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.     

20 ps pulse generation by an excimer laser pumped double self-Q-switched distributed feedback dye laser

The behaviour of an excimer-laser-pumped distributed feedback dye laser (ELP DFDL) using a mixture of saturable absorber and laser dye as an active medium was studied. In a DFDL self-Q-switching occurs because of the population inversion dependence of the feedback. If the DFDL contains absorber saturation of the absorption by the leading edge of the created laser pulse also causes Q-switching. As a result of this double self-Q-switching, mixing a saturable absorber into the laser dye, the laser pulses become shorter and more stable. This was demonstrated experimentally. Mixing Rhodamine B into the dye solution of a Coumarin 153 ELP DFDL, a six-fold reduction in the pulse duration and a more than two-fold reduction in the pulse energy instability were observed. The experimental results were in good qualitative agreement with the predictions of a simple rate equation model.     

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.     

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.     

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.     

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 tunable picosecond pulses in a simple distributed feedback dye laser under N2-laser pumping

Simple possibility of single tunable picosecond pulse generation in a conventional inexpensive distributed feedback dye laser (DFDL) is demonstrated. It is shown that when a TEA N₂-laser is used for pumping no diffraction grating is necessary in the DFDL optical scheme for operation in the picosecond regime. Hence wide-range spectral tuning from 357 to 665 nm was easily achieved. When pumped with a 0.6 ns 40 kW pulse of the TEA N₂-laser the DFDL generated pulses as short as 7 ps with time-bandwidth product better than 0.6 and peak power ? 10 kW. At a repetition rate of 50 pps the shot-to-shot energy stability of a single picosecond pulse was ±18% at ±7% stability of the TEA N₂-laser.     

Mathematical modeling of ruby laser as a pumping source of a “self Q-switched” distributed feedback dye laser

A mathematical model describing the dynamic emission of the ruby laser as a pumping source of a distributed feedback dye laser (DFDL) has been adapted. The suggested model allows the temporal behavior investigation of the ruby laser and the DFDL on mode characteristics and, moreover, investigating the affect of laser input parameters on the output laser pulses in the ruby laser and in the DFDL.The numerical solutions of a coupled nonlinear rate equations system of the adapted model that predict the generation of picoseconds pulses, with neglecting the effect of refractive index variation, are discussed (feedback process is achieved only by optical gain). The model estimates the density of the emitted radiation, energy density of the first excited state, and the output power of the DFDL. The adapted mathematical model is in good agreement with the available experimental data.     

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。     

Demonstration of a nine lines distributed feedback dye laser using three pairs of pump beams

Controllable, maximum nine-wavelength operation of a wavefront divided, multiple beam pumped, distributed feedback dye laser (DFB), is reported for the first time. Equally spaced three to nine lines have been obtained by pumping a dye solution with three pairs of excitation beams derived from the same source. Experimental results lead to a nine line model of a distributed feedback dye laser (DFDL). The dye cell was excited by the 2nd harmonic of a laboratory built, cavity dumped, passively q switched and mode-locked Nd:YAG laser, to induce a temperature phase grating in the dye solution. Different features studied included threshold conditions, simultaneous induction of multiple gratings, impact of pump polarizations, and temporal and spectral characteristics of the emitted lines. This work on the DFDL is in agreement with most of the published results on semiconductor DFB lasers [1, 2, 3] and opens a new era of research. This multi-wavelength operation of a DFDL is based on the nonlinear effects of an overwritten multiple dynamic grating on a R6G dye solution in ethanol. PACS 42.60.By     

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.     

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.     

Pulse linewidth and lifetime broadening study of multi-pulse pumped distributed feedback dye lasers

Results on characterization of spectral width and lifetime broadening mechanism in picoseconds multiple-pulse pumped distributed feedback dye lasers (DFDL) is presented. An experimental study was carried out to investigate the impact of pump pulse energy, dynamic grating length and dye concentration on the spectral width and lifetime characteristics of single and multi-pulse pumped DFDL. To implement this study the solution of Rh6G in ethanol was pumped by 2nd harmonic of a passively q.switched and modelocked ND:YAG laser. Further to study the effect of grating chirp factor on spectral characteristics of the luminescence spectra of the DFDL, the dye cell was pumped by multiple time delayed pulses. Results show that pump power, grating length, dye concentrations and temperature effects cause spectral and life time broadening of simultaneously oscillating multiple lasing lines.     

10 ps High Power Laser System at 248 nm

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10 ps High Power Laser System at 248 nm

A simple 10 ps KrF laser system consisting of quenched dye laser oscillator pumped by a XeCl laser, a distributed feedback dye laser (DFDL), a three-stage dye amplifier and a two-stage KrF amplifier are described. The output of the laser system is 140 mJ with 10 ps pulse width by using polarization-multiplexing amplification. A focused output laser intensity of about 4×1015 W/cm2 is obtained. The saturation fluence for KrF laser is obtained with this laser.     

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.     

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.     

Laser frequency stabilization and large detuning by Doppler-free dichroic lock technique: Application to atom cooling

We present results of a study of frequency stabilization of a diode laser (λ = 780 nm) using the Doppler-free dichroic lock (DFDL) technique and its use for laser cooling of atoms. Quantitative measurements of frequency stability were performed and the Allan variance was found to be 6.9 × 10¹¹ for an averaging time of 10 s. The frequency-stabilized diode laser was used to obtain the trapping beams for a magneto-optic trap (MOT) for Rb atoms. Using the DFDL technique, the laser frequency could be locked over a wide range and this enabled measurement of detuning dependence of the number and temperature of cold atoms using a relatively simple experimental set-up.     

Dye laser pulse shortening and stabilization by Q-switching

The properties of passive Q-switched short-cavity dye lasers (SCDL) and passive Q-switched distributed-feedback dye lasers (DFDL) are investigated theoretically by using rate-equation models. The calculations, in agreement with experimental results, predict a significant decrease of the pulse energy fluctuation and the pulse duration of both the SCDL and DFDL, when passive Q-switching is used.