Showing papers on "Laser linewidth published in 1972"

Ultrasensitive response of a CW dye laser to selective extinction

Abstract: The sensitivity of a broad-band dye laser to selective intracavity absorption is proportional to the number of oscillating modes. This result is obtained from a rate equation model, taking into account the spectral homogeneity, but spatial inhomogeneity of the laser saturation. An increase of absorption sensitivity by a factor of 105, compared to a single-pass measurement, is observed in an experiment with an iodine vapor absorption cell inside the cavity of a CW dye laser. The fluorescence of an external iodine vapor cell provides a convenient selective absorption monitor.

High-resolution pattern replication using soft X rays

Abstract: A soft X ray lithographic technique capable of contactless replication of submicrometre linewidth planar-device patterns is described. Special soft X ray exposure masks have been developed for the 4-14 A wavelength region. Elastic-surface-wave-transducer patterns with 1.3 µm electrode spacings were fabricated onto such masks using electron-beam techniques, and were successfully replicated.

Critical-Point Anomalies in the Electron-Paramagnetic-Resonance Linewidth and in the Zero-Field Relaxation Time of Antiferromagnets

Abstract: A theory is presented for the anomalies in the electron-paramagnetic-resonance (EPR) linewidth and zero-field relaxation time of antiferromagnets. The analysis applies to the paramagnetic state immediately above the N\'eel point in systems where the dominant spin-spin interaction is the isotropic exchange coupling. It is assumed that the dipolar coupling is the principal source of anisotropy. The EPR linewidth and the relaxation rates for fluctuations in the total magnetization are separated into critical and noncritical parts; the latter are approximated by their values in the high-temperature limit. The anomalous increases in the linewidths and the relaxation rates are shown to arise from processes in which a fluctuation in the total magnetization decays into two fluctuations of the staggered magnetization via the dipolar coupling. The predictions of the theory are compared with linewidth measurements in RbMn${\mathrm{F}}_{3}$, Mn${\mathrm{F}}_{2}$, MnO, and MnS.

Direct Optical Coupling to Surface Excitations

Abstract: A method is described of directly coupling an optical beam to surface excitations. Using this technique the frequency and linewidth of surface plasmons in doped germanium and in gold and surface phonons in calcium molybdate are determined. The method also allows the dispersion curve to be measured.

Single longitudinal mode operation of a transversely excited CO 2 laser

Abstract: High peak-power output has been obtained from a transversely excited CO 2 laser in a single longitudinal and lowest order transverse mode. An intracavity etalon was used for mode selection in a laser system designed to operate effectively at reduced pressures.

Frequency selective optical memory

Abstract: A frequency selective optical memory device formed of a material that exhibits inhomogeneous line broadening and whose elemental regions on scanning by an intense light (laser) beam will become saturated only at a homogeneous linewidth related to the frequency of the applied laser pulse in the overall inhomogeneous line bandwidth. Each elemental region can be scanned in frequency and this gives the memory device a third dimension as far as data storage is concerned greatly increasing its storage capacity.

Motional narrowing in the electron-spin-resonance-spectrum of pentavalent vanadium-compounds

Abstract: The activation energy of the hopping frequency of the vanadium-3d 1-electron is derived from the temperature dependence of the ESR linewidth in the following semiconducting, pentavalent vanadium-compounds: NaxV2O5, LixV2O5 (x <0.02), V2O5 weakly doped with WO3 or MoO3 (E a ≈0.07 eV). In V2MoO8, vanadium-3d 1-electrons are responsible for the electronic conductivity, too.

The effect of pressure and temperature on the half-width of the methane absorption at 3.39μ

Abstract: A determination of the self-broadened linewidth of methane at 2947.88 cm −1 has been made using a stabilized, single-mode helium-neon laser. The width at half-maximum has been found to be 0.16±0.01 cm −1 at atmospheric pressure. By taking into account neighbouring methane components, the variation of the absorption coefficient in the high-pressure region can also be accounted for. The variation of the linewidth with temperature T has also been determined and was found to be close to T −1 . The strength of the methane line nearest the laser emission is 1.76±0.04 atm −1 cm −2 ; this line was found to be located 0.002±0.001 cm −1 from the laser emission.

Resonance-Narrowed-Lamb-Shift Measurement in Hydrogen, n = 3

Abstract: A new measurement of the Lamb shift in the $n=3$ state of atomic hydrogen is reported. The experiment was performed in zero magnetic field with a fast hydrogen beam. The radio-frequency spectroscopy measurements were made with both a single oscillating field and two separated oscillating fields. The final result for the Lamb shift was $\mathcal{S}(\mathrm{H}, n=3)=(314.819\ifmmode\pm\else\textpm\fi{}0.048)$ MHz. In a further experiment, the separated-oscillating-field technique was used to narrow the resonance so that the linewidth was less than the natural linewidth.

Measurements of the laser linewidth due to quantum phase and quantum amplitude noise above and below threshold. I

Abstract: The natural linewidths and line shapes due to quantum phase and quantum amplitude noise have been investigated above, within and below the threshold region of laser operation using a Fourier spectroscopic technique. Outside the threshold region the linewidths of the laser spectrum were found to be inversely proportional to the laser power, and measurements confirm the “factor of two” difference in the linewidth equation. Within the threshold region the results are in agreement with calculations of Hempstead, Lax and Risken. A Mach-Zehnder interferometer with optical path differences up to 1500 meters was used for the measurements. The method of investigation combines a high spectral resolution with a good signal-to-noise ratio. The method is suited to linewidth measurements of a laser both above and below threshold and allows the technical and natural linewidths to be clearly distinguished.

Solid laser with a high spatial coherence of radiation

Abstract: It was established experimentally that the use of unstable resonators with large equivalent Fresnel numbers made it possible to generate a single transverse mode in a homogeneous active medium. The angular divergence of this mode was close to the diffraction limit. A neodymium-glass laser with a divergence of 2 10−5 rad along one coordinate was developed.

Spontaneous-Emission Profiles of Argon-Ion Laser Transitions

Abstract: Experimental studies are reported of spontaneous-emission profiles observed in the axial and radial directions from high-current arc discharges of the type used in cw argon-ion lasers. The greatly increased sensitivity from a new computer-oriented method of line-profile analysis has permitted observation of linewidth parameters over a wide range of discharge current and pressure. These studies have shown the existence of several interesting new effects and have required a substantial modification of previously held concepts regarding the nature of line broadening in these discharges. A new theory for line-profile analysis in the radial direction is presented which incorporates the Tonks-Langmuir potentials and provides a correction for an arbitrary number of charge-exchange collisions in the radial acceleration of ions to the wall. A modification of the earlier theory of Kagan and Perel is suggested which brings that method of transverse line-profile analysis into reasonably close agreement with the present (more complex) method of analysis. Values for the mean radial velocity and electron temperature are obtained from profile analysis in the transverse direction. Studies of ion and neutral temperatures based on Voigt profile analysis in the axial direction are presented, along with the determination of the average electron density based on Stark broadening of the neutral and ionic lines. Precise values of the natural widths on the major argon-ion laser transitions are determined through extrapolations of the axially observed Lorentz-width data taken at low pressures to zero discharge current.

Oscillator-amplifier dye-laser system using N 2 laser pumping

Abstract: An N 2 laser pumped dye-laser system is described which uses an oscillator-amplifier arrangement and fast-flow dye cells in order to achieve spectral narrowing and spatial coherence without sacrificing power.

Spectral distribution of amplified spontaneous emission

Abstract: A theory is described which accounts for the dependence of the spectral distribution of amplified spontaneous emission on the length and inversion density of the active medium. For an inhomogeneously broadened line an unanticipated dip occurs in the plot of linewidth against length at lengths slightly greater than the critical length, but is explained by a simple physical analysis. Agreement occurs between the theory and that of Yariv and Leite (1963) in the regime over which their theory is expected to work. Observations by other workers on the spectral distribution of amplified spontaneous emission systems are discussed.

FM-CW radar range measurement with a CO 2 laser

Abstract: FM-CW radar range measurement by a CO 2 laser is reported. Nonlinear variation of the laser power output is obtained when the reflected signal is mixed within the laser cavity. This variation is attributed to frequency pulling/pushing and to power-dependent refractive index changes in the laser medium.

Electron Spin Relaxation in Liquid Crystals

Abstract: The dominant spin relaxation process for many paramagnetic species in fluid solution results from the anisotropy in the magnetic interactions coupled to the molecular rotational diffusion.1 Rotation of the molecule modulates the energies of the spin levels and also induces transitions between them. The line broadening caused by this mode of relaxation provides a useful technique for investigating the nature and rate of the reorientation process. Although the results of such studies have appeared they are invariably for systems in which the rotation is rapid.2,3 As a consequence the line shape for non-degenerate transitions is Lorentzian and all of the dynamic information is contained in the linewidth. In general this width is determined by the Fourier transform of the correlation functions of certain rotation matrices, but in practice the dominant contribution comes from the transform at zero frequency. In other words only the correlation time for the molecular motion can be obtained from the linewidth.

Effect of Surface Roughness on Ferrimagnetic Resonance Linewidth Measurements

Abstract: From room‐temperature ferrimagnetic resonance linewidth measurements on both single‐crystal and polycrystalline ferrite and garnet specimens, it is concluded that the surface contribution to the linewidth may be represented by ΔHsurface=ξ4πMs/d, where 4πMs is the saturation magnetization, d the sphere diameter, and ξ is a parameter dependent on the surface condition. Experimental results are presented in a manner which clearly indicates the direct dependence on 4πMs and the inverse dependence on sphere diameter which represents the ratio of the surface region volume to total volume. The parameter ξ is shown to vary with surface finish for coarse and medium textured surfaces. By comparing the linewidths of polished spheres with the extrapolated results for spheres of infinite diameter obtained from plots of ΔH vs 1/d, it is verified that the surface effects may be removed by polishing. Finally, it is emphasized that linewidths of polycrystalline materials may be very inaccurate if the surface is not polish...

Magnetic properties and resonance linewidths of Zr- and Ti-subsituted Ca-V garnet

Abstract: Neel temperature and ferrimagnetic resonance linewidth measurements were carried out in the composition Y 3-2x-y Ca 2x+y Fe 5-x-y M y V x O 12 , where M=Zr or Ti. It was revealed, that both of the Zr and Ti substitutions in this system reduced the value of K 1 /M s effectively, and this led to the remarkable linewidth reduction. The lowest value of linewidth obtained was 1.8 Oe at the composition of x=0.4 and y=0.4 for M=Zr.

Apparatus for stabilizing a laser to a gas absorption line

Abstract: There is disclosed a frequency-stabilized laser in which a first component of the output beam is passed through a gaseous frequency standard cell in a first direction and then detected while a second component of the beam is passed through the cell in a second direction slightly less than 180* from the first direction so as to avoid subsequent interaction with the apparatus. The detected signal as a function of frequency has a narrow peak centered on the absorption line of the gas. The width of this peak is the homogeneous linewidth of the absorbing gas, which is typically much narrower than the Doppler-broadened absorption line. The detected signal is applied through a feedback loop to control the tuning of the laser resonator.

High Resolution Michelson Interferometer for Spectral Investigations of Lasers

Abstract: An extremely stable Michelson interferometer with an optical path difference up to several thousand meters has been developed for the precise investigation of the frequency behavior of lasers. The theoretical value for the spectral resolution is of the order of 10(12). The spectral resolution of a real system is determined by external disturbances and was measured to be close to 10(1l). The capability and the characteristics of the system are discussed.