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Quantum Electronics, IEEE Journal of

Issue 7 • Date July 2001

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Displaying Results 1 - 15 of 15
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  • Chaotic self-pulsation and cross-modulation in a wavelength-selective external-cavity laser diode

    Page(s): 911 - 918
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (126 KB) |  | HTML iconHTML  

    Chaotic self-pulsation in a single wavelength external-cavity laser diode is observed. It is shown that the self-pulsation is caused by interdependencies between the optical output power and the compound cavity losses through the refractive index of the laser diode material. Refractive index changes result in a detuning between the externally selected wavelength and the weak internal-mode structure of the anti-reflection coated laser diode. This detuning is directly related to the compound cavity losses. On the one hand, a change in optical output power results in a change of the refractive index via the carrier density. On the other hand, it results in a change of refractive index via temperature changes. Compared to the carrier induced refractive index change, the temperature induced refractive index change is opposite in sign, a factor of ∼10 2 smaller and slower. The switch-on and switch-off time of the self-pulsation is governed by the carrier life time. The repetition rate of the self-pulsation is governed by the thermal time constant and is in the megahertz region. Cross-modulation resulting from the thermal induced refractive index change is demonstrated. In a two-wavelength double external-cavity laser diode, optical power at one wavelength effects the optical power at the other wavelength. This cross-modulation is shown to be related to previous experiments on a laser neural network. A novel technique is introduced to measure the thermal impedance of a laser diode that is based on the cross-modulation. View full abstract»

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  • Comprehensive modeling of vertical-cavity laser-diodes by the method of lines

    Page(s): 928 - 935
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    A comprehensive numerical model for the analysis of vertical-surface emitting-lasers is presented. An optical, electrical, and thermal submodel are introduced. The complete analysis is based on the method of lines. The temperature distribution and the current density are calculated in the whole structure. The optical behavior is investigated with a full vectorial wave equation in cylindrical coordinates. Multimode effects are considered when calculating the optical output power. A rate equation for electrons and holes is used, which includes diffusion and recombination effects inside the quantum well. By combining all submodels a self consistent solution is found View full abstract»

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  • Broadband mid-infrared generation with two-dimensional quasi-phase-matched structures

    Page(s): 877 - 887
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    We report the use of highly elliptical pump beams to generate broadband, spatially-chirped mid-infrared light in periodically poled lithium niobate (PPLN). We fabricated PPLN crystals with a fan-out grating period varying continuously from 25.5 to 31.2 μm across a 15-mm width and pumped them in both optical parametric generator and monolithic optical parametric oscillator configurations with a Q-switched Nd:YAG laser. Although the fan-out grating pattern is typically thought of as a continuously varying 1-D quasiphase-matched (QPM) structure, the elliptical pump beam illuminates the full 2-D structure of the fan. The phase-matching and gain characteristics of the crystals prefer noncollinear optical parametric generator operation for elliptical pump beams; however, collinear operation was achieved with polished plane- parallel crystal endfaces such that the Fresnel reflections set up a low- finesse monolithic cavity in the crystals themselves. The generated signal and idler beams were spatially chirped in the near field and angularly chirped in the far field while covering spectral bands as large as 1250 cm-1. With a simple modification, this system also offers an easy way to generate broadband optical frequency combs across the signal and idler spectral bands. We also present theoretical and modeling considerations for large-aperture pumped or flood illuminated 2-D QPM structures. The Fourier transform of the spatial variation in the nonlinear coefficient in a crystal generates a 2-D map of available grating vectors in wave vector mismatch space. This method can be used to glean phase-matching information from complicated 2-D structures that would be difficult to analyze using other methods View full abstract»

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  • Universal discriminant for continuous-wave operation of laser diodes

    Page(s): 919 - 922
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB) |  | HTML iconHTML  

    We propose a simple and powerful criterion for defining continuous-wave (CW) operation of laser diodes. Our criterion is represented by a quasi-triangular region in the plain spanned by dimensionless parameters α and β. These parameters, deduced from the characteristics of the laser diode operating under pulsed current injection, represent the effects of the turn-on voltage and the series resistance on the increase in the CW threshold. We demonstrate the validity of our criterion using blue-green lasers made from II-VI semiconductors as examples View full abstract»

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  • Design of the active structure of high-performance 1.55-μm In 1-x-yGayAlxAs strained MQW lasers

    Page(s): 923 - 927
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    We have used Harrison's model and the anisotropic parabolic approximation to calculate the band structure of In1-x-yGa yAlxAs compressively strained quantum wells (QWs). To design 1.55 μm wavelength lasers, the relations between the well width, gain, and composition are presented. The well number and the cavity length are optimized to obtain a low threshold and high maximum operating temperature (550-560 K) QW laser. Several empirical formulas are presented for further applications View full abstract»

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  • Transversely pumped nonlinear conversion structure which generates counterpropagating guided waves: theory and numerical modeling

    Page(s): 863 - 872
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    A transversely pumped, nonlinear conversion structure which generates counterpropagating, guided signal and idler beams is examined. Existing scalar theory is extended to include the vector nature of the electromagnetic fields. Based on these results, a detailed simulation of proposed GaAs-AlGaAs structures is described. The results of the simulations highlight pitfalls not obvious in the original work. The simulations indicate, however, that proper design of the structure should provide a compact, highly efficient method of nonlinear optical conversion. In particular, a structure designed to convert light at 980 nm to light at 1.55 μm is predicted to have a threshold intensity of 4.9 MW/cm2, which is comparable to thresholds observed in parametric oscillators which use periodically poled lithium niobate View full abstract»

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  • Modeling pulse shape of Q-switched lasers

    Page(s): 888 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    A general approach describing the pulse shape and temporal width of Q-switched lasers has been derived. Based on a normalized intermediate variable describing the ratio of population inversion density at the beginning of Q-switch to that at threshold, a generalized characteristic equation that governs passively and actively Q-switched lasers is derived. From the characteristic equation, the pulse symmetry property and pulse width can be described and easily calculated for any given operating parameters, and the waveform of the laser pulse can be reconstructed without solving the laser rate equations. An approach is also given for the case of intracavity frequency-doubled Q-switched lasers. Theoretical results show agreement with experiments for a diode pumped Nd:YAG laser system that is passively Q-switched by a Cr4+ :YAG absorber View full abstract»

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  • Performance characteristics of buried heterostructure VCSELs using semi-insulating GaInP:Fe regrowth

    Page(s): 945 - 950
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB) |  | HTML iconHTML  

    We have fabricated GaAs-AlGaAs buried heterostructure vertical cavity surface emitting lasers, emitting at 850 mm, using semi-insulating GaInP:Fe regrowth and investigated their static properties. Lasers of different size (10-21 μm) have threshold currents in the range 2.8-7.0 mA, and produce a maximum output power of 1.7-6.0 mW at room temperature. The variation of threshold current with device size shows that the leakage current at the regrowth interface accounts for a significant part of the injection current. In spite of this, a differential quantum efficiency in the range 20%-30% is obtained which indicates that the regrowth interface is smooth and does not introduce any significant scattering loss. Studies of the transverse mode properties suggest that the GaInP provides weak guiding, resulting in single mode operation up to an output power of 0.7 mW and a beam divergence of only 60 for lasers as large as 10 μm View full abstract»

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  • A spatial digital filter method for broad-band simulation of semiconductor lasers

    Page(s): 936 - 944
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB) |  | HTML iconHTML  

    A novel method to simulate semiconductor lasers is presented that captures accurately the real and imaginary parts of the active medium response in a broad frequency range. It is a time-domain approach based on a spatial digital filter in the role of the optical field propagator. Careful treatment of numerical dispersion makes it possible to utilize effectively most of the available numerical bandwidth and obtain a realistic description of the laser dynamics View full abstract»

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  • Tunneling-injection quantum-dot laser: ultrahigh temperature stability

    Page(s): 905 - 910
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    We propose a genuinely temperature-insensitive quantum dot (QD) laser. Our approach is based on direct injection of carriers into the QDs, resulting in a strong depletion of minority carriers in the regions outside the QDs. Recombination in these regions, which is the dominant source of the temperature dependence, is thereby suppressed, raising the characteristic temperature T0 above 1500 K. Still further enhancement of T0 results from the resonant nature of tunneling injection, which reduces the inhomogeneous line broadening by selectively cutting off the nonlasing QDs View full abstract»

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  • Perturbations of conduction in liquids by pulsed laser-generated plasma

    Page(s): 856 - 862
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    The observation of optical perturbations of electrical conduction processes in aqueous solutions by laser-produced plasmas is reported. The irradiation of a liquid in a conduction cell with a pulsed tightly focused Q-switched Nd+3:YAG laser produces plasma that modifies the conductivity of the medium and generates a voltage pulse that can be recorded at the cathode using the same procedure, as in optogalvanic spectroscopy. At low voltages across the cell, this electrical pulse is a positive voltage change, which returns to the equilibrium potential in times much longer than the laser pulse duration. Increasing the cell voltage, this electrical pulse becomes a damped oscillation. Beyond those values, the pulse inverts its sign at the cathode. Results also show that there is a change in cell conductivity in a long-term regime. An interpretation with a first-order model suggests that this behavior could be explained as an excess of ionization, followed by diffusion controlled by recombination in the bulk of the solution View full abstract»

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  • Second harmonic generation at the quantum-interference induced transparency in semiconductor quantum wells: the influence of permanent dipole moments

    Page(s): 873 - 876
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    The influence of permanent dipole moments of quantized states on intersubband second harmonic generation based on quantum-interference induced transparency in semiconductor quantum wells is explored using the harmonic balance method. The permanent moments are found to be quite important: they affect the transparency condition, especially at larger pump intensities. Hence, both the conversion efficiency and the optimal interaction path length change significantly when accounting for the permanent moments, and the conversion efficiency is reduced View full abstract»

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  • Chaos shift keying with an optoelectronic encryption system using chaos in wavelength

    Page(s): 849 - 855
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    A chaos shift-keying modulation scheme in which the transmitter and the receiver are nonlinear time-delayed feedback systems is described. The change in the chaotic dynamics is discussed when different parameters are used to encode digital signals. The time-delay parameter is shown to assure the best conditions for data recovery View full abstract»

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  • Electrooptic effects in GaAs-AlGaAs narrow coupled quantum wells

    Page(s): 897 - 904
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB) |  | HTML iconHTML  

    The linear and quadratic electrooptic coefficients in narrow single and strongly coupled GaAs-AlxGa1-xAs quantum wells have been measured. The quadratic electrooptic effect is enhanced over that of conventional square quantum wells for both TE and TM polarization in all the structures considered, by up to six times in the case of 2-nm-wide GaAs-Al0.2Ga0.8As strongly coupled quantum wells. The origin of the enhanced quadratic electrooptic effect was found to correlate with a larger red shift in the absorption edge exciton and strong Coulombic coupling of the bound exciton states with the quasi-continua 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