New designs and simulations of a 10-kW average-power longitudinally pumped dye laser amplifier

New designs of a 10-kW average-power longitudinally pumped dye laser amplifier pumped by a copper laser and its operating simulations are presented. The new designs, which use a center-hole mirror, make it possible to pump longitudinally without dichroic mirrors. The simulations take into consideration the time-dependent excited-state absorption of both the laser and the pump beam. Dye laser amplifiers, with an input dye laser average power of 10 kW, are simulated. The simulation results suggest that a better than 50% extraction efficiency can be obtained with two pump beams of more than 1 kW. The results also suggest that an amplified gain of 10 with an extraction efficiency of approximately 50% can be obtained with the double-pass amplifier.     

Copper vapor laser pumped by pulse-periodic high-frequency discharge

We present the results of numerical experiments considering the physical processes specific to the laser based on self-terminating atomic transitions of copper and study of the output characteristics of this laser numerically. The laser is pumped by trains of high-frequency (10?70 MHz) current oscillations with the repetition rate of 2?30 kHz. Inductive-type electrodeless discharge pumping is regarded. The calculations were carried out for a small set of the specified basic parameters providing a way to partially optimize the performance of the laser over its basic output characteristics and to reveal its features. The feasibility of efficient laser pumping by high-frequency discharge is demonstrated. In our numerical experiments the maximum value of the physical efficiency was about 6% and the maximum average laser output power was as high as 174 W. These values were obtained for a discharge chamber with a volume of 1.7 L.     

All-solid-state tunable DCM dye laser pumped by a diode-pumped Nd:YAG laser

Lasing is observed near 620 nm in a DCM dye doped TiO(2)-content organically modified silicate (ORMOSIL) pumped by frequency-doubled radiation from a diode-pumped Q-switched Nd:YAG laser. The laser wavelength is tunable over 60 nm. A conversion efficiency of 18% is obtained at its central wavelength of 621 nm. The laser output energy has only a 10% reduction after 27,000 pulses at a pump repetition rate of 30 Hz and a pump intensity of 1 J/cm(2). An all-solid-state, compact, long-lifetime, and tunable dye laser has been demonstrated.     

Thermo-optical model of repetitively pumped solid-state lasers

A thermo-optical model describing the cavity stability and TEM00-mode volume of a repetitively pumped solid-state laser is developed and verified experimentally. The model predicts a maximum theoretical TEM00 Gaussian-mode radius in the laser rod. This maximum mode radius is caused by a bifocusing of the cavity mode and is present even in gain-polarized materials that nominally suppress the effect of birefringence on beam polarization. The mode limitation effect is not eliminated by conventional optics and is reduced only marginally by the often-described technique of placing a second identical laser head in the cavity. A maximum mode radius implies a fundamental limit on the TEM00-mode energy that can be extracted from a given laser cavity.     

Fixed-wavelength operation of a copper-laser-pumped dye laser injection seeded by low-power He-Ne lasers

The design and operating characteristics of a dye laser pumped by a 3-W copper-vapor laser (CVL) and injection seeded by low-power (1-5 mW) He-Ne lasers at 633 nm are reported. An extremely simple optical arrangement is used wherein the output mirror of the He-Ne laser and a third mirror form the dye laser cavity. Laser efficiency in fixed-wavelength operation has been investigated for variable CVL pump power, He-Ne injection power and polarization, and cavity output coupling for a standard Rhodamine 590/Rhodamine 640 dye solution. Over 90% of free-running (unseeded) laser power is obtained in fixed-wavelength (seeded) operation at low CVL pump powers (≤1 W), dropping to approximately 60% at 3-W pump power. Maximum CVL pump to dye laser optical conversion efficiency in narrow-band, fixed-wavelength operation at 633 nm was 12%.     

Suppression of amplified spontaneous emission from a four-pass dye laser amplifier

We demonstrate a new design for a four-pass dye laser amplifier that can be used to reduce amplified spontaneous emission (ASE) in the amplifier output beam. Compared with the results obtained from normal operation of the four-pass dye laser amplifier without a frequency-selective device, by using a diffraction grating in the amplifier we can reduce the ASE ratio by a factor in excess of 10 and increase output energy by ~4%. The obtained ASE ratio of the four-pass amplifier system is <1.5%.     

Micromachining of a piezocomposite transducer using a copper vapor laser

A 1-3 piezocomposite transducer with front face dimensions of 2×2 mm has been micromachined using a copper vapor laser. The device consists of PZT5A piezoceramic pillars with a 65-μm pitch suspended in a low viscosity thermosetting polymer. The kerf width is 13 μm, and the transducer thickness is 170 μm, making the device suitable for ultrasonic reception at frequencies close to 10 MHz     

Numerical simulation of the amplification of a short laser pulse by a ytterbium doped amplifier longitudinally pumped by short pump pulses

A simple and original derivation making it possible to analytically compute the performances achievable with an end pumped ytterbium (Yb) amplifier pumped by a pump pulse and seeded by a laser pulse both shorter than the upper-level lifetime is presented. This may be useful when amplifiers or lasers are pumped by a Ti:sapphire laser. The case of a Yb:YAG amplifier is numerically investigated and it is shown that, in these conditions, the resulting efficiency can reach quantum efficiency.     

Atomic vapor filter for two-dimensional Rayleigh imaging experiments with a narrow-band KrF excimer laser

An optical transition of atomic iron can be used to build a two-dimensional absorption filter that operates in the tuning range of a narrow-band KrF excimer laser (0.05-cm(-1) bandwidth). Iron atoms with a number density of 2 × 10(13) cm(-3) are produced by thermal dissociation of iron pentacarbonyl [Fe(CO)(5)]. With this filter it is possible to discriminate Mie and surface-scattered light against Rayleigh scattering. For Rayleigh scattering from the exhaust gas of a methane-air flame at a measured temperature of 1970 K, the ratio of transmission for Rayleigh scattering to transmission for Mie scattering is 16.8. Single-shot scattering from the exhaust gas of a high-pressure burner is presented as an application.     

Oscillation characteristics analysis of transversely and coaxially pumped Ti-diffused Nd:MgO:LiNbO3 waveguide lasers

Abstract

A theoretical analysis of oscillation characteristics is developed for Ti-diffused Nd:MgO:LiNbO₃ waveguide lasers by using the formalism of mode overlap. Simple and explicit expressions in terms of mode sizes are derived for effective mode volume and coupling efficiency between pump mode and laser mode, which are directly proportional to the threshold pump power and slope efficiency, respectively, both for transverse and coaxial pumping considering the spatial distribution of the pump beam and the laser beam. A comparison for the two pumping configuration has shown that the transverse pumping requires much higher input pump power and has much lower slope efficiency than the coaxial pumping. The fundamental transverse mode (TM ₀) oscillation conditions relative to the cavity loss are also discussed for the two pumping configurations.

Indexing terms: Ti-diffused Nd:MgO:LiNbO ₃ waveguide laser, effective mode volume and coupling efficiency, threshold pump power and slope efficiency, transverse and coaxial pumping, single mode oscillation condition.     

Experimental and theoretical investigation of a multipass, plane mirror, femtosecond dye laser amplifier

Femtosecond pulses of a passive mode-locked Rhodamine-6G dye laser are amplified in a double-stage, three-pass, plane mirror, Sulforhodamine-101 amplifier system. Saturable filters (Schott glass RG645 and Malachite Green) are used to suppress amplified spontaneous emission. Input pulses of 110-fs duration are broadened to 240 fs in the amplifier system and recompressed to 75 fs in a prism-pair compressor. Using a 20-Hz Q-switched Nd:YAG pump laser of 50-mJ second-harmonic output energy, we obtained amplified and recompressed pulses of 180-μJ energy at 625 nm starting with 40-pJ input pulses. The small-signal amplification dynamics is studied numerically. Relevant gain dye and saturable filter parameters are derived. The influence of amplified spontaneous emission is analyzed.     

Scaling up of a high average power dye laser amplifier and its new pumping designs

Scaling up of a high average power dye laser amplifier is discussed. Differences in the characteristics between a high average power dye laser amplifier with transverse pumping and longitudinal pumping are presented by a simple theory and simulations. The simulation results for dye laser amplifiers of 10-kW average output power show that longitudinal pumping is as efficient as transverse pumping with the potential of orders of magnitude lower dye flow rate. New pumping designs are also proposed for a dye laser amplifier aimed to achieve high gain with high efficiency to reduce the number of amplifier stages. Simulation results suggest that the new designs, in comparison with a conventional amplifier, can produce several orders of magnitude higher gain without decreasing the conversion efficiency.     

Ultraviolet HeCd laser pumped by a high-frequency electron beam

An electron beam with a large cross section and with a repetition rate of 3×10⁵ pulses per second in a packet has been obtained for the first time. With this beam a HeCd high-pressure laser has been developed and high-frequency lasing on the Cd ion at a wavelength of 325 nm has also been achieved for the first time. Pis’ma Zh. Tekh. Fiz. 23, 44–47 (March 26, 1997)     

Operation of a Ti:sapphire laser pumped by a 499-nm green laser

We report, for the first time, to our knowledge, the operation of a tunable Ti:sapphire laser pumped by a third-order Raman XeCl-H(2) laser system at 499 nm with a 60-ns pulse duration. The slope efficiency is 59% for this laser, producing pulses of 20-ns duration. The highest conversion-energy efficiency obtained is 41%, with an output energy of 1.2 mJ. The tuning range for a single set of cavity mirrors is 680-834 nm and is limited mainly by the mirror reflectivity. This study shows that a combined laser system based on a XeCl excimer laser can offer wavelength diversity.     

Spatial coherence of the generalized diffraction-filtered resonator copper vapor laser

The results of a study on the spatial coherence of a generalized diffraction-filtered resonator (GDFR) copper vapor laser (CVL) for various magnifications are presented. The coherence width and output power are compared with that of unstable resonators (UR's) of equivalent magnifications. It is established, by use of reversal shear interferometry, that the GDFR CVL beam has better spatial coherence and average power characteristics than the UR CVL beam for equivalent resonator magnifications.     

Characteristics of a broadband dye laser using Pyrromethene and Rhodamine dyes

A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full width at half-maximum from 592 to 610?nm was created for the use in a dual-pump broadband coherent anti-Stokes Raman spectroscopy (CARS) system called width increased dual-pump enhanced CARS (WIDECARS). The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes was used in the amplifier dye cell. To create this laser, a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640 and Pyrromethene dyes 597 and 650, as well as mixtures of these dyes.