Theoretical study of a new energy extraction scheme of a chemically pumped pulsed iodine laser amplifier

A new energy extraction scheme of a chemically pumped pulsed large-scale iodine laser based on a high-pressure pulsed singlet oxygen generator is proposed. In previous investigations only low-pressure oxygen generators have been considered. Since they require a high iodine density for an efficient amplifier operation, the lifetime of the stored energy is correspondingly small and thus only small-sized iodine amplifiers appear to be technically feasible. We found, however, that when the singlet oxygen is generated at high-pressure, the iodine density required can be considerably reduced so that the lifetime of the stored energy becomes sufficiently long to fill up large amplifier cells. A numerical model is developed and the extractable energy is theoretically estimated. It is shown that 0.2J/1·pass can be extracted when an input pulse of 20 ns duration (FWHM) and 1 J/cm² fluence is fed into the amplifying medium.     

Small signal gain measurements in a small scale HF overtone laser

The overtone gain medium of a small-scale HF overtone laser was probed using a sub-Doppler tunable diode laser. Two-dimensional spatially resolved small signal gain and temperature maps were generated for several ro-vibrational transitions in the HF (v=2→v=0) overtone band. Our results compare well with previous measurements of the overtone gain in a similar HF laser device. Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +1-505/846-4807, E-mail: kevin.hewett@kirtland.af.mil     

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     

Experiment and modeling of a small-scale,supersonic chemical oxygen-iodine laser

We report on detailed experiment and modeling of a small-scale, supersonic chemical oxygen-iodine laser. The laser has a 5 cm long active medium and utilizes a simple sparger-type O₂(¹ ) chemical generator and a medium-size pumping system. A grid nozzle is used for iodine injection and supersonic expansion. 25 W of cw laser emission at 1.315 µm are obtained in the present experiments. The small size and the simple structure of the laser system and its stable operation for long times make it a convenient tool for studying parameters important for high-power supersonic iodine lasers and for comparison to model calculations. The lasing power is studied as a function of the molar flow rates of the various reagents, and conditions are found for optimal operation. Good agreement is found between the experimental results and calculations based on a simple one-dimensional semi-empirical model, previously developed in our laboratory and modified in the present work. The model is used to predict optimal values for parameters affecting the laser performance that are difficult to examine in the present experimental system.     

Efficient distributed feedback solid state dye laser with a dynamic grating

We present the first operation of a distributed feedback solid state dye laser with a dynamic, pump-induced grating. Broadly tunable, narrow band operation in the region of 616 nm (604–649 nm) has been demonstrated with perylene red laser dye doped in poly(methyl methacrylate) (PMMA), when pumped with a frequency doubled Nd:YAG laser. Conversion efficiencies of 20%, corresponding to 35% optical-to-optical efficiency, have been measured. The laser bandwidth was between 0.01 and 0.04 nm, and smooth tuning over more than 200 GHz has been demonstrated. Received: 29 March 1999 / Published online: 24 June 1999     

Formation of diffraction-free beams by laser generation of conical radiation in a Kerr medium

Received: 16 June 1998     

Spectral properties of a Tm:Ho:YAG laser in active mirror configuration

3+ :Ho³⁺:YAG laser is operated in active mirror configuration. This laser is characterised by a rather thin crystal (3 mm thickness in our experiment) and a very short resonator (about 3.2 mm). Therefore this laser is well suited for operation in a single longitudinal mode. Single-frequency operation is demonstrated with and without an intracavity etalon. It is further shown that single-frequency emission is reached with a stable cw emission. With a slight detuning of the outcoupling mirror, spiking can be achieved, resulting in an emission on different lines. The assignment of the observed laser lines to the known transitions between Stark sublevels of the ⁵I₇ and the ⁵I₈ level is discussed and compared with predictions in the literature. Received: 2 December 1997     

Bichromatic pulsed source in the visible and infrared

A source of bichromatic coherent radiation is described with independent tunability in wavelength, energy and pulse duration. The system is able to deliver pulses in the visible to infrared region with possible extension into the ultraviolet. Pulse durations can be tailored to be from 15 ps to 310 fs with collimated beam fluences of several mJ/cm². Received: 28 January 2002 / Revised version: 24 April 2002 / Published online: 12 July 2002     

A frequency-doubled pulsed chemical oxygen-iodine laser

The intracavity second-harmonic generation of pulsed chemical oxygen-iodine laser radiation was investigated. A pulsed chemical oxygen-iodine laser with a maximum output energy of 6.14 mJ was used. The second-harmonic output of 0.5 mJ was demonstrated using a lithium iodate crystal. The conversion efficiency of 8% was limited by intracavity losses. Numerical simulation predicts that a conversion efficiency of 75% can be obtained with 1% intracavity losses.     

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     

Ultrahigh-efficiency TEM<Subscript>00</Subscript> diode-side-pumped Nd:YVO<Subscript>4</Subscript> laser

Ultrahigh-efficiency TEM₀₀ operation is demonstrated in a diode-pumped Nd:YVO₄ laser in a bounce amplifier geometry using a specially designed astigmatically optimised cavity configuration. Optical efficiency >68% is demonstrated and up to 27.1 W of output power for multimode operation. For single-mode TEM₀₀ operation, an output power of 23.1 W for 39.5 W of diode pumping was produced with beam propagation parameters of M_x ²=1.3 and M_y ²=1.1. Received: 10 October 2002 / Revised version: 9 December 2002 / Published online: 19 March 2003 RID="*" ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: a.minassian@ic.ac.uk     

On the performance of an ArF and a KrF laser as a function of the preionisation timing and the excitation mode

An X-ray preionised ArF and KrF excimer laser has been studied with three different spiker-sustainer excitation circuits. We observed large differences in the laser performance, when the preionisation delay timing was varied on a nanosecond timescale. The behaviour of both lasers was found to be equivalent. The observations can be understood by considering the effect of the discharge excitation technique on the preionisation process. An excitation mode with a prepulse well above the steady-state voltage V_SS with a subsequent reversed overshoot voltage for initiating the discharge, in combination with a well-timed preionisation pulse is found to give the best results. Optimum output energies of 50 mJ with ArF and 175 mJ with KrF were obtained from an active volume of 60×1.5×1.2 cm in the so-called swing mode, with the preionisation applied 60 ns before the discharge breakdown. Received: 23 February 1999 / Revised version: 4 June 1999 / Published online: 16 September 1999     

A new 3D multipass amplifier based on Nd:YAG or Nd:YVO4 crystals

We report on new, simple and efficient multipass amplifiers using prisms or corner cubes to perform several passes in different planes of incidence. This scheme provides an optimised overlap between the signal passes and the pumped volume. We investigated our amplification geometry with Nd:YAG and Nd:YVO₄ crystals: the use of a low-doped (0.3%) Nd:YVO₄ crystal allowed better thermal behaviour and higher performance. We amplified a pulsed microlaser (110 mW of average power at 1064 nm) and obtained a diffraction-limited output beam with an average power of 5.7 W for 15 W of pump power and a small-signal gain of 56 dB in a six-pass configuration. Received: 5 March 2002 / Revised version: 6 June 2002 / Published online: 25 September 2002 RID="*" ID="*"Corresponding author. Fax: +33-1/6935-8700, E-mail: Sebastien.forget@iota.u-psud.fr     

Dye laser pumped, continuous-wave KTP optical parametric oscillators

4 (KTP) optical parametric oscillators (OPOs) with pump and idler resonant cavities. With a linear two-mirror cavity the pump power at threshold was 70 mW. The single-frequency signal and idler output wavelengths were tuned in the range of 1025 to 1040 nm and 1250 to 1380 nm by tuning the dye laser in the range of 565 to 588 nm. With a dual three-mirror cavity the threshold was 135 mW. Pumped by 500 mW of 578 nm radiation the 1040 nm single-frequency signal wave output power was 84 mW. Power and frequency stable operation with a spectral bandwidth of less than 9 MHz was obtained by piezo-electrically locking the length of the pump resonant cavity to the dye laser wavelength. Similar performance was achieved by placing the idler resonant OPO inside the resonator of the dye laser. With this system power stable and single-frequency operation was achieved with a spectral bandwidth of less than 11 MHz for the idler wave. Received: 3 February 1998/Revised version: 9 March 1998     

Lasing performance of a chemical oxygen iodine laser (COIL) with advanced ejector-nozzle banks

Experimental results have demonstrated that the use of ejector-nozzle concepts can allow to achieve simultaneously high chemical efficiency and high pressure recovery in a chemical oxygen iodine laser. The estimated small-signal gain of the gain medium generated by these nozzle banks was from 0.5 to 0.8 %/cm. In laser experiments with all nozzle banks (NB-1–NB-5), Pitot pressures of the order of 80 Torr and Mach numbers of ∼2 in the cavity-mixing chamber have been achieved. The geometry of a given ejector-nozzle bank and gas-flow conditions affect the power extraction and chemical efficiency. The main factors for high efficiency and high power are small mixing scale, high area for the oxygen flow, dilution of chlorine by helium, and the arrangement of nozzles. A chemical efficiency of 25% at a power level of ∼900 W was obtained for NB-1 having the smallest mixing scale, parallel injection of all flows, and dilution of oxygen by helium. The highest power of ∼1.2 kW with a chemical efficiency of 19.5% and 160 W/cm² of specific output power was achieved with NB-5 having the largest area for the oxygen flow and dilution of oxygen by helium. Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +7-8462/355-600, E-mail: nikolaev@fian.smr.ru     

Seven-terawatt Ti:sapphire laser system operating at 50 Hz with high beam quality for laser Compton femtosecond X-ray generation

We present a 7-TW Ti:sapphire laser system operating at 50 Hz for laser Compton femtosecond X-ray generation. This laser system delivers 8.4 W of average output power at a repetition rate of 50 Hz with a pulse width of 24 fs. It demonstrates successful management using a dynamically stable resonator in the regenerative amplifier and compensation for thermal lensing by a convex mirror in a ring-type four-pass power amplifier. We also present the results of closed-loop corrections for distorted wavefronts of amplified and compressed laser pulses, using an adaptive optical system consisting of a Shack–Hartmann-type wavefront sensor and a deformable mirror. This closed-loop correction results in dramatic improvements, reducing wavefront distortions below 0.05 λ rms. Received: 31 October 2002 / Revised version: 3 March 2003 / Published online: 5 May 2003 RID="*" ID="*"Corresponding author. Fax: +81-298/61-3349, E-mail: ito@festa.or.jp     

Tunable and high-energy Q-switched operation of an alexandrite slave ring laser

Narrow bandwith tunable Q-switched operation of an alexandrite oscillator was used for injection-locking of a high-energy alexandrite slave ring laser. Pulses with up to 600 mJ in energy over a 600 cm^–1 tuning range were obtained.     

Table-top KrF amplifier delivering 270 fs output pulses with over 9 W average power at 300 Hz

Applying the combination of a solid-state Ti:Sa laser system and a newly developed wide-aperture, discharge-pumped KrF amplifier, output pulses with over 9 W average power at 300 Hz have been achieved in a single output beam. The frequency-tripled seed pulses of the Ti:Sa system – delivering approximately 10 μJ energy at 248 nm – were amplified to over 30 mJ using a 3-pass off-axis amplification scheme. The optical set-up has been fitted to the amplifier’s parameters, and stored-energy measurements were carried out with different parameters in order to optimize the operational conditions of the device for the highest average power. Received: 10 June 2002 / Published online: 25 September 2002 RID="*" ID="*"Corresponding author. Fax: +49-551/503-599, E-mail: jbekesi@llg.gwdg.de     

Single picosecond UV pulse generation by mode-locking of an excimer laser-pumped dye laser

A single picosecond ultraviolet pulse has been generated based on mode-locking of a dye laser pumped by a long pulse XeCl laser to serve as the input source for a high-power ps KrF laser system. A short-pulse uv dye laser (BBQ) pumped by an additional XeCl laser was used to selectively amplify a single pulse from a mode-locked pulse train with the pulse separation of 3.2 ns. The amplified single pulse was frequency-doubled to 248 nm with the pulse duration of 20 ps.     

Review on diode-pumped alkali vapor laser

Diode-pumped alkali vapor lasers (DPAL) are attracted much attention during recent years for its numerous potential applications. Development of DPAL is reviewed in this paper. The key techniques of DPAL are summarized and analyzed in detail, including the interactions between buffer gas and alkali vapor, pumping structure and power scaling magnification. Novel techniques used in DPAL are discussed, such as hydrocarbon-free DPAL and unstable cavity with transverse pumping. Blue-violet lasers by frequency doubling of DPAL are also introduced specifically. In addition, potential applications and the prospects of DPAL are concluded briefly.