A high-power subpicosecond distributed feedback dye laser system pumped by a mode-locked Nd: YAG laser

The design and operation characteristics of a distributed feedback dye laser (DFDL) system pumped by the second harmonic of a flashlamp pumped mode-locked Nd: YAG laser are described. The DFDL oscillator facilitates a large tuning range with nearly Fourier limited pulse durations of about 1.6 ps. The combined action of saturated absorption and amplification results in a pulse shortening to about 600 fs, with small fluctuations in the pulse duration. Output pulse energies of more than 400 J are achieved, corresponding to a peak power of more than 650 MW. Since the dye amplifiers are pumped by pulses of only 25 ps duration the amplified spontaneous emission (ASE) is very low, typically less than 10^–4.     

Undamped relaxation oscillations due to self-gain-switching of laser dye mixtures

Undamped relaxation oscillations were observed from a short, simple dye laser using a laser dye mixture which was pumped at 337 nm using ns pulses. The dye solution contained Rh101 as first laser dye, together with DTDCI in double function as saturable absorber and second laser dye. Two trains of intense laser pulses were generated near 619 and 685 nm, with pulse durations of ca. 4 and 2 times the resonator transit time, respectively. This method of short-pulse generation is related to double mode-locking of dye lasers. Model calculations are used to describe the pulse generation by self-gain-switching, and to estimate radiative and nonradiative contributions towards saturation of the absorber dye.     

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.     

Studies on widely tunable ultra-short laser pulses using energy transfer distributed feedback dye laser

This paper presents both theoretical and experimental study of the characteristics of Nd: YAG laser pumped energy transfer distributed feedback dye laser (ETDFDL). Using theoretical model proposed, the behavior of ETDFDL such as the characteristics of donor DFDL, the acceptor DFDL, the dependence of their pulse width and output power on donor-acceptor concentrations and pump power are studied for dye mixture Rhodamine 6G and Cresyl Violet in detail. Experimentally using prism-dye cell configuration, the ETDFDL output is obtained and the output energy of DFDL is measured at the emission peaks of donor and acceptor dyes for different pump powers and donor-acceptor concentrations. In addition, the DFDL linewidth measurement has been carried out at the lasing wavelengths of the donor and acceptor dyes using Fabry-Perot etalon and the tunability of DFDL is measured to be in the wavelength range of 545-.     

Generation of 320 fs pulses with a distributed feedback dye laser

A new achromatic distributed feedback dye laser (DFDL) arrangement is described. The experimental conditions for subpicosecond pulse generation with the new device were investigated. For the first time, stable generation of subpicosecond pulses (350 fs) at 616 nm was achieved with a DFDL. The simultaneous spectral and autocorrelation measurements showed that the amplified DFDL pulses are nearly transform limited, having a pulse form close to the sech² shape.     

Theory of passive mode-locking of CW dye lasers with contacted and non-contacted absorbers

A theoretical treatment of the influence of a saturable absorber in close contact with a highly reflecting mirror on a light pulse is given. The shaping of a Gaussian pulse during a single passage through such an absorber is calculated for various absorber lengths. The influence of absorber position and length on the pulse parameters and the stability of a continuously pumped dye laser are investigated. The shortest pulses and the most favourable operation conditions of the laser are to be expected in the case of a short contacted saturable absorber.     

Properties of a distributed feedback dye laser with integrated amplifier

Several properties of a compact laser light source built up by a distributed feedback dye laser (DFDL) and an amplifier realized with only one dye solution cuvette are discussed. It is shown that in this arrangement the region of single pulse generation with respect to the pump energy applied to the DFDL is extended in comparison with a pure DFDL oscillator set-up. This effect is mainly caused by the radiation coupled back from the amplifier into the DFDL oscillator. The results of numerical simulations are discussed and compared with some experimental facts published in a previous paper.     

超短脉冲分布反馈染料激光器稳定工作条件分析

 利用耦合波理论,分析了一种作为KrF准分子激光MOPA系统的振荡源-亚皮秒超短脉冲分布反馈染料激光器（DFDL）的输出模式,指出实际的分布反馈染料激光器工作在单纵模状态是周期性增益调制的必然结果。数值模拟结果表明,DFDL输出光谱出现多条谱线的精细结构或调制现象,这是由多个顺序相干脉冲产生的。可以利用这种光谱调制现象来控制激光器的泵浦强度,获得稳定的单脉冲。光谱测量结果表明,在2倍泵浦阈值左右DFDL能够获得稳定的单模单脉冲输出。     

Steady state photoisomer accumulation in the absorber jet of the passively mode-locked femtosecond dye laser

In continuous were passively mode-locked dye lasers a steady state distribution of two isomers of the saturable absorber dye can be established. We report the first intracavity transmission measurement and estimation of the amount of the photoisomer of DODCI in the femtosecond CPM ring laser. Comparison with a simple model based on rate equations allows to estimate the quantum yield of a photo-back reaction. The obtained dependence of the photoisomer concentration on the laser wavelength and pulse energy can be used in theories describing the generation process for adequate estimation of its part in the modelocking regime.     

New single-pulse generation technique for distributed feedback dye lasers

The distributed feedback dye laser (DFDL) generates a train of picosecond pulses when pumped well above threshold. This DFDL emission can be quenched by injecting a laser pulse into DFDL. By proper timing of the quencher laser pulse, only the first DFDL pulse is generated while the successive pulses are suppressed. Operational characteristics and practical design considerations of such a quenched DFDL are given. With 2.5 ns long pump pulses from a N₂ laser, a shortest DFDL pulse of 17 ps was obtained at 380 nm.     

Theory of passively mode-locked cw dye lasers

The circulation of an ultrashort light pulse in a continuously pumped modelocked dye laser with a linear cavity configuration containing the active dye, the saturable absorber and a bandwidth-limiting elements is treated. The steady-state condition that the pulse shape reproduces after each cavity round-trip leads to a nonlinear integro-differential equation for this pulse shape. An approximate method for the solution of this equation not limited to the case of low laser gain and small pulse energies is given. The stable single pulse region and characteristic pulse parameters, as energy, duration, intensity and asymmetry, are considered in dependence on the laser parameters.     

Tunable energy transfer distributed feedback dye laser using pyronin B and crystal violet dye mixture

Using pyronin B and crystal violet dye mixture, the characteristics of energy transfer distributed feedback dye laser (ETDFDL) pumped by 532 nm Nd:YAG laser were investigated. The characteristics of donor DFDL and acceptor DFDL as well as the dependence of their pulse widths and output powers on pump power and acceptor concentrations were studied. The output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and acceptor concentrations, and tunability was observed from 570 to 645 nm using prism dye cell arrangement.     

Modeling a distributed feedback dye laser pumped by a Nd-glass laser

A mathematical model has been developed to describe the dynamic emission of a distributed feedback dye laser (DFDL) pumped by a Nd-glass laser. The model is based on the coupled-wave theory. It allows the investigation of the temporal behavior of the Nd-glass pumping laser source and the DFDL pulses. The model allows studying the effect of the variation of the laser input parameters of the Nd-glass laser, such as maximum amplification coefficient, loss coefficient and pumping rate on the characteristics of DFDL pulses regarding the pulse width, delay time and separation time. The feedback process of the DFDL is provided either by changes of the refractive index or by optical gain or by both together. The model estimates the following: temporal behavior of the density of emitted radiation, energy densities of the first excited singlet and triplet states, DFDL output power, cavity decay time and the temperature of the produced grating. The numerical solution of the nonlinear coupled rate equation system predicts the generation of DFDL picosecond pulses. The calculated results are in good agreement with the available experimental data. The calculations were done using rhodamine 6G dissolved in ethanol as the investigated matrix.     

Novel achromatic distributed feedback dye laser for subpicosecond operation

The optical pump arrangement of distributed feedback dye lasers (DFDLs) having a grating beam splitter is analyzed in detail. The upper limit of the pump spectral bandwidth and beam divergence are given as a function of the length of the excited volume. A novel achromatic pump arrangement is reported which is capable of producing a short, high visibility interference pattern even if a divergent pump source of several nm bandwidth is used. The DFDL pulse duration has an estimated lower limit of 200 fs.     

An oscillator-amplifier distributed feedback dye laser system,pumped by a single TEA N2 laser

In this paper we describe a simple and inexpensive Distributed Feedback Dye Laser (DFDL) system for picosecond pulse generation. This system consists of an oscillator-amplifier DFDL, either in the grating or in the prism configuration: both stages are pumped by a single TEA nitrogen laser with improved beam quality. Single pulses having duration of 26 ps are obtained at a frequency up to 100Hz; the overall pulse-to-pulse stability is, at the maximum frequency, of about 25%. This system is particularly well-suited for time-resolved fluorescence microscopy studies where short tunable laser pulses of low energy are required.     

Tunable picosecond energy transfer distributed feedback dye laser using Rhodamine 6G and Thionine dye mixture

The characteristics of Nd:YAG laser pumped energy transfer distributed feedback dye laser (ETDFDL) is studied both theoretically and experimentally. Using theoretical model proposed the behaviour of ETDFDL for dye mixture Rhodamine 6G and Thionine is studied in detail. The characteristics of donor DFDL, the acceptor DFDL, the dependence of their pulse widths and output powers on donor–acceptor concentration and pump power are studied. The output energy of DFDL is measured experimentally at the emission peaks of donor and acceptor dyes for different pump powers and donor–acceptor concentrations. In addition, the tunability of DFDL emission is measured both in donor and acceptor emission ranges.     

Energy transfer in solid-state dye lasers based on methyl methacrylate co-doped with sulforhodamine B and crystal violet

Laser action in methyl methacrylate(MMA)co-doped with sulforhodamine B and crystal violet dyes was investigated.The dye mixture was incorporated into a solid polymeric matrix and was pumped by a 532-nm Nd:YAG laser.Distributed feedback dye laser(DFDL)action was induced in the dye mixture using a prism arrangement both in the donor and acceptor regions by an energy transfer mechanism.Theoretically,the characteristics of acceptor and donor DFDLs,and the dependence of their pulse widths and output powers on acceptor–donor concentrations and pump power,were studied.Experimentally,the output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and different acceptor–donor concentrations.Tuning of the output wavelength was achieved by varying the period of the gain modulation of the laser medium.The laser wavelength showed continuous tunability from 563 nm to648 nm.     

Pulse compression in AO Q-switched diode-pumped Nd:GdVO4 laser with Cr4+:YAG saturable absorber

By simultaneously using both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber in the cavity, for the first time, a diode-pumped doubly Q-switched Nd:GdVO₄ laser has been realized. The pulse duration is obviously compressed in contrast to the actively acoustic-optic Q-switched laser. By considering the Gaussian transversal distribution of the intracavity photon density and the longitudinal distribution of the photon density along the cavity axis as well as the influence of turnoff time of the acoustic-optic (AO) Q-switch, we provide the coupled rate equations for a diode-pumped doubly Q-switched Nd:GdVO₄ laser with both an acoustic-optic (AO) modulator and a Cr⁴⁺:YAG saturable absorber. These coupled rate equations are solved numerically, and the dependence of pulse width, pulse energy and peak power on the incident pump power at different pulse repetition rates is obtained. The numerical solutions of equations agree well with the experimental results.This revised version was published online in August 2005 with a corrected cover date.     

Two-wavelength operation of a femtosecond ring dye laser

We report on two-wavelength operation of a CPM ring dye laser employing Rhodamine 6G as gain medium and a new styryl dye as saturable absorber. Two trains of femtosecond pulses at different wavelengths are simultaneously generated under proper alignment of the laser. The secondary pulse train is attributed to the laser action of the absorber dye. Auto- and cross-correlation measurements are performed to determine the temporal characteristics of the laser in the double mode-locking regime.