Showing papers on "Laser linewidth published in 1980"
TL;DR: In this paper, the effect of optical feedback on the spectral characteristics of channel-substrate planar single-mode laser diodes operating at room temperature is reported. And the impact on the performance of interferometric sensor systems using such sources is discussed.
Abstract: The effect of optical feedback on the spectral characteristics of channel‐substrate planar single‐mode laser diodes operating at room temperature is reported. The impact on the performance of interferometric sensor systems using such sources is discussed. The linewidth for the free‐running laser at 10‐mW output power was determined to be less than 5 MHz at room temperature. Broadening on the order of 40 times the intrinsic linewidth was observed for 0.1% feedback and increased with increasing feedback. The presence of self‐oscillation modes was observed at 0.04% feedback. Satellite modes symmetrically located with respect to the primary mode appeared in the spectrum for feedback greater than 0.04%. These satellite modes are attributed to self‐oscillation in the laser induced by feedback. As the feedback was increased, the satellite mode spectrum began to overlap that of the primary mode, reducing the effective coherence length from 60 m (for the single‐mode linewidth) to less than a few centimeters.
99 citations
TL;DR: In this paper, the authors measured the locking frequency width and locking gain of an AlGaAs double-heterostructure laser with respect to locking frequency and gain, and the relation of the locking bandwidth versus the ratio of locked laser to injected power was consistent with the analysis on injection locking phenomena.
Abstract: Injection locking of an AlGaAs double-heterostructure laser was studied with respect to locking frequency width and locking gain. The relation of the locking bandwidth versus the ratio of locked laser to injected power was consistent with the analysis on injection locking phenomena by Adler. Measured maximum locking bandwidth was 3 GHz, when locking gain was 23 dB. The 40 dB maximum gain was observed with the 500 MHz locking bandwidth. By measuring the beat notes between two temperature-stabilized free running AlGaAs lasers, the linewidth was estimated as 10 MHz.
79 citations
TL;DR: In this article, the authors measured the optical homogeneous linewidth of the 4F3/2/4I9/2 transition of Nd3+ in oxide and fluoride based glasses.
Abstract: Optical homogeneous linewidths of the 4F3/2–4I9/2 transition of Nd3+ in oxide and fluoride based glasses are measured for host composition ranging from simple binary to multicomponent glasses. Homogeneous linewidths at 300 K exhibit a broad range of values, varying by approximately a factor of 4. The ratio of homogenous to inhomogeneous linewidth also varies over a broad range, from 0.16 for a sodium barium borate glass to 1.86 for a rubidium phosphate glass. In addition, the homogeneous linewidth is inversely dependent to the ∼2.5 power of the velocity of sound from host to host. This dependence is not predicted by existing theories of the line broadening process.
78 citations
TL;DR: Test patterns in the form of diffraction gratings are used for testing and monitoring linewidths on integrated circuit structures, and an-automatic setup for rapid testing of wafers is described.
Abstract: Test patterns in the form of diffraction gratings are used for testing and monitoring linewidths on integrated circuit structures. The first and second diffraction orders produed by a laser beam are evaluated to give the width of the grating lines. Measurements on chrome masks show that this technique is accurate to 5% down to linewidths of 0.5 μm. The design of a test set for factory type mask testing is presented. Also, experiments are reported on the testing of patterns on Si wafers directly after. photoresist development and after various etching steps, and an automatic setup for rapid testing of wafers is described.
73 citations
TL;DR: In this paper, a contribution to the homogeneous linewidth of optical transitions in amorphous hosts is calculated, where the microscopic process is diagonal in the phonon interaction with two level systems (TLS) common to amorphized materials.
Abstract: A contribution to the homogeneous linewidth of optical transitions in amorphous hosts is calculated. The microscopic process is diagonal in the phonon interaction with two level systems (TLS) common to amorphous materials, and diagonal in the coupling between TLS and the optical center. The model predicts an optical homogeneous linewidth proportional to the square of the temperature at low temperature.
72 citations
TL;DR: In this paper, the output characteristics of a high-intensity laser oscillator are examined by means of a semiclassical density-matrix approach, and a basic instability in the laser equations is revealed.
Abstract: The output characteristics of a high-intensity laser oscillator are examined by means of a semiclassical density-matrix approach. Unlike previous investigations the time derivatives of the field and material quantities are retained, and a basic instability in the semiclassical laser equations is revealed. This instability accounts for the recently reported spontaneous pulsations in xenon laser oscillators. The pulsations can be interpreted as a consequence of spectral holeburning in inhomogeneously broadened lasers, and stability criteria are derived for both standing-wave and traveling-wave oscillators. In simplest terms the pulsations should occur in any inhomogeneously broadened laser where the product of the homogeneous linewidth and the cavity lifetime is less than unity.
70 citations
TL;DR: In this paper, the Stokes spectrum and the dependence of Raman gain upon pump laser bandwidth in a narrow linewidth Raman medium are analyzed in terms of a closed set of multimode equations.
Abstract: The development of the Stokes spectrum and the dependence of Raman gain upon pump laser bandwidth in a narrow linewidth Raman medium are analyzed in terms of a closed set of multimode equations. The analysis predicts that the Stokes gain coefficient takes on its maximum value, which is independent of bandwidth, when the Stokes spectrum replicates the pump spectrum. It is also shown that in the absence of dispersion the spectrum of a weak Stokes wave is driven to duplicate the pump spectrum, and that for noise input the average power generated in the Stokes wave is independent of the pump bandwidth.
66 citations
TL;DR: Near-monochromatic gains in a Raman amplifier pumped by a laser with a bandwidth up to 30 times wider than the molecular linewidth are observed.
Abstract: We have observed near-monochromatic gains in a Raman amplifier pumped by a laser with a bandwidth up to 30 times wider than the molecular linewidth. This gain enhancement is obtained when the corresponding temporal fine structure of the pump and Stokes waveforms are superimposed in the amplifier.
66 citations
TL;DR: In this paper, a molecular beam magnetic resonance experiment, using laser fluorescence for state selection and beam detection, has been performed on I2, where 20 ΔF=±1 hyperfine transitions were observed in the v=0, J=13 level of the ground electronic state.
Abstract: A molecular beam magnetic resonance experiment, using laser fluorescence for state selection and beam detection, has been performed on I2. Twenty ΔF=±1 hyperfine transitions were observed in the v=0, J=13 level of the ground electronic state. The transitions had a FWHM linewidth of 5–15 kHz in the 100–400 MHz region and were observed in zero external field. eqQ, spin rotation, tensor spin–spin, and scalar spin–spin interactions of −2 452 583.7(16), 3.162(8), 1.58(5), and 3.66(3) kHz, respectively, were obtained. Using these X 1Σ state constants, the precise optical data of Hackel, Casleton, Kukolich, and Ezekiel [Phys. Rev. Lett. 35, 568 (1975)] were reanalyzed to obtained hyperfine properties of the v=43, J=12 B 3Π0 electronic state. In the same order as above, these constants are −558 669(8), 190.13(12), −100.2(7), and 0.2(4) kHz. These values for both the X and B states differ significantly from those previously reported. Neither magnetic octupole nor electric hexadecupole interactions were required, h...
63 citations
TL;DR: An oscillator-amplifier KrF discharge laser system capable of providing up to 400 mJ output with 0.1-cm-1linewidth in a 20-ns pulse is described in this paper.
Abstract: An oscillator-amplifier KrF discharge laser system capable of providing up to 400 mJ output with 0.1-cm-1linewidth in a 20-ns pulse is described. The output beam divergence is described and shown to be affected by the discharge current. The output beam is near the diffraction limit in the direction parallel to the discharge and about three times the diffraction limit transverse to the discharge. Operation with XeCl at up to 250 mJ with similar linewidth and spatial quality is also described.
62 citations
IBM1
TL;DR: In this article, the authors quantitatively studied the optical projection printing with a diffracted image of two bars of equal width and space and an aspect ratio of three, using the four-dimensional integral for partially coherent imaging.
Abstract: Optical projection printing is quantitatively studied, using the diffracted image of two bars of equal width and space and an aspect ratio of three. Hopkins' four-dimensional integral for partially coherent imaging is used for the numerical analysis. Diffraction-limited lenses with a circular pupil are used. Constant intensity profiles in an absorptionless photoresist and nonreflective substrate are evaluated. Then the tolerances ot defocus and intensity are derived using a linewidth tolerance of ±2.5 percent of the mask linewidth which varies from 0.5, 0.75, 1, 1.5, 2, to 2.5 µm. The illuminations used have σ = 0, 0.5, 0.7, 0.78, 1, 1.3, and infinity.
TL;DR: In this article, the ESR g-factor, linewidth and spin susceptibility of (TMTSF) 2 PF 6 are each found to have a distinct temperature dependence, and it is shown that spin-phonon scattering is the dominant relaxation mechanism.
TL;DR: In this article, two photon spectra of the 1B2u state of benzene•h6 and benzened6 have been examined in a supersonic molecular beam/multiphoton ionization experiment.
Abstract: The two photon spectra of the 1B2u state of benzene‐h6 and benzene‐d6 have been examined in a supersonic molecular beam/multiphoton ionization experiment. The effect of channel three nonradiative decay on the resonance linewidths was followed through energies greater than 6000 cm−1 above the origin, 3000 cm−1 past the fluorescence cutoff region. The linewidth data suggest a leveling off of the channel three broadening at energies greater than T00+6000 cm−1. A new progression in the benzene‐h6 spectrum was revealed adjacent to the 1410 1n0 progression (n=1 to 5) which had previously been obscured in the rotational envelope of these bands. New structure and well resolved expected structure is seen in the benzene‐d6 spectrum as the 1410 1n0 progression is followed out to n=5.
TL;DR: For a localized vibrational transition which is subject to both inhomogeneous and homogeneous broadenings, study of temperature dependence of its linewidth can still be used to identify the mechanism of vibrational dephasing as discussed by the authors.
Abstract: For a localized vibrational transition which is subject to both inhomogeneous and homogeneous broadenings, study of temperature dependence of its linewidth can still be used to identify the mechanism of vibrational dephasing In the Raman spectra of naphthalene, temperature dependence of the line shape, the linewidth, and the vibrational frequency is investigated for the 764 cm−1 internal mode which is localized even in the neat crystal At 2 °K the line is found to be a Gaussian and, thus, inhomogeneously broadened At higher temperatures the line shapes are between a Lorentzian and a Gaussian A computer simulation method is used to separate the homogeneous and the inhomogeneous components of the linewidth The temperature dependence of the homogeneous linewidth is explained by a mechanism of dephasing which involves a T2′ process due to an off‐diagonal mixed mode quartic anharmonic interaction with 140 cm−1 phonons This process produces a modulation broadening but no T1 relaxation The observed temper
TL;DR: In this article, a distributed feedback laser operation in which a classical electromagnetic field obeying Maxwell's equations interacts with an active medium according to the laws of quantum mechanics is considered, and the theory describes arbitrarily intense two-mode operation of fundamental and higher modes in both index and gain grating configurations.
Abstract: This paper treats distributed feedback laser operation in which a classical electromagnetic field obeying Maxwell's equations interacts with an active medium according to the laws of quantum mechanics. The theory describes arbitrarily intense two-mode operation of fundamental and higher modes in both index and gain grating configurations. Spacial hole burning and finite atomic linewidth are included in the analysis and are shown to give marked changes in some laser intensity profiles.
TL;DR: In this paper, a near-resonant laser beam in sodium vapor with concentration of ∼10 15 at/cm 3 is found to generate several distinct non-linear, near-reonant, nearaxis emissions Spectral, angular and polarization characteristics of the many emission features obtained with a tunable pulsed dye laser are given.
TL;DR: In this article, the authors investigated the predissociation of the b 4 Σ g - state of O2 + using fast ion beam laser spectroscopy (FIBLAS) techniques.
Abstract: The predissociation of the b 4Σ g - state of O2 + is reinvestigated by fast ion beam laser spectroscopy (FIBLAS) techniques. The high spectroscopic resolution achieved in the photofragment spectrum, leads to the observation of several hundred lines which are classified in the (3-0), (4-1) and (5-2) bands of the b 4Σ g --a 4II u transition of O2 +. By linewidth analysis, the lifetimes of the v′ = 4 and v′ = 5 levels of the b 4Σ g - state, above the O+(4S) + O(3P) dissociation limit, are studied as a function of the various vibrational, rotational and fine structure quantum numbers. Our results, in good agreement with previous measurements, are interpreted within the framework of a new theoretical a priori study of the predissociation mechanism of O2 +. A complete understanding of the phenomena still requires further experimental investigation and we indicate possible directions of research in this field. As a test experiment, our study of the predissociation of O2 + in the b 4Σ g - state gives a clear exam...
TL;DR: Polarization spectroscopy was used for the first time known to the authors to measure the homogeneous linewidth and excited-state lifetime of an inhomogeneously broadened transition of an absorbing impurity ion in a crystalline host.
Abstract: Polarization spectroscopy was used for the first time known to the authors to measure the homogeneous linewidth and excited-state lifetime of an inhomogeneously broadened transition of an absorbing impurity ion in a crystalline host. The observed line shapes agree with those predicted by a density-matrix calculation.
TL;DR: In this article, the authors measured the impact-broadened Lorentzian linewidth from the normalised absorption, detected as fluorescence, in the 5-20 GHz region of the line wings.
Abstract: Broadening of the sodium resonance lines by noble gases has been measured by observing fluorescence while scanning a laser across the lines. The impact-broadened Lorentzian linewidth is determined from the normalised absorption, detected as fluorescence, in the 5-20 GHz region of the line wings. Comparison with theory indicates reasonable overall agreement, but the increased precision of these measurements indicates many discrepancies of as much as 25%.
TL;DR: In this article, the linewidth of a single longitudinal mode AlGaAs/GaAs double heterostructure laser was measured using a Fabry-Perot interferometer with spacers of 30 cm, 3.2 m, and 10 m. The full width at half maximum was estimated to be less than 1 MHz when the current level exceeds 1.15 times the threshold.
Abstract: Interferometric measurement of the linewidth has been carried out on a single longitudinal mode AlGaAs/GaAs double heterostructure laser by using a Fabry-Perot interferometer with spacers of 30 cm, 3.2 m, and 10 m. The full width at half maximum was estimated to be less than 1 MHz when the current level exceeds 1.15 times the threshold, which was near the estimated theoretical limit.
TL;DR: Results of experiments investigating the effects of optical pumping and atomic motion on cw degenerate four-wave mixing in atomic sodium vapor are presented, finding distortions of the atomic velocity distribution to be essential for efficient cw generation.
Abstract: Results of experiments investigating the effects of optical pumping and atomic motion on cw degenerate four-wave mixing in atomic sodium vapor are presented The signal strength is found to decrease as (sin θ)−2, where θ is the angle between the object and pump waves; however, the linewidth for generation is Doppler free and is independent of θ Agreement is found with a simple model of the mixing process Distortions of the atomic velocity distribution (produced in our experiments by optical pumping) are found to be essential for efficient cw generation A new modulation scheme for the discrimination against background is used
TL;DR: In this paper, a synchronously mode-locked cw dye laser suitable for high-resolution spectroscopy in the frequency domain is described, where the number of oscillating modes has been reduced to restrict the laser bandwidth to the order of the Doppler width of the molecular transitions.
Abstract: A synchronously mode‐locked cw dye laser suitable for high‐resolution spectroscopy in the frequency domain is described. The number of oscillating modes has been reduced to restrict the laser bandwidth to the order of the Doppler width of the molecular transitions. By frequency locking one of the oscillating laser modes to a reference cavity, the linewidth of each mode of the frequency comb has been narrowed to less than 500 kHz. The tuning of the central frequency extends from 5650 to 6300 A in the case of R6G. The mode spectrum of the laser can be continuously translated in frequency over several gigahertz.
TL;DR: The rotational distribution of the water molecule through rotational transitions in near resonance with those of the OH was found to decrease with increasing rotational excitation, and tended to level off to a constant value.
Abstract: The homogeneously broadened linewidth of OH due to collisions with water molecules was found to decrease with increasing rotational excitation, and tended to level off to a constant value. This observed dependence is a manifestation of the rotational distribution of the water molecule through rotational transitions in near resonance with those of the OH. The constant value at high rotational excitation reflects the nonresonant contributions to the homogeneous linewidth similar to those due to nonpolar molecules.
TL;DR: In this paper, collisional broadening of rotational Raman lines has been investigated for the gases nH2, nD2 and HD between 20 and 300 K. The experimental results are compared with theory.
Abstract: Collisional broadening of rotational Raman lines has been investigated for the gases nH2, nD2 and HD between 20 and 300 K. For H2 and D2 the dependence of the linewidth on ortho-para composition has been investigated. For a number of systems the pressure shift of the Raman lines has also been determined. The experimental results are compared with theory.
IBM1
TL;DR: In this article, the authors applied the technique of nuclear spin decoupling to the optical regime and measured the homogeneous optical linewidth (FWHM) measured by photon echoes, measured by on-resonance nutation of 19F in an external magnetic field of 375G.
Journal Article•
TL;DR: In this paper, a method of correcting the EPR linewidth of a nitroxide that is inhomogeneously broadened by unresolved hyperfine structure is presented, which allows correction for the inhomogeneous broadening in practically all cases in which the Nitroxide tumbles in the motional narrowing region by using only a hand-held programmable calculator.
TL;DR: In this article, the authors discuss techniques for achieving resolution beyond the natural linewidth, limited by the difference between the decay rates rather than their sum, which provides the possibility of enhanced spectral resolution.
TL;DR: In this article, a microwave ferrite is described and the physical phenomenon exploited is the gyromagnetic resonance that appears when the material is subjected to both a static magnetic field and to a microwave field.
Abstract: Publisher Summary This chapter describes a microwave ferrite. The physical phenomenon exploited is the gyromagnetic resonance that appears when the material is subjected to both a static magnetic field and to a microwave field. This effect is inherently non-reciprocal, which accounts for the tensorial nature of the magnetic permeability. This non-reciprocity is widely used in various devices. The saturation magnetization is a fundamental quantity, not only as a factor of efficiency, but also because of the existence of a natural resonance in the internal fields. Consequently, magnetization is the first quantity to be considered in the choice of material for a given application. As in any resonance effect, the linewidth is of prime importance. It is fundamentally related to the damping effects of spin movements, which seem possible to approach by considering either the linewidth off-resonance or the non-linear effects related to the spin waves. Conversely, the linewidth of the main mode observed at resonance, on the polycrystals, is broadened by the magnetocrystalline anisotropy effects or by spurious effects related to faults and porosity. Ferrites now used at microwave frequencies have spinel, G, or hexagonal structures.