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Quantum Electronics, IEEE Journal of

Issue 2 • Date Feb. 2007

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Displaying Results 1 - 18 of 18
  • Table of contents

    Page(s): 99 - 100
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  • Strain Characteristics of CO2-Laser-Carved Long Period Fiber Gratings

    Page(s): 101 - 108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1424 KB) |  | HTML iconHTML  

    Unique strain characteristics of long period fiber gratings (LPFG) fabricated by a focused CO2 laser beam carving periodic grooves on the fiber are investigated for the first time to our knowledge. Resonant wavelength, transmission attenuation, and polarization dependent loss (PDL) of the CO2-laser-carved LPFG are found to depend strongly on the tensile strain applied, and their strain sensitivities are dependent on the depth of grooves and/or the initial refractive index modulation. The average strain sensitivity of resonant wavelength for LPFG is increased by 229 times and is up to -102.89 nm/mepsiv by means of carving periodic grooves on the fiber. When a stretching force is applied to the LPFG, the resonant wavelength can "blue" shift by -11.84 nm, the absolute value of peak transmission attenuation and the maximum PDL can be increased by 25.913 and 26.535 dB, respectively. The CO2-laser-carved LPFG combines the features of the three types of LPFGs reported previously, i.e, the CO 2-laser-induced LPFGs without physical deformation, the corrugated LPFGs fabricated by hydrofluoric acid etching, and the microbend-induced LPFGs. The mechanisms of refractive index modulation in the CO2-laser-carved LPFGs under tensile strain are rather complicated and may be regarded as a combination of the stress-relaxation-, the groove-, the strain-, and the microbend-induced refractive index perturbations View full abstract»

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  • Doubly Passively Self-Q-Switched Cr4+:Nd3+:YAG Laser With a GaAs Output Coupler in a Short Cavity

    Page(s): 109 - 115
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    By using a GaAs as both an output coupler and a saturable absorber, we present a doubly passively self-Q-switched Cr4+:Nd3+:YAG laser in a short cavity for the first time to our knowledge. This laser can generate more symmetric pulse shape and shorter pulsewidth in comparison with the solely self-Q-switched Cr4+:Nd3+:YAG laser. The output pulse energy and peak powers are higher than those in our previous doubly passively Q-switched lasers. By considering the Gaussian spatial distribution of the intra-cavity photon density and the free carrier absorption (FCA) in GaAs wafer, a set of modified rate equations have been introduced to describe the performances of the doubly Q-switched Cr 4+:Nd3+:YAG laser with GaAs coupler. The numerical solutions of the equations and the experimental results are found to agree with each other very well. The effect of FCA process in GaAs wafer has been discussed and proved to play an important role in the pulse compression and symmetry View full abstract»

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  • Characterization of the Main Semiconductor Laser Static and Dynamic Working Parameters From CW Optical Spectrum Measurements

    Page(s): 116 - 122
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    We present a complete characterization of the work parameters of several types of semiconductor lasers. Static parameters as: power, linewidth and linewidth enhancement factor and also dynamic parameters such as: relaxation oscillations, relative intensity noise and damping rates are calculated using measurements of the optical spectrum of the lasers operated in continuous-wave mode. Methods for the calculation of these parameters are described and applied to the lasers under test by means of a single general setup and a single set of measurements View full abstract»

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  • Controlling a Semiconductor Optical Amplifier Using a State-Space Model

    Page(s): 123 - 129
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    We derive nonlinear and linear state-space control models for a multichannel semiconductor optical amplifier. Verified against the governing partial differential equations through simulation, the linear model tracks modulations up to 20% qualitatively well. Linear feedback control is then employed to design two interchannel crosstalk suppressing systems, one using state feedback into the electronic drive current and the other using optical output feedback into an optical control channel; the controller designed with the linear model is seen to work well even with 100% modulations of the nonlinear system. This linear state-space model opens the way for further robust analysis, design and control of integrated active photonic circuits View full abstract»

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  • Passive Optical Network Approach to Gigahertz-Clocked Multiuser Quantum Key Distribution

    Page(s): 130 - 138
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    We present the application of quantum key distribution (QKD) technologies to fiber-based broad-band passive optical access networks. This application is based on our 850-nm wavelength gigahertz clock-rate single-receiver system, is compatible with existing telecommunications fiber and exploits a wavelength band not currently utilized in access networks. The developed QKD networks are capable of transmitting over distances consistent with the span of access links for metropolitan networks (10 km), at clock frequencies ranging up to 3 GHz View full abstract»

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  • Frequency Uncertainty for Optically Referenced Femtosecond Laser Frequency Combs

    Page(s): 139 - 146
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    We present measurements and analysis of the currently known relative frequency uncertainty of femtosecond laser frequency combs (FLFCs) based on Kerr-lens mode-locked Ti:sapphire lasers. Broadband frequency combs generated directly from the laser oscillator, as well as octave-spanning combs generated with nonlinear optical fiber are compared. The relative frequency uncertainty introduced by an optically referenced FLFC is measured for both its optical and microwave outputs. We find that the relative frequency uncertainty of the optical and microwave outputs of the FLFC can be as low as 8times10-20 and 1.7times10-18, with a confidence level of 95%, respectively. Photo-detection of the optical pulse train introduces a small amount of excess noise, which degrades the stability and subsequent relative frequency uncertainty limit of the microwave output to 2.6times10-17 View full abstract»

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  • Phase Correlation and Linewidth Reduction of 40 GHz Self-Pulsation in Distributed Bragg Reflector Semiconductor Lasers

    Page(s): 147 - 156
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    In this paper, self-pulsation (SP) in a distributed Bragg reflector (DBR) semiconductor laser without a saturable absorber is experimentally and theoretically investigated. Detailed experimental characterizations of the SP DBR laser are reported in the optical and radio-frequency domains. Phase correlation between the longitudinal modes selected by the DBR mirror has been experimentally demonstrated. A theoretical model based on coupled rate equations for three modes has been developed to study the time evolution of phases and amplitudes of the modes. The carrier density modulation, resulting from the beating between adjacent longitudinal modes generates four-wave mixing (FWM) and is responsible for mutual injection locking, leading to passive mode-locking. The calculated power spectral density of the frequency noise derived from the model is in agreement with experimental results and proves that the phases of the longitudinal modes are identically correlated through the FWM process in this type of SP lasers View full abstract»

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  • Raman Scattering and Nd3+ Laser Operation in NaLa(WO 4)2

    Page(s): 157 - 167
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    The continuous-wave laser operation of Nd-doped tetragonal NaLa(WO 4)2 crystal is studied at room temperature by optical pumping in the spectral region overlapping AlGaAs diode laser emission. This crystal has inhomogeneously broadened optical bands. From the room-temperature spectroscopic parameters determined it is found that the optimum Nd concentration for the 4F3/2rarr4IJ laser channels must be in the 3-5 at.% range. For J=11/2 and 13/2 channels (lambdaap1.06 and 1.3 mum) the most favourable polarization configuration is parallel to the crystallographic c axis, while for J=9/2 little polarization dependence of the laser efficiency is predicted. Laser operation was achieved with a 3.35 at.% Nd-doped sample grown by the Czochralski method. The laser operation was tested in an hemispherical optical cavity pumped by a Ti:sapphire laser. Stimulated emission at lambda=1056 nm was achieved for a wide spectral pumping range, lambda=790-820 nm. Stimulated Raman scattering was achieved in the picosecond regime with an efficiency similar to that of monoclinic KY(WO4)2 reference compound View full abstract»

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  • Saturation of 1047- and 1064-nm Absorption in Cr4+:YAG Crystals

    Page(s): 168 - 173
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    To investigate the physical mechanism of the saturation process in Cr4+:YAG crystals we solved the three coupled rate equations which describe the saturable absorber. We experimentally verified this model using two lasers with nanosecond pulses and continuous-wave radiation. We used crystalline and ceramic Cr4+-doped YAG saturable absorbers with various initial transmissions. The ratio between the ground and the excited-state absorption cross section at 1064 nm was measured to be between 3.8 plusmn 0.2 and 4.7 plusmn 0.2 for crystalline and 3.6 plusmn 0.1 for ceramic Cr4+:YAG. The ratio between the above named cross sections at 1047 nm was found to be 6.2 plusmn 0.2 for both crystalline and ceramic Cr4+:YAG. With these results the ground-state and the excited-state absorption cross sections at 1047 nm were calculated to be (9.55plusmn0.01)times10-19 cm2 and (1.54plusmn0.03)times10-19 cm2, respectively View full abstract»

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  • Resonant Saturable Absorber Mirrors for Dispersion Control in Ultrafast Lasers

    Page(s): 174 - 181
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    We discuss a concept for incorporating dispersion compensation into a saturable absorber mirror. This integrated device relies on an absorber layer embedded in a resonator structure and can provide negative dispersion of several 1000 fs2, similar to the spectral phase characteristics of a Gires-Tournois interferometer. A similar integration is possible also for semiconductor gain structures, as they are employed in semiconductor disk lasers. We will provide a detailed analysis of the dispersion compensation capacities of our approach, linking dispersion scaling and nonlinear properties of the device. The theoretical part will be illustrated by dispersion measurements on prototypical devices. We believe that our concept paves the way for fully integrated vertical semiconductor femtosecond lasers but may also find numerous applications in solid state lasers and femtosecond fiber lasers View full abstract»

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  • Micro-Displacement Sensor With Large Dynamic Range Based on Photonic Crystal Co-Directional Coupler

    Page(s): 182 - 187
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    A novel micro-displacement sensor based on a photonic crystal (PhC) co-directional coupler and its sensing technique are presented. The coupler consists of a fixed and a movable PhC segments. Due to the translational symmetry of the PhC structure, this sensing technique is valid for a large displacement on the order of na (n is an integer, and a is the lattice constant of the PhC). After optimization, the outputs of the sensor are approximately sine functions of the displacement, thus it has the potential to achieve high resolution using a subdivision approach. These two characteristics ensure the large dynamic range of the micro-sensor. The properties of the micro-displacement sensor are analyzed using the coupled-mode theory and simulated using the finite-difference time-domain method View full abstract»

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  • On Charge Transport and Low-Frequency Noise in the GaN p-i-n Diode

    Page(s): 188 - 195
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    The current-voltage (I-V) characteristics and low-frequency noise of the GaN p-i-n diodes were investigated in temperature range from 10 K to 300 K. We found that the reverse biased p-i-n diode made of GaN/AlGaN exhibits features of the space charge limited (SCL) current flow and its I-V characteristics can be approximated by the power law I~Vn relation. This phenomenon can be attributed to the presence of the multiple charge traps in the intrinsic region of device. It has been demonstrated that the direct tunneling from traps to bands may occur in diodes at forward and reverse bias with strong support of the Frenkel effect. The low frequency noise in our devices does not depend on temperature in both bias directions under cryogenic conditions. The observed low-frequency noise features support the hypothesis that excess tunneling current and recombination at grain boundaries are origins of the 1/f low-frequency noise in the diode at forward bias. The 1/f noise in the reverse bias regime can be described as a composition of many Lorentzian noise components that originate from traps, which have specific depth distribution View full abstract»

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  • Slow Light Based on Coherent Population Oscillation in Quantum Dots at Room Temperature

    Page(s): 196 - 205
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    We develop a model for slow light based on the coherent population oscillation of quantum dots at room temperature. With the absorption dip and corresponding variation of the refractive index due to the coherent population beating induced by the pump and probe signal, quantum dots can be used as a slow-light medium. Our theoretical model matches the experimental results very well. We also experimentally and theoretically demonstrate that both the forward-bias injection current and reverse-bias voltage can change the group index in a semiconductor quantum-dot waveguide. Our results indicate that quantum-dot devices can be potentially used as electrically and optically controllable slow light devices View full abstract»

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  • Time and Spectrum Resolved Model for Quasi-Three-Level Gain-Switched Lasers

    Page(s): 206 - 212
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    We derive and compute a model to describe the spectral dynamic behavior of quasi-three-level laser resonators operated in gain-switched conditions. This model, based on rate equations, predicts both intensity and spectrum evolutions of the laser output. It is specifically applied to a Yb:YAG laser resonator, and the effects of intracavity losses on the emitted wavelength are also investigated. The phenomena forecasted by our model are in very good agreement with our experiments View full abstract»

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  • IEEE Journal of Quantum Electronics information for authors

    Page(s): 213
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    Freely Available from IEEE
  • IEEE Journal of Quantum Electronics publication information

    Page(s): 214
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    Freely Available from IEEE
  • [Front cover]

    Page(s): 215
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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