Spectral purity of pulsed dye lasers

High-spectral purity of pulsed dye lasers is required by many experiments. Unfortunately, the dye laser output is usually accompanied by a spectrally broadband background of spontaneous emission (ASE). We have carried out detailed studies of the ASE background using a dye laser operating with an oscillator, pre- and main amplifier.Dedicated to Prof. Dr. Herbert Welling on the occasion of his 60th birthday     

A subpicosecond dye laser pumped by a xenon ion laser

A pulsed xenon ion laser has been used to pump a rhodamine 6G dye laser utilizing a ring resonator. The dye laser has been passively mode-locked; a pulsewidth of 0.5 ps and a 50 kW peak power have been obtained.Work partly supported by Italian C.N.R.     

A novel picosecond distributed feedback dye laser arrangement for excimer laser pumping

A distributed feedback dye laser arrangement is described which can generate pulses at the subharmonic wavelengths of the main excimer laser lines (308 nm, 248 nm, 193 nm, etc.). The laser can be pumped with broadband lasers, such as the XeCl^* laserpumped dye laser with competing cavities. The laser is designed to be used as a part of a femtosecond, terawatt excimer laser system.     

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.     

Ultrafast ytterbium-doped bulk lasers and laser amplifiers

We review recent achievements with ultrafast bulk lasers and amplifiers based on Yb:YAG and Yb:glass. Special attention is paid to those aspects of the quasi-three-level nature of these gain media that are important for short-pulse generation. The potential of Yb-doped media for efficient short-pulse generation and amplification is compared to their Nd-doped counterparts. Received: 4 January 1999 / Revised version: 15 March 1999 / Published online: 26 May 1999     

Theory of the synchronously pumped picosecond dye laser

The circulation of a synchronously mode locked dye laser pulse in a linear cavity configuration containing a dye cell as an active medium and a bandwidth-limiting element is treated. The condition that the pulse shape reproduces after each cavity round-trip provides a nonlinear integro-differential equation for the steady-state pulse shape. For the solution of this equation an approximate method, not limited to small pulse energies, is given and the pulse duration, intensity, energy, asymmetry of the pulse shape, stable regions and other interesting parameters are discussed.     

A novel double grazing-incidence single-mode dye laser

Using only one grating and plane parallel glass plate in a novel double-grazing incidence configuration, twice higher dispersion is obtained, resulting in twofold narrowing of the single-pass linewidth, compared to the single grazing-incidence scheme. This laser cavity design features several-times improved signal-to-noise ratio and enhanced stability. Single-mode operation of 210±50 MHz is demonstrated.     

Passive mode locking of the continuous wave DCM dye laser

The first passive mode locking of the continuous wave (cw) DCM dye laser is reported. Subpicosecond pulses as short as 0.68 ps were obtained over the spectral region from 655 to 673 nm from a simple linear cavity with no dispersion optimisation. The dye 1,3 Diethyl 4,2 quinolythiacarbocyanine iodide (DQTCI) was used as the saturable absorber.     

Subpicosecond,widely tunable distributed feedback dye laser

A simple, achromatic, widely tunable distributed feedback dye laser arrangement is described. It makes use of a microscope objective, which images a transmission grating into the active medium. With this arrangement subpicosecond operation and broad tunability (400–760 nm) is reported.     

Comparative study of spectral narrowing of a pulsed Ti:Sapphire laser using pulsed and CW injection seeding

We report a comparative study of a pulsed as well as continuous-wave (cw) injection seeding of a Ti:Sapphire laser pumped by aQ-switched frequency-doubled Nd³⁺:YAG laser for achieving narrow spectral bandwidth. The results have indicated that the Ti:Sapphire laser using either a pulsed or a cw injection seeding could achieve efficient energy extraction in a narrow spectral bandwidth. In the case of pulsed injection seeding, the injection energy required for the complete injection seeding critically depended upon the timing of the Ti:Sapphire laser with respect to the delayed onset of the slave laser. On the other hand, in the case of cw injection seeding, the spectral bandwidth of the Ti:Sapphire laser was efficiently narrowed down to approximately 0.01 cm^–1 with an injection power of less than 1 mW. In both types of injection seeding, characteristics observed experimentally were compared with those obtained by a numerical simulation code based on the one-dimensional rate-equation model.     

Spatially-hole-burned distributed feedback dye laser produced tunable single picosecond pulses

A new type of distributed feedback dye laser is described in which the Bragg grating is formed by spatial hole-burning. With a simple excimer laser pumped arrangement, single high stability 6 ps pulses were generated. The pulses were nearly transformlimited and were 33 times shorter than the rise time of the pulse which created the Bragg grating.on leave from JATE University, Department of Experimental Physics, Dóm tér 9, H-6720 Szeged, Hungary     

Astigmatically compensated cw dye laser resonators using lenses

The compensation of the astigmatism of Brewster-angled dye cells can be performed with lenses as well as with spherical mirrors. The advantages of cw dye laser resonators using lenses lie in the linear configuration of the optics and the convenient adjustability of astigmatism compensation. An output efficiency of 30% already at 1.6W pumping power has been observed. In addition, ring laser resonators with lenses have been investigated and they delivered up to 400 mW single mode power in travelling wave operation at less than 2 W pumping power.     

Gain depletion due to amplified spontaneous emission in multi-pass laser amplifiers

Calculations of the effects of amplified spontaneous emission (ASE) in laser amplifiers designed to amplify sub-picosecond pulses are presented. A one-dimensional code is used with some simple approximations to account for aspect ratio variation in cases of cylindrical symmetry. Gain depletion due to ASE is compared for various multi-pass geometries. Optimisation for short pulse amplification of a telescopic, beam-expanding, 4-pass amplifier is considered.On leave from Electrotechnical Laboratory, Tsukuba, Ibaraki, Japan     

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.     

An analysis of the free-electron laser small-signal gain in a resonator gaussian mode

A simplified analysis of the small-signal gain in the presence of a Gaussian mode is presented for several undulator designs. For a filamentary electron beam, an analytical expression of the gain is obtained and found to be in agreement with previous work and with computer simulations. A general expression of the small-signal gain for the optical klystron FEL is given.     

Performance studies of a pulsed HF laser with a sliding discharge plasma cathode

The plasma electrode design concept is applied for the first time to an HF laser. The discharge along the surface of a dielectric (sliding discharge) is used as a plasma cathode for the main laser discharge. The laser operates at atmospheric pressure with a gas mixture of He/SF₆/C₃H₈. Details are presented on the efficiency of energy transfer, the dependence of laser performance on circuit parameters, gas mixture, relative energy loading and time delay between the plasma electrode and main discharges. The F atom production rate is estimated from the linear dependence of the output energy on the electric charge passed through the discharge. Output energies of 600 mJ were obtained at 1.6% efficiency from a small active discharge of 108 cm₃ volume and 38 cm length, while the maximum specific input and output energies were 370 J/1 and 5.7 J/1, respectively. These values compare favourably with those reported in the literature for non-chain-reaction-type gas mixtures at 1 atm pressure and demonstrate that the plasma electrode design is a powerful scheme for developing gas-discharge lasers.     

Off-axis amplification scheme for short-pulse amplifiers

A novel geometry is presented for transversally pumped, short-pulse dye and discharge-pumped excimer amplifiers. Significant increase of the homogeneity and of the cross-section of the active medium seen by the short pulses is accomplished by proper choice of the incident angle of the beam to be amplified. The proposed scheme makes it possible to substitute the sophisticated wide aperture, homogeneously pumped amplifiers by standard devices.     

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.     

Two-wavelength self-seeded pulsed tunable laser

A compact self-seeded pulsed tunable laser is described. Its optical cavity comprises a diffraction grating, operating at a grazing angle of incidence as a spectral selector and narrow-band spectral gate. The grating couples two partially overlapping laser channels: a highly selective master laser and a nonselective slave laser. Due to the implemented efficient intracavity self-seeding the laser emits spectrally pure single-longitudinal-mode radiation at two independently tunable wavelengths, with an efficiency and output energy that are typical for nonselective lasers. Results of the experimental investigation of the laser’s output characteristics are presented. Received: 12 March 2001 / Revised version: 10 December 2001 / Published online: 7 February 2002     

Properties of an ultrashort-pumped near-IR high gain dye amplifier

An ultra-short-pumped optical dye amplifier operating in the near-IR (720 nm) has been developed. We present an experimental study of the input–output characteristics of this simple device in a traveling wave collinear configuration. In essence, the combined effects of the ultrafast nature of the anisotropy induced by the exciting laser pulse along with the short transit time across the length of the cell allow for optimal output conditions given the number of molecules in the active volume. Two distinct amplifying regimes have been observed depending on photon density. Typical gain values of 10⁴ of the narrow bandwidth (∼9 nm) subpicosecond output signal were measured. The 8-mm² beam cross section enables this photon amplifier to be utilized in time-gated imaging applications. Received: 12 December 2001 / Revised version: 13 May 2002 / Published online: 25 October 2002 RID="*" ID="*"Corresponding author. Fax: +1-819/564-5442, E-mail: Daniel.Houde@Usherbrooke.ca