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Quantum Electronics, IEEE Journal of

Issue 11 • Date Nov 2001

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Displaying Results 1 - 14 of 14
  • Low phonon energy, Nd:LaF3 channel waveguide lasers fabricated by molecular beam epitaxy

    Page(s): 1469 - 1477
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    We report the first fabrication and laser operation of channel waveguides based on LaF3 planar thin films grown by molecular beam epitaxy. To our knowledge, this is the lowest phonon energy dielectric material to have shown guided-wave laser operation to date. A full characterization, in terms of spectroscopy, laser results, and propagation losses, is given for the planar thin films upon which the channel waveguides are based. Two channel-fabrication methods are then described, the first involves ion milling and the second takes the novel approach of using a photo-definable polymer overlay. Laser operation in Nd-doped samples is demonstrated at 1.06, 1.05, and 1.3 μm, and the potential for mid-infrared laser sources based on such guides is discussed View full abstract»

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  • Isotropic photonic structures: Archimedean-like tilings and quasi-crystals

    Page(s): 1427 - 1434
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB) |  | HTML iconHTML  

    We present a detailed numerical study of Archimedean-like tilings and quasi-crystals. Archimedean-like tilings are periodic structures like conventional 2D photonic crystals. However, the use of two kinds of polygons for the tiling and thus, the use of crystal unit cells of several atoms, can lead to a 12-fold local symmetry. We show that Archimedean-like tilings offer a much higher degree of isotropy than a conventional 2D Bravais lattice because the gap widths are almost independent of the light propagation direction. Besides, the conditions for gap opening and the mean gap widths remain similar to those met for conventional triangular and honeycomb lattices. The comparison between Archimedean-like tilings and quasi-crystals is carried out in two steps according to the level of the refractive index modulation. In the case of strong modulation, we show that Archimedean-like tilings with a few atoms per unit cell are simple and well-working alternatives to complex quasi-crystals. They can present the same degree of isotropy for the same positions and widths of the photonic gaps. A good fit is also found between quasi-crystals and periodic structures constructed from the simplest approximants, thereby showing the importance of short-range wave-lattice interactions in that case. In a second step, we consider weakly (or moderately) modulated structures, where long-range interactions are possible. A quasi-periodic (fractal) structure recently reported in the literature is compared to an Archimedean tiling of very large unit cell (181 atoms). Surprisingly, the unusual quasi-crystal gap at long wavelength cannot be reproduced for the Archimedean tiling in spite of its very large unit cell size View full abstract»

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  • The spectral switch of partially coherent light in Young's experiment

    Page(s): 1377 - 1381
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (123 KB)  

    The spectral switch in Young's two-slit experiment with partially coherent light is studied based on the propagation law of partially coherent light. It is shown that, by varying the source correlation, slit parameter and observation distance, the on-axis spectrum changes gradually, and the spectral switch can take place, where the spectral shift exhibits a rapid transition from red to blue shift or vice verse View full abstract»

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  • Accurate determination of the weak optical absorption of piezoelectric crystals used as capacitive massive bolometers

    Page(s): 1396 - 1400
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (105 KB) |  | HTML iconHTML  

    The resonant frequency in a piezoelectric crystal is strongly temperature dependent. This physical property may be exploited to measure small overheating of the material induced by a weak optical absorption. A sample of congruent LiNbO3 is exposed to a laser beam, with a wavelength λ chosen inside the transparency window. One of the piezoelectric resonances is selected and used as an internal thermal probe to record both dynamical and steady state overheating induced by the residual absorption k of the material. A bolometer-type equation describing the time dependence of the sample temperature is used to determine k accurately, the capacitance-rather than frequency-being the temperature-sensitive electrical parameter of the resonance View full abstract»

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  • Assessment and modeling of aging in electro-absorption distributed Bragg reflector lasers

    Page(s): 1382 - 1387
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB) |  | HTML iconHTML  

    We describe a protocol for assessing aging in the tuning section of a multisection distributed Bragg reflector laser integrated with amplifier, tap coupler, and electro-absorption modulator. Under accelerated aging, we observe a transient change of nonradiative recombination followed by saturation. A simple model of aging of the Bragg section of the tunable lasers enables prediction of changes in each wavelength channel using information obtained from a single channel only View full abstract»

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  • Temporal fluctuation in photorefractive wave mixing

    Page(s): 1388 - 1395
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB) |  | HTML iconHTML  

    We analyzed the physical origin of the temporal fluctuation of the photorefractive space-charge field, and found that fluctuation mainly results from fluctuations in the free-charge-carrier density which is, in turn, due to the very small fluctuations of the input total intensity and the thermal excitation. We studied the influence of various externally-controlled parameters such as the grating wave vector, the applied electric field, and the moving velocity of the grating on the fluctuation of the photorefractive space-charge field. We present experimental results for temporal fluctuations in photorefractive BaTiO 3:Ce two-wave mixing and in BaTiO3 self-pumped phase conjugation. The experimental results show agreement with the theoretical result View full abstract»

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  • Modeling, characterization, and experimental/numerical comparison of signal and fluorescence amplification in Ti,Er:LiNbO3 waveguides

    Page(s): 1460 - 1466
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB) |  | HTML iconHTML  

    A complete model for signal and fluorescence amplification in Ti,Er:LiNbO3 waveguides under 1480 and 980 nm excitation, which includes transitions involving high energy levels, is presented. Most of the waveguide parameters that the model requires have been determined or checked in situ. In order to numerically solve the proposed model, the overlapping factors method has been adapted to these waveguides and improved, obtaining a large computing time reduction with sufficiently accurate results. Finally, results from signal gain and ASE spectral measurements and numerical simulations have been compared. The remarkable agreement confirms both the model assumptions and the used characterization techniques. Moreover, the unusually short computing time which is consumed makes the model suitable for design and optimization processes View full abstract»

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  • VCSEL design using the bidirectional beam-propagation method

    Page(s): 1435 - 1440
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB) |  | HTML iconHTML  

    We present an optical modeling approach for calculating vertical-cavity surface emitting laser (VCSELs) modes based on the bidirectional beam propagation method. Compared with existing approaches, it is flexible, efficient, and convenient. To demonstrate and validate the approach, we examined several design problems for oxide-confined VCSEL devices. Specifically, we modeled the blue-shift phenomenon in small oxidized VCSELs and compared our calculations with previous results. We also examined the dependence of the threshold gain on different oxide-aperture shaped designs and on the thickness and placement of an aperture layer View full abstract»

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  • Gain, refractive index change, and linewidth enhancement factor in broad-area GaAs and InGaAs quantum-well lasers

    Page(s): 1449 - 1459
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (242 KB) |  | HTML iconHTML  

    We report experimental and theoretical results for the injection-level dependence of the gain, refractive index variation, and linewidth enhancement factor (α) for four different quantum-well (QW) laser structures. Two of the lasers have GaAs QW layers that vary in width while the other two have InGaAs active layers that vary in QW depth. Experimental Hakki-Paoli data are used to compare gain, index change, and α-parameter between these pairs of devices. The results of two simulations are compared to the experimental data. The first is based on the approximation of parabolic bands for both the conduction and valence bands while the second employs the k·p method to refine the calculation of the valence bands. Our findings include: (1) narrower and deeper QWs yield lower α values; (2) modeling results from the k·p method are only slightly improved over those from the parabolic band model; (3) at high injection levels, stimulated emission below threshold is a prominent effect in these devices; and (4) at high injection levels, carriers in the barrier energy states above the well are shown to be responsible for increasing α values View full abstract»

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  • Grating-based surface-emitting tapered unstable resonator laser simulations and experiments

    Page(s): 1441 - 1448
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    We have fabricated and characterized tapered unstable resonator lasers with two slightly different resonator geometries, one with a linear taper and one with a nonlinear taper, to investigate the effect of resonator geometry on the performance characteristics. Special attention has been paid to the modal behavior and its dependence on drive current. We investigate the modal behavior by monitoring the focused spot produced by an integrated focusing grating coupler. To aid in the design of the lasers and the analysis of the measurement results, we implemented numerical simulations based on the beam-propagation method and obtained good agreement between measurements and simulations. We find that the threshold current, the efficiency and the optical field stability, including filamentation threshold, are significantly improved by adjusting the shape of the current injection region to the diverging field profile in the tapered section. Improvements in threshold current and efficiency are attributed to a more efficient use of the injected carriers, while improvement in optical field stability is attributed to reduced carrier induced phase front distortion. We conclude that a relatively small modification of the resonator geometry can lead to large improvements in laser performance View full abstract»

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  • Normal-incidence, high-temperature, mid-infrared, InAs-GaAs vertical quantum-dot infrared photodetector

    Page(s): 1412 - 1419
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (154 KB)  

    The growth, fabrication, and characterization of a normal-incidence, high-temperature, mid-wavelength infrared, InAs-GaAs vertical quantum-dot infrared photodetector with a single Al0.3 Ga0.7As current-blocking barrier are described and discussed in detail. A specific detectivity ≈3×109 cmHz1/2/W is measured for a detector temperature of 100 K at a bias of 0.2 V. Detector characteristics are measured for temperatures as high as 150 K. The superior low bias performance of the vertical quantum-dot infrared photodetector ensures its compatibility with commercially available silicon read-out circuits necessary for the fabrication of a focal plane array View full abstract»

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  • Threshold gain and single-mode oscillation of two-dimensional photonic bandgap defect lasers

    Page(s): 1420 - 1426
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB) |  | HTML iconHTML  

    Defect laser behavior was simulated as a function of various parameters. When the crystal size was increased from 8×8 to 12×12 cylinders, the quality factor of the defect cavity increased from 6×103 to 5×106 while the threshold gain decreased by two orders of magnitude, It was predicted that a triangular-lattice photonic defect laser would be polarized in the Γ-M direction. The defect laser studied usually showed multi-mode oscillation with a large defect radius, where the threshold gain was small. When the refractive indices of the cylinders and the defect, surrounded by air, were both 3.5, single-mode oscillation and a small threshold gain (4 cm-1) were, nevertheless, achieved at suitable device parameters that made the side-mode suppression ratio sufficiently large at 103. A single-mode oscillation and a small threshold gain (less than 20 cm(-1)) were also predicted over the entire defect radius range when the defect refractive index was decreased from 3.5 to 1.5 View full abstract»

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  • Edge-coupled InGaAs p-i-n photodiode with the pseudowindow defined by an etching process

    Page(s): 1409 - 1411
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (55 KB) |  | HTML iconHTML  

    We have fabricated an edge-coupled InGaAs p-i-n photodiode (EC-PD) with its pseudowindow defined by conventional photolithographic processes and its facet formed by etching. Through fine tuning the window thickness, the transit-time-limited bandwidth was largely increased and device bandwidth was improved from ~8 GHz toward ~20 GHz. Such a tuning process is in fact a controlled selective chemical etching process, and optimizes the window thickness through reducing the thickness of undepleted absorption region. Although after tuning, the device preserves low leakage, the anisotropic chemical etching results in a sloped and reentrant facet that degrades the optical coupling efficiency and thus the device responsivity, which drops from 0.5 to 0.4 A/W at 1.3-μm wavelength for a device without an anti-reflection coating. For the EC-PD with the optical input facet formed by etching instead of the cleavage process, the device yield can be improved and direct die separation is feasible, which amounts to a huge cost reduction. Furthermore, an edge-coupled photodiode array, which requires several reliable diodes in series, can be realized View full abstract»

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  • Laser resonator design using optical ray tracing software: comparisons with simple analytical models and experimental results

    Page(s): 1401 - 1408
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (159 KB) |  | HTML iconHTML  

    Software simulation of complex resonator and optical system designs offer the potential to couple traditional opto/mechanical tolerance analysis with the required system performance. One such a software platform, ASAP, and the methodology to perform tolerance analyses has been evaluated and validated for the case of the crossed Porro resonator. Simulation results and experimental measurements are presented and discussed 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