Showing papers on "Laser linewidth published in 1968"
TL;DR: In this article, an accurate measurement of the Raman scattering cross section of the 992 cm−1 line of benzene was made directly using a cw argon laser as the light source.
Abstract: An accurate measurement has been made of the Raman scattering cross section of the 992 cm−1 line of benzene. Previous cross-section measurements were either made indirectly by comparison with the Rayleigh scattering cross section or by using a pulsed light source. In the present measurement the cross section was measured directly using a cw argon laser as the light source. The results give a peak differential cross section of 1.05(±0.08)×10−29 cm2 per molecule, per steradian, per wavenumber of linewidth, per plane of polarization for an incident light beam with a wavelength of 4880 A, and a linewidth of 2.3 (±0.05) cm−1. Allowing for the wavelength dependence and the optical dispersion, our total cross section agrees to within 20% with two other results. The Raman scattering cross sections of other liquids have been measured by use of the 992 cm−1 line of benzene as a reference. These values, together with details of the absolute cross-section measurement, are presented.
131 citations
TL;DR: In this article, a microscopically correct Hamiltonian with Bose operators of light and Fermi operators of the optically active electrons in the medium is considered and the effect of these heatbaths is taken into account in a quantum mechanically consistent fashion.
Abstract: Our treatment is based on a microscopically correct Hamiltonian which contains the Bose-operators of the light modes and the Fermi-operators of the optically active electrons in the medium. The coupling between modes and atoms is taken from quantum-electrodynamics. Besides that, the light modes may interact with external “heat baths” like the mirrors, scattering centers etc., while the atoms interact with lattice vibrations, incoherent light fields etc. Using recently developed methods the effect of these heatbaths is taken into account in a quantum mechanically consistent fashion. In the present paper we apply quantum mechanical Langevin equations for the field and electron operators which contain dissipation and fluctuation terms. The elimination of the electron operators by an iteration procedure finally leaves us with a set of coupled nonlinear field equations which are shown to be quantum mechanically consistent. They are solved in the Heisenberg picture below threshold by linearization and well above threshold by quantum mechanical quasi-linearization. The solutions show that the line width of the signal mode below threshold is due to the vacuum fluctuations in the idler and vice versa, whereas the thermal noise of the resonator and the spontaneous emission noise of the medium may be neglected. Above threshold the linewidth is caused by the undamped diffusion of the phase difference between signal and idler, to which the vacuum fluctuations of both modes contribute in equal parts. The phase sum of both modes adiabatically follows the slow phase diffusion of the external pump light, produced by a laser, and therefore contributes to the linewidth too. Well above threshold the amplitudes are stable. Correlation and cross-correlation functions of their small residual fluctuations are calculated.
128 citations
TL;DR: In this article, the position and linewidth of the main resonance in the spin-wave spectra of 80% Ni−20% Fe evaporated films 150 to 3200 A at frequencies from 0.8 to 4.0 GHz, at room temperature and with the static magnetic field perpendicular to the film plane have been performed.
Abstract: Measurements of the position and linewidth of the main resonance in the spin‐wave spectra of 80% Ni‐20% Fe evaporated films 150 to 3200 A thick at frequencies from 0.8 to 4.0 GHz, at room temperature and with the static magnetic field perpendicular to the film plane have been performed. The center field for resonance was independent of thickness and consistent with the Kittel resonance condition for the uniform precession. The linewidth was about 30 Oe (measured as the field separation of inflection points on the absorption curve), independent of film thickness and frequency. The linewidth data have been compared to previous data for resonance with the static field parallel to the film plane and interpreted in terms of relaxation processes for the uniform precession. In general, frequency‐swept linewidths, not field‐swept linewidths, are proportional to the relaxation rate and are the quantities which should be compared. The frequency‐swept linewidth for perpendicular resonance is equal to that obtained for parallel resonance in films thinner than 500 A. This result indicates that two‐magnon scattering between the uniform precession mode and spin‐wave states for which the exchange energy term is large (wavenumber k appreciably different from zero) does not contribute to the perpendicular resonance linewidth and is the origin of the linewidth increase with thickness for parallel resonance. It appears that scattering to states with k≈0 and exchange conductivity broadening are the most reasonable sources for the residual 30 Oe linewidth.
93 citations
TL;DR: In this article, a family of sealed-off, single-frequency, TEM 00q -mode CO 2 lasers with output powers up to 15 watts was described and their short-term frequency stability was investigated.
Abstract: This paper describes a family of sealed-off, single-frequency, TEM 00q -mode CO 2 lasers with output powers up to 15 watts. Short-term frequency stability[1],[2] measurements of the beat note of two free-running lasers in typical laboratory setups are discussed thereafter. The preliminary measurements indicate a short-term stability of about 5 parts in 1012for an observation time of 0.05 seconds, and about 5 parts in 1013, disregarding the discrete spectral lines resulting from 60-Hz modulation by power supply ripple. One or two orders-of-magnitude improvement is predicted, leading to the possibility of measuring the linewidth limit imposed by quantum noise.
62 citations
TL;DR: In this paper, the asymptotic behavior of ultrasonic attenuation near the critical points of isotropic Heisenberg magnets is studied with the help of the scaling law ideas.
56 citations
TL;DR: In this article, light scattering from two-magnon excitations in RbMn${\mathrm{F}}_{3} was observed and the shape and polarization of the spectrum were compared with theoretical predictions of Elliott et al.
Abstract: We report the observation of light scattering from two-magnon excitations in RbMn${\mathrm{F}}_{3}$. The shape and polarization of the spectrum are compared with theoretical predictions of Elliott et al. and confirm the importance of magnon-magnon interactions. Temperature dependences of the frequency and linewidth of the two-magnon spectrum are also given.
51 citations
TL;DR: In this paper, a mode-locked Nd:YAG laser is described which produces pulses 30 psec in duration at a 2.6 nsec repetition rate at a locking range over ≈35 GHz, although the free-running oscillating linewidth is only about 10 GHz.
Abstract: A mode‐locked Nd:YAG laser is described which produces pulses 30 psec in duration at a 2.6 nsec repetition rate. The locking range extends over ≈35 GHz, although the free‐running oscillating linewidth is only about 10 GHz. Also discussed is the behavior of the phase of the pulsetrain with changing cavity length. The measured phase shifts provide a means for frequency stabilizing the mode‐locked laser. A technique for inducing nondamped relaxation oscillations which modulate the mode‐locked pulsetrain is described.
49 citations
TL;DR: In this article, a quantum mechanical theory of superconducting tunnel junctions including noise is developed and applied to the calculation of the frequency pulling, linewidth of the radiation, and voltage power spectrum in the ac Josephson effect.
Abstract: A quantum mechanical theory of superconducting tunnel junctions including noise is developed. The theory is applied to the calculation of the frequency pulling, linewidth of the radiation, and voltage power spectrum in the ac Josephson effect.
47 citations
TL;DR: The minimum obtainable pulse duration for a mode-locked ruby laser is the reciprocal linewidth, which amounts to approximately 2 ps as mentioned in this paper, and the present correspondence describes a system achieving this limit.
Abstract: The minimum obtainable pulse duration for a mode-locked ruby laser is the reciprocal linewidth, which amounts to approximately 2 ps. The present correspondence describes a system achieving this limit.
46 citations
01 Oct 1968
TL;DR: In this paper, a Lamb-dip stabilized laser that operates at 1.15259 μ in pure low-pressure (0.12-torr) neon is described, and the saturation maximum at molecular line center produces an emission feature whose linewidth is less than 5 parts in 109.
Abstract: Stabilized lasers usually exhibit systematic frequency shifts larger than their resettability; this phenomenon is well illustrated by the 6328-A helium-neon laser. We describe a Lamb-dip stabilized laser that operates at 1.15259 μ in pure low-pressure (0.12-torr) neon. Optical heterodyne experiments indicate an accuracy exceeding 1 part in 109; short and medium term precisions of 1 : 1010are easily achieved. We also report the successful operation of a wavelength reference based on the saturation of sharp molecular absorption. In the first experiments the P(7) line of the v 3 band of methane is saturated inside the cavity of a 3.39-μ helium-neon laser. The saturation maximum at molecular line center produces an "emission" feature whose linewidth is less than 5 parts in 109. The pressure-induced offset is expected to be less than 1 part in 1010. Size scaling is expected to improve these first results by at least 1 decade.
46 citations
TL;DR: An optical linewidth of 20 Hz of laser light scattered by spherical particles undergoing Brownian motion has been measured experimentally by photon-counting statistics using the theory of the intensity-fluctuation distribution of Gaussian-Lorentzian light as mentioned in this paper.
Abstract: An optical linewidth of 20 Hz of laser light scattered by spherical particles undergoing Brownian motion has been measured experimentally by photon-counting statistics using the theory of the intensity-fluctuation distribution of Gaussian-Lorentzian light.
TL;DR: In this paper, the authors measured the polycrystalline linewidth ΔHpoly at X-band and room temperature and determined from single crystals the first-order anisotropy constant, K 1.5.
Abstract: On the garnets Y3−2xCa2xFe5−x−yVxInyO12, with x ≤ 1.5 and y ≤ 0.5, we have measured the polycrystalline linewidth ΔHpoly at X‐band and room temperature and have determined from single crystals the first‐order anisotropy constant, K1. Since the single‐crystal linewidth of these materials is but a few oersteds and the polycrystalline samples had less than 1% porosity and second phase, the observed ΔHpoly is attributed to anisotropy broadening, according to Schlomann. The introduction of indium reduces both | K1 | and ΔHpoly, for example: x = 0.63y = 0TC = 280°C4πMs = 650 GΔHpoly = 98 Oex = 0.80y = 0.50TC = 155°C4πMs = 750 GΔHpoly = 8 Oe. That last value is the lowest yet reported in the range of T ≈ 23 TC.
TL;DR: In this article, the profiles of several electron-impact-broadened Ar II lines emitted by a high-density Z-pinch plasma have been recorded using a rapid scanning Fabry-Perot interferometer.
Abstract: The profiles of several electron-impact-broadened Ar II lines emitted by a high-density Z-pinch plasma have been recorded using a rapid scanning Fabry-Perot interferometer. The plasma electron density was determined by Fabry-Perot interferometry in conjunction with a laser light source. Measurement of the relative intensity of an Ar III line and a nearby Ar II line enabled the plasma temperature to be estimated. The measured Ar II linewidths are compared with those predicted by the impact approximation using straight-line perturber orbits and neglecting lower-state broadening. In all cases studied the ratio of experimental to theoretical linewidth was at least a factor of 2. The cause of these large discrepancies, and the implications of the results for other emitting species, are to be discussed in a subsequent paper.
TL;DR: In this article, the authors reduced the linewidth by taking the fluorescent light, not from all atoms in the assembly, but from a sample biased in favour of those which have survived as excited atoms for times longer than the average.
Abstract: The linewidth in level-crossing experiments as normally carried out is the sum of the natural widths of the levels concerned. We have reduced the linewidth by taking the fluorescent light, not from all atoms in the assembly, but from a sample biased in favour of those which have survived as excited atoms for times longer than the average. This was achieved by pulse techniques. Improved resolution was obtained of the components on the wing of the zero-field level-crossing curve for the level 3 2P3/2 in 23Na. The values obtained for the hyperfine-coupling constants are a = 185 ± 040 MHz, b = 30 ± 06 MHz, in agreement with values found in double-resonance experiments. The present values do not represent the limit of the method, since the experiment was designed to investigate the technique, not to make precision measurements. A theoretical analysis of the method reveals that level-crossing curves obtained by this technique may, in certain circumstances, have undesirable satellites. It is shown how the line profile may be controlled and improved without too great a sacrifice in statistical accuracy.
TL;DR: In this article, the experimental considerations for obtaining phonon attenuation in solids by Brillouin scattering are described, and measurements of room temperature damping of longitudinal hypersonic waves in α-quartz, fused silica, and calcium fluoride are reported.
Abstract: In this paper some of the experimental considerations for obtaining phonon attenuation in solids by Brillouin scattering are described. Measurements of room temperature damping of longitudinal hypersonic waves in α-quartz, fused silica, and calcium fluoride are reported. The observed phonon frequency and linewidth for backward scattering of 6328-A light in these solids is typically ∼ 30 GHz and ∼ 30 MHz (FWHM), respectively. This corresponds to a damping length of \sim 60 \mu , which is inaccessible by conventional ultrasonics techniques.
TL;DR: In this article, it was shown that, both for a four-and three-level laser, one can get as much power at the second harmonic wavelength as that which can be obtained at the laser wavelength.
Abstract: The optimum coupling for intracavity second harmonic generation has been theoretically studied. It has been shown that, both for a four- and three-level laser, one can get as much power at the second harmonic wavelength as that which can be obtained at the laser wavelength. It is also shown that, for both cases, an optimum value for lw/w_{0} exists, where l is the nonlinear crystal length, and w and w 0 are the spot sizes of the laser beam, respectively, in the laser material and in the nonlinear crystal.
TL;DR: In this article, the authors measured the off-resonance loss in polycrystalline YIG on samples with a controlled (and generally rather large) porosity, which can conveniently be expressed in terms of an equivalent linewidth, which is a function of the dc magnetic field strength.
Abstract: The off‐resonance loss has been measured in polycrystalline YIG on samples with a controlled (and generally rather large) porosity. The results can conveniently be expressed in terms of an equivalent line‐width, which is a function of the dc magnetic field strength. It is defined as the width that an absorption peak with Lorentzian profile would have if the off‐resonance absorption of this reference profile at a given dc field matches the actually observed absorption. The equivalent linewidth of polycrystals is in most cases much smaller away from resonance than it is near resonance. For YIG the equivalent linewidth at X‐band is approx 10 Oe both at low and high dc fields but rises to 50–600 Oe (depending upon the porosity) in the vicinity of resonance. The experimental results are compared with theoretical predictions. based upon the assumption that the line broadening is primarily caused by inhomogeneity of the local saturation magnetization. It is shown that the linewidth, the magnetic hardness coeffic...
Patent•
06 Nov 1968
TL;DR: In this paper, a gas laser oscillator is coupled to one or more glass laser amplifiers to produce a high intensity and high coherence output which is matched to the peak of the fluorescent emission of the glass laser.
Abstract: A gas laser oscillator optically coupled to one or more glass laser amplifiers is provided. A high output from the gas laser is optically coupled to the single lowest order mode of the first stage of the glass amplifier. By matching the output of the gas laser to the peak of the fluorescent emission of the glass laser an amplified output results which output has high intensity and high coherence.
TL;DR: The standard equations of thin film optics are applied to multiplate resonant reflectors of the kind used with ruby lasers and the numerical results show considerable disagreement with predictions based on approximate theory.
Abstract: The standard equations of thin film optics are applied to multiplate resonant reflectors of the kind used with ruby lasers. The numerical results show considerable disagreement with predictions based on approximate theory. A design is proposed that gives high reflectivity and is insensitive to thickness errors.
TL;DR: In this article, multiple photon echoes were observed in Cs vapour at 8521 A. The measured homogeneous linewidth of the transition corresponds to the spontaneous emission rate.
TL;DR: In this paper, light field-induced saturation peaks in the velocity distribution inside a 0.63-μ He-Ne gas laser were investigated by measuring the resultant frequency-dependent single-pass gain reduction of an additional 1.15-μ he-Ne laser beam.
Abstract: Light-field-induced saturation peaks in the Ne 2p_{4} velocity distribution inside a 0.63-μ He-Ne gas laser are investigated by measuring the resultant frequency-dependent single-pass gain reduction of an additional 1.15-μ He-Ne laser beam.
TL;DR: In this article, the linewidth W has been computed for various absorber thicknesses, assuming that both the source and absorbing material have the natural linwidth Γ.
TL;DR: In this article, it is shown that a second line ωqr that is regressively connected to ωpq is examined in a double resonance experiment, and a similar hole appears in an exactly corresponding region of the line profile, due to the disturbance of the spin population on the common level q. This has been called burning a hole in the line.
Abstract: In a high‐resolution nuclear magnetic resonance spectrum where the dominant line‐broadening influence is the spatial inhomogeneity of the magnetic field, it is possible to impose a sufficiently weak rf field (H2) on a given line ωpq such that saturation is localized in a restricted region of the sample volume. This has been called “burning a hole” in the line. When a second line ωqr that is regressively connected to ωpq is examined in a double resonance experiment, a similar hole appears in an exactly corresponding region of the line profile, due to the disturbance of the spin population on the common level q. This correlation, which arises from the intramolecular nature of the coupling, forms the basis of a technique for measuring frequency separations with a precision that is not primarily limited by the inhomogeneous linewidth. Experimental evidence suggests a reliability of ±1 mHz. The persistence of this effect down to rf levels as low as γH2 / 2π = 0.005 Hz distinguishes it from the well‐known coher...
TL;DR: In this article, the ferromagnetic linewidth, spin-wave anisotropy, and crystalline anisotropic properties of CdCr 2 Se 4 were investigated when doped with Ag.
TL;DR: In this article, spontaneous and stimulated Raman emission in liquids with various Raman linewidths under short pulses excitation was observed, showing the absence of self-trapping and Brillouin stimulated scattering.
Abstract: Observation of spontaneous and stimulated Raman emission in liquids with various Raman linewidths under short pulses excitation shows the absence of self-trapping and Brillouin stimulated scattering, and the normal behavior of unperturbed stimulated Raman emission. The transient effect in liquids with small linewidths makes possible a determination of the linewidth of the laser light, and the duration and intensity of the pulses.
TL;DR: In this article, the conduction electron polarization in the paramagnetic state of dilute alloys of Co and Fe in a host matrix of platinum has been investigated by observing the nuclear magnetic resonance of the platinum host.
Abstract: We have performed an investigation of the conduction‐electron polarization in the paramagnetic state of dilute alloys of Co and Fe in a host matrix of platinum. This has been done by observing the nuclear magnetic resonance of the platinum host. Our measurements of Knight shift, linewidth, and relaxation time have been made as functions of impurity concentration (0.005–0.1 at. %), temperature (1.4°–300°K), and magnetic field (4–22 kG). We find that for small values of H/T the strength of the interaction between the conduction electrons and the local moments increases linearly with H/T. For higher values of H/T, but before saturation of the Brillouin function is expected to set in, we see a saturation of the linewidth with increasing 1/T, but not as a function of increasing H. We find the net shift of the center of gravity of the line is zero with respect to the Knight shift of pure platinum metal, and that the linewidth increases linearly with impurity concentration. These results provide evidence for int...
IBM1
TL;DR: In this paper, a simplified theory was presented which treated the problem as a four-wave parametric interaction, and accounts for such experimental details as the doublet stucture of the violet light and the fact that the components of the doublets have different intensities.
Abstract: Two simultaneous laser pulses incident on a cell of potassium vapor at 350°C generate an intense (1-kW) beam of violet light at about 4000 A. The incident pulses are a 2-MW ruby beam and a 300-kW ruby-generated Stokes beam nearly resonant with the potassium 4P3/2- 4S1/2transition. A simplified theory is presented which treats the problem as a four-wave parametric interaction, and accounts for such experimental details as the doublet stucture of the violet light and the fact that the components of the doublet have different intensities.
TL;DR: In this article, a gallium arsenide (GSA) was made in a configuration that allows intense ionization to be produced at 78°K in material having initial electron densities of the order of 5 \times 10^{17} cm-3 above a certain threshold ionization density.
Abstract: High-field domains passing through n -type gallium arsenide pulsed above a critical field produce electron-hole pairs by impact ionization, resulting in emission of recombination radiation of band gap energy. Specimens have been made in a configuration that allows intense ionization to be produced at 78°K in material having initial electron densities of the order of 5 \times 10^{17} cm-3Above a certain threshold ionization density, stimulated emission occurs; the linewidth is of the order of 30 A and emission is mainly within an angle of 7 degrees to the normal to the plane parallel polished faces of the specimen. The threshold current varies little with temperature up to 170°K and above this increases linearly. At currents above the threshold, the spectrum broadens somewhat; the output power is measured to be about 3 watts. The near-field pattern shows that lasing occurs over small separated areas that vary in location from pulse to pulse. Overall power efficiency of the device is low; if, however, only the lasing areas are considered, the efficiency comes much nearer to the theoretical maximum which, it is argued, is about 5 percent. Time dependence of the spectral distribution is complicated and evidence is given to show that carrier heating is an important phenomenon. The lasing process is similar to that occurring in a junction diode laser; some points of difference are discussed. The output frequently shows an unexplained strong polarization.
TL;DR: In this article, the authors studied the linear response of a laser medium to a rectangular pulse signal input, both theoretically and experimentally, and derived the pressure dependence in a mixture of CO 2, N 2, H 6 of 1:0.88:4.
Abstract: As part of a general program of research on time response of a laser medium to optical transients, we have studied the linear (small-signal) response to a rectangular pulse signal input, both theoretically and experimentally. The theory for the case of Lorentzian homogeneously and Gaussian inhomogeneously broadened transitions has been developed using a two-level density matrix formulation. The results are negligibly different for the two broadening mechanisms for an amplifying medium, where the line center contribution is most important. The step response of a laser is measured experimentally and the bandwidth of the medium is deduced. Its pressure dependence in a mixture of CO 2 , N 2 , H 6 of 1:0.88:4.53 is determined.
TL;DR: In this article, the linewidth of the Rayleigh scattered light from flexible polymers is calculated on the basis of the Rouse model, and the contributions from translational diffusion and intrachain molecular motion are interrelated.
Abstract: The linewidth of the Rayleigh scattered light from flexible polymers is calculated on the basis of Rouse model In general, the contributions from translational diffusion and intrachain molecular motion are interrelated, but, for usual cases where the size of molecule is comparable to or less than the wave length of the incident light, the result is approximately expressed as a simple superposition of separate effects The linewidth due to the translational motion decreases with decreasing scattering angle, whereas the linewidth due to the intrachain molecular motion remains constant The ratio of magnitudes of these two effects is overwhelmingly large, and the effect of intrachain molecular motion seems almost indetectable