Single Laser Line Research Articles

Nd:LNA laser optical pumping of 4He: Application to space magnetometers

We have observed Hanle signals and n=0, p=1 parametric resonances of 23S1 metastable helium atoms in a discharge cell by optically pumping the helium atoms with a tunable Nd:LNA laser. These resonances were used to construct a sensitive magnetometer for the measurement of very small magnetic fields. Since magnetometer sensitivity is proportional to the slope of the parametric resonance signal (signal amplitude divided by linewidth), the slopes for single-line laser pumping were compared with similar quantities obtained from conventional helium lamp pumping. Laser pumping yielded 45 times greater slopes with comparable power requirements, thus establishing the potential for developing ultrasensitive resonance magnetometers using single-line laser pumping.

Effects of translational and rotational nonequilibrium on cw chemical laser performance

A previous model used to describe cw chemical laser performance is generalized to include rotational as well as translational nonequilibria. The resultant equations are simplified by the realistic assumption that translational and rotational relaxation rates are fast compared with convection, chemical pumping, and collisional deactivation rates. As a consequence, translational and rotational relaxation are in equilibrium with stimulated emission. A further simplification is introduced by the assumption |1-(R(t)/R(r))|(Delta nu (h)/Delta nu (d) << 1, where R(t)/R(r) is the ratio of translational to rotational relaxation rates, and Delta nu (h)/Delta nu (d) is the ratio of homogeneous to Doppler widths. The resultant system of equations is independent of rotational relaxation. An amplifier solution is presented that predicts saturation effects in accord with experiments. Fabry-Perot oscillator solutions are also presented for a multiline saturated laser and a partly saturated single-line laser. The present results provide a basis for simplification of numerical codes. It is concluded that a reasonable first estimate for cw chemical laser performance can be obtained by assuming rotational equilibrium and translational nonequilibrium.

Efficient multi and single line atomic fluorine lasers

Intense multi- and single-line laser operation is reported from semiconductively preionised atomic fluorine lasers employing an optimised capacitor transfer excitation circuitry. The performance and spectral characteristics of these lasers are discussed and compared to the characteristics of previously described atomic fluorine lasers. The efficiency of one of these lasers described, at optimum conditions, is reaching a value as high as 0.14%. To the best of our knowledge, this is the highest efficiency reported up date, for an atomic fluorine laser.

Frequency measurement of the solitary ethyl alcohol laser line

We measured the frequency, the relative polarization and the pump frequency offset of the single FIR laser line obtained by optically pumping ethyl alcohol C2H5OH with a cw CO2 laser.

Excitation ahead of shock fronts in krypton measured by single line laser absorption

The number densities of the metastable 5s[1 1/2]2 state and the 5s[1 1/2]1 state of krypton ahead of shock fronts have been determined from the measured absorption of single line laser radiation. Shocks with Mach numbers from 12 to 21 were investigated at preshock pressures from 0.7 to 2.7 kPa. An exponential rise of this excitation precursor having time constants of about 8 ws is found. The metastable concentration atM = 20 is about 10 ppm. The experimental results agree within an order of magnitude with published model predictions for argon and xenon shocks.

Emission spectrum of a CO2laser with an intracavity diffraction selector

Selection of a single laser line was considered for CO2 lasers with nonselective resonators and with resonators which include a diffraction selector. A method was developed for calculating numerically the lasing spectrum of CO2 lasers having selective resonators: this method enables the spectra to be analyzed over a wide range of operating conditions. The results of experiments performed were in good agreement with the calculations.

New method for measuring extremely low optical absorptions

A new highly sensitive method is described for the measurement of optical absorption and its wavelength dependence in extremely low loss materials (e.g. starting materials for optical fibres). The optical absorption — as distinct from scattering losses — is measured calorimetrically at low temperatures via the temperature rise due to the absorbed heat. Low temperature as compared with room temperature calorimetry is several orders of magnitude more sensitive due to the drastically decreased specific heat and the higher resolution of the temperature measurements. We have measured an optical absorption coefficient as low as 3 dB km −1 (7 × 10 −6 cm −1) in a Suprasil I glass rod of only 5 cm in length. In principle, by our method absorption coefficients even smaller than 10 −6 cm −1 can be determined in a sample of the same length. Since the optical power necessary for this method amounts to only a few mW no single strong laser lines are required as in room temperature calorimetry and also low power light sources which are continuously tunable can be used. Our method is also sensitive enough to distinguish between absorption in the bulk and at the surfaces. Measurements on Suprasil I samples show an absorption peak around 600 nm probably due to OH-impurities in the bulk and a background absorption caused by dissipative processes at the two surfaces.

Optically pumped continuous Bi 2 and Te 2 lasers

Continuous laser oscillation of optically pumped Bi 2 and Te 2 molecules was achieved. By pumping with a single argon laser line more than 80 Te 2 laser lines in the range of 550 nm to 660 nm were observed. For Bi 2 conversion efficiences of 10% and multiline output powers up to 350 mW were obtained. Some properties and operating conditions for these new dimer lasers are discussed.

Photographic recording of the emission spectrum of a single-pulse CO2laser by parametric conversion in a proustite crystal

The emission spectrum of a single-pulse transverse-discharge CO2 laser was recorded using just one pulse. This was done by parametric conversion of the infrared output radiation of this laser to the sensitivity range of photographic materials. The conversion took place in a proustite crystal pumped by a ruby laser. The width of the conversion band was ~1 μ in the wavelength range 10.6 μ and the energy conversion efficiency was 3×10−3. The minimum energy which could be detected in a single CO2 laser line was 0.25 mJ for a spectral resolution of 0.3 cm−1.

The distribution function of photoexcited electrons in semiconductors subject to laser illumination

The steady-state form of the distribution function of electrons in the conduction band of a semiconductor, when the electrons are photoexcited from an impurity level by one or two monochromatic laser beams, is analysed for non-polar acoustic and for both non-polar and polar optical phonon scattering. A single laser line does not alter the Maxwellian distribution, but inverts the population near the band edge. Two laser lines induce non-Maxwellian elements into the distribution function whose character depends upon the laser bandwidths relative to the bandwidth for acoustic phonon scattering. Small bandwidths give rise to spikes in the distribution, but bandwidths comparable to the range of frequencies involved in acoustic phonon scattering may produce, in the absence of strong optical phonon scattering, profound deviations from the Maxwellian form. Numerical solutions of the Boltzmann equation for a few illustrative cases are presented.

Pulsed HF Laser Holographic Interferometry

Two-dimensional holographic interferometry has been accomplished at wavelengths near 3 microm. The source is a pulsed hydrogen fluoride oscillator-amplifier system. Transverse excitation is achieved with a fast bank discharging into a simple electrode configuration. The spatial detector is a thin film of bismuth, exposed by local evaporation by a single line of the HF laser emission spectrum. Double exposure interferograms covering areas up to ~10 cm(2) in the object plane have been obtained with single-line laser energies of less than a joule.

Experimental dependence of two-photon absorption efficiency on statistical properties of laser light

The fluorescence intensity excited by two-photon absorption of the 514.5 nm argon laser line has been investigated for various oxasol derivatives. The fluorescence intensity was dependent on the statistical properties of the 514.5 nm argon laser line and was a factor 1.52-1.86 larger for absorption of a multifrequency laser line than in the case of a single frequency laser line.

Cw single-line CO laser on the v = 1 → v = 0 band

cw single-line laser oscillation has been achieved on the P(9), P(10), and P(11) transitions in the v = 1 → v = 0 band of CO. The observations were made on a conventional electrical discharge slow-flow device filled with a mixture of He, N2, Xe, and CO.