Solvent dependent characteristics of XeCl pumped UV dye lasers

The characteristics of near uv dye lasers pumped with short duration, 308 nm pulses from a XeCl laser are described with particular emphasis on the parameters influencing high average power operation. The solvent is shown to effect the operation of all dye lasers studied, particularly the photochemical stability. Measurements of the efficiency, as a function of the integrated pump energy have been made for a series of dye-solvent combinations. With the best combinations, average output powers in excess of 1W and conversion efficiencies greater than 25% were obtained at a repetition rate of ∼100 Hz.     

An experimental study and theoretical analysis of the mode characteristics of a narrow line-width,pulsed dye laser oscillator at different pump powers

This paper presents an experimental study and theoretical analysis on the effect of pump power on the divergence, pointing, line-width and wavelength stability of a narrow line-width, high repetition rate dye laser oscillator. The dye laser oscillator, based on the hybrid multiple-prism grazing-incidence grating cavity, was pumped by copper vapor laser (CVL). The dye laser mode characteristics were studied at CVL average pump powers of 2, 4 and 8 W. The single pulse dye laser divergence/pointing stability was studied by far-field intensity distributions. The line-width and wavelength stability were studied using a high resolution wave-meter. The experimental results were theoretically analyzed in terms of dye laser mode structure drift induced by beam pointing instability, beam divergence and thermally induced optical path length fluctuation. A comprehensive theoretical treatment on pointing stability of dye laser beam and its influence in the dye laser wavelength stability is presented. The theoretical and experimental trends were found to be in good agreement.     

Picosecond duration laser pulse generation by simultaneous active-passive mode-locking in Ar+ ion and dye lasers

We use a rate equation model to analyse a technique for the generation of picosecond duration laser pulses in argon pumped dye lasers. The system is based on passive mode-locking of the Ar⁺ laser by saturable absorption of the dye which is inserted in the Ar⁺ laser cavity. Simultaneously, the dye is forced to oscillate in a regime of synchronously pumped mode-locking. The system is relatively simple, does not require the use of an acousto-optical light modulator and can be easily implemented in commercially available lasers. Pulses shorter than 100 ps and having an average power of 20 mW were obtained at a repetition rate of 110 MHz. Good agreement between the model and experimental results was also obtained.     

On the stability of the output characteristics of a grazing incidence grating dye laser transversely pumped by a copper vapor laser

The output characteristics of a high repetition rate pulsed dye laser has both short-term fluctuations and long-term drift. In high power high repetition rate lasers flow induced variations dominate over those due to other factors. In this paper it is shown by dye laser measurements that bandwidth fluctuations can be traced to the effective changes of the resonator dispersion due to fluctuations in the penetration depth of the pump beam in the dye medium. Short-term wavelength fluctuations can be traced to instantaneous deflection of the dye laser axis by the refractive index changes due to absorption of the pump beam. The fluctuations in both the bandwidth and the wavelength decreases with increasing flow rates within a laminar region. A copper vapor laser operating at 5.6 kHz repetition rate pumped the Rhodamine 6G dye laser used. The wavelength fluctuation of ±0.0035, 0.0030, 0.0004 nm and the bandwidth fluctuation of ±710, 132, 45 MHz over approx. 60 minutes were observed at 1.2, 3.7, 5.5 lpm flow rates respectively.     

Single mode operation of a narrow bandwidth dye laser using a single prism, grazing incidence grating long cavity

The single mode pulsed dye laser is an attractive tool for many spectroscopic applications. Long cavity tunable dye lasers generally operate in multi-longitudinal modes within the bandwidth of gain profile. Single longitudinal mode oscillation can be obtained by either making the cavity short enough or introducing an additional loss mechanism, in which all modes but one have a gain less than their loss. A new technique to achieve single mode operation in a long cavity dye laser, based on Rhodamine 6G dye in ethanol and ethylene glycol solution, pumped by a high repetition rate copper vapor laser, is reported. This laser, which operates in three modes in grazing incidence grating configuration (cavity length of 16 cm), has been made to lase in single mode by increasing the loss in the resonator through beam walk-off.     

Temporal dynamics of high repetition rate pulsed single longitudinal mode dye laser

Theoretical and experimental studies of temporal dynamics of grazing incidence grating (GIG) cavity, single-mode dye laser pumped by high repetition rate copper vapour laser (CVL) are presented. Spectral chirp of the dye laser as they evolve in the cavity due to transient phase dynamics of the amplifier gain medium is studied. Effect of grating efficiency, focal spot size, pump power and other cavity parameters on the temporal behaviour of narrow band dye laser such as build-up time, pulse shape and pulse width is studied using the four level dye laser rate equation and photon evolution equation. These results are compared with experimental observations of GIG single-mode dye laser cavity. The effect of pulse stretching of CVL pump pulse on the temporal dynamics of the dye laser is studied.     

Photo-stability of laser dye solutions under Copper-vapour-laser excitation

The photo-stability of laser dyes, Rhodamine-6G, Rhodamine-B, and Kiton-Red, under high repetition rate (6.3 kHz) Copper-vapour-laser (CVL) irradiation has been investigated. Exhaustive photo-bleaching of these dyes in different solvents has been carried out to study the extent to which the dye photo-degraded products would interfere with the lasing process in high-power CVL-pumped dye lasers. Our results indicate that the photo-degradation of dyes occurs predominantly through excited-state intermolecular reactions, involving the singlet state, rather than the process of nonlinear optical absorption in individual molecules. Received: 13 March 2000 / Revised version: 2 August 2000 / Published online: 21 March 2001     

Polarization and power characteristics of pulsed dye lasers with transverse pumping

Starting from the classical theory on molecular luminescence in liquids, rate equation for two-polarization-mode laser oscillation under transverse pumping with intense excitation have been set forth neglecting the influence of orientational relaxation of the dye molecules. Hence, the laser output power and polarization under different configurations have been obtained. The results show that the dye laser is partially polarized even when the pump beam is unpolarized and no polarizing elements exist in the cavity. If we define a reference plane consisting of the axes of the pump beam and the dye laser, the laser system has to adopt the plane perpendicular to the reference plane as the polarization direction in order to yield a highly efficient, linearly polarized laser output. Experiments on a copper-vapor laser pumped dye laser verified these analytical results.     

Characteristics of a hybridly mode-locked cw dye laser

We present experimental and theoretical results on the characteristics and random variations of subpicosecond pulses generated by a synchronously pumped cw dye laser with saturable absorber. The analysis of the power spectra indicates rapid fluctuations of the pulse duration of 40–50%, energy fluctuations of 3%, and a jitter of the repetition time of 0.1% corresponding to an absolute jitter of 12 ps. The latter is caused mainly by the temporal jitter of the pump laser. A mismatch of the lengths of the dye and the pump-laser cavity can result in a nonstationary mode-locking regime with a periodic change of the pulse parameters. The interpretation of the experimental results are supported by computer simulations of the pulse evolution process.     

Pulse structure studies and absolute cavity length determination for a synchronously pumped picosecond dye laser

Second harmonic cross correlation functions of a pulse with its near neighbor have been studied in a synchronously pumped cw dye laser. Measurements were made both as a function of dye laser cavity length mismatch and the number of cavity round trips separating the correlated pulses. The pulse envelope is found to have a characteristic interpulse frequency determined by the pump laser, whereas the pulse substructure has a characteristic frequency determined by the dye laser cavity length. The cross correlation measurements allow experimental determination of the dye laser length corresponding to exact synchrony. In contrast to theoretical predictions the length of exact synchrony corresponds to optimum pulse shape and duration. Our results are discussed in terms of a simple model which leads to pulse duration estimates as much as twice those obtained by conventional analysis of autocorrelation traces.     

Fluctuations in synchronously mode-locked dye lasers

We present detailed experimental data on random fluctuations of the pulse properties of a cw rhodamine 6G dye laser synchronously pumped by an acousto-optically mode-locked argon ion laser. It is shown that quantitative information about the fluctuations of the energy, the pulse repetition time and the duration of the pulses can be obtained from the power spectrum of the laser intensity which is measured with the use of an electronic spectrum analyser. This method is capable of revealing small, subpicosecond temporal pulse jitter. We show that the dye laser pulses exhibit an absolute r.m.s. jitter of 20 ps which is induced by the pump laser. The relative jitter in a dual system can be less than 1 ps because well defined correlations of the output fluctuations exist when two lasers are pumped by a common source.     

高功率准连续激光二极管抽运的Nd：YVO4激光器

对高功率准连续激光二极管端面抽运的Nd:YVO4固体激光器进行了实验研究。研究了抽运功率、温度、重复率及输出镜的透过率对激光器输出功率的影响。当激光二极管重复率达到720Hz、抽动功率33.2W时,激光输出最大平均功率为11W。     

High average power from a long pulse dye laser

A reliable rhodamine 6G dye laser with a 60μs pulse duration, a repetition rate up to 100 Hz and an average power of 4W is described.     

A reliable high average power dye laser

A flashlamp-pumped dye laser with an average output power of 6.6 W at 100 Hz repetition rate is described, which utilizes thyristors as switching elements instead of the normally used spark gaps. Using a simmering-mode operation of the flashlamps, no high voltage sparks are required to initiate the discharge even at low capacitor voltages. In this way the amplitude and time jitter of the laser output pulse are decreased and the life and reliability of the laser considerably increased.     

Picosecond and subpicosecon pulse generation in synchronously pumped mode-locked cw dye lasers

Generation of tunable near-infrared picosecond and subpicosecond pulses in a synchronously pumped cw mode-locked Oxazine-1-perchlorate dye laser has been investigated for different values of the important system parameters. The experimental results confirm the predictions of a simple theoretical model which describes the steady-state pulse duration in terms of gain modulation strength, pump power, intracavity bandwidth, pump pulse length and cavity detuning. For a pump-pulse length of 100 ps and a bandwidth of more than 500 Å for the intracavity tuning element dye-laser pulses as short as 0.35 ps have been obtained. Under these conditions up to 100 mW of average output power were provided. In addition, mode-locking of an Oxazine 750 dye laser by synchronous pumping with the cw train of pulses obtained from the Oxazine-1-Perchlorate laser is reported.     

Efficient lasing action from Rhodamine-110 (Rh-110) impregnated sol-gel silica samples prepared by dip method

Rhodamine-110/sol-gel samples are prepared by sol-gel technique using dip method. Concentration dependent photophysical studies of these samples have indicated about the least possibility of aggregate formation. The lasing action of Rh-110 in silica samples is studied as a function of dye concentration. An efficient laser emission is observed when the samples are transversely pumped at 337.1 nm and 1.5 Hz repetition rate using a nitrogen laser (400 μJ energy/pulse and 4 ns pulse duration). The maximum of 166% laser efficiency of dye doped sol-gel samples compared to Rhodamine-6G (Rh-6G) in methanol is achieved. The photostability is also measured by using N₂ laser at 1 Hz and it is found nearly 165 pulses. The possible reasons for the photodegradation of the dye molecules are discussed in detail.     

被动调Q自拉曼Nd∶GdVO4激光器

对激光二极管(LD)抽运的自拉曼Nd∶GdVO4被动调Q激光器进行了详细的理论和实验研究。实验中采用Nd∶GdVO4晶体同时作为激光介质和拉曼晶体,分别用了两块不同初始透射率的Cr4 ∶YAG晶体,得到并比较了采用不同初始透射率的Cr4 ∶YAG晶体时被动调Q自拉曼激光器的性能。测量了平均输出功率、脉冲宽度和脉冲重复率随抽运功率的变化关系。当Cr4 ∶YAG的初始透射率为0.91,输入功率是5.7 W时,得到的拉曼光的最高功率为244.6 mW,相应的转换效率为4.3%。通过数值求解基频光和拉曼光空间分布的速率方程并应用到被动调Q自拉曼Nd∶GdVO4激光器。获得的理论结果与实验结果大致相符。     

Operation of a high power,broadly tunable infrared dye laser

We discuss the operation and performance of a ruby pumped infrared dye laser with a wide tuning range and a high out-put power. The longitudinally pumped infrared laser was operated in the Littrow configuration without an intracavity beam expander. The dye, IR 125, exhibited a tunability range that extended from 8325 Å to 9375 Å. The dye laser had a pulse duration of 20 ns and an output power of 12.5 MW with a 2.3 joule ruby pump. The maximum output power of the infrared laser was limited by the damage threshold of the tuning element.     

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。     

Tunable infrared difference-frequency generation with a high-repetition pulsed dye laser

An output from a cresyl-violet dye laser, pumped by the second harmonic of a Q-switched Nd:YAG laser, is mixed with the pumping light in a LiIO₃ crystal to produce an infrared output tuned from 2.8 to 3.4 μm with a repetition rate of 20 pps.