Signal Gain Coefficient Research Articles

Gain measurement and upconversion analysis in Tm/sup 3+/, Ho/sup 3+/ co-doped alumino-zirco-fluoride glass

The small signal gain coefficients were measured in Tm/sup 3+/,Ho/sup 3+/ co-doped alumino-zirco-fluoride glass. A gain of 15%/cm at 2.05 /spl mu/m was obtained for pump power density of 42 kW/cm/sup 2/. The temperature increase of the glass was found to be more than 150 K with this pump power, which was estimated from a comparison between fluorescence intensities of Tm/sup 3+/ /sup 3/F/sub 4/-/sup 3/H/sub 6/ and Ho/sup 3+/ /sup 5/I/sub 7/-/sup 5/I/sub 8/. An upconversion rate constant of 12.5/spl times/10/sup -17/ cm/sup 3/ sec/sup -1/ from a coupled (Tm/sup 3+/ /sup 3/F/sub 4/, Ho/sup 3+/ /sup 5/I/sub 7/) level to a coupled (Tm/sup 3+/ /sup 3/H/sub 5/, Ho/sup 3+/ /sup 5/I/sub 6/) level was determined by fitting the experimentally obtained gain coefficients to the calculated one which takes into consideration any temperature increase.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Comparison of laser-produced plasma target materials for pumping the 109-nm Xe/sup 2+/ Auger laser

We compared cadmium, copper, gold, and zinc targets to stainless steel for laser-produced plasma pumping the Xe/sup 2+/ 109 nm laser. A unique target geometry allowed us to measure the laser output using two materials under identical conditions. Small signal gain coefficients and maximum output powers are presented for each material relative to stainless steel; we observed a /spl sim/20% improvement in the gain coefficient and a /spl sim/112% improvement in total energy using a cadmium target. This increase probably results from an improved overlap of the laser-produced plasma emission spectrum with the Xe inner shell 4d photoionization cross section, although published data to support this hypothesis are scarce and inconsistent. >

Injection Locking of a Modified-Unstable-Resonator XeCl Laser by Using a Line-Narrowed Hemiconfocal Oscillator

An injection-locked XeCl excimer laser with a modified positive-branch confocal unstable resonator was developed and the output characteristics were investigated. We utilized the hemiconfocal scheme in the line-narrowed oscillator in order to obtain a seed beam with high energy as well as narrow linewidth. In this case we obtained 0.05 cm-1 linewidth with 10 µ J output energy. The maximum output energy of the injection-locked oscillator was 110 mJ, which is 15% greater than that with free-running oscillation. We also presented a new method which can simply measure the power gain of the amplifier, by which the small signal gain coefficient of the amplifier was measured to be 10%/cm.

Theoretical Analysis on Supersonic Flow Chemical Oxygen-Iodine Laser Performances Using an Instantaneous Mixing Assumption.

Numerical simulation of a supersonic flow chemical oxygen-iodine laser is performed and its gain characteristics are studied. It is assumed that the flow is quasi-one-dimensional and the O2-I2 mixing takes place instantaneously at the iodine injector. The numerical results clearly show that the gas cooling by the supersonic expansion is very effective in obtaining high gain. It is shown that a small signal gain coefficient of 1.5∼2 m<-1> is attained downstream of the nozzle exit. It is also shown, however, that the temperature rise due to the chemical reactions which persist in the flow is quite detrimental to the laser performance.

Numerical Simulation of Supersonic Flow CO Chemical Laser Solving Navier-Stokes Equations.

The flow field of a supersonic flow CO chemical laser is simulated solving two-dimensional Navier-Stokes equations, and the effects of viscosity, shock waves and the mixing process on the small signal gain coefficients are studied. The calculated flow pattern agrees very well with the chemiluminescence from the laser cavity which was observed previously. Both the calculation and the experiment show that the O2 streams and the dissociated CS2 streams collide with each other at the nozzle exits, generating oblique shock waves. It is also shown that mixing of the O2 streams and the dissociated CS2 streams is significantly slow, and the temperature and gain distributions in the mixing layer are strongly influenced by the shock waves and expansion waves. The calculated distributions of the small signal gain coefficients along the flow agree fairly well with the measured values in the region near the nozzle exits where the three-dimensional effects are relatively weak.

Soft-x-ray amplification of the Lyman- alpha transition by optical-field-induced ionization.

We report the first observation of amplification of spontaneous emission on the Lyman-\ensuremath{\alpha} transition of hydrogenlike lithium ions by optical-field-induced ionization. Using a subpicosecond KrF laser (0.5 ps, 50 mJ) focused at ${10}^{17}$ W/${\mathrm{cm}}^{2}$, singly ionized lithium ions have been further ionized to fully stripped states, resulting in the population inversion with respect to the ground state of the hydrogenic ions. A small signal gain coefficient of 20 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ was obtained.

Amplification in Ni-like Nb at 204.2 � pumped by a table-top laser

We identified for the first time the 3d94d1S − 3d94p1P line in Ni-like Nb at 204.2 A that was predicted to show gain. When pumped with a train of pulses containing less than 1 J per pulse, significant emission was recorded at 204.2 A following the second and the third pulses. We measured the small signal gain coefficient per Joule of incident laser energy to be 1.49±0.42 cm−1 J−1 for this laser transition, which is higher by several orders of magnitude than that reported for other collisional laser systems in this wavelength range.

Linear regime of time-varying double resonance in a medium with Doppler-broadened spectral lines

A time-varying regime of a double resonance in a system with a common upper level, with Doppler-broadened spectral lines, is described theoretically. The light field with the lower frequency (the signal) is assumed to be weak in comparison with that with the higher frequency (the pump). The nature of the interaction between the fields is determined substantially by the parameter n, which is the square root of the ratio of oscillator strengths in the pump and signal channels. At n > 0.5, and at sufficiently large distances, the resultant optical field is described as a superposition of the fields of a 2π pump pulse and an exponentially growing signal pulse of steady-state shape which is coupled with the pump pulse. The signal gain coefficient is described as a function of the pump frequency and the pump pulse energy by means of a probability integral of complex argument. At n < 0.5, the signal pulse undergoes a pronounced dispersive spreading with increasing distance traversed, and the rate of amplification of this pulse is lower than exponential. The shaping of the signal pulse is studied as a function of the detuning from resonance in the signal and pump channels.

Optical Characteristics of a 3kW DC Discharge-Excited CO Laser.

Optical characteristics of a transverse DC discharge-excited 3-kW CO laser were investigated experimentally. Significant changes of oscillation spectra with gas temperature and a resonator position were observed. The number of oscillation lines for single-line oscillation was about three times as many as normal multi-line oscillation. A novel averaged small signal gain coeffi-cient for the multi-line oscillation, which could be used for the Rigrod's formula, was defined. This is useful to design an optimum resonator also for multi-line oscillation. The small signal gain coefficient increased with decreasing gas temperature and gas pressure. The spatial dis-tribution of the small signal gain coefficient was measured, showing a strong asymmetry effect of DC discharge. The maximum of the averaged small signal gain coefficient was 0.40m-1 and that of a localized small signal gain coefficient was 0.7m-1.

FEL gain parametrization

In this note we discuss simple formulae reproducing the FEL gain in a wide region of small signal gain coefficients.

Numerical calculation of the small signal gain in Er:Ti:LiNbO/sub 3/ channel waveguides

The overlap integral describing the small signal gain coefficient in Er:Ti:LiNbO/sub 3/ channel waveguides is numerically evaluated, and the results are used to discuss the polarization dependence and the influence of the erbium ion distribution. It is shown that bleaching is obtained at a substantially lower pump power for an extraordinarily polarized mode. A study of the influence of the overlap and the mode confinement at different pump bands indicates that the poorer overlap between the pump and signal mode at shorter pump wavelengths can be compensated for by an improved overlap with the erbium ions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effects of Injection of Various Gases on the Gain Characteristics of a Supersonic Flow CO Chemical Laser

Experimental studies are conducted on a supersonic flow CO chemical laser to obtain data on the reaction zone structure and the small signal gain coefficients when various gas additives are injected at the reactant interface. The additives are Ar, O2, N2O and CO. It is shown that the chemiluminescence from the laser cavity and the flow structure do not depend strongly on the kind of injected species, although the injection of gas additives considerably enhances the mixing. On the other hand, the measured small signal gain coefficients depend strongly on the injected species. The injection of O2 leads to the higher gains than that of Ar since the formation of the vibrationally excited CO molecules is promoted. The injection of N2O and CO also raises the gains due to the favorable effects of VV transfer.

Gain characteristics of an Er/sup 3+/-doped multicomponent glass single-mode optical fiber

Experimental results on gain characteristics of an Er/sup 3+/-doped multicomponent glass single-mode optical-fiber amplifier are reported. This amplifier shows a gain spectrum with twin gain peaks of 1.535 and 1.543 mu m, providing a broadened gain bandwidth. The apparent 6-dB gain bandwidth is 12 nm. Furthermore, the signal gain of 17 dB and 15-mW pump power is realized at a signal wavelength of 1.536 mu m, and a signal gain coefficient of 1.4 dB/mW is achieved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gain and saturation measurements in a discharge excited F2 laser using an oscillator amplifier configuration

The small-signal gain coefficient and the saturation intensity of a F2 pulsed discharge molecular laser at 157 nm have been measured using two discharge devices in an oscillator-amplifier configuration. The small signal gain coefficient was measured to be 5.2±0.4% cm−1 at 3 atm total pressure and 1.5 cm electrode spacing and 4.1±0.4% cm−1 at 2 atm total pressure and 2 cm electrode spacing while the values of the saturation intensity were 5 MW/cm2 and 4.6 MW/cm2, respectively.

Amplification Characteristics of a Discharge Excited F2Laser

Abstract The small signal gain coefficient and the saturation intensity of a molecular-fluorine pulsed-discharge laser at 157 nm have been measured using two discharge devices in the oscillator-amplifier configuration. At 3 atm total gas pressure and 1·5 cm electrode spacing the small signal gain coefficient and the saturation intensity of the 3Π2g → 3ΠI2u transition were measured to be 5·2% cm−1 and 5 MW cm−2 respectively.

Investigation on the Theoretical Modeling of a Supersonic Flow CO Chemical Laser

Small signal gain coefficients of a supersonic flow CO chemical laser are calculated using a theoretical model which was developed previously and compared with the corresponding experimental results. It is shown that the model predicts the gain characteristics only qualitatively. The measured small signal gain coefficients are rather small compared with the calculated results. In the present investigation, the theoretical model is improved significantly by modifying the relaxation rate constants and by including the effects of the boundary layers which develop in the optical test section. However, further improvement on the theoretical model is necessary by including the effects of the nozzle boundary layers and shock waves.

Measurements of Small Signal Gain Coefficients of a Supersonic Flow CO Chemical Laser

Small signal gain coefficients of a supersonic flow CO chemical laser are measured using a shock tunnel facility. A high temperature mixture of CS2, CS, S2, S and Ar is produced in a shock tube, where the thermal dissociation of CS, diluted in Ar is accomplished by a reflected shock wave. The shock-heated mixture is exhausted through two-dimensional supersonic nozzles mounted at the end of the tube and mixed with the supersonic streams of O2. Then, the vibrationally excited Co molecules are produced in the mixed streams. In the present paper, the dependence of the small signal gain coefficients on the downstream distance from the nozzle, the plenum conditions and the transition branch is studied. The data obtained in the present experiments are available to examine the propriety of the theoretical model which was developed previously.

Gain, absorption and saturation intensity measurements of an X-ray preionized, discharge pumped XeCl laser

The small signal gain and absorption coefficients of a high uniformity, X-ray preionized XeCl laser have been measured. Their time evolution and wavelength dependence have been simultaneously detected with high resolution. Two distinct estimates of the saturation intensity were obtained by means of a Rigrod-type analysis of the intracavity intensity and by using saturated gain measurements.

Measurements of small signal gain coefficients of a supersonic flow CO chemical laser.

Small signal gain coefficients of a supersonic flow CO chemical laser are measured using a shock tunnel facility. A high temperature mixture of CS2, CS, S2, S and Ar is produced in a shock tube, where the thermal dissociation of CS, diluted in Ar is accomplished by a reflected shock wave. The shock-heated mixture is exhausted through two-dimensional supersonic nozzles mounted at the end of the tube and mixed with the supersonic streams of O2. Then, the vibrationally excited Co molecules are produced in the mixed streams. In the present paper, the dependence of the small signal gain coefficients on the downstream distance from the nozzle, the plenum conditions and the transition branch is studied. The data obtained in the present experiments are available to examine the propriety of the theoretical model which was developed previously.

Investigation on the theoretical modeling of a supersonic flow CO chemical laser.

Small signal gain coefficients of a supersonic flow CO chemical laser are calculated using a theoretical model which was developed previously and compared with the corresponding experimental results. It is shown that the model predicts the gain characteristics only qualitatively. The measured small signal gain coefficients are considerably small compared with the calculated results. In the present investigation, the theoretical model is improved significantly by modifying the relaxation rate constants and including the effects of the boundary layers which develop in the test section. However, further improvement on the theoretical model is necessary by including the effects of the nozzle boundary layers and shock waves.