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Quantum Electronics, IEEE Journal of

Issue 9 • Date Sept. 1988

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Displaying Results 1 - 22 of 22
  • Suppression of feedback oscillations in free-electron lasers

    Page(s): 18005 - 18006
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    The suppression of feedback oscillations in a free-electron laser (FEL) oscillator has been investigated. It is found, through numerical simulation that a narrow attenuating strip inserted in a waveguide will not reduce FEL performance at the desired frequency and will attenuate feedback oscillations. Simulations are presented for a 5-mm-wavelength FEL with a 40-dB attenuator inserted in the interaction region.<> View full abstract»

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  • A linewidth formula for semiconductor-optical fiber ring lasers

    Page(s): 1807 - 1810
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    The authors derive a formula of linewidth for a semiconductor-optical-fiber ring laser by using coupled rate equations for the active and passive cavity. It is shown that the linewidth is not only the function of the two-cavity length ratio and time delay in fiber, but also the function of light intensity ratio of the two cavities and the phase shift introduced by junctions between the gain medium and the optical fiber.<> View full abstract»

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  • Efficient laser diode side pumped neodymium glass slab laser

    Page(s): 1811 - 1813
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    The authors report efficient pulse operation of an Nd:glass slab laser-side-pumped by laser diode arrays. 7.5 mJ output and a slope efficiency of 29% were obtained with 35 nJ pump energy at 0.8 mu m in 200 mu s pulses. The wide absorption band at 0.8 and low laser loss in this phosphate glass allow for efficient pump light absorption and straightforward scalability to high power. The authors demonstrate 22% optical efficiency in a long pulse, multimode diode pumped laser oscillator based on a phosphate laser glass, LHG-8, highly doped with Nd/sub 2/O/sub 3/. The strong and wide absorption bands in such phosphate glasses allow efficient pumping while somewhat relaxing the expensive wavelength selection requirements for laser arrays compared with crystal line host materials. With such materials, smaller slab thickness or rod diameters that are feasible with Nd:YAG can be used in the side-pumping geometry.<> View full abstract»

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  • Bistable direction switching in an off-axis pumped continuous wave ruby laser

    Page(s): 1818 - 1820
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    A report is presented of the observation of hysteretic bistable direction switching in a single-mode CW ruby laser system. This effect is only observed when the pump beam which is focused into the ruby rod is misaligned with respect to the rod end faces. At low pump powers, the ruby lases in a mode nearly collinear with the pump axis. At a higher pump power the ruby switches to a mode that is collinear with the rod end faces and preserves the original polarization. The effect is large enough to switch the beam by an angle equal to twice the diffraction angle. The observations show that under steady-state pumping, a CW ruby laser can exhibit bistable operation in its output direction and power. A calculation using the heat equation with two concentric cylinders with one as a heat source (pump laser) and the outer wall of the other held at 77K, gives an increase in core temperature of about 0.01 K. Therefore, the increase in temperature is not large enough to change the index of refraction to account for such large macroscopic effects.<> View full abstract»

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  • Effects of electron prebunching on the radiation growth rate of a collective (Raman) free-electron laser amplifier

    Page(s): 1825 - 1828
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    Experiments are reported on the effects of electron prebunching in a mildly relativistic, low-current (200-KV, 1-A) free-electron laser amplifier operating in the collective (Raman) regime at a frequency of approximately 10 GHz. Prebunching is established by injecting an electromagnetic wave into a bifilar helical wiggler and then transporting the bunched beam into a second magnetic wiggler region. The wave growth rate is deduced from measurements of the radiation intensity as a function of interaction length. Observations show that prebunching can increase the radiation growth rate manyfold as compared with a system without prebunching. Studies are presented both in the small-signal (linear) regime, and in the nonlinear (saturated) regime.<> View full abstract»

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  • Thermal shifts of the spectral lines in the /sup 4/F/sub 3/2/ to /sup 4/I/sub 11/2/ manifold of an Nd:YAG Laser

    Page(s): 1829 - 1832
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    A report is presented of the thermal shifts of eleven of the twelve lines from the /sup 4/F/sub 3/2/ Stark energy levels to the /sup 4/I/sub 11/2/ energy levels in an Nd:YAG laser for a temperature change from 20-200 degrees C. The thermal shift difference between the Stark sublevels R/sub 1/, R/sub 2/ in /sup 4/F/sub 3/2/ is found to be about -0.6+or-0.6 cm/sup -1//100 degrees C. Within experimental uncertainty, all of the lasing lines either moved to longer wavelength or remained unchanged with increasing temperature.<> View full abstract»

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  • Gain characteristics of an axial gas discharge interacting with a transverse rotating magnetic field

    Page(s): 1833 - 1836
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    Gain measurements within an axial discharge interacting with a transverse rotating magnetic field are presented. The effects of applied voltage and magnetic field strength on centerline gain are discussed. This is followed by an investigation of the radial gain profile and the saturation intensity. Observed values of the small signal gain and the saturation intensity were 0.85 m/sup -1/ and 160 W/cm/sup 2/, respectively.<> View full abstract»

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  • Surface emitting semiconductor lasers

    Page(s): 1845 - 1855
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    A description is given of the research progress in developing a vertical-cavity surface-emitting (SE) injection laser based on GaAlAs/GaAs and GaInAsP/InP systems. Ultimate laser characteristics, device design, state-of-the-art performances, possible device improvement, and future prospects will also be discussed. The authors propose a vertical-cavity surface emitting semiconductor laser. To reduce the threshold current, they improved the laser reflector and introduced a circular buried heterostructure. The microcavity structure, which is 7 mu m long and 6 mu m in diameter, was realized with a threshold of 6 mA. Thus, possibilities of an extremely low threshold current SE laser device and a densely packed two-dimensional array are suggested.<> View full abstract»

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  • A single-wavelength DFB structure with a synchronized gain profile

    Page(s): 1864 - 1872
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    A distributed-feedback structure having a predominant gain at an edge wavelength of the Bragg reflection band is proposed and analytical results are presented. The structure has both refractive-index and gain-loss profiles with the same period. Since the gains per period at two edge wavelengths of this structure is substantially different, the selective amplification at the single wavelength is less sensitive to both fabrication accuracy and matching conditions than other single-wavelength schemes which utilize refractive-index profile alone.<> View full abstract»

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  • Theory of mode hopping and phase conjugation characteristics in degenerate four-wave mixing

    Page(s): 1893 - 1907
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    A large-signal theory of noncollinear degenerate four-wave mixing (DFWM) is presented, taking into account the pump depletion and the full nonlinear polarization density appropriate for the noncollinear geometry. Phases of all of the interacting fields, as well as the amplitudes, are obtained as functions of the spatial coordinate. Owing to the completeness of the set of analytic solutions, considerable physical insights into the physics of DFWM are obtained. The DFWM exhibits a variety of rich behaviors, including hysteresis and bistability, multistability, and multiple isolated branches. The authors show that all of these behaviors can be explained in a unified way, that is, in terms of mode hopping characteristics.<> View full abstract»

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  • High-power narrow-band operation and Raman frequency conversion of an electron-beam pumped krypton excimer laser

    Page(s): 1908 - 1914
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    A Kr excimer laser pumped by a relativistic electron beam has generated high-power output by using a cavity composed of a Si mirror and M/sub g/F/sub 2/ mirror. The threshold gas pressure for laser oscillation is 10 atm, and the maximum output power achieved so far is 6.6 MW at 15 atm. The maximum power is limited by the surface damages on the mirrors. This laser output, oscillating at 145.7 nm, has a spectral width of 0.8 nm (FWHM). Efficient spectral narrowing down to 0.1 nm has been achieved with a 32 degrees apex angle MgF/sub 2/ prism inserted in the cavity giving 3.5 MW peak power at 15 atm of Kr gas pressure. Wavelength conversion by stimulated Raman scattering in high-pressure H/sub 2/ has been demonstrated for efficient extension of the laser wavelength.<> View full abstract»

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  • Room temperature near-infrared tunable Cr:La/sub 3/Ga/sub 5/SiO/sub 14/ laser

    Page(s): 1922 - 1926
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    Laser operation was achieved in a Cr-doped crystal of La/sub 3/Ga/sub 5/SiO/sub 14/. The laser had a free-running wavelength of 960 nm at room temperature from 862 to 1107 nm. Up to 80 mW output power has been measured with 1.5 W of pump power absorbed from a krypton ion laser. The /sup 4/T/sub 2/ fluorescence spectrum showed a peak at 890 nm indicating an unusually large Franck-Condon shift. At room temperature the fluorescence lifetime was 5.3 mu s and the fluorescence quantum yield was measured to be about 14%.<> View full abstract»

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  • Parametric study of the CuBr laser with hydrogen additives

    Page(s): 1927 - 1935
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    A systematic investigation of the electric parameters of the CuBr laser plasma during the excitation pulse in their correlation to the laser output characteristics is presented. Based on the electric parameters, the temporal course is calculated of the electron density during the discharge. The authors offer a simple mechanism which generally explains how the hydrogen occurred in the copper vapor laser. The mechanism consists of shielding copper ionization by the process of electron detachment from negative hydrogen ions.<> View full abstract»

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  • Theory of intracavity frequency doubling in passively mode-locked femtosecond lasers

    Page(s): 1877 - 1883
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    The authors construct a quantitative theoretical model of an intracavity frequency-doubled and passively mode-locked laser, supported by experimental observations with a colliding pulse mode-locked femtosecond dye laser. The major findings are that for second-harmonic conversion efficiencies consistent with continuing laser operation (<5%): (1) a stable mode-locking regime always exists, although it narrows somewhat with increasing conversion efficiency; and (2) the duration of the fundamental pulses can always be preserved, even in the femtosecond time domain, by readjusting saturable gain and saturable loss under the same conditions. Both the model and observations contrast with previous studies of actively mode-locked and synchronously mode-locked lasers containing intracavity frequency-doubling crystals View full abstract»

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  • Analysis of the nonlinear coaxial coupler

    Page(s): 1915 - 1921
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    The authors present an analysis of the nonlinear properties in the coaxial fiber coupler. Two approaches are used, numerical beam propagation calculations in the radially symmetric waveguide and analysis of the coupled equations describing the interaction of the local modes. The two methods are compared and the region of validity of the local node analysis is then determined. They examine in detail the critical power condition for this structure and show how the design considerations to achieve this conditions can be understood View full abstract»

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  • Organometallic vapor phase epitaxial growth of (AlxGa 1-x)0.5In0.5P and its heterostructures

    Page(s): 1856 - 1863
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    Low pressure organometallic vapor-phase epitaxial growth of Ga0.5In0.5P and (AlxGa1-x) 0.5In0.5P is examined. Epitaxial layers of bulk materials are characterized using photoluminescence, electroreflectance, Raman scattering spectroscopy, and surface morphology studies to determine lattice match and optimum growth conditions. Lattice matching at the growth temperature produces featureless growth surfaces, while lattice matching at room temperatures results in minimum photoluminescence linewidth but cracked surfaces due to tensile strain during growth. Raman scattering spectra of the quaternary reveal a three mode structure, with spectral peaks due to GaP-like, InP-like, and AIP-like LO phonons. Heterostructures are investigated including quantum shifts from a series of superlattices. These materials are incorporated in double-heterostructure lasers and single-quantum-well laser with graded-index separate confinement heterostructure View full abstract»

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  • Periodic resonators for average-power scaling of stable-resonator solid-state lasers

    Page(s): 1821 - 1824
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    Thermal lensing of solid-state laser gain media causes the resonator-mode parameters to vary with pump power. For a single-rod laser system, this effect limits the output-power range for stable laser operation. For multirod laser systems, the power range for stable operation can be increased beyond the limit of single-rod resonators by placing the rods in a periodic resonator structure View full abstract»

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  • Experimental and theoretical studies of complex pulse evolutions in a passively mode-locked ring dye laser

    Page(s): 1884 - 1892
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    A detailed experimental and theoretical study has been made of the role of group velocity dispersion and self-phase modulation arising from time-dependent absorption saturation and the optical Kerr effect in a Rhodamine 110 CPM dye laser. Periodic pulse evolutions are observed, when both positive and negative frequency chirp are present, that are reminiscent of those governed by the nonlinear Schrodinger equation but that are, in fact, distinctly different. Similar results have been obtained with the standard Rhodamine 6G system, and it is believed that the theoretical model is generally applicable to any passively mode-locked femtosecond dye laser. An important consequence of these results is that they permit the absolute value of the group velocity dispersion in the laser cavity to be estimated View full abstract»

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  • The influence of power level on injection laser linewidth and intensity fluctuations including side-mode contributions

    Page(s): 1873 - 1876
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    The contribution of side modes to the main-mode line-width is calculated as function of power output using analytic relations and verified using a series of Monte Carlo calculations. For well-behaved lasers having photon lifetimes of 0.88 and 1.57 ps and gain compression of 10% or less, it is found that the total linewidth decreases monotonically with increasing power output. These lasers have main-mode to side-mode ratios in the range 100-300 at 3 mW output; they exhibit side-mode contributions to main-mode linewidth of 17 and 57% respectively at a power level of 10 mW and modal ratios of 940 and 390. When the gain compression exceeds 10% as it may in lasers running at 10 mW or more, the linewidth can reach a minimum and then increase with increasing power level, in accordance with laboratory observation on some lasers View full abstract»

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  • Transverse modes of plane-mirror waveguide resonators

    Page(s): 1936 - 1946
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    The author examines what familiar first-order theory predicts about plane-plane resonator behavior, stressing the similarities and differences between circular-bore and square-bore devices. The effects of moving a mirror away from the guide are discussed, and illustrated with novel results for the modes and losses of single-guide and U-folded designs with square bores. It appears that laser performance cannot be accurately predicted by previous treatments which use only a few (1-3) waveguide nodes View full abstract»

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  • Theory of wavelength tuning in two-segment distributed feedback lasers

    Page(s): 1837 - 1844
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    A description is given of a theory of wavelength tuning in two-segment distributed-feedback (DFB) semiconductor lasers. Continuous tuning with a range of at least several angstroms (more than 100 GHz) is feasible. For the first time the tuning mechanism of two-segment DFB lasers is explained in terms of the fundamental phase and amplitude reflection properties of the waveguide gratings. The theoretical framework developed provides physical insights into the wavelength tuning mechanism and can be used in the development of novel and more efficient tuning structures View full abstract»

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  • Lineshape measurement of semiconductor lasers below threshold

    Page(s): 1814 - 1817
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    A novel heterodyne method for measuring the linewidth ranging from 100 MHz to 100 GHz is developed. The line shape of 1.3-μm DFB (distributed-feedback) lasers biased below threshold is measured by the use of this method. The center-frequency shift and the linewidth are determined as functions of the bias current, showing linear dependencies on the bias current. From this result, the linewidth enhancement factor is estimated View full abstract»

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Aims & Scope

The IEEE Journal of Quantum Electronics is dedicated to the publication of manuscripts reporting novel experimental or theoretical results in the broad field of the science and technology of quantum electronics..

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Meet Our Editors

Editor-in-Chief
Aaron R. Hawkins
Brigham Young University