Pulse properties of a synchronously mode-locked,cavity dumped,picosecond dye laser system

A synchronously mode-locked, cavity-dumped picosecond dye laser is described. The structure and intensity of the picosecond pulses measured under different conditions are reported. It was found that the structure of the pulses from the synchronously pumped dye laser depends critically on the length of the Ar⁺ laser pulses. At the shortest Ar⁺ laser pulses of about 70 ps the dye pulses are as short as 1.1 ps. With Ar⁺ laser pulses of 200 ps the dye laser pulses contains a broad satellite pulse which contains a large fraction of the total intensity. When a cavity dumper is added to the system one gets dye laser pulses 15–20 ps long with a substructure, which indicates incomplete mode-locking. Well mode-locked 1.5–2.0 ps pulses were obtained in the red part of the dye laser action spectrum, i.e. 620–650 nm for R6G, 595–608 nm for R 110 and 657–662 nm for RB, respectively. Addition of mode-locking dyes also improved the pulse quality at some wavelengths.     

Generation of tunable subnanosecond laser pulses with a nitrogen laser pumped dye laser amplifier system

A simple method for generating single tunable subnanosecond dye laser pulses is described. A Rhodamin 6G dye laser is transversely pumped by a subnanosecond UV pulse of a TEA nitrogen laser. The narrowband output of the dye laser is amplified and shortened in a synchronously pumped amplifier. Narrowband pulses with a duration of 30–40 ps (fwhm) and a pulse power of 30 kW are obtained. They are tunable over the range of 580–600 nm.     

Frequency tunability and temporal characteristics of a DAMC distributed feedback dye laser

The frequency tunablity characteristics of a simple prism configuration distributed feedback dye laser (DFDL) pumped by a low pressure nitrogen gas laser are described. Tunability is studied as a function of the refractive index of the dye solution and also as a function of the angle of the interfering beams of the pump laser. The tunability range for the dye studied is from 440 to 480 nm with a spectral width of 0·1 Å and the time duration of the DFDL pulses was 50 ps.     

300 Femtosecond pulses at 497 nanometer generated by an excimer laser pumped cascade of distributed feedback dye lasers

The setup is a cascade of 3 lasers: A competing cavity dye laser pumped by a XeCl excimer laser, followed by two distributed feedback dye lasers. The typical durations of the pulses from the lasers are 100 ps, 5 ps, and 300 fs, respectively. The output pulses at 497 nm are amplified up to 500 MW. The shortest pulse duration obtained was 198 fs.     

Dual picosecond dye lasers synchronously pumped by a mode locked cw yag laser

The performance of a novel dual dye laser system synchronously pumped by the frequency doubled output of a mode-locked CW-YAG laser is evaluated in relation to pulsewidth, pulse substructure, pulse spectral width and timing jitter. The behavior of the system is adequately described by a theoretical model which includes the time dependent gain and losses due to frequency bandwidth, cavity length mismatch and output coupler. The jitter is significantly reduced from that obtained with CW gas laser pumping as a result of the shorter pump pulse (50 ns instead of ≈100 ps). A routine operating condition uses 2-plate birefringen filters, 0.8 W pump power at 532 nm, to yield two 2.0 ps pulses having a cross correlation width of 3.8 ps, and 30 mW average power from each laser.     

Generation of tunable picosecond pulses in the medium infrared by down-conversion in AgGaS2

Picosecond pulses from a mode-locked Nd:YAG laser and a traveling-wave dye laser are mixed in an AgGaS₂ crystal to generate pulses at the difference frequency. The dye laser is tunable between 1200 nm and 1460 nm resulting in a tuning range of the parametric pulses from 3.9 μm to 9.4 μm. The spectral bandwidth is quite narrow. A value of Δ?=6.5 cm^-1 was measured which is constant over the whole tuning range. Several percent of the Nd:YAG laser photons are converted to infrared photons. Pump pulses of 21 ps give parametric pulses of 8 ps.     

Excimer-laser-pumped ps-dye laser

Generation of single dye laser pulses of 12 ps pulse width (FWHM) and 1.2 mJ pulse energy is described using only one XeCl-excimer laser as pump source. At 1 Hz pulse repetition rate the stability of amplitude and pulse width of these pulses is excellent.     

Subnanosecond amplified spontaneous emission pulses by a nitrogen pumped dye laser

Pulses of 100 ps duration and peak power up to 100 kW are obtained with a dye laser pumped by an atmospheric pressure nitrogen laser of 0.5 ns duration. The shortening of the dye laser pulses is attributed to amplified spontaneous emission.     

High power subpicosecond pulse generation from a synchronously pumped dye laser combined with an external compressor

A new scheme of subpicosecond pulse generation based on a dye laser is described. Output pulses of 15 ps from a rhodamine-6G laser pumped synchronously by a frequency-double mode-locked Nd: YAG laser are compressed into 0.8 ps pulses of 2 MW by two passes of saturable absorber (DODCI) and saturable amplifier (rhodamine-6G). The technique is useful for generating widely tunable, high power repetitive subpicosecond pulses.     

A short resonator dye laser pumped by a travelling wave N2-laser

A tunable dye laser is described, which is pumped by 300 ps pulses from a travelling wave N₂-laser. Due to the short resonator length pulses with only 50 ps duration are emitted.     

Mode-locking of cw dye laser using externally modulated pumping laser

A new mode-locking method of tunable dye laser is described. This simple and practical method requires only an external intensity modulator to the pumping source. After the simple analytical considerations, the experimental work was done using an Ar laser pumped Rhodamin 6G dye laser and an acousto-optic modulator. As results, stable continuous trains of mode-locked pulses were obtained throughout in the ordinary lasing range 570–630 nm. The pulse width, estimated to be 30–50 ps by SHG autocorrelation measurements, is limited by the bandwidth of Lyot filter used. It is also shown experimentally that this method can be applicable for the suppression of the growth of double pulses in passive mode-locking with saturable absorber (DODCI).     

Tunable picosecond pulses from a short-cavity dye laser under ultra-high pressure using diamond-anvil cell

It is demonstrated that broadly tunable picosecond pulses are generated from a dye laser of very short cavity utilizing a diamond-anvil cell, which operates at pressures up to 10 GPa. The pulses as short as 5 ps are obtained from the rhodamine 6G dye laser pumped by a frequency-doubled Q-switched Nd: YAG laser. The way of tuning is based on the pressure induced shift of the emission peak of the dye. The laser is tunable over 20 nm by changing the pressure of the cell within 4 GPa.     

Simple generation of 400–700 nm picosecond dye laser pulses with nanosecond laser pumping

New results in the experimental study of the spectro-temporal selection (STS) method to produce picosecond dye laser pulses are presented. Adjustability of the picosecond pulse wavelength, possibility of extension of the STS method to different dyes and to UV pump wavelength, stability of the output pulse duration and intensity, and the concentration effect on pulse duration, are reported for the first time. From these results, production of high power picosecond (50–100 ps) dye laser pulses spectrally adjustable between 400 and 700 nm is obtained with a standard nanosecond pump laser, in a compact and simple device.     

Rapid scanning autocorrelator for measurements of picosecond laser pulses

A rapid scanning autocorrelation interferometer for measurements of picosecond laser pulses is described which uses a rotating prism as scanning device in one arm of the interferometer to permit continuous display of autocorrelation traces at audio frequencies on an oscilloscope. Scan widths of more than 500 ps with high linearity can be achieved. Autocorrelation measurements of picosecond pulses from a synchronously pumped mode-locked dye laser are presented.     

A novel pumping arrangement for tunable single picosecond pulse generation with a N2 laser pumped distributed feedback dye laser

A novel excitation scheme for a N₂ laser pumped distributed feedback dye laser is described. The dye laser generates 80–100 ps pulses with a time-bandwidth product better than 0.6. Several tuning methods are proposed, and a number are investigated experimentally. Continuous tuning over a 50 Å range without mode-hopping is demonstrated.     

Nonlinear optical properties of an azo-based dye irradiated by picosecond and nanosecond laser pulses

The nonlinear optical properties of an azo-based dye were investigated using Z-scan technique employing 38 ps pulses at 532 and 1064 nm, and 6 ns laser pulses at 532 nm. Large nonlinear absorption and nonlinear refraction were observed at both ps and ns 532 nm in the azoic dye. When excited at ps 1064 nm, this dye displayed a large two-photon absorption cross-section (σ₂=1810 GM). Meanwhile, the optical nonlinearity mechanism was discussed in terms of molecular structure, excitation wavelength, and pulse width.     

Efficient amplification of sub-picosecond pulses of a non-CW dye laser

Efficient amplification in a dye laser amplifier is investigated theoretically and experimentally. A five-level rate equation approach is considered including rotational relaxation of the dye molecules. The effects of the pump pulse duration and of the parameters of the input pulse are discussed. The results are compared with experimental data for 0.5 ps pulses of a pulsed dye laser. Conversion efficiencies >10% are achieved for a single pass amplifier using Nd:YAG pump pulses of 2 ns while an effective fluorescence lifetime of 1.7±0.2 ns is determined for the gain medium rhodamine 6G. The triple pass amplifier stage of the laser system achieves an energy conversion of 4% with 40 J output pulses.     

Narrow linewidth,short pulse operation of a nitrogen-laser-pumped dye laser

Subnanosecond pulses, of 0.02 Å bandwidth, are generated by a nitrogen-laser-pumped dye laser with intracavity double prism beam expander, and holographic diffraction grating. Pulsewidths to below 450 ps, with peak powers greater than 10 kW, are obtained from 200 kW, 3.5 ns pumping pulses.     

A microchip-laser-pumped DFB-polymer-dye laser

A miniaturized, high repetition rate, picosecond all solid state photo-induced distributed feedback (DFB) polymer-dye laser is described by applying a passively Q-switched and frequency-doubled Cr⁴⁺:Nd³⁺:YAG-microchip laser (pulse width Δτ=540 ps, repetition rate ν=3 kHz, pump energy E_pump=0.15 μJ) as a pump source. A poly-methylmethacrylate film doped with rhodamine B dye serves as active medium. The DFB-laser pulses are temporally and spectrally characterized, and the stability of the thin polymer/dye film at high repetition rates is analyzed. The shortest DFB-laser pulses obtained have a duration of 11 ps. After the emission of 350000 pulses the intensity of the DFB-laser output has decreased by a factor of two and the pulse duration has increased by a factor of 1.2. For single DFB-laser pulses of 20-ps duration the spectral bandwidth is measured to be Δλ=0.03 nm, which is only 0.005 nm above the calculated Fourier limit assuming a Gaussian profile for the temporal shape of the pulses. Coarse wavelength tuning of the DFB laser between 590 and 619 nm is done by turning the prism. Additionally, a fine tuning of the DFB-polymer-laser wavelength is achieved by changing the temperature of the polymer/dye layer (=-0.05 nm/°C) in the range from 20 to 40 °C. Received: 1 March 2001 / Revised version: 23 May 2001 / Published online: 18 July 2001     

Transient behaviour of pulsed dye lasers

Some aspects of the transient behaviour of pulsed dye lasers are investigated both theoretically and experimentally. Relaxation oscillations induced in the output from a dye cell by an external reflector have been observed and explained, using a rate equation approximation to the physical situation in the dye cell. These oscillations are shown to play an important part in the generation of short laser pulses from long cavity dye lasers. Finally, it is proposed that 10 ps pulses can be obtained from conventional dye lasers pumped by 100 ps pulses from a high-pressure nitrogen laser.