By Topic

Quantum Electronics, IEEE Journal of

Issue 8 • Date Aug 1993

Filter Results

Displaying Results 1 - 20 of 20
  • Stability and dynamic properties of multi-electrode laser diodes using a Green's function approach

    Page(s): 2282 - 2301
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1640 KB)  

    In DFB (distributed feedback) lasers, the shape of the longitudinal intensity and carrier density distributions changes above threshold as a result of spatial hole burning. The longitudinally distributed coupling of spontaneous emission into the lasing mode also plays an important role for the noise properties. The authors demonstrate how both effects can be included in a dynamic analysis. They extend their previously developed theory for multielectrode lasers to enable calculation of stability properties as well as small-signal modulation responses and noise spectra. The theory is used to study global and local stability of the stationary solutions (modes). The numerical results for several laser structures are presented. It is shown that symmetric DFB lasers are likely to exhibit pitchfork bifurcations in their static tuning characteristics as the current is increased. The authors discuss how the presence or proximity of such instabilities can affect the modulation and noise properties, and in particular, the spectral linewidth View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reduction of optical shot noise from light emitting diodes

    Page(s): 2302 - 2305
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    The mechanism responsible for the reduction of optical shot noise from high impedance driven light-emitting diodes is addressed. It is shown that the electronic feedback mechanism is the same as that for laser diodes with spontaneous recombination. Quantum noise reduction below the optical shot noise level is due to the effect of negative feedback on the recombination rate that occurs when the junction voltage and carrier number are permitted to respond to the underlying (Poisson) stochastic recombination process as in a light-emitting diode or laser diode driven by a high impedance source. Extensive measurements on light-emitting diodes confirm the magnitude of the noise suppression predicted from semiclassical theory View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Impact of amplified spontaneous emission on carrier density for measurement of optical nonlinearities in GaAs/AlGaAs multiple quantum wells

    Page(s): 2306 - 2312
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    It is shown that amplified spontaneous emission (ASE) can affect the measurement of nonlinear optical properties in semiconductors through its reduction of the excess carrier density. When the optical excitation area is large, lateral ASE can reduce the carriers within a much shorter period of time than the normal carrier lifetime. Just after ASE is over, the time-integrated surface photoluminescence signal may be used as a measure of the carrier density, which is the carrier density experienced by an ns probe in ps pump experiments. When the excited carrier density is at 1020 cm-3, surface ASE is also possible and is observed, even with small spot sizes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The semiconductor waveguide facet reflectivity problem

    Page(s): 2273 - 2281
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    The problem of the facet reflectivity of a semiconductor slab waveguide is reexamined as an extension of Ikegami's original approach that includes radiation-like modes. Using a guide-within-a-guide geometry, the radiation-like modes are included as modes bound to a thick air-cladding guide that contains the core profile of interest. In this model, the coupling from the fundamental model to radiation modes can be analyzed using a relatively simple analysis. The cross-coupling to the radiation modes for the simple double heterostructure waveguide is considered in detail and is shown to be important only for a large core-cladding index differences and for strong model confinement that results in a true facet loss. The conditions for this are the same as for low threshold lasers so that the loss sets a maximum limit on the equivalent internal quantum efficiency. A separate 1D finite-element numerical mode matching program, which treats evanescent and propagating radiation modes, is used as a comparison. The two methods of accounting for radiation modes are shown to be in good agreement. Modern graded core cases are treated as general examples. Specific quantum well laser structures taken from the literature, including II-VI and III-V structures spanning wavelengths from 0.5 μm to 10.0 μm, are also considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mid-infrared phase modulation via Stark effect on intersubband transitions in GaAs/GaAlAs quantum wells

    Page(s): 2313 - 2318
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Mid-infrared (~10 μm) electrorefractive effects of intersubband transitions in step GaAs/GaAlAs quantum wells are experimentally analyzed. A method for studying infrared electrorefraction of a two-dimensional structure via the Stark effect is used. The anomalous dispersion is measured over the entire spectral range of the transition and is found to be consistent with the Kramers-Kronig relations in the case of a Lorentzian absorption shape. A solution of Maxwell's equations in the multiquantum well structure is detailed and leads to a good agreement with experimental data. A standard interferometer and a lock-in technique allow a quasi-direct determination of phase and amplitude modulation with very good sensitivity. A theoretical approach based on a Lorentzian model and the solution of Maxwell's equations for a multiple QW (quantum well) structure agreed well with the data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Semivectorial Helmholtz beam propagation by Lanczos reduction

    Page(s): 2385 - 2389
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    By using the finite-difference method to perform Lanczos reduction, a semivectorial Helmholtz beam propagation algorithm is demonstrated. The applicability of this algorithm is no longer limited to paraxial beams and scalar fields. Mode indices of rib waveguides are calculated and compared to previously published data. Losses of Y -branch for two orthogonal polarizations are also presented. This algorithm is more efficient than the conventional beam propagation method in determining the mode index. To calculate the radiation loss however, it requires much more computational effort. More than 30 Krylov vectors are needed to avoid numerical dissipation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Capacitance allocation and its role in the performance of doubling-circuit pulsed gas lasers: its application to the N2 laser

    Page(s): 2371 - 2378
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    An investigation of the optical output for all possible combinations between the capacitances, C1 and C 2, in a doubling circuit N2 laser is presented. It is shown that a maximum optical output appears when C 1=C2 for constant total capacitance. The maximum value increases when the total capacitance increases and the system approaches saturation for capacitance values higher than 20 nF each. This behavior of the optical energy is due to a similar behavior of the current, which becomes maximum when the best coupling of the two loops of the system is achieved through capacitance equality, and the oscillatory behavior of the system is minimized. When this equality is disturbed, either with weak (C1>C2 ) or strong (C2<C1) coupling of the system, the current and optical outputs decrease. In both cases, the undesirable oscillatory behavior of the system increases. The electric parameters R1,L1 of the spark-gap loop and R2,L2 of the laser channel loop are calculated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pulsing behavior of a three-level laser with saturable absorber

    Page(s): 2390 - 2396
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A numerical study of a three-level laser model that includes a saturable absorber is presented. The theory models the laser as a lumped element. This assumption is valid as long as the laser pulses are much longer than the cavity. The model is intended to be somewhat representative of an erbium-doped fiber laser without trying to mimic the operating parameters of such a laser too closely. As expected, the presence of the saturable absorber causes the laser to be unstable under certain operating conditions. The question of stability is explored by examining small perturbations of the steady-state solutions of the rate equations. It is found that the predictions of this stability analysis are in excellent agreement with the behavior of the solutions of the full time-dependent rate equations. It is also found that under certain conditions the laser may pass from pulsed to stable operation simply by raising the pump power View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A novel small-period wiggler and simulations of its free-electron laser

    Page(s): 2263 - 2266
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    A small-period wiggler constructed of edgy-wound bifilar-helical conducting sheets with ferromagnetic cores, which is intended for free-electron lasers, is presented. The performance characteristics of the wiggler fields with a 100 mm period are measured. A field as high as 1500 G has been obtained. Free-electron lasers with this small-period wiggler have been investigated numerically with a three-dimensional nonlinear theory. Simulation results estimated that a radiation power of 20.2 MW and a frequency of 170 GHz with an efficiency of 5.1% can be obtained. It is feasible to make Raman free-electron lasers with this type of wiggler operating in the millimeter and submillimeter wavelength range with a relatively low electron energy (<500 keV) beam View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Carrier-dependent nonlinearities and modulation in an InGaAs SQW waveguide

    Page(s): 2319 - 2324
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    The authors report measurements of optically induced carrier-dependent refractive index changes and their saturation in an InGaAs single quantum well centered within a linear multiple quantum well guided-wave Fabry-Perot resonator using diode laser sources. A low-excitation nonlinear refractive cross-section, σn=-1×10-19 cm3, was deduced for probe wavelengths near the TM (transverse magnetic) absorption edge, falling only to σn=-3.1×10-20 cm3, at over 0.16 μm from the band edge. For an incident irradiance of 18 kW/cm 2, refractive index changes in the InGaAs quantum well as large as -0.16 were deduced near the absorption edge, while the index change at a wavelength 0.16 μm from the absorption edge was -0.055. This large off-resonant index change is attributed to an enhanced free-carrier contribution within a 2D system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 1.27μm atomic argon laser parameters in fission-fragment excited He/Ar and He/Ne/Ar gas mixtures

    Page(s): 2356 - 2363
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    The authors examine the power efficiency of the fission-fragment-excited atomic argon laser operating on the 1.27-μm (3d'[3/2]1-4'p[3/2]1) argon transition as a function of pump power, gas mixture, and pressure. The maximum measured power efficiency was 1.1±0.3% for a gas pressure of 1300 torr and a He/Ar ratio of 99.88/0.12. Neon addition to the He/Ar gas mixture increased both the energy deposited in the gas and the energy output without decreasing efficiency for a neon gas fraction of less than 0.5. Small-signal gain and saturation intensity are between 0.15-0.27%/cm and 25-200 W/cm2 for pump rates of 7.5-30 W/cm 3 in He/Ar and He/Ne/Ar gas mixtures. The laser threshold as a function of total pressure and argon concentration is presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical parameter oscillation with detuned intracavity sum-frequency generation

    Page(s): 2334 - 2341
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The authors consider frequency up-conversion by means of an optical parametric oscillator (OPO), in which sum-frequency generation (SFG) takes place in a crystal preceding the OPO crystal in the resonator. The SFG crystal produces light with a frequency at the sum of the pump and OPO signal frequencies. Only the OPO signal is resonated. A small detuning (phase mismatch) of the SFG crystal yields stable steady-state operation with quantum efficiency greater than 40% for a factor of 34 variation in the pump intensity. Detuning also reduces the power loading on the OPO crystal. As an example, conversion of 1.064 μm radiation to 589 nm radiation is discussed. For this example, power conversion efficiency exceeding 85% is possible View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Fraunhofer-wavelength magnetooptic atomic filter at 422.7 nm

    Page(s): 2379 - 2384
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    A demonstration of the first magnetooptic atomic filter that overlays a strong solar Fraunhofer line is reported. Compared with alkali magnetooptic filters, this filter enjoys a large reduction in solar interference and a significant decrease in the number of noise passbands. The filter utilizes the strong Ca(4p1P1-4s1 S0) transition at 422.7 nm. Under the weak magnetic field experimental conditions, a maximum transmission efficiency of 55% and a symmetrical double-peaked transmission spectrum with 1.5 GHz wide passbands were observed. The filter's frequency response was measured with a laser intensity modulation technique. No falloff was observed at 176 MHz, the highest frequency available with the apparatus. Calculations indicate that further improvements in filter performance can be achieved by optimizing the magnetic field and the cell temperature View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Intracavity shaping of mode-locked laser pulses

    Page(s): 2397 - 2404
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    A laser synthesizer of optical pulses is proposed. It is based on injection locking of numerous weakly coupled laser oscillators with a common resonator. A proper shaping of the susceptibility through shaping the pump beam reduces the dispersion of all orders due to the resonance transition and leads to generation of pulses close to the inverse bandwidth of the gain medium. A simple intracavity shaping mechanism allows synthesis of higher-order time supermodes directly from the laser. This technique could be applied to both active and passive mode-locked lasers with homogeneously and inhomogeneously broadened transitions. The possibility of using a compound gain medium is also discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Applications of highly nonlinear chalcogenide glass fibers in ultrafast all-optical switches

    Page(s): 2325 - 2333
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    Applications of chalcogenide glass fibers in ultrafast all-optical switches have been investigated. Ultrafast all-optical switching has been accomplished in an optical Kerr shutter configuration using As2S3-based glass fiber. The nonlinear refractive index of the As2S3-based glass is estimated to be n2=4.0×10-14 (cm2/W ), which is higher by two orders of magnitude than that of silica glass fiber. Nonlinear absorption due to two-photon absorption has been revealed to be negligible, and up to a 2π-phase shift has been obtained. Switching speed and switching power were investigated experimentally and through calculations. A switching time of 12 ps and a switching power of 5 W can be achieved using a 10-ps gate pulse and only a 1-m chalcogenide glass fiber. However, signal transformation due to cross-phase modulation and group velocity dispersion is not negligible for shorter gate pulses. Lower switching power is possible by reducing the transmission loss and the core area and by optimizing the driving conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-efficiency low-pressure Blumlein nitrogen laser

    Page(s): 2364 - 2370
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    An 0.8% efficiency, low-pressure Blumlein-type nitrogen laser is described. Its good efficiency is attributed to the optimization of the discharge chamber geometry and to the use of a low-inductance spark gap (<10 nH). The laser provides pulses with energies greater than 5 mJ and pulse widths not exceeding 4 ns. The design is simple in construction and operation. Stable operation is achieved for voltages ranging from 8 to 14 kV, pressures between 70 and 250 torr, and frequencies limited to 20 Hz View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of EM field in lasers with rotating mirror Q-switch

    Page(s): 2405 - 2412
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    A fast-Fourier-transform (FFT) computational scheme based on a Fourier expansion technique is developed to calculate the development of an electromagnetic (EM) field from spontaneous noise inside a loaded rotating mirror Q-switched laser. A rate equations analysis is also carried out, using the FFT-calculated dependence of the diffraction loss on the fixed Q-switch mirror tilt angle. The computational results are compared with the output characteristics of an eye-safe (λ=1.54 μm) erbium glass laser. The experiments are in good qualitative and quantitative agreement with the predictions of the FFT mode. The model reveals short-duration intense spatial regions, as well as two types of temporal modulations of the laser output pulses. These modulations are attributed to the inhomogeneous development of the laser field in the longitudinal and transverse laser resonator direction. These irregularities must be taken into account when calculating eye-safety levels of rotating mirror Q-switched lasers View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental and numerical study of stimulated Raman scattering in an astigmatic focus

    Page(s): 2267 - 2272
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    An astigmatic focus has been used to increase the conversion efficiency of a Raman cell at high pump energy. Experimental and numerical results show that the increased conversion is due to the reduction of cascade second order Stokes. It is shown that other effects, namely Brillouin scattering, anti-Stokes generation, and ground-state depletion, are negligible for the present experimental setup. The experimental and numerical calculations are in agreement. In particular, good agreement was obtained for the cross-over energy, i.e., the pump energy where the ordinary and the astigmatic focus give the same Stokes energy. Below this energy an ordinary focus gives a higher conversion than an astigmatic focus, while above this energy this is reversed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evidence for continuous visible chemical lasing from the fast near resonant energy transfer pumping of atomic sodium

    Page(s): 2346 - 2355
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    Energy transfer from selectively formed metastable states of SiO is used to pump sodium-atom laser amplifiers at λ≈569 nm (4d2D-3p2P), λ≈616 nm (5s2S-3p2 P), and λ≈819 nm (3d2D -3p2P). The a3Σ+ and b3Π states of SiO are generated in high yield from the Si+N2O→SiO+N2 reaction. The energy stored in the triplet states is transferred in a highly efficient collisional process to pump sodium atoms to their lowest excited 3d2 D, 4d2D, and 5s2S states. Adopting a sequence in which high concentrations of silicon and sodium atoms are mixed and oxidized, a continuous amplification (gain condition) is monitored which suggests the creation of a population inversion among the receptor sodium-atom energy levels and forms the basis for full cavity oscillation on the Na4 d2D-3p2P transition at 569 nm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stimulated rotational Raman conversion in H2, D2 , and HD

    Page(s): 2342 - 2345
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Stimulated rotational Raman conversion has been efficiently demonstrated in all three molecular hydrogen isotopes with a 532-nm Q-switched pump source. Optimum gas pressures and pump focusing have been determined. Single pass conversion efficiencies of 80%, 75%, and 65% have been achieved at the first Stokes wavelengths with H2 , D2, and HD, respectively. The maximum efficiency is generally limited by further Raman conversion of the initially generated Stokes light. The thresholds were found to increase in the order H2 <D2<HD as expected. With the 100 cm lens, the threshold for HD is ~8 times that for H2. The relative thresholds of H2 and D2 are reasonably consistent with the calculated steady-state gains based on the population statistics and the linewidth data. Intermediate frequency shifts such as these may be useful by themselves, or in combination with other nonlinear techniques, as methods to achieve specific wavelengths for system applications 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