making use of soliton laser wave evolution shape and single-pass small signal analysis, we find that this laser has two special advantages over the previous electromagnetic wave undulator free-electron lasers. One is a very small mass-shift effect because of the special characteristics of soliton laser; the other is that it has an additional frequency tuning effect based on the conventional free-electron laser's tunability. We also obtain the small signal gain and present some discussion.     

Multiphoton parametric processes during interaction of counterpropagating light pulses with sodium vapour

The visible ( 589nm) and IR ( 820nm) radiation has been detected, when two counterpropagating light pulses, nondegenerate in frequency, interacted with sodium vapour. The generated IR radiation was attributed to the fluorescence between 3D and 3P sodium levels, while conical geometry of visible radiation indicated the parametric origin of detected emission.     

YAG激光同步泵浦染料激光器产生38fs光脉冲

研究表明,不用碰撞脉冲锁模技术,而由一台简单的线型腔染料激光器,就可成功地产生短达38飞秒的光脉冲。这种激光器用六镜折叠腔,其中有Rh6G和DOPCI两个喷流和一个棱镜对色散补偿器,用连续锁模Nd:YAG激光器的倍频输出同步泵浦。染料激光脉冲的平均功率为20mW,脉冲重复频率近100MHz。     

Effects of partial decoupling of electronic and nuclear spin on the relaxation of an optically pumped alkali vapour

Summary The effects of a static magnetic field on the relaxation of an alkali vapour by isotropic collisions with very short correlation time are studied. relaxation transients are specifically considered. The analytical approach to the problem allows us to get the number and structure of eigenobservables, both the subset of degenerate eigenobservables, whose relaxation is not affected by the magnetic field, and the subset of nondegenerate eigenobservables with magnetic-field-dependent relaxation rates. First-order approximations to modified relaxation rates are also analytically derived.

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Riassunto Si studiano gli effetti di un campo magnetico statico sul rilassamento di un vapore alcalino mediante collisioni isotrope con tempo di correlazione molto breve. L’approccio analitico al problema ci permette di ottenere il numero e la struttura di autoosservabili, sia il sottogruppo delle autoosservabili degenerate, il cui rilassamento non è influenzato dal campo magnetico, sia il sottogruppo di autoosservabili non degenerate con valori di rilassamento dipendenti dal campo magnetico. Si derivano anche analiticamente approssimazioni di prim’ordine ai valori di rilassamento modificati.

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Резюме Исследуется влияие статического магнитного поля на релаксацию пароь щелочных металлов в результате изотропных соударений с очень малым временем корреляции. В частности, рассматривается релаксационный переходной процесс. Аналитический подход к проблеме позволяет получить число и структуру собственных значений: подсистему вырожденных собственных величин, релаксация которых не зависит от магнитного поля и подсистему невырожденных собственных значений, для которых релаксация зависит от магнитного поля. Аналитически выводятся приближения первого порядка для модификации релаксационных переходов.

     

溴化亚铜激光泵浦的可调谐微微秒染料激光

本文首次报道了利用脉宽为25ns重复率为10kHz的溴化亚铜激光泵浦混有饱和吸收体DODCI的超短腔染料激光,产生出30ps光脉冲.在理论上对混入DODCI的超短腔染料激光脉冲压缩效应作了分析计算,计算结果与实验基本一致.在实验上又通过一个放大-色散系统实现对此染料激光脉冲的同步放大和调谐,并达到傅里叶变换极限.