共查询到20条相似文献,搜索用时 0 毫秒
1.
《Philips Journal of Research》1995,49(3):293-313
Periodically segmented waveguides were fabricated in flux-grown KTP for quasi-phasematched second-harmonic generation (SHG) of a light beam with a wavelength of 425 nm. Diode-pumped violet laser sources are proposed on the basis of these waveguides. We shall show that a pulsed operation of the pump diode laser at a 940 MHz repetition rate enables the construction of sources with a very compact geometry, which are insensitive to temperature fluctuations. These sources may still be considered as quasi-continuous wave (cw) for applications in high-density optical recording.The most compact type of violet laser source has a size of 1 × 1 × 2 cm3. It contains only the diode pump laser, the KTP waveguide and a miniature lens to couple the pump beam to the waveguide. Time-averaged violet output powers up to 85 μW have been generated for many hours at room temperature without requiring an active temperature control. This output power may be sufficient for reading an optical disc.By optical feedback of a portion of the transmitted pump beam via an external grating it is possible to generate higher violet powers. In this way, the pump laser is forced to operate in a single spectral mode, the wavelength of which can be tuned to coincide with the phase-matching wavelength of the waveguide. This grating-controlled laser system is shown to generate a 425 nm beam with powers up to 0.5 mW. The total length of the device is about 7 cm. 相似文献
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Second-harmonic generation in a double-quantum-well nanostructure is analyzed. Optimization of the structure design from the viewpoint of attaining the highest intensity of the second-harmonic wave at the output is considered. Relationships between the quantum-well parameters in a structure satisfying the double-resonance condition are established. The dependence of the optical characteristics of the system on the quantum-well parameters is studied and the problem of optimization of the second-harmonic intensity is solved. It is demonstrated that the highest conversion efficiency is attained under the conditions where the second-harmonic generation coefficient is maximum. 相似文献
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Waveguides for quasi-phasematched frequency doubling were fabricated using an applied electric field to produce periodic poling and ion-exchange to produce channel waveguides. A blue output power of 12 mW was achieved with 146 mW of infrared light in a 3.6 mm-long waveguide 相似文献
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《Electron Devices, IEEE Transactions on》1958,5(2):76-84
A field theory of a crossed field periodic structure is given. Taking into account the effect of space charge, an integral equation method is employed to obtain a general dispersion equation for a structure supporting any space harmonic. The case of pure scalloping is treated in detail and the results are applied to forward and backward-wave amplifiers and backward-wave oscillators. Criteria for gain and oscillations are derived and corresponding expressions for the gain and start oscillation current are obtained. These results include the effect of all space harmonics. 相似文献
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Both single- and double-resonance operating regimes are analyzed, and the latter is found to enable very high conversion efficiencies of pump to harmonic if accompanied by quasiphase matching by periodic alternation of the field direction. The self-consistent procedure of level energies and wave function calculation is also described 相似文献
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We study the multisubband electron mobility in a barrier delta doped AlχGal-χAs parabolic quantum well structure under the influence of an applied electric field perpendicular to the interface plane. We consider the alloy fraction χ = 0.3 for barriers and vary x from 0.0 to 0.1 for the parabolic well. Electrons diffuse into the well and confine within the triangular like potentials near the interfaces due to Coulomb interaction with ionized donors. The parabolic structure potential, being opposite in nature, partly compensates the Coulomb potential. The external electric field further amends the potential structure leading to an asymmetric potential profile. Accordingly the energy levels, wave functions and occupation of subbands change. We calculate low temperature electron mobility as a function of the electric field and show that when two subbands are occupied, the mobility is mostly dominated by ionised impurity scattering mediated by intersubband effects. As the field increases transition from double subband to single subband occupancy occurs. A sudden enhancement in mobility is obtained due to curtailment of intersubband effects. Thereafter the mobility is governed by both impurity and alloy disorder scatterings. Our analysis of mobility as a function of the electric field for different structural parameters shows interesting results. 相似文献
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Hamid H.S. Javadi 《Microelectronics Reliability》1996,36(10):1499-1513
Current-voltage characteristics of the electrically conductive silver-filled epoxy Ablefilm ECF-563 preform switches to a high-resistive state under low bias voltage. The observed phenomena is argued to be an intrinsic property of electrically conducting composite materials caused by strong localized centers that introduce space charge. 相似文献
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D. Yu. Kopeichenko I. N. Onishchenko G. V. Sotnikov 《Journal of Communications Technology and Electronics》2007,52(8):835-841
The electrodynamic analysis of the topography of magnetic fields generated in a spatially periodic structure is performed. The structure is a solenoid containing periodically spaced rings made from materials with different electric and magnetic properties. The system of equations relating the amplitudes of spatial harmonics of the magnetic field is derived and numerically analyzed. Dependences of the amplitudes of longitudinal and transverse components of the modulated magnetic field on the ring dimensions, the current frequency, and the magnetic and electric properties of the ring materials are investigated. The field amplitudes obtained during the complete electrodynamic analysis are compared with the amplitudes of a periodic magnetic field obtained in the impedance approximation. 相似文献
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The study is focused on a theoretical treatment of electrons in quantum dots produced by a nonuniform electric field in a heterostructure with a single quantum well. A nonuniform electric field can be formed with the use of a mosaic electrode with a regular system of nanometer-sized apertures. A structure involving a one-aperture electrode deposited onto the surface is considered. The potential in the entire region between the electrode plates is calculated numerically. The analytical expression for the depth of the potential well is derived, and the potential profile in the vicinity of the bottom of the well is determined. The energy level structure in the vicinity of the bottom of the potential well is calculated. The geometric characteristics of the mosaic electrode most favorable for conservation of electron spin in the quantum dots of this type are determined. It is shown that in the quantum dots of this type the spin lifetime can be expected to lie within the microsecond region at a liquid-helium temperature. 相似文献
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An accurate full-wave analysis of discontinuities in shielded microwave structures by the method of lines is presented for use in microwave integrated circuit design. The input currents are derived from a sinusoidal source representation and modeled by inhomogeneous boundary conditions. Interacting discontinuities can be treated without segmentation. Inhomogeneous boundary conditions are introduced to account for the excitation. Analysis shows that in discretizing the differential operators additional source terms which result in inhomogeneous differential equations are obtained. A deterministic equation for the current distribution is derived. For higher flexibility, nonequidistant discretization is used. The scattering parameters are presented for the microstrip step discontinuity and for a single-filter structure with interacting discontinuities, namely a coupled line filter. The filter characteristics are compared with measurements. Measurements verify the filter calculations 相似文献
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By applying a femtosecond electric pump pulse to a polymer, biexcitons are obtained and the relation between its yield and the photoexciting process is also presented. The simulations are performed within the framework of an extended version of one-dimensional Su–Schrieffer–Heeger tight-binding model combined with a nonadiabatic evolution method. In the discussions, effects of both the photoexciting energy and intensity are considered. The main result is that the yield ratio of biexcitons and excitons increases rapidly with the photoexciting intensity, and there exists a critical photoexciting intensity, beyond which the yield efficiency of biexcitons is even higher than that of excitons. The result theoretically verifies that, by increasing the photoexciting intensity, we can obtain biexcitons efficiently, which is consistent with the experimental speculation. 相似文献
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The mobility of charge carriers μ in a parabolic quantum well in an electric field E directed along the size-confinement axis is calculated. With consideration for scattering of charge carriers at a rough surface,
the mobility μ is shown to decrease with increasing E. A physical interpretation of this effect is proposed. 相似文献
16.
A. V. Borzdov D. V. Pozdnyakov V. M. Borzdov A. A. Orlikovsky V. V. V’yurkov 《Russian Microelectronics》2010,39(6):411-417
A Monte Carlo simulation is run to study the electron transport in a thin undoped GaAs quantum wire under the influence of
a transverse applied electric field. Phonon and surface-roughness scattering are included. Electron drift velocity is investigated
as a function of roughness amplitude at a temperature of 77 or 300 K and a longitudinal electric field of 104 or 105 V/m. A transverse applied field is shown to provide a means of controlling drift velocity, affecting the scattering rate. 相似文献
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Electric field induced optical second harmonic generation (EFISHG) measurement is capable of probing carrier motions in organic devices. By measuring nonlinear polarization induced in active layer of organic devices, the carrier motion is visualized. After summarizing the conventional SHG measurement as a tool for material characterization, we show that the EFISHG is a way for probing carrier motions, and thus extends the potentiality of the conventional SHG measurement. We employ the EFISHG measurement to probe carrier behaviors in double-layer metal-insulator–metal diodes, e.g., Au/TIPS-pentacene/PI/ITO diodes, and demonstrate how the time-resolved SHG measurement probes carrier motion in the diodes, in terms of the I–V and C–V characteristics. Results give an insightful picture on the carrier injection, and the succeeding carrier transport. 相似文献
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Dai Taguchi Hiroshi Masada Takaaki Manaka Mitsumasa Iwamoto Takao Nishiura Tetsuya Iizuka Toshifumi Takemori 《Organic Electronics》2012,13(12):2801-2806
By using time-resolved electric-field-induced optical second-harmonic generation measurement, we studied carrier motion in pentacene field-effect transistors (FETs) with poly-4-vinylphenol (PVP) and with polyimide (PI) gate-insulator whose active layers were depleted by pre-biasing. Upon removal of the pre-biasing, channel formation proceeded as a two-step process in FETs with PVP gate-insulator and a conduction channel was formed eventually. On the other hand, no conduction channel was formed in FETs with PI gate-insulator but two-step carrier propagation was observed in a similar way. Results showed that a local electric field induced on the gate-insulator surface gives a significant effect on the carrier injection and the following carrier transport. 相似文献
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The electron heating by a strong longitudinal electric field and the energy losses due to the scattering of nonequilibrium electrons by polar optical phonons in rectangular GaAs/AlGaAs quantum wells are studied. A simple model is suggested to calculate the rate of energy losses due to the scattering of electrons by nonequilibrium optical phonons. Some of the experimental results on the heating of charge carriers in quantum wells are discussed, and it is shown that taking nonequilibrium optical phonons into account significantly improves the agreement between the theoretical and experimental data. 相似文献