Distributed Feedback Dye Laser Research Articles

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.

A five line distributed feedback dye laser

A multiple grating distributed feedback dye laser is described where laser emission is produced in a dye solution by the interference patterns of two pairs of frequency doubled Nd:YAG laser beams. Two pairs of pulses can induce five gratings that support oscillation of five lines and three pairs of pulses are expected to induce nine lines. The maximum number of laser lines depends upon the number of pump pulses and the time delay between the adjacent pairs of beams. For two pairs of excitation beams, derived from the same source through wave-front or amplitude phase division techniques, the output lasing lines varied from two to a maximum of five as the delay between the pairs of pump pulses is varied.

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– 680 nm .

Model of temperature grating relaxation times in distributed feedback dye lasers

A theoretical model and its experimental realization for the temperature grating relaxation time constant and its impact on the temporal and the spectral profiles of a Q-switched and modelocked Nd:YAG laser pumped distributed feedback dye laser (DFDL) is reported. Boundary conditions for different types of excitation pulses have been established to predict the effect of temperature phase gratings on laser gain build-up and temporal elongation of the DFDL pulses. The proposed transient grating method is useful in measuring grating relaxation time constants for lasing dye solutions. The proposed mathematical model is demonstrated by measurement of the relaxation time constant of R6G in ethanol at 10-3M. The measured relaxation time constant of 16+/-0.2 ns is very close to the tabulated values determined using other techniques.

A hybrid laser system consisting of a frequency-doubled, narrow-line-width, distributed-feedback dye laser oscillator and a high saturation-fluence Ce:LiCaAlF6 crystal amplifier

A tunable narrow-band picosecond dye laser emitting in the ultraviolet region was amplified using a Ce:LiCaAlF6 crystal pumped by the fourth-harmonic emission of a Nd:Y3Al5O12 laser. The single-pass gain obtained exceeded 2 in the spectral range of 288 to 297 nm.

Numerical simulation of a pulsed laser pumped distributed-feedback waveguided dye laser by coupled-wave theory

A dynamic model of pulsed laser pumped distributed-feedback (DFB) waveguided dye laser based on a coupled-wave theory is described. Due to the periodical distribution of the intensities of pump source and stimulated emission along the waveguide, the rate equations of the population densities are turned into the equations of the Fourier coefficients. Coupled-wave equations of optical fields are used to simulate the laser oscillation. Besides the temporal evolution of the output intensity, the spectra can also be obtained by the Fourier transform of the optical fields. Two different configurations of the waveguided dye laser, prefabricated DFB (mainly index coupling), first- and second-order holographic DFB (dynamic gain-coupling), are considered in the model. The simulation shows that: 1) the temporal waveforms of the holographic DFB consist of sharp spikes; 2) the broadened spectral widths resulted from the possible nonuniformities in propagation constant or grating period are less than 50 pm except for the second-order holographic DFB; and 3) strong parasitic oscillations can be observed in the second-order holographic DFB with terminal reflection. These results and the comparisons of some of them to the experiments are reported.

Energy transfer distributed feedback dye laser using Rhodamine B–Acid blue 7 dye mixture

The characteristics of energy transfer distributed feedback dye laser (ETDFDL) are studied both theoretically and experimentally in a mixture of Rhodamine B and Acid blue 7 dyes pumped by 532 nm Nd:YAG laser. The behaviour of donor and acceptor DFDL, the dependence of their pulse width and output power on pump power and donor–acceptor concentrations are studied. Experimentally, the tunability is achieved over the spectral range 565–680 nm using a prism dye cell arrangement. The output energy of DFDL is measured at the emission peaks of donor and acceptor for different pump powers and donor–acceptor concentrations. The output pulse of DFDL is found to be as narrow as 40-ps duration, which is nearly 100-fold shorter than the pump pulse. The pulse linewidth is of the order of 0.1 Å.

Direct generation of a tunable nearly transform-limited picosecond pulse in the ultraviolet region using a distributed-feedback dye laser

A new design and the characteristics of operating a distributed-feedback dye laser (DFDL) pumped by the fourth-harmonic emission of a Q-switched Nd:YAG laser are described. An ultraviolet nearly transform-limited picosecond pulse was generated by means of two right-angle prisms in the pumping geometry, and the laser wavelength was continuously tunable from 318 to 369 nm using two dye solutions (BM-terphenyl and BMQ). The application of this DFDL to the lifetime measurement of a fluorescent dye is also presented.

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.

Wide-Wavelength-Range Operation of a Distributed-Feedback Dye Laser with a Plastic Waveguide

A compact distributed-feedback (DFB) dye laser with a plastic waveguide was developed. The DFB operation was attained by the interference of two pumping beams from a frequency-doubled pulsed Nd:YAG laser, and a wavelength range between 560 nm and 994 nm was continuously covered. The dye chip can instantaneously exchanged in any spectrum region. The threshold energy was decreased to the order of 100 µJ with the waveguide configuration. The maximum life of the dye chip was 106 shots.

Nd:YAG laser pumped energy transfer distributed feedback dye laser in Rhodamine 6G and Acid blue 7 dye mixture

The characteristics of Nd:YAG laser pumped energy transfer distributed feedback dye laser (ETDFDL) is studied theoretically and experimentally in a mixture of Rhodamine 6G and Acid blue 7 dyes. The characteristics of donor DFDL, the acceptor DFDL, the dependence of their pulse width and output power on donor–acceptor concentrations, pump power and lengths of the excited region are studied. Experimentally the output energy of DFDL is measured at the emission peak of donor and acceptor for different pump powers, donor, acceptor concentrations and length of the active medium. In addition, the tunability of DFDL emission both in donor and acceptor emission ranges is measured.

Fabrication of a distributed-feedback dye laser with a grating structure in its plastic waveguide.

Two approaches of fabricating grating structures for waveguided plastic dye lasers are described and compared for lasing performance. Rhodamine6G-doped poly(methyl methacrylate) (PMMA) film on a PMMA substrate was used for the waveguide, and a distributed-feedback (DFB) laser operation with a single-propagation mode was demonstrated. The performances of both types of permanent grating structured DFB dye laser were better than those of a DFB dye laser on a plain waveguide with a dynamic grating formed by the interference of two pump beams. Wide tuning range is expected by use of a multistripe DFB laser with different grating pitches.

Multiwavelength distributed-feedback dye laser array and its application to spectroscopy

A multiwavelength, multistripe tunable laser array is proposed, and its application to absorption spectroscopy is demonstrated. Laser waveguides doped with Rhodamine 6 G dye were integrated on a plastic chip, and simultaneous output at different wavelengths was obtained by use of a distributed-feedback technique. A very low threshold of 3 muJ was attained, and spectrally narrowed output (<0.1 nm) was obtained. A scheme for digital spectroscopy is also proposed based on this laser array, and absorption spectroscopy of sodium atoms without wavelength scanning is demonstrated by use of a sodium-vapor cell.

New quenching scheme for the generation of a nearly transform-limited picosecond pulse in a distributed feedback dye laser

We report on the generation of a background-free nearly transform-limited picosecond pulse using a simple quenching scheme in a distributed feedback dye laser. The pulsewidth and spectral linewidth were 65 ps and 10 pm, respectively. The product of these values is 0.650, which is close to the transform limit of 0.441 for a Gaussian pulse.

Rotational level dependence of ground state recovery rates for OH X 2Π(v″=0) in atmospheric pressure flames using the picosecond saturating-pump degenerate four-wave mixing probe technique

We report the first direct measurement of the rotational level dependency of the rate of recovery of initially depleted levels in the electronic ground state X 2Π(v″=0) of OH produced in different flame environments at atmospheric pressure. The initial depopulation of a specific rotational level is accomplished by an intense picosecond pump pulse at 308 nm to partially saturate the electronic A 2Σ–X 2Π(0,0) transition. The recovery of the depleted ground state population then is monitored by probing the same level via the (1,0) band at 283 nm using picosecond degenerate four-wave mixing (DFWM). Both laser wavelengths were derived from the pulse-amplified and frequency doubled output of two independently tunable distributed feedback dye lasers operated with Rh101 and Rh6G in ethanol, respectively, and pumped with the second harmonic of a frequency doubled ps-Nd:YAG laser. It is shown that the rate of repopulation of the depleted ground state levels decreases by 54% and 50% with increasing rotational quantum number, N″, ranging from 2–16 and 2–13 for stoichiometric CH4/air and H2/O2/He flames, respectively. Within experimental error their absolute values in both flames are equal and are not noticeably sensitive to an unequal depletion of the Zeeman sublevels, as created for different polarization configurations of the saturating pump beam and the DFWM probe beams. The rate of (1.8±0.4)×109 s−1 averaged over all rotational transitions investigated is smaller by a factor of 3 than the corresponding average rate of the temporal DFWM signal intensity decay determined by us previously. The rate also is smaller than total depopulation rates obtained in the excited A 2Σ+ state of OH for similar flame conditions.

A tunable picosecond dye laser for use in dioxin analysis.

A distributed-feedback dye laser with a quenching cavity was designed and constructed for generating a tunable picosecond pulse with a narrow spectral linewidth. This nearly transform-limited pulse was succeedingly amplified by a triple-pass off-axis amplifier. The pulse duration and the spectral linewidth were 60 ps and 9.4 pm, respectively. The amplified pulse was frequency-doubled by second-harmonic generation, producing a 0.5-mJ pulse with no background emission. The potential advantage of this laser in the analysis of dioxin based on supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry is discussed.

Development of tunable picosecond dye laser for multiphoton ionization of dioxin precursors in supersonic jet/time-of-flight mass spectrometry.

A distributed-feedback dye laser has been developed for achieving the efficient multiphoton ionization of chlorobenzene and dichlorobenzene, that is, precursor molecules of dioxins. This tunable picosecond laser with a narrow spectral line width, that is, a nearly transform-limited pulse, provides a more efficient ionization than the nanosecond laser, which is currently in use in supersonic jet spectrometry. The advantage of picosecond over nanosecond and femtosecond lasers is also discussed on the basis of the theoretical model reported in a previous paper.

Distributed-feedback sol-gel dye laser tunable in the near ultraviolet

Laser emission in the near ultraviolet region was observed from a distributed-feedback solid-state dye laser based on Exalite 377E dye-doped sol-gel silica slabs. The output performance of the laser was studied in detail. Pumped at 308 nm, wavelength tuning from 367 to 383 nm with the emission linewidth of 80 pm has been achieved. Exalite 377E-doped sol-gel silica distributed feedback laser showed a slope efficiency of 4.4% and a pump energy threshold of approximately 100 μJ (15 mJ/cm2 in energy density). The variation of output energy as a function of the number of pump pulse at 0.5 Hz repetition rate was also investigated.

Organic solid-state distributed feedback dye laser with a nonmorphological modification grating

We report an organic solid-state distributed feedback laser consisting of an organic active layer and a Bragg grating without morphological change. The active layer consists of 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostryl)-4H-pyran as a laser dye, tris(8hydroxyquinoline) aluminum as a host, and poly(methyl methacrylate) as a binder. The threshold and linewidth of the laser are 400 μJ/cm2 and 1.5 nm, respectively. With this laser, the Bragg grating exists out of the active layer and the grating surface is flat, which are very important for device fabrication and electric driving of the laser.

Collisional dependence of polarization spectroscopy with a picosecond laser

The collisional dependence of polarization spectroscopy (PS) with a picosecond-pulse laser is investigated theoretically with a perturbative treatment and experimentally by probing hydroxyl (OH) in a flow cell with a buffer gas of argon. Using a frequency-doubled distributed-feedback dye laser (DFDL), the PS signal strength is monitored as a function of pressure using a nonsaturating pump beam and a saturating pump beam. The collisional dependence of the PS signal is found to decrease significantly with a saturating pump beam. Increasing the flow-cell pressure by a factor of 50 (from 10 torr to 500 torr), the PS signal strength produced with a nonsaturating pump beam decreases by a factor of 18 while that produced with a saturating pump decreases by only a factor of 3. A third-order perturbative (weak-field) approach is used to develop an analytical expression for the PS signal generated by single-mode, exponentially decaying laser pulses. This expression correctly predicts the experimental results acquired with the nonsaturating pump beam. The analytical solution is used to examine the effects of pulse length on the collisional dependence of the weak-field PS signal strength. Results are also presented for a numerical simulation of the time-dependent density matrix equations for the high intensity case.