Dye Laser Performance Research Articles

Studies on 20 kHz pulse repetition rate class narrow line-width dye laser

This paper presents a first comprehensive study on 20kHz pulse repetition rate (PRR) class dye laser with an emphasis to bring out the role of dye solution flow rate on the laser power, line-width, wavelength stability and pulse characteristics of a narrow line-width dye laser. The study was performed for Rh6G–ethanol dye solution for flow rates from 2 to 12lpm. The dye laser based on glass dye cell and the pump source was copper hydrogen bromide (Cu–HBr) laser at a fixed average power of 8W and repetition rate of 18kHz. The dye laser resonator was grazing incidence grating (GIG) cavity with double prism beam expander. A high precision wavelength-meter was used to record the online variation in dye laser line-width and wavelength. It is established that the dye solution flow rate significantly affected the dye laser performance. The best dye laser spectral purity was obtained at 3–4lpm flow rate regime. The line-width and wavelength stability worsened both below and above the flow rates of 3–4lpm. The best dye laser output power was obtained at 9lpm flow rate and it decreased only slightly as flow rate is increased to 12lpm. The dye solution flow rate also affected the dye laser pulse shape and width.

Thermal analysis studies of doping effects on the conformational motions of polymer chains in solid solutions with lasing molecules

The advancement of the solid-state dye laser performance largely depends on the systematic study of the dye-matrix interactions at the nanoscopic scale. The current work deals with blends of a comparatively inert dye host, poly(methyl methacrylate) (PMMA), with nonionic/apolar (substituted perylenes) and ionic/polar (rhodamine 6G, pyrromethene 567) dyes at ≈10−4 mol L−1 loading. Differential scanning calorimetry (DSC) and thermally stimulated currents (TSC) were used to explore the relative strength of inter- and intramolecular guest-host interactions by monitoring blending-induced modifications of the high-temperature signals: the segmental relaxation, the space-charge relaxation, and the liquid-liquid transition. Both techniques revealed the antiplasticizing role of the oligomeric organics on the relaxation dynamics of polymer segments, evidenced by clear glass-transition temperature upshifts. It becomes apparent that this effect is independent of the size, polarity, and ionicity of the dopant, signifying a common mechanism underway. It is suggested that, at least for the dyes under investigation, the chromophores simply fill the voids within the matrix, imposing strong steric hindrances on the rearrangement of the long-range structure. A comparison between the present results and earlier low-temperature dielectric data reveals that the large-scale relaxation dynamics show stronger perturbations due to blending, in comparison to the localized rotational motion of the pendant groups. DSC provided estimates for the unconverted monomer percentages in the solid blends. These were also determined more accurately by nuclear magnetic resonance (NMR), which additionally confirmed that the tacticity of the chains is not affected by the presence of the dye.

The effect of dye photodegradation on the performance of dye lasers

Detailed experimental study of laser dye stability and the subsequent effects of photodegradation products on the operation of a Nd:YAG laser pumped Rhodamine-6G pulsed dye oscillator has been carried out. Deterioration of laser output on account of dye photodegradation resulting in the loss of active dye molecules and the generation and accumulation of reaction products that introduce a loss at the laser and pump wavelengths has been theoretically simulated in terms of a time dependent rate equation model. Our experimental observations have been found to be in good agreement with our theoretical estimates. We have also investigated the deterioration in the performance of a copper vapour laser pumped tunable dye laser with a high average power and a high repetition rate operating over an extended period of time. Our theoretical model, when suitably modified, provided useful estimates for the extent of deterioration in laser performance of such a dye laser with a high average power and a high repetition rate on account of photodegradation of the active dye molecules.

Single-mode operation of a long-pulse flashlamp pumped dye laser

We describe the achievement of single-mode operation of a flashlamp pumped long-pulse, /spl sim/700 ns dye laser, with output energy of about 350 mJ using a linear optical cavity with a "twisted mode" configuration. Measurements indicate that the laser frequency chirps by about 40 MHz over the entire pulse. Homodyne measurements indicate that the instantaneous bandwidth is close to the transform limit. This represents a significant advance in dye laser performance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dye laser studies using zig-zag optical cavity

We report a substantial advance in dye laser performance using a zig-zag optical cavity. This configuration drastically reduces the effects of intrapulse medium disturbances due to acoustics and thermal lensing on pulse duration, beam quality, and extraction efficiency. Laser outputs of up to 2 J were observed from Coumarin-498 dye pumped by a KrF excimer laser. The dye laser output faithfully replicates the hat-top KrF laser pump pulse over the entire 1.7-/spl mu/s pulse duration. An intrinsic laser photon conversion efficiency (Photons/sub inPhotons/sub absorbed/) of 44% was measured. When unstable resonator optics were used, beam qualities of about 2 XDL were measured.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Generation of femotsecond pulses by a pulsed laser system

A new concept of fs pulse generation is introduced using a synchronously coupled dye laser under non-cw conditions. Microsecond pulse trains derived from a specially designed mode-locked Nd:glass laser with ≈ 200 pulses of 2–3 ps duration serve as pump radiation. Superior dye laser performance is achieved with drastically lowered stability requirements and increased power level. For Rhodamin 6G intense pulses of energies of 100 nJ and durations of as short as 90 fs are generated at 572 nm in a simple four-mirror cavity. A single-step dye amplifier operated by the synchronized pulses of the same pump laser produces single pulses of 150 fs duration and 10 μJ energy. For hybrid mode-locking, the amplified pulses have been compressed to 68 fs by the help of a conventional grating pair.

Optically biased tunable femtosecond dye laser and spectral windowing of the compressed second harmonic of Nd:YAG

We describe a technique for enhancing tunable ultrashort pulse pumped dye laser performance based on the use of "long" pump pulses to optically bias the cavity toward minimal losses. Increases in dye laser output power of 155 percent and powers as high as 125 mW have been measured with pulse durations under 300 fs. Optical pulses as short as 180 fs are reported for this ultrashort pulse pumped dye laser oscillator. We also report the first measurements of the spectral windowing of compressed 532 nm pulses for temporal pulse shaping, in the optimal group velocity dispersion limit. Temporal pulse shaping is demonstrated with small losses in power and minimal pulse broadening.

Effects of secondary chemical reactions upon the performance of dye lasers

The effect of absorption at the lasing wavelength due to the accumulation of reaction products from the photodegradation of a laser dye is analyzed theoretically. This analysis is used as a basis for the representation of data from dye degradation experiments in terms of absorption at the lasing wavelength. Studies of the effects of flashlamp pulse rate and time on the inferred absorption for a number of different dyes reveal the influence of secondary chemical reactions. The most significant effects are shown to be associated with spontaneous reactions where the reactants and products have markedly different molar absorptivities at the lasing wavelength.

Excited singlet-state absorption in dyes and their effect on dye lasers

The performance of dye lasers with excited singlet-state absorption (ESA) at the pump and the lasing wavelengths is analyzed for short pulse pumped systems in the medium range of pumping intensities. Analytical and numerical solutions are presented for a wide range of the variable parameters such as ESA cross sections, the cavity reflectivity, and the pumping intensity. An experiment is described for measuring ESA cross sections in the pumping as well as the lasing regions, and the results for rhodamine 6G and rhodamine B are given, showing that due to ESA, the effective gain of the laser will be much lower than that expected from previously published data on the stimulated emission cross sections.

Photoquenching III. Analysis of the dependence of pulsed-laser-pumped dye laser performance on pumping conditions and on the dye molecular characteristics

Computer calculations are presented for the study of pulsed-laser-pumped dye laser (PLPDL) systems. A set of coupled differential equations for the population of the ground and excited siglet states of the dye medium and for the transient dye laser intensity are solved for various combinations of dye parameters and pumping conditions to yield the gain function and the dye laser intensity profile. It is shown that photoquenching effects due to the absorption of the exciting pulse by the lasing state of the dye and to the self absorption of dye Liser light by the dye medium determine the PLPDL performance. A delay time depending on the pumping intensity is predicted for dye systems exhibiting significant photoquenching. The efficiency of a PLPDL system will generally reach an optimum value for the range of pumping intensities employed.