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Quantum Electronics, IEEE Journal of

Issue 6 • Date Jun 1998

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Displaying Results 1 - 15 of 15
  • Gigahertz InGaAs-based vertical Schottky diode optical detectors by substrate removal

    Page(s): 991 - 999
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    In this paper, we present high-performance InGaAs vertical Schottky diode optical detectors and document design criteria and fabrication processes. The photodiodes are n-type and have an asymmetric contact structure with a rectifying anode and ohmic cathode. The vertical structure is achieved through InP substrate removal which exposes the back surface of the epitaxial layers. Ohmic contact is made to the exposed back surface. High-quality Schottky diodes with φBn≈0.85 V are reproducibly achieved through an etching pretreatment, resulting in dark currents below 10 pA/μm2 . Substrate removal and mesa definition result in low parasitic capacitance without the need of air bridges and allow accurate fiber-to-detector alignment. Responsivities greater than 0.7 A/W are obtained when a transparent conductor is used as the ohmic contact. RC-limited bandwidths as high as 19 GHz are measured for 20×20 μm2 devices View full abstract»

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  • Polarization-controlled single-mode VCSEL

    Page(s): 1009 - 1015
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    Relative intensity noise (RIN) in a vertical-cavity surface-emitting laser (VCSEL) was greatly reduced through the use of polarization control to eliminate competition between two orthogonal polarization states by ensuring there was only one polarization state. Polarization was stable with optical feedback of up to 10%. Polarization control was achieved by inducing a small loss anisotropy in fundamental transversal mode VCSEL's. Anisotropic post structures, such as a rectangular post, an oblique post, or a zigzag-sidewall post, were found to be effective in creating loss anisotropy without serious degradation of other VCSEL characteristics such as light-output power or beam profile View full abstract»

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  • Higher order transverse modes of an unstable-cavity laser

    Page(s): 955 - 965
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    We present measurements of the higher order transverse modes of an unstable-cavity HeXe gas laser. We have studied the one-dimensional strip-resonator modes and the two-dimensional square- and circular-resonator modes. The experimental intensity profiles showed generally good agreement with theoretical profiles based upon virtual-source diffraction theory. We also measured the quantum-limited linewidths and excess-noise factors of several of these modes View full abstract»

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  • Cooling schemes for longitudinally diode laser-pumped Nd:YAG rods

    Page(s): 1046 - 1053
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    Longitudinal diode laser pumping causes pronounced inhomogeneous heating of the laser material. The effect of the thermal load on the mechanical and optical properties is significantly influenced by the method used for cooling the pumped surface. Four methods for longitudinally pumped Nd:YAG rods were compared experimentally and with finite-element (FE) analysis. The pumped surface exposed to air or to flowing water, a sapphire plate pressed onto the pumped surface and composite rods, having an undoped pumped end, were investigated. The comparison includes temperature and stress distributions with the emphasis on thermal lensing. Careful validation of the FE code with experiments allowed to numerically comparing the cooling methods under identical conditions View full abstract»

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  • Intersubband χ3 in coupled InGaAs-AlGaAs multiple quantum wells

    Page(s): 975 - 981
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    The third-order nonlinearity, χ3(ω,ω,-ω), is measured for a mid-infrared intersubband transition in strained InGaAs-AlGaAs multiple quantum wells (MQW's). The high conduction band offset of this system allows an intersubband transition at 3.1 μm. The level structure of the quantum well is designed to include a meta-stable trapping level, resulting in a peak saturation intensity of 6 MW/cm2 at Brewster's angle, approximately 20 times lower than would be found in a square quantum well with similar linewidth. A near-resonant n2 of 8.4×10-7 cm2/W at 3.1 μm is calculated. The off-resonant n2 is also calculated and shown to be attractive at wavelengths as short as 1.55 μm View full abstract»

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  • Accurate gas diagnostics for sealed-off CO2 lasers using near-infrared DFB semiconductor lasers

    Page(s): 949 - 954
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    The selective spectroscopic detection of CO2 and H2O in the gas mixture of a 400-W sealed-off CO2 slab laser is reported. The detection is based on the acquisition of absorption Voigt profiles of two vibrational overtone transitions of CO 2 and H2O, obtained using two InGaAsP distributed feedback (DFB) semiconductor lasers. This spectroscopic method enables a direct absolute measurement of the temporal evolution for the concentrations inside the laser active volume. Monitoring takes place during laser operation without gas extraction. The experiments carried out on CO2 and H2O abundances confirm the paramount importance of wall desorbance phenomena in all-metal radio frequency (RF) excited lasers View full abstract»

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  • Self-pulsation in two-section DFB semiconductor lasers and its synchronization to an external signal

    Page(s): 1000 - 1008
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    A model of self-pulsation in two-section distributed feedback (DFB) lasers without a saturable absorber is developed by using generalized rate equations. The introduction of an effective differential gain in our model allows us to take into consideration both material and structural effects. The self-pulsation conditions are derived from a linear stability analysis. A mechanism based on a negative effective differential gain is proposed to explain the origin of self-pulsation in such lasers. By considering an injected optical signal, the optical synchronization of self-pulsating lasers is studied using nonlinear simulations. This leads to the determination of some locking-range properties, which are then compared to experimental and analytical results View full abstract»

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  • Anomalous light reflection at the surface of a corrugated thin metal film

    Page(s): 1054 - 1060
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    The process of excitation of surface electromagnetic waves (SEW's) in corrugated thin metal film is investigated theoretically and experimentally. The existence of an anomalous increase of the reflection coefficient is demonstrated. The excitation of long-range plasmons in thin metal films opens new possibilities for sensor applications View full abstract»

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  • Effects of internal loss on power efficiency of mid-infrared InAs-GaInSb-AlSb quantum-well lasers and comparison with InAsSb lasers

    Page(s): 1016 - 1030
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Experimental studies of the lasing efficiency of optically pumped 4-μm GaInSb-InAs-AlSb multiple-quantum-well (MQW) lasers that emitted >1-W peak power/facet at 80 K indicated that internal loss is the main factor that limits the power output. The internal loss coefficient and internal quantum efficiency were determined by measuring the lasing efficiency versus temperature for devices of different facet reflectivities and lengths. The internal loss coefficient was found to increase from ~18 cm-1 near 70 K to ~60-100 cm-1 near 180 K, while the internal quantum efficiency remained constant at ~47% (or ~67% with the correction for the finite absorption of the active region) from 70 to 130 K. The increase of internal loss and the decrease of external quantum efficiency versus temperature were found very similar to those of double-heterostructure InAsSb-GaSb lasers and were similarly interpreted in terms of intervalence band carrier absorption. Extrapolation of power performance for improved devices with lower internal loss indicated that high-efficiency multi-watt quasi-CW output with a broad-area brightness of ~1 MW/cm2.sterad is possible View full abstract»

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  • Optical properties of an InGaAs-InP interdiffused quantum well

    Page(s): 982 - 990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A comprehensive model is developed for the calculation of polarization-dependent absorption coefficients and refractive index of the InGaAs-InP interdiffused multiple-quantum-well at room temperature for wavelengths ranging from 1.1 to 2.4 μm. Groups III and V types of interdiffusion are considered separately. The as-grown structure is a latticed-matched In0.53Ga0.47As-InP structure with a well width of 60 Å. The optical transitions consist of a full quantum-well calculation together with Γ,X, and L valleys contributions and through the Kramers-Kronig transformation to link the real and imaginary parts of the dielectric functions. The results show that group-III-only interdiffusion produces compressive strain and results in a band-edge red shift and refractive index enlargement, while the tensile strain induced by group-V-only interdiffusion results in a vice verse effect. This provides a left and right tunable band edge and positive and negative index steps dependent on the interdiffusion process. A small and constant birefringence of 0.005 at around 1.55 μm can also be obtained over a 50-nm wavelength range by using group-V-only interdiffusion. These properties have strong implications in realizing a tunable and high-performance device as well as for photonic integrations View full abstract»

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  • Q-switch regime of 3-μm Er:YAG lasers

    Page(s): 1031 - 1040
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A mathematical model, based exclusively on spectroscopic data concerning radiative, nonradiative, and energy transfer processes, is proposed and used to simulate the Q-switch regime of a 3-μm Er:YAG laser. The connection between the main energy transfer mechanisms that make possible generation on the self-saturated transition 4I 11/24I13/2 (upconversion from 4I13/2 and 4I11/2 and cross relaxation from 4S3/2) and the giant pulse characteristics are discussed. The radiative as well as nonradiative losses during optical pumping and giant pulse generation are defined and evaluated. A particular attention is given to the frustrated total internal reflection (FTIR) Q-switch which demonstrated real qualities for 3-μm erbium lasers. The reasons responsible for experimental performances of Q-switched Er:YAG lasers inferior to those predicted by the mathematical modeling are analyzed View full abstract»

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  • Measurement of temporal behavior of electron density in a discharge-pumped ArF excimer laser

    Page(s): 942 - 948
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    Time-resolved number densities of electrons in a discharge-pumped ArF excimer laser are measured by an interferometric method. The peak electron density is 6.7×1015 cm-3 at a total gas pressure of 2.5 atom, a gas mixture ratio of F2-Ar-He=0.2-10.0-89.8, and a charging voltage of 24 kV for a 68-nF storage capacitor bank. The dependences of the electron density and laser output power on the Ar and F2 fractions in Ar-F2-He mixture and on the Ne-He mixing ratio in Ar-F2 -He-Ne mixture are investigated, and the effects of Ar-F2 -He-Ne mixing ratio on the ArF laser discharge are discussed. The experimental data of the peak electron density are also compared with the results of a computer simulation. A good agreement between them was obtained by considering the fact that the actual discharge volume occupied only part of the electrode width View full abstract»

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  • Theory of backward second-harmonic and third-harmonic generation using laser pulses in quasi-phase-matched second-order nonlinear medium

    Page(s): 966 - 974
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    Recently, we have observed backward second-harmonic generation (SHG) using subpicosecond and nanosecond laser pulses in periodically poled lithium niobate crystals. The conversion efficiency in terms of energy density per pulse measured in the experiments agrees well with that based on our theory. In this paper, we present our theoretical investigation of this process in detail. Although the temporal behaviors of the second-harmonic radiation are determined by the same functions as those for the forward SHG, the amounts of pulse broadening and conversion efficiencies are quite different for the two configurations. In addition, we have investigated saturation of the conversion efficiencies. We have also considered effective third-harmonic generation based on cascaded second-order nonlinear processes. For a few optimized spatial periods of the domains, we have estimated the conversion efficiencies View full abstract»

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  • Modulation and single-spike switching of a diode-pumped Er3+ :LiYF4 laser at 2.8 μm

    Page(s): 1041 - 1045
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    An Er3+:YLF laser at 2.8 μm pumped with two polarization-coupled diode lasers is built. The emission properties of the laser are studied. The threshold is 107 mW and the slope efficiency is 33%. The laser output is modulated by either chopping the pump beam or by chopping the resonator mode. Single-spike switching using a rotating mirror is demonstrated for the first time in bulk material lasers at 2.8 μm. Single spikes (pulse duration: 200-500 ns) are emitted with repetition rates up to 137 Hz. The temporal shape of the spikes is nearly Gaussian. Pulse duration and repetition rates are ideal for micro surgical applications. Rotating-mirror Q-switching was employed as other standard switching devices, such as acoustooptic or electrooptic modulators that were presently available to us introduce lasses to the cavity that cannot be compensated with the highest achievable gain in our system View full abstract»

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  • Stimulated emission by E×B drifting electrons grazing a diffraction grating

    Page(s): 933 - 941
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    It has been recently proposed that generation of relativistically upshifted radiation by an E×B drifting electron beam grazing a diffraction grating combines the Smith-Purcel free-electron laser (FEL) merits of short wavelengths at low beam energies, with efficiencies much higher than the 1/2 Ng conventional FEL limit. The small-signal theory is studied here, including the effect of drift velocity shear from the equilibrium (unbunched) space-charge fields. The dependence of the small-signal gain on the device parameters is determined and the startup current is evaluated. The effect of thermal beam spreads is analyzed and found that the oscillation startup current is much less sensitive to thermal spreads than a similar grating FEL 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