Showing papers on "Laser linewidth published in 1981"
TL;DR: In this article, the backscattered light amplitude is measured from one end of a fiber as a function of optical frequency by tuning a HeNe laser over its linewidth.
Abstract: The backscattered light amplitude is measured from one end of a fiber as a function of optical frequency by tuning a HeNe laser over its linewidth. Fourier transform by a low‐frequency electronic spectrum analyzer then reveals the spatial distribution of scattering and of the fiber losses.
504 citations
TL;DR: In this paper, a systematic increase of the linewidth of luminescence, absorption and excitation spectra of undoped GaAs-Ga 1-x A l x As Multi-Quantum structures with decreasing layer thickness was reported.
327 citations
TL;DR: In this article, a new class of multipulse sequences specifically designed for low-power requirements is introduced, and it is found that of all sequences tested BR-24 leads to optimum performance.
236 citations
TL;DR: In this paper, a theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed, and the inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
Abstract: A broadening of the apparent linewidth of the semiconductor laser modes with external optical feedback is observed. This is shown to be due to the coherent nature of the feedback and multiple reflections in the external cavity. A theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed. The inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
132 citations
TL;DR: In this paper, the Lorentzian lineshape of a single longitudinal mode AlGaAs semiconductor laser is directly observed by optical heterodyne detection and a remarkable reduction in the spectral linewidth to less than 50 kHz is achieved with external grating feedback.
Abstract: The Lorentzian lineshape of a single longitudinal mode AlGaAs semiconductor laser is directly observed by optical heterodyne detection. A remarkable reduction in the spectral linewidth to less than 50 kHz is achieved with external grating feedback. The experimental linewidth is in reasonable agreement with the theoretical value, which is obtained by finesse calculation of the active Fabry-Perot cavity.
115 citations
TL;DR: In this article, a modulated laser beam, incident on a surface, gives rise to a time-varying surface displacement, which can be detected by means of a laser interferometer, thereby forming the basis for a novel imaging system.
Abstract: A modulated laser beam, incident on a surface, gives rise to a time-varying surface displacement. This displacement can be detected by means of a laser interferometer, thereby forming the basis for a novel imaging system. Preliminary results to demonstrate the viability of such a technique are presented.
96 citations
TL;DR: In this paper, it was shown that a convolution of unresolved superhyperfine splitting with a near-isotropic g strain and a distribution in the strongly angle-dependent zero-field interaction underlies the anisotropic Linewidth in spectra of high-spin hemoproteins.
68 citations
TL;DR: Measurements of the SO(2) absorption cross section between 290 and 317 nm have been made using a frequency-doubled dye-laser source with a 0.05-nm linewidth and offers greatly extended wavelength coverage compared with previous measurements.
Abstract: Accurate measurements of the SO2 absorption cross section between 290 and 317 nm have been made using a frequency-doubled dye-laser source with a 0.05-nm linewidth. The spectrum is applicable to the differential absorption method of detecting SO2 and offers greatly extended wavelength coverage compared with previous measurements.
66 citations
TL;DR: A variety of shadowing techniques have been developed for fabricating simple structures with lines and spaces in the 100 A linewidth regime as discussed by the authors, where a smooth vertical step with precisely determined depth is produced in a substrate by reactive ion etching.
Abstract: A variety of shadowing techniques have been developed for fabricating simple structures with lines and spaces in the 100 A linewidth regime. In the basic technique, a smooth vertical step with precisely determined depth is produced in a substrate by reactive ion etching. This step is shadowed at a shallow angle by evaporation in order to deposit material on the vertical wall. The substrate is then etched at normal incidence with an ion beam to remove the thin layer of material outside the step. This leaves a thin rectangular line of material at the step. By alternately evaporating different materials and by adding lithography and etching steps, more complex structures can be made. Applications of these structures in wire grating optical polarizers and the use of long thin wires for studying electron localization are described. Optical polarizers with extinction ratios of nearly 200 to 1 have been made. This demonstrates some of the unique capabilities of the shadowing technique since high quality polarize...
64 citations
TL;DR: In this article, a high-resolution photoelectron spectrometer using molecular beam sampling is described, which is based on a multichannel detection system based on dual microchannel plates with a resistive anode position encoder, achieving an instrumental resolution of better than 10 meV FWHM.
Abstract: A high‐resolution photoelectron spectrometer which uses molecular beam sampling is described. Photons from a rare‐gas resonance lamp or UV laser are crossed with the beam from a differentially pumped supersonic nozzle source. The resulting photoelectrons are collected by an electrostatic analyzer of a unique design consisting of a 90° spherical sector preanalyzer, a system of lenses, and a 180° hemispherical deflector. A multichannel detection system based on dual microchannel plates with a resistive anode position encoder provides an increase in counting efficiency by a factor of 12 over the equivalent single channel detector. The apparatus has demonstrated an instrumental resolution of better than 10 meV FWHM, limited largely by the photon source linewidth. A quadrupole mass spectrometer is used to characterize the composition of the molecular beam. Extensive differential pumping is provided to protect the critical surfaces of the analyzer and mass spectrometer from contamination. Because of the near el...
60 citations
TL;DR: In this paper, a single axial mode output from an unstable resonator Nd: YAG oscillator was obtained by controlling the Q-switch following prespiking pulses.
TL;DR: Resolution sufficient to resolve second-order Doppler broadening has been obtained for the Ca (1)S(0)-(3)P(1) transition (657 nm) by using an atomic beam and optical Ramsey fringe techniques.
Abstract: Resolution sufficient to resolve second-order Doppler broadening (3.9 kHz) has been obtained for the Ca 1S0–3P1 transition (657 nm) by using an atomic beam and optical Ramsey fringe techniques. Laser-beam separations up to 21 cm yield Ca linewidths (HWHM) as narrow as 1 kHz. As resolution is increased to approach, then exceed, the second-order linewidth, large asymmetries, shifts, and shape changes occur in the Ramsey fringe profile.
TL;DR: In this paper, the authors measured the spectral linewidth of a single longitudinal mode AlGaAs semiconductor laser by converting it into intensity noise and a Michelson interferometer was used and a time delay was introduced.
Abstract: Quantum phase noise of a single longitudinal mode AlGaAs semiconductor laser is measured by converting it into intensity noise. A Michelson interferometer is used and a time delay is introduced. Results on spectral linewidth and noise spectrum are in good agreement with theoretical analyses based on a rate equation. Spectral linewidth of the semiconductor laser decreases from 100 MHz to 4 MHz in proportion to (I/Ith−1)−1 at the bias level of I/Ith=1.05 − 1.4.
TL;DR: A lidar with high spectral resolution can be used to measure atmospheric temperature profiles according to conservative performance calculations using the temperature-dependent Rayleigh-scattering linewidth with two stabilized Michelson interferometers in parallel.
Abstract: A lidar with high spectral resolution can be used to measure atmospheric temperature profiles according to conservative performance calculations. The technique analyzed relies on determining the temperature-dependent Rayleigh-scattering linewidth with two stabilized Michelson interferometers in parallel. From ratios of four integrated flux values from two photomultipliers, one can determine temperature profiles within a 1 K standard deviation to 5 km with 50-m height resolution in 1¼ min using a laser of 1-W average power and a telescope of 30-cm diam.
TL;DR: In this article, the authors detect predissociation as attenuation of the SF + 5 ion signal from a SF 6 molecular beam crossed by a line tunable cw CO 2 laser.
TL;DR: In this article, the spatial distribution of the atmospheric parameters measured with the differential absorption lidar technique is restored for pulsed emission only if the laser emission is monochromatic.
Abstract: The spatial distribution of the atmospheric parameters measured with the differential absorption lidar technique is restored for pulsed emission only if the laser emission is monochromatic. Due to the finite linewidth of the laser lines, a systematic error is introduced in the measurement of the local optical thickness, which is shown to depend on the propagation of the laser pulse along the line of sight and on the ratio γ L γ a of the laser linewidth to the absorption linewidth. Relative errors as large as 20% may be made under the usual experimental conditions for γ L γ a ≈ 1 . A 1% limit on this error is only obtained if γ L γ a ⪅0.3.
TL;DR: In this article, simple analytical expressions for the oscillation frequency, linewidth, FM noise spectrum and frequency modulation characteristics of a diode laser with external grating feedback are given.
Abstract: Simple analytical expressions are given for the oscillation frequency, linewidth, FM noise spectrum and frequency modulation characteristics of a diode laser with external grating feedback. The analytical expressions are found to be in good agreement with experimental results and to be useful for quantitative predictions and optimisations of the external feedback controlled diode laser performance.
TL;DR: In this article, the vibronic bands of the 1'1Bu←1'1Ag (S2←S0) transition of octatetraene narrow significantly in a seeded free jet.
Abstract: The fluorescence excitation spectrum from 2980 to 2650 A of trans, trans‐1,3,5,7‐octatetraene in a free jet has been measured monitoring emission in the region 3250 to 3500 A. The vibronic bands of the 1 1Bu←1 1Ag (S2←S0) transition of octatetraene narrow significantly in a seeded free jet of ∼8 ppm octatetraene in helium (FWHM∼200 cm−1 for the room temperature static gas; FWHM∼35 cm−1 in the jet). Although absolute intensities of the vibronic bands are not determined, there is significant intensity in the origin, and the vibronic development involves only a few modes. Estimated translational, rotational, and vibrational temperatures of ∼1,<45, and <170 K, respectively, were achieved in the expansion. The major source of the observed linewidth is attributed to coupling of the 1 1Bu state to the lower 1Ag states.
TL;DR: Coherent anti-Stokes Raman scattering (CARS) from the pure rotational Raman lines of N(2) gas is employed to measure the instantaneous rotational temperature of the gas at room temperature and below.
Abstract: Coherent anti-Stokes Raman scattering (CARS) from the pure rotational Raman lines of N2 gas is employed to measure the instantaneous (10-nsec) rotational temperature of the gas at room temperature and below. An entire rotational CARS spectrum is generated by a single laser pulse using a broad-bandwidth dye laser and is recorded on an optical multichannel analyzer. A best-fit temperature is obtained for individual experimental spectra by comparison with calculated spectra. Good agreement between CARS temperatures and thermocouple temperatures is observed.
TL;DR: In this article, the third-order susceptibilities for a Doppler-broadened two-level system were calculated for four-wave mixing on the angle θ between the pump and signal fields, and the reflection coefficient was shown to have a narrow field of view that is inversely proportional to the ratio of the width to the homogeneous linewidth.
Abstract: Third-order susceptibilities are calculated for a Doppler-broadened two-level system. The dependence of four-wave mixing on the angle θ between the pump and signal fields is studied, and the reflection coefficient is shown to have a narrow field of view that is inversely proportional to the ratio of the Doppler width to the homogeneous linewidth. For the collinear geometry, θ = 0°, the frequency dependence of the nondegenerate case is analyzed and shown capable of yielding a real-time narrow-bandwidth optical filter whose bandwidth is limited by the homogeneous linewidth.
TL;DR: In this paper, a far infrared cyclotron resonance (CR) experiment in a selectively doped AlxGa1−xAs ‐GaAs heterojunction is presented, where quantum oscillations appear in the CR line amplitude as theoretically predicted for a twodimensional electron gas.
Abstract: Far‐infrared cyclotron resonance (CR) experiments in a selectively doped AlxGa1−xAs ‐GaAs heterojunction are presented. Quantum oscillations appear in the CR line amplitude as theoretically predicted for a two‐dimensional electron gas. The CR linewidth is found to depend on the infrared photon energy, and its correlation with the static mobility is interpreted in the framework of the Ando and Uemura’s model for a two‐dimensional electron gas in a high magnetic field.
TL;DR: In this paper, the power and linewidth of an array containing up to 100 indium microbridges have been measured and it was shown that the power scales as N 2 and the linear width as 1/N for an array with N junctions.
Abstract: Coherent microwave radiation from arrays containing up to 100 indium microbridges has been directly detected. As expected the power scales as N2and the linewidth as 1/N for an array containing N junctions. Design criteria and fabrication methods for these arrays are discussed.
IBM1
TL;DR: The hole burning involves a new mechanism, in which optically induced spin flips of neighboring nuclei shift the optical transition frequency outside its homogeneous linewidth.
Abstract: Optical hole burning has been observed in the 5941-A transition of Pr(3+) in a charge-compensated tetragonal site of CaF(2) . The Pr(3+) ground state is doubly degenerate and shows a large first-order hyperfine splitting, which is clearly resolved because of the very narrow inhomogeneous linewidth of 650 MHz. The hole burning involves a new mechanism, in which optically induced spin flips of neighboring nuclei (here (19)F) shift the optical transition frequency outside its homogeneous linewidth. This mechanism was confirmed by optical rf double resonance.
TL;DR: In this paper, the Smith-Purcell free-electron laser was used to generate millimeter-wave radiation in the band from 53 to 73 GHz with power levels of approximately 100 mW with beam currents of 90 to 100 mA.
Abstract: Millimeter-wave radiation in the band from 53 to 73 GHz has been generated by means of a Smith-Purcell free-electron laser. Power levels of approximately 100 mW were observed with beam currents of 90 to 100 mA; the threshold currents ranged from 35 to 82 mA. The electronic tuning transconductance and the linewidth were also measured, yielding $\frac{\mathrm{df}}{\mathrm{dV}}=0.25$ MHz/V and $\ensuremath{\Delta}fl~0.4$ MHz, respectively. The measured results agree well with predictions based on a linear theory.
TL;DR: In this article, the effects of P or B doping and annealing on the localized gap states in CVD a-Si have been investigated using E.S.R. signals.
Abstract: The effects of P or B doping and annealing on the localized gap states in CVD a-Si have been investigated using E.S.R. An E.S.R. signal with g = 2·0055 disappears with P or B doping and a signal with linewidth depending on temperature at g = 2·0043 and one with linewidth (∼20 G) independent of temperature at g ∼ 2·011 appear in heavily P- and B-doped samples, respectively. These two signals are similar to photo-induced E.S.R. signals observed in undoped GD a-Si, and it is proposed that they arise from negative and positive charge states of weak bonds in a-Si, respectively. The dependences of the spin densities of these signals on doping and measurement temperature have been explained by this proposed model.
TL;DR: In this paper, an analysis and experimental results for spectral narrowing and mode control of a continuously tunable TE CO 2 laser using a three mirror resonator is reported, with an estimated linewidth of ⪅0.5 GHz.
TL;DR: The linewidth and intensity of the four-wave degenerate mixing signal in Na vapor have been observed as functions of He buffer-gas pressure with cw single-mode dye-laser beams, and a quantitative comparison with theory is made.
Abstract: The linewidth and intensity of the four-wave degenerate mixing signal in Na vapor have been observed as functions of He buffer-gas pressure with cw single-mode dye-laser beams. The width is independent of He pressure, and a quantitative comparison with theory is made. We also report the observation of a new effect, a four-wave mixing Raman-type resonance between two equally populated hyperfine levels.
TL;DR: In this paper, a pressure-induced extra resonance in four-wave mixing (PIER4) was observed using single-mode continuous-wave dye laser, which was verified by the theory of nonlinear susceptibility.
Abstract: We report observation of a pressure-induced extra resonance in four-wave mixing (PIER4 signal) using single-mode continuous-wave dye lasers. The narrow laser linewidth permits for the first time a quantitative verification of the frequency, intensity, and pressure dependence of the PIER4 signal predicted by the theory of the nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}$.