By Topic

Quantum Electronics, IEEE Journal of

Issue 8 • Date Aug. 2002

Filter Results

Displaying Results 1 - 19 of 19
  • Introduction to the feature section on growth of heterostructure materials on nanoscale substrates

    Page(s): 973 - 974
    Save to Project icon | Request Permissions | PDF file iconPDF (158 KB)  
    Freely Available from IEEE
  • Toward two-dimensional self-organization of nanostructures using wafer bonding and nanopatterned silicon surfaces

    Page(s): 995 - 1005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    The structure of ultrathin silicon layers obtained by molecular hydrophobic bonding is investigated. The twist and tilt angles between the two crystals are accurately controlled. The buried Si|Si interface is observed by transmission electron microscopy and by grazing incidence X-ray techniques. For low twist angle values (ψ<5°) plane view observations reveal well-defined dislocation networks. Cross-section observations give evidence that the dislocation networks are localized at the bonding interfacial plane with no threading dislocation. Grazing incidence small angle X-ray scattering measurements confirm the good quality of the bonding interface as well as the quality of the dislocation networks. Grazing incidence X-ray diffraction is also used and shows the long-range order of the periodic strain field in the silicon layer. It shows, especially, the interaction between the dislocations. X-ray reflectivity was employed and estimated that the interfacial thickness (i.e., thickness of the bonding) lower than 1 nm decreases when the twist angle increases. The nanopatterned surface is then investigated by scanning tunneling microscopy and X-ray methods. To validate these substrates for long-range order self-organization, the growth of Si and Ge quantum dots is finally achieved. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full vectorial finite-element solution of nonlinear bistable optical waveguides

    Page(s): 1120 - 1125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (273 KB)  

    The accurate computation of the propagation constants and field distributions of different modes in nonlinear optical dielectric waveguides is addressed in this paper. Using the vector finite-element formulation of the beam propagation method, combined with the imaginary distance propagation technique, both linear and nonlinear modes can be accurately calculated. The proposed technique is applied to obtain the fundamental TE nonlinear mode of a strip-loaded waveguide, and the excellent agreement seen with published results shows its high numerical precision. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Feedback effects at stable and unstable resonant external cavity lengths

    Page(s): 1097 - 1101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB) |  | HTML iconHTML  

    External feedback applied to a high-power semiconductor laser is found to be responsible for a drop in output power and an increased noise-level when the optical external cavity length is an integral multiple of the optical internal cavity length. The power drops and extra noise originates from a scan of the quasi-single-mode laser over its internal cavity modes, caused by a lack of interferometric stability. In the case of interferometric stability, the wavelength of the laser exhibits a staircase-like dependence on the external cavity length. All experimental results can be described by a simple rate equation model. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • CHD2OH optically pumped by a waveguide CO2 laser: new far-infrared laser lines from the CD2 wagging vibrational mode

    Page(s): 1029 - 1030
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (178 KB) |  | HTML iconHTML  

    For the first time, a wide tunability waveguide CO2 laser was used to pump the CHD2OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD2 wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-power 980-nm ridge waveguide laser diodes including an asymmetrically expanded optical field normal to the active layer

    Page(s): 1081 - 1088
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (271 KB) |  | HTML iconHTML  

    We propose a new ridge waveguide laser diode (LD) which supports an asymmetrically expanded optical field normal to the active layer in order to increase the maximum kink-free output power and reduce the aspect ratio of output beams. The dependence of maximum kink-free output power on facet reflectivity was analyzed from the viewpoint of the total optical power in the cavity. It was clarified that the maximum kink-free output power is influenced by the facet reflectivity which affects the refractive index changes of the ridge region via the total optical power in the cavity. More than 600 mW of maximum kink-free output power and an aspect ratio of less than 2.5 were achieved in experiments with 980-nm ridge waveguide LDs by means of this proposed new structure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simple model for a distributed feedback laser integrated with a Mach-Zehnder modulator

    Page(s): 1062 - 1074
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (463 KB) |  | HTML iconHTML  

    Presents a time-domain traveling-wave algorithm for the modeling of the large-signal dynamic response of a distributed feedback laser integrated with a Mach-Zehnder (MZ) modulator. The influence of residual optical feedback from the output of the modulator facet on the dynamic frequency chirp is studied. It is found that the difference in frequency chirp between the turn-on and -off states (i.e., adiabatic chirp) of a π/2-shifted 2 ×2 MZ modulator is minimal and is independent of-the residual optical feedback. In addition, it can be shown that the presence of chirped frequency spikes (i.e., transient chirp), due to the change in refractive index as a result of the rapid variation of the bias voltage, can broaden the linewidth and distort the spectrum of the modulated optical signal. Furthermore, the possibility of doubling the modulation frequency of MZ modulators using a dual-arm dual-signal modulation format is investigated. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Investigations regarding the maskless pendeo-epitaxial growth of GaN films prior to coalescence

    Page(s): 1006 - 1016
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (353 KB)  

    Pendeo-epitaxy employs lateral growth from etched seed forms to achieve a marked reduction in dislocation density in a material. In this research, high-resolution X-ray diffraction and atomic force microscopy of GaN stripes and the laterally grown wings confirmed transmission electron microscopy results regarding the reduction in dislocations in the latter regions. Micro-Raman and X-ray diffraction measurements showed the wings to be tilted ≤0.15° due to tensile stresses in the stripes induced primarily by the mismatch in the coefficients of thermal expansion between the GaN stripe and the SiC substrate. A strong, low-temperature D°X peak at ≈3.466 eV with a FWHM of ≤300 μeV was measured in the wing material by micro-photoluminescence. Films grown at 1020°C exhibited similar vertical [0001] and lateral [112~0] growth rates. Increasing the growth temperature increased the latter due to the higher thermal stability of the (112~0) GaN and initiated growth of spiral hillocks on the (0001) surface of the stripes. The latter were due to adatom diffusion to heterogeneous steps previously nucleated at the intersections of pure screw or mixed dislocations. The (112~0) surface was atomically smooth under all growth conditions with a root mean square roughness value of 0.17 nm. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Self-assembling Ge(Si)/Si(100) quantum dots

    Page(s): 975 - 987
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The morphological evolution of self-assembled epitaxial quantum dots on Si(100) is reviewed. This intensely investigated material system continues to provide fundamental insight guiding the growth of nanostructured electronic materials. Self-assembled quantum dots are faceted, three-dimensional islands which grow atop a planar wetting layer. Pure Ge growth at higher substrate temperatures results in narrower island size distributions but activates additional strain-relief mechanisms which will alter the optical and electronic properties of the dots. Optical and electrical characterization has shown that electrons and holes are confined to different regions of the dot. This results in a spatially indirect, type II recombination mechanism. Emerging device applications which exploit properties of these nanoscale Ge islands are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Accurate methods for study of light emission from quantum wells confined in a microcavity

    Page(s): 1031 - 1038
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (317 KB) |  | HTML iconHTML  

    Photomodulated reflectance (PR) and conventional reflectance studies have been performed on an InGaP/AlGaInP/Alx1Gay1As/Alx2Gay2As resonant-cavity light emitting diode structure in the red spectral region. The PR spectra show prominent signals from the Fabry-Perot cavity mode and the quantum-well (QW) ground state excitonic transition. This high-precision technique, and its variations as functions of incidence angle and temperature, as reported in this article, allow one to investigate light emission from the QW confined in a microcavity with relation to the Fabry-Perot mode, and is the only known nonconductive, nondestructive method of doing so. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Growth of Si and Ge nanostructures on Si substrates using ultrathin SiO2 technology

    Page(s): 988 - 994
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB) |  | HTML iconHTML  

    Using scanning reflection electron microscopy and a high-temperature scanning tunneling microscopy (STM), we study the growth processes of Si and Ge nanostructures on Si substrates covered with ultrathin SiO2 films. Si windows are formed in the ultrathin SiO2 films by irradiating focused electron beams used for SREM or field emission electron beams from STM tips before or during heating samples. Ge nanoislands are grown only at the Si window positions by depositing Ge on the samples and by subsequent annealing of them. Moreover, Ge nanoislands about 7 nm in size and ultrahigh density (>1012/cm2) are grown on the ultrathin SiO2 films. These nanoislands can be manipulated by STM when they are separated from Si substrates by the ultrathin SiO2 films. Si, Ge, Ge/Si and Si/Ge/Si nanoislands can also be grown on the Si windows by selective growth using Si2H6 and GeH4 gases. These nanoislands are found to be stable on the Si windows during high-temperature annealing. These results indicate that ultrathin SiO2 technology is useful for growing Si and Ge nanostructures on given areas. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time reversal terahertz imaging

    Page(s): 1110 - 1119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (359 KB)  

    We describe a technique for imaging in the terahertz regime using time reversal of single-cycle pulses. Specifically, the time-reversal symmetry of Maxwell's wave equation is exploited to reconstruct the transmission function of a diffracting aperture by inverting the diffracted fields. After deriving a time-reversed form of the Huygens-Fresnel diffraction integral, we demonstrate through simulation and experiment the reconstruction of one-dimensional and two-dimensional (2-D) objects. A means to obtain data efficiently for reconstruction of 2-D apertures is described. The spatial resolution determined by the Sparrow criterion is found to correspond to approximately 30% of the peak wavelength and 85% of the mean wavelength of the power spectrum of the single-cycle waveform. Finally, the modulation transfer function for the imaging method is simulated and is shown to be nearly diffraction-limited when compared to an ideal imaging system. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-speed digital modulation characteristics of oxide-confined vertical-cavity surface-emitting lasers-numerical simulations consistent with experimental results

    Page(s): 1089 - 1096
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (393 KB) |  | HTML iconHTML  

    The vertical-cavity surface-emitting laser (VCSEL) is a preferred light source for short-distance high-speed fiber-optic communication links. We simulate the digital modulation behavior of typical oxide-confined VCSELs under realistic working conditions with a comprehensive model that includes the detailed geometry when calculating the optical fields and that accurately accounts for the dynamic effects of carrier density and temperature on the modal distributions. The intrinsic output characteristics of single- and multimode VCSELs were studied as functions of bias and modulation depth under a 27-1 pseudorandom bit sequence current modulation at 2 and 10 Gb/s. The data were used to create numerical eye diagrams that show, e.g., the significant impact of the bit pattern history and the noise on the timing jitter in both single- and multimode VCSELs. For the single-mode VCSEL, the choice of the bias current and modulation depth was less critical due to its higher damping of the relaxation oscillations. The simulated VCSELs were fabricated and experimentally evaluated. The measured eye diagrams showed the same characteristic features as those in the simulations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nanoheteroepitaxy for the integration of highly mismatched semiconductor materials

    Page(s): 1017 - 1028
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (679 KB) |  | HTML iconHTML  

    We describe an ongoing study of nanoheteroepitaxy (NHE), the use of nanoscale growth-initiation areas for the integration of highly mismatched semiconductor materials. The concept and theory of NHE is briefly described and is followed by a discussion of the design and fabrication by interferometric lithography of practical sample structures that satisfy the requirements of NHE. Results of NHE growth of GaAs-on-Si and GaN-on-Si are described, following the NHE process from nucleation through to coalescence. Micro-Raman measurements indicate that the strain in partially coalesced NHE GaN-on-Si films is <0.1 GPa. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pulsed laser action in Tm,Ho:LuLiF4 and Tm,Ho:YLiF4 crystals using a novel quasi-end-pumping technique

    Page(s): 1102 - 1109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (378 KB) |  | HTML iconHTML  

    A number of good quality thulium and holmium-codoped LuLiF4 and YLiF4 single crystals were successfully grown by the Czochralski crystal growth method under a CF4 atmosphere. Using a novel diode-pumped, quasi-end-pump scheme incorporating two lens ducts, pulsed laser action is achieved in 5%Tm, 0.5% Ho:LuLiF4 and 5%Tm, 0.5% Ho:YLiF4 crystals, at various pulse repetition frequencies and temperatures. At 10 Hz and at an operating temperature of 273 K, slope efficiencies (optical to optical efficiencies) with respect to the incident pump energies of 12.9% (9.2%) and 7.4% (5.2%) were demonstrated in the grown Tm, Ho:LuLiF4 and Tm, Ho:YLiF4 crystals, respectively. Free running laser output energies in excess of 30 mJ (LuLiF4) and 17 mJ (YLF) were measured. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • All-optical switching at multi-100-Gb/s data rates with Mach-Zehnder interferometer switches

    Page(s): 1053 - 1061
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    We present experimental and theoretical results on ultrafast nonlinear dynamics in InGaAsP semiconductor optical amplifiers (SOAs). Carrier heating, spectral hole burning, and two-photon absorption are analyzed by heterodyne pump-probe experiments which deliver basic model parameters like gain-phase coupling parameters of the material. The impact on the device performance induced by these physical effects is verified by cross-gain/cross-phase experiments on InGaAsP-based SOAs and Mach-Zehnder interferometer switches. In the co-propagation arrangement, the switching window with maximum transmission is shown to be 1.5 ps which translates into demultiplexing capabilities beyond 600 Gb/s. Calculations based on a distributed rate equation model show that, for high-speed applications, the switching window can be limited by pulse saturation and by subpicosecond nonlinear effects. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measuring timing jitter with optical cross correlations

    Page(s): 1047 - 1052
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    The use of optical cross correlations for characterizing timing jitter is investigated. Applications, limitations, and correspondence to radio frequency measurements are presented and clarified. The probability density function of the timing jitter of semiconductor mode-locked lasers is deconvolved from the cross-correlation measurements with the aid of pulse characterization techniques. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extremely small-chirp electroabsorption-modulator integrated distributed feedback laser diode with a shallow quantum-well absorption layer

    Page(s): 1075 - 1080
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB) |  | HTML iconHTML  

    We have developed an extremely small-chirp electroabsorption modulator integrated with a distributed feedback laser diode (EAM-DFB-LD) with a novel shallow quantum-well (QW) absorption layer. By using a shallow QW absorption layer, the estimated lifetime of the photogenerated holes and thus the estimated concentration of the holes generated by optical absorption has been reduced to 9% of that for a conventional QW. It was experimentally confirmed that the excess chirp due to the pileup of carriers has been reduced to 10% of that for a conventional QW, and this result is consistent with the estimates. The shallow QW EAM-DFB-LD has shown a chirp parameter |α| less than 0.7 over the entire range of the EAM reverse bias voltage of 0-3 V. Finally, successful 10-Gb/s return to zero transmission has been confirmed through both positive dispersion (+425 ps/nm) and negative dispersion (-425 ps/nm). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Hybrid organic light-emitting device fabricated with semiconducting polyimide via mixed vapor deposition polymerization

    Page(s): 1039 - 1046
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Hybrid organic light-emitting devices (HOLEDs) were fabricated with the active molecularly doped polyimide (AMDPI) thin film as a hole-injecting-transporting layer through the mixed vapor deposition polymerization (VDP) process. As a comparison, the polyimide thin film as a hole-injecting-transporting layer was also prepared for a HOLED via VDP. Both the AMDPI and polyimide thin films were almost optically transparent over the entire visible range because the bandgap energy was ∼2.9 eV. HOLEDs with the AMDPI thin film showed a higher luminance and efficiency than that with the polyimide thin film. In particular, the application of a lithium-aluminum cathode significantly enhanced the luminance and the efficiency of HOLEDs with the AMDPI thin film. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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