Superradiant Laser Research Articles

A very short OPFIR superradiant laser

A very short OPFIR superradiant laser was studied theoretically and experimentally. The density matrix equations of a three-level quantum system for NH3 gas was solved for the gains of the FIR signal and the IR signal in the very short OPFIRL system. The output characteristics of the OPFIR superradiant laser were calculated numercally. A curve showing the relation between the length of the sampe tube of the OFFIRL and the corresponding optimum pressure was obtained. In our experiment, a 10cm OPFIRL and a 5cm OPFIRL were constructed and operated successfully. The output characteristics were meassured and the calculated results were verified.

Dynamical conflict between raman and optical pumping processes, both in the MIR and FIR emissions, in a superradiant NH3 laser

The processes which determine the spontaneous emission in ammonia gas pumped by a CO2 laser are investigated. We demonstrate that the FIR emission is dominant and the MIR emission is conditioned by this effect. We have also observed that the CO2 emission mode and the collisions with a buffer gas have a great influence on the laser process. Some new lines have been produced and assigned.

Classical and quantum treatment of amplifier and superradiant free-electron laser dynamics

We describe the quantum initiation for free-electron lasers and derive the collective instability threshold starting from the electron position and the momentum quantum fluctuations. We obtain the Glauber distribution P(α) for the field, that is, a displaced Gaussian, which represents the superposition of a coherent field (stimulated emission) and an incoherent one (spontaneous emission). We define and discuss the concept of superradiance for free-electron lasers, both in a classical framework and at a quantum statistical level, stating the conditions under which the effect should be observed.

Superradiant dye solution laser with two-photon picosecond optical pumping

A superradiant (superfluorescent) dye solution laser with two-photon picosecond pumping was constructed for the first time. A preliminary study was made of the principal characteristics of the output radiation of this laser which performed up-conversion of the frequency of the pump radiation. The physical mechanisms governing the operation of lasers of this type were analyzed.

Increasing the brightness of a superradiant uv nitrogen laser

A retroreflection system is described that produced a 64-fold increase in the brightness of a N/sub 2/ laser. (AIP)

Gain saturation effects in a superradiant XeF laser

Strong superradiant emission from a XeF TEA laser optimized for maximum gain operation is described. A small signal gain of 0.37 cm −1 has been measured by varying the length of the active medium. Pulse shortening effects, ascribed to saturation induced gain oscillations, are evident in the output pulse shape.

Coherence and beam geometry of a superradiant dye laser

This paper reports the observation of a well defined radiation mode emitted from a superradiant dye laser pumped by a pulsed nitrogen laser. Beam geometry and spatial coherence of the dye laser are studied in connection with the pumping geometry. It is shown that under favorable pumping conditions most of the excited molecules radiate into the same spatial mode by stimulated emission. The associated mode structure is also calculated based on a model of a properly phased dipole distribution. The calculated emission pattern reproduces the observed far field pattern closely.

Laser action in krypton fluoride and N2 in a fast pin laser

Fifty μJ of uv laser energy in a krypton fluoride excimer laser and 4.5 mJ of uv energy in the superradiant nitrogen laser have been obtained in a fast pin discharge using transmission-line excitation techniques.

Tunable superradiant emission from a planar dye laser

A new, simple scheme to tune a double-pass, superradiant dye laser is reported. A planar cell with a thickness below 100 microm filled with a highly concentrated (4-5 x 10(-)-M/liter) solution of Rhodamine 6G in ethanol is used. An unsaturated gain value of 1.7 cm(-) has been measured with flashlamp pumping, and the amplifier has been found to operate at a well saturated regime. Smooth laser linewidths ranging from broadband, gain narrowed values of 10 nm to narrowband values of 8 GHz have been achieved by using appropriate frequency dispersive feedback elements and suitable cell thickness. A 5-GHz output has been observed with a 25-microm gap cell. The absence of a resonant cavity avoids modal structure and ensures improved frequency and intensity stability. The reported configuration should be scalable up as far as output energy is concerned. Simultaneous two-wavelength operation is possible. Pumping with a frequency-doubled Nd-laser should allow a further reduction of the usable cell thickness with narrower output bandwidths.

Far-infrared super-radiant laser action in heavy water

Super-radiant output from D 2O pumped by up to 10 J pulses of the CO 2 P(32), R(12) and R(22) laser transitions gave measured energies of 330 mJ, 240 mJ and 120 mJ respectively. In the R(12) case the emission was at 361 μm and 385 μm in the intensity ratio of 1:2, the average power was 1–2 MW and peak powers of about 5 MW were measured.

Configurations for high-power pulsed CH3F 496-μm lasers

The generation of high-power pulses from optically pumped CH3F at 496 μm was investigated in a simple one-mirror superradiant laser, a dielectric waveguide laser, and an oscillator-amplifier configuration. All three configurations were found to produce linearily polarized temporally smooth pulses with a lowest-order transverse intensity profile. The superradiant mode produced approximately twice the output of the oscillator-amplifier mode while the cavity always produced the lowest output. A maximum FIR output of 2.3 kW corresponding to an energy conversion efficiency of 0.35% was obtained which is 35% of the theoretical maximum.

Far-infrared superradiant laser action in methyl fluoride

Submillimeter laser pulses exceeding 1-MW power have been generated superradiantly in CH3F gas pumped by 200 MW of 9.55-μ CO2 TEA laser radiation. When far-infrared output was restricted to operation on the 496 line alone, 0.5 MW was achieved within a bandwidth of 100 MHz.

Near-infrared dye laser emission from ultraviolet nitrogen-laser-pumped dye solutions

We report superradiant near-IR dye laser emission, with peak of emission in the 690-930-nm range, from nitrogen-laser ( \lambda = 337 -nm)-pumped dye solutions including aluminum phthalocyanine chloride and seven polymethine cyanine dyes.

High Power Optically Pumped Far Infrared Lasers

Intense superradiant laser action in the far infrared (FIR) has been observed in several gases optically pumped with a CO/sub 2/ transversely excited atmospheric-pressure (TEA) laser. A maximum FIR power of 100 kW was observed from CH/sub 3/F at 496 mu m. Characteristics of the system and possibilities of scaling to higher powers are also discussed.

Further evidence of dimer emission from superradiant travelling wave laser of concentrated aqueous solution of rhodamine 6G and B

The new emission bands of the superradiant travelling-wave lasers from concentrated aqueous rhodamine B and rhodamine 6G were quenched by the addition of a small amount of triton X-100. This further supports the hypothesis that the new emission band could be due to the dimers of the dyes.

Superradiant emission at 5106, 5700, and 5782 Å in pulsed copper iodide discharges

Superradiant laser emission at 5106, 5700, and 5782 Å is reported from pulsed discharges in copper iodide vapor at temperatures near 600°C. This conclusion is supported by pulse shortening of the visible emission and a marked increase in the relative visible intensity compared to the copper resonance radiation as the critical temperature range is approached. Electrical dissociation of the copper iodide, electron impact excitation of the copper atoms, and radiation trapping of the 3248- and 3274-Å resonance lines are proposed as the principal inversion mechanisms. Below <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim450\deg</tex> C, where insufficient copper iodide is vaporized to provide resonance trapping, the upper laser level lifetimes are ∼10 ns, whereas at higher temperatures trapping is complete and the effective <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2</inf> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</inf> lifetimes are 615 and 370 ns, respectively. The reservoir temperature at which stimulated emission is observed is in good agreement with calculations of the threshold ground-state copper densities required for resonance trapping. These experiments indicate that practical copper laser systems operating at substantially reduced temperatures can be developed provided instabilities in the copper iodide discharges can be overcome.

Superradiant picosecond laser emission from transversely pumped dye solutions

Superradiant picosecond laser emission has been obtained from dye solutions transversely pumped with the second harmonic of a mode-locked ruby laser. This provides a convinient scheme for obtaining ultrashot dye laser pulses in the visible range of the spectrum.

Parametric study of superradiant laser action in molecular nitrogen excited by a high-energy electron beam

Excitation of the molecular nitrogen laser by a high-energy electron beam is shown to be controlled by E/p in a manner similar to other forms of electrical excitation. The electric field is produced by the increasing net current. Both the beam current and the nitrogen pressure for maximum laser power are found to vary directly as the laser diameter for the two diameters considered. Scaling of laser power with length is found to be limited by the high optical gain of the laser transition which causes the active medium to become superradiant before the full length is excited.

Recombination in light-pulse excited silicon at medium-high carrier concentration levels

Recombination in silicon has been studied by exciting gold on n_type silicon surface-barrier diodes. The excitation was short light pulses from a superradiant laser and the diodes were reverse biased at more than the depletion voltage. The energy in the light pulse was monitored and a comparison was made with the measured charge in the resulting current pulse in the diode. In this way recombination losses could be determined. At high light intensities (1010−6×1011 photons/cm2 in a 1-nsec excitation pulse) superlinear recombination of carriers is observed, causing the collected charge to decrease by up to 50% of the value expected from the observed quantum detection efficiency of approximately unity observed at lower levels. This is attributed to recombination near the surface at the high carrier densities reached, both during the light pulse and during the charge reservoir time tA (the time for extraction of space-charge-limited current from the cathode). This causes the recombined charge to increase with both light intensity and tA. The observed recombination may be of practical importance when operating semiconductor detectors at high light levels or with heavily ionizing nuclear particles.

Spectral narrowing in double-pass superradiant lasers

Analytical results are obtained for the important spectral narrowing and rebroadening behavior of mirrorless and single-mirror superradiant laser amplifiers including the effects of both the right and left traveling waves. These results make possible a straightforward quantitative interpretation of experimental data.