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Quantum Electronics, IEEE Journal of

Issue 5 • Date May 2000

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Displaying Results 1 - 14 of 14
  • Real-time optical spectrum analysis based on the time-space duality in chirped fiber gratings

    Publication Year: 2000 , Page(s): 517 - 526
    Cited by:  Papers (58)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    Based on time-space duality, we deduce a time-domain equivalent to the Fraunhofer (far-field) approximation in the problem of spatial diffraction. We can use this equivalence to carry out a real-time optical spectrum analysis, which is shown to be realizable by using, as the dispersive media, filtering devices based on chirped distributed resonant coupling. In particular, we present the design of linearly chirped fiber gratings (reflection configurations) and linearly chirped intermodal couplers (transmission configurations) to work as real-time spectrum analyzers. The proposed systems are shown to work properly by means of simulation tools. Furthermore, we use joint time-frequency signal representations to get a better understanding of the physical processes that determine the behavior of these systems. In this way, we demonstrate that the propagation of a given signal through a chirped fiber grating (or a chirped intermodal coupler), under the temporal Fraunhofer conditions, translates into a temporal separation of the spectral components of the signal. The results of our study indicate potential important applications based on this effect. View full abstract»

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  • Optical intensity modulator based on a novel electrooptic polymer incorporating high /spl mu//spl beta/ chromophore

    Publication Year: 2000 , Page(s): 527 - 532
    Cited by:  Papers (15)  |  Patents (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (143 KB)  

    We have synthesized a novel electrooptic (EO) polymer based on a high /spl mu//spl beta/ chromophore incorporating tricyanobutadiene acceptors. A crosslinked polyurethane network was also adopted to enhance its thermal stability. In order to find the optimum poling condition for the polymer, the influence of the electric poling profile on optical characteristics such as the EO effect, thermal stability, and damage was investigated. Then a high-speed intensity modulator using the EO polymer was designed and fabricated. The measured half-wave voltage V/sub /spl pi// was 4.5 V at the wavelength of 1.31 /spl mu/m. Accordingly, the achieved EO coefficient r/sub 33/ was as high as 25 pm/V, and the thermal stability of the poled polymer was as high as 95/spl deg/C. Finally, the modulator was successfully operated up to 40 GHz. View full abstract»

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  • Studies of the spatial distribution and beam quality of Stokes output from a Raman generator pumped by a broad-band KrF laser

    Publication Year: 2000 , Page(s): 533 - 540
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB)  

    One-dimensional stimulated Raman scattering (SRS) theory is extended to three dimensions by the concept of transverse modes associated with the Fresnel number. Two simplified models are introduced to evaluate the beam parameters and waist position under low gain. The dependence of waist size and position of the Stokes beam on the focus position and Rayleigh length of the focused pump laser is analyzed and verified by experiment. The Fresnel number approach is utilized to evaluate the energy density distribution and the mode structure of the pump laser in a Raman cell under high gain. The different configurations are classified and relevant mode formulation and spatial distribution are discussed. The experimental result shows that the beam quality of the Stokes output from a Raman generator depends essentially on the pump configuration and the geometric parameters of the pump laser and is insensitive to the practical pump power, which agrees with the theoretical analysis. The results obtained are adopted to improve the beam quality of the first-order Stokes output from the Raman generator with different configurations. View full abstract»

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  • Beam-quality studies of nanosecond singly resonant optical parametric oscillators

    Publication Year: 2000 , Page(s): 541 - 549
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    A numerical model for a singly resonant, nondegenerate optical parametric oscillator, which includes diffraction and idler absorption, has been developed. This model requires just one equation for the resonated signal field to be numerically integrated, while the pump and idler fields are reconstructed from their analytic solutions and the dynamics of the signal field. Typical results from our simulations are, for example, output intensities and threshold fluencies, which can be compared with those obtained from experiments. The spatial beam quality of output beams produced by our model is evaluated via the M/sup 2/ factor. We present results from the simulation which are consistent with experimental evidence, particularly in reference to the impact of idler absorption. View full abstract»

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  • Optical signal processing using nonlinear distributed feedback structures

    Publication Year: 2000 , Page(s): 550 - 555
    Cited by:  Papers (38)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (162 KB)  

    We analyze the optical signal processing functionality of periodic structures consisting of alternating layers of materials possessing opposite Kerr nonlinearities. By elaborating an analytical model and employing numerical simulations, we explore the performance of proposed passive optical limiters and switches. We prove that the proposed limiters provide true limiting by clamping the transmitted intensity at a level which is independent of the incident intensity. We explore the response of optical switches for signal and pump beams having the same and different frequencies. We describe and quantify the performance of the proposed structures in the realization of all-optical OR gates and optical hard-limiters. In addition, we prove that, for fabrication errors as large as 10%, qualitative device functionality remains, with performance only modestly degraded. View full abstract»

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  • Full-vectorial finite-element beam propagation method for nonlinear directional coupler devices

    Publication Year: 2000 , Page(s): 556 - 562
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (167 KB)  

    A new full-vectorial beam propagation algorithm based on the computationally-efficient finite element method is presented which can accurately model nonlinear directional couplers. The robust perfectly matched layer boundary condition is incorporated into the formulation so as to effectively absorb the unwanted radiation out of the computational domain. The accuracy of the proposed vectorial propagation approach is demonstrated through comparison with other semivectorial approaches and the weaknesses of the commonly-used scalar approaches are highlighted. The proposed full-vectorial approach considers only two transverse components of the magnetic field without destroying the sparsity of the matrix equation, so it is numerically very efficient. View full abstract»

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  • Analysis of an intermediate-mode-assisted directional coupler using Bloch theory

    Publication Year: 2000 , Page(s): 563 - 573
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (353 KB)  

    The exact numerical solution of the intermediate-mode-assisted directional coupler problem is obtained using the Bloch wave approach. The approach is based on a calculation of the Bloch waves and their matching with the ideal modes of an uniform waveguide. The approximate results obtained from the paraxial wave equation and from the three-mode model are compared with the exact ones. It is shown that the paraxial approximation, as well as the three-mode approximation, provide only a qualitatively correct physical picture. Using the Bloch wave approach, however, one obtains quantitatively correct results. It is demonstrated that one can control the exchange of power between two distant identical coupled waveguides using an embedded periodic structure along the z direction. The power exchange control is based on a symmetry of Bloch waves and results from the interaction of the lowest order waveguide modes with the high-order modes. View full abstract»

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  • Enhanced TOAD performance by negative frequency-detuned signal and control picosecond optical pulses

    Publication Year: 2000 , Page(s): 574 - 582
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    A numerical investigation has been undertaken of the operating characteristics of Terahertz Optical Asymmetric Demultiplexer (TOAD) devices subject to frequency-detuned signal and control picosecond optical pulses, taking into account the wavelength dependence of the differential gain coefficient and carrier density linewidth enhancement factor. It is shown that, by shifting the signal pulses toward lower frequencies compared with that of control pulses, the contrast ratio can be significantly enhanced and the amplitude modulation can simultaneously be considerably decreased. The switching energy demonstrates small changes over a broad frequency detuning range. The simulations show excellent agreement with published experimental measurements. Furthermore, two operational modes for the TOAD configuration are identified. View full abstract»

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  • Photo-enhanced native oxidation process for Hg/sub 0.8/Cd/sub 0.2/Te photoconductors

    Publication Year: 2000 , Page(s): 583 - 589
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (130 KB)  

    Proposes an easy and reproducible vapor-phase photo surface treatment method to improve the device performance of the Hg/sub 0.8/Cd/sub 0.2/Te photoconductive detector. We explore the effect of surface passivation on the electrical and optical properties of the HgCdTe photoconductor. Experimental results, including surface mobility, surface carrier concentration, metal-insulator-semiconductor leakage current, 1/f noise voltage spectrum, the 1/f knee frequency, responsivity R/sub /spl lambda//, and specific detectivity D* for stacked photo surface treatment and ZnS or CdTe passivation layers are presented. These data are all directly related to the quality of the interface between the passivation layer and the HgCdTe substrate. We found that, by inserting a photo native oxide layer, we can shift the 1/f knee frequency, reduce the noise power spectrum, and achieve a lower surface recombination velocity S. A higher D* can also be achieved. It was also found that HgCdTe photoconductors passivated with stacked layers show improved interface properties compared to the photoconductors passivated only with a single ZnS or CdTe layer. View full abstract»

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  • Highly uniform operation of high-performance 1.3-/spl mu/m AlGaInAs-InP monolithic laser arrays

    Publication Year: 2000 , Page(s): 590 - 597
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    We describe the fabrication of monolithically integrated 1/spl times/12 arrays of 1.3-/spl mu/m strain-compensated multiquantum-well AlGaInAs-InP ridge lasers. The laser array shows highly uniform characteristics in threshold current, slope efficiency, and lasing wavelength with a standard deviation of 0.08 and 0.27 mA, 0.012 and 0.007 W/A, and 0.59 and 0.57 nm, respectively, at 20/spl deg/C and 100/spl deg/C. Besides, each laser on the array exhibits a low threshold current of 8 mA at 20/spl deg/C and 21 mA at 100/spl deg/C, a characteristic temperature of 92 K, and a slope efficiency drop of 0.7 db between 20/spl deg/C and 80/spl deg/C. A low thermal crosstalk of less than -4 dB can be obtained from one diode as the injected current of other elements is increased to 70 mA. Also, each laser on the array has a negligible degradation after a 24-hr burn-in test at 80 mA and 100/spl deg/C. An expected lifetime of more than 20 years is estimated for the lasers when operating at 10 mW and 85/spl deg/C. The lasers have a small-signal modulation bandwidth of about 9 GHz at 25/spl deg/C and a low relative intensity noise of -155 dB/Hz without an isolator at 2.5 GHz. It can transmit a 2.5-GHz signal to 50 km through standard single-mode fiber and to 308 m through multimode fiber, with a clear eye opening in OC-48 data-rate tests. View full abstract»

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  • Theoretical and experimental investigations of a diode-pumped quasi-three-level laser: the Yb/sup 3+/-doped Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (Yb:GdCOB) laser

    Publication Year: 2000 , Page(s): 598 - 606
    Cited by:  Papers (29)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (293 KB)  

    We present a theoretical and experimental analysis of a diode-pumped Yb/sup 3+/-doped Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (Yb:GdCOB) laser. A new model for a diode-pumped quasi-three-level laser is described. The effects of absorption saturation, temperature profile, and the beam quality M/sup 2/ factor of the pump diode have been taken into account, for the first time to our knowledge. We have obtained a good agreement between experimental measurements and theoretical calculations with two different pump wavelengths, 902 and 976 nm. Our model has given good predictions of the laser performances for different crystal temperatures and different M/sup 2/ factors of the pump beam. As much as 440 mW of output power (at 1082 nm) have been achieved for 640 mW of absorbed pump power at 976 nm, corresponding to one of the highest slope efficiencies (81%) ever obtained with Yb-doped lasers. View full abstract»

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  • A coherent all-solid-state laser array using the Talbot effect in a three-mirror cavity

    Publication Year: 2000 , Page(s): 607 - 614
    Cited by:  Papers (10)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (213 KB)  

    Lateral mode coupling in a diode-pumped Nd:YAG microchip laser array is demonstrated with a Talbot cavity for the first time. The relatively low laser gains of solid-state lasers compared with diode lasers and CO/sub 2/ lasers, to which the Talbot cavity has already been applied successfully, are solved by employing a novel auxiliary Talbot cavity configuration. A brighter twin-peak far-field pattern indicating an out-of-phase array mode, whose spot is 9.3 times smaller than that obtained by incoherent superposition of the individual microchip laser outputs, is obtained from the phase-locked microchip laser array with a mode-selecting slit. Without the mode-selecting slit, a far-field pattern with a single narrow peak is obtained, showing that the array is locked in an in-phase mode, presumably because of multiple reflections in the auxiliary Talbot cavity. View full abstract»

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  • Influence of energy-transfer upconversion on the performance of high-power diode-end-pumped CW lasers

    Publication Year: 2000 , Page(s): 615 - 619
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (134 KB)  

    The influence of energy-transfer upconversion (ETU) on the performance of diode-end-pumped lasers is studied by including ETU effects into the space-dependent rate equations. The dependence of ETU rates on the mode-to-pump size ratio and on the output mirror transmission is derived. Experiments for Nd:YAG and Nd:YVO/sub 4/ crystals are performed to validate the present model. It is found that the ETU process increases the sensitivity of the output power to the output mirror transmission but its influence on the output power is not significant for low output transmission. View full abstract»

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  • Numerical simulation and analytical description of thermally induced birefringence in laser rods

    Publication Year: 2000 , Page(s): 620 - 626
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB)  

    The results of numerical simulations based on finite-element methods for thermally induced birefringence in Nd:YAG crystal rods are compared with measurements and analytical solutions. A novel analytical solution for inhomogeneous pumping is presented. It is shown that the behavior of thermally induced birefringence is very sensitive to the pump geometry. 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..

Full Aims & Scope

Meet Our Editors

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