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Quantum Electronics, IEEE Journal of

Issue 3 • Date Mar 1996

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Displaying Results 1 - 25 of 28
  • Methanol and the optically pumped far-infrared laser

    Page(s): 392 - 399
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    New results on the generation and spectroscopic analysis of optically pumped far-infrared (FIR) laser emission from CH3OH have been obtained as part of a systematic study of methanol isotopomers as FIR laser sources utilizing the extended line coverage available from a recently developed high-resolution CO2 laser of high efficiency. For normal CH3OH, six new short-wavelength lines have been found using a 2 m long Fabry-Perot FIR laser cavity. Accurate heterodyne frequency measurements are reported for 14 CH3OH FIR laser lines, nearly all above 100 cm-1, as well as accurate frequency offsets for most of the corresponding CO2 pump lines. Spectroscopic assignments are presented for nine high-frequency FIR laser lines in four pump systems View full abstract»

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  • Analytical formulas for the optical gain of quantum wells

    Page(s): 493 - 501
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    Analytical expressions for the quantized energy levels in quantum wells, the optical gain, the differential optical gain, and the linewidth enhancement factor are presented based on a simple parabolic-band gain model. Explicit formulas show clearly the dependence of these factors on well width, doping, and photon energy. The optical gain in the form of g=g0 In(N/N0) is derived using explicit approximations in the Fermi functions, where g0 is the proportionality constant, N is the injected carrier density, and N 0 is the transparency carrier density. The approximate formulas are shown to provide not only an efficient way of computing the gain-related parameters but also a convenient way of getting physical insights into the overall interplay of quantum well parameters View full abstract»

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  • A ridge waveguide DFB laser model including transverse carrier and optical effects

    Page(s): 408 - 416
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    In this paper, a steady-state model for ridge waveguide DFB lasers is presented. The complex two-dimensional semivectorial optical mode in the transverse direction is solved using a finite difference scheme without introducing any approximations. The electron and hole diffusion in the lateral direction is also considered, Along the longitudinal direction, a novel “Superposition of Spectral Power Method” is used, based on the coupled mode formulation. This model enables one to examine the interaction between the optical and carrier profiles for different injection levels and arbitrary transverse index profiles. As such, it is useful for studying CW characteristics such as lasing wavelength and threshold current. Finally, the results from this model are compared with experimental data from a varying ridge width laser array fabricated from a 1.55 μm InGaAsP-InP compressively strained multiquantum-well loss-coupled DFB structure View full abstract»

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  • Theory for passive mode-locking in semiconductor laser structures including the effects of self-phase modulation, dispersion, and pulse collisions

    Page(s): 478 - 492
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    We present a theory for passive mode-locking in semiconductor laser structures using a semiconductor laser amplifier and absorber. The mode-locking system is described in terms of the different elements in the semiconductor laser structure. We derive mode-locking conditions and show how other mode-locking parameters, like pulse width and pulse energy, are determined by the mode-locking system. System parameters, like bandwidth, dispersion, and self-phase modulation are shown to play an important role in mode-locking conditions and results. We also discuss the effects of pulse collisions and positions of the mode-locking elements inside the cavity on mode-locking stability and show that these effects can be easily included in the presented model. Finally, we give a number of design rules and recommendations for fabricating passively mode-locked lasers View full abstract»

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  • Properties of Bragg reflectors composed of isotropic dielectric layers cladded with birefringent media

    Page(s): 513 - 518
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    The reflectance of an asymmetric periodic dielectric stack comprising a periodic stratified dielectric film bounded by a positive birefringent uniaxial medium on one side and by an isotropic dielectric material on the other side are calculated by using the 4×4 transfer matrix formalism. The results show that the values of the reflectance have a strong dependence on the structure parameters, the incident polarization, and the optical axis orientation. The dependence of the reflectance on the optical axis orientation suggests that this effect could be used for the fabrication of a new kind of Bragg reflector View full abstract»

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  • Sources of error and noise in a magnetic mirror gyro

    Page(s): 543 - 548
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    A ring laser gyroscope biased by a magneto-optic mirror offers a promising alternative to mechanical dither, for applications requiring no dither and able to tolerate lower performance. The effect of the important mirror parameters: optical loss, scatter and transverse Kerr effect, on gyro performance, is defined. Explicit expressions, obtained from the literature and supplemented by new calculations, are given for the expected null-shift, random walk, and scale-factor nonlinearity; numerical values are listed for a typical magnetic mirror, indicating where improvements are required for potential applications View full abstract»

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  • Dynamic behaviour of the frequency-locking in a hybrid bistable system with delay and input modulation

    Page(s): 549 - 552
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    We report the difference of frequency-locking behaviour between short and long delay in a hybrid bistable system with delayed feedback and modulated input intensity. The oscillation behaviour inside the locking regions for long delay and its physical origin are discussed View full abstract»

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  • Thermal lens and beam properties in multiple longitudinally diode laser pumped Nd:YAG slab lasers

    Page(s): 365 - 370
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    The focal length of the thermal lens and the beam quality factor (beam propagation factor) M2 for a multiple longitudinally diode pumped slab laser is deduced for pump and output powers up to 16 and 4.5 W, respectively. Due to the geometry of the arrangement, a stronger thermal lens is observed in the plane with the larger pump spot radius as predicted by an analytical model for slab geometries. In addition, the second stable zone of an asymmetric resonator is found to be advantageous for improved beam properties at high output powers View full abstract»

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  • Single-shot high-speed signal detection by multiple-angle spectral interferometry

    Page(s): 519 - 524
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    A novel technique for detecting ultra-fast signals at speeds beyond those of conventional electrical circuits is described that uses the coherent correlation between the signal wave and that of a modulated local oscillator. The spectral components of the signal beam interfere with their counterparts of the light from the local oscillator in a multiple-angle scheme. It is found that this scheme allows the mutual convolution of the interfering lights to be spatially displayed on the observation plane as an interference pattern. Typical applications of this technique include serial-to-parallel conversion of the signal light and packet detection. In an experiment, single-event high-speed signals of several mW are successfully detected by using two independently oscillating light sources for the signal and local beams. Finally, we discuss the deployment of this technique in optical communication systems View full abstract»

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  • Broad-range tunable wavelength conversion of high-bit-rate signals using super structure grating distributed Bragg reflector lasers

    Page(s): 463 - 470
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    Tunable wavelength conversion of a 10 Gb/s signal over a broad wavelength range of about 90 nm is achieved by using a super structure grating distributed Bragg reflector laser. The extinction ratio dependence of converted signal light on input signal light power and bias current to the laser active region is discussed. The extinction ratio becomes large when the input signal light power increases and the bias current decreases. Bit error rate measurements show that error-free, penalty-free wavelength conversion is achieved when the extinction ratio is large (12.5 dB) and that the bit rate which error-free wavelength conversion is possible increases as the input signal light power increases. Twenty Gb/s signal wavelength conversion is also demonstrated View full abstract»

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  • Quasicontinuous wavelength tuning in super-structure-grating (SSG) DBR lasers

    Page(s): 433 - 441
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    The paper describes the design of a super-structure-grating distributed Bragg reflector (SSG-DBR) laser for broad quasicontinuous wavelength tuning with stable single-mode operation. The phase distributions and the effective coupling coefficients of SSG's are optimized to obtain both broad tuning range and high mode selectivity. A computer-aided simulation of wavelength tuning, where the effects of the waveguide loss increase and inhomogeneous gain spectrum are included, provides an optimum cavity structure and indicates the possibility of more than 70 mm quasicontinuous tuning in a 1.55 μm InGaAsP-InP SSG-DBR laser. Experimental results for 34 nm quasicontinuous tuning with a properly designed device are also presented View full abstract»

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  • Dynamic laser control using feedback from a gain grating

    Page(s): 371 - 377
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    We demonstrate that self-induced gain gratings can provide nonlinear optical feedback that results in single frequency selection and passive self Q-switching of a conventional linear laser cavity. An experimental Nd:YAG laser system is described that yields a temporally-smooth 20 ns pulse at 1.064 μm. In addition, we show that the feedback has phase-conjugate properties that permit “flower-like” mode formation even though the azimuthal symmetry of the cavity is broken View full abstract»

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  • Optical properties of pulsed generation in capillary gas lasers with internal-mirror waveguide resonators

    Page(s): 388 - 391
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    The angular distribution and coherence of pulsed capillary lasers with the optical feedback implemented by waveguide Fabry-Perot resonators with internal mirrors have been theoretically studied. We have shown that spatially-coherent, low divergence radiation can be generated even for short pulse duration if the cavity parameters (the refractive index of the capillary wall and the waveguide dimensions) are properly chosen View full abstract»

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  • Near 10 μm intervalence subband optical transitions in p-type In 0.49Ga0.51P-GaAs quantum well structures

    Page(s): 471 - 477
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    In this paper, the intervalence subband optical transitions in p-doped In0.49Ga0.51P-GaAs quantum well structures are theoretically investigated. The intervalence subband optical transitions are modelled by the multiband effective mass equations incorporating the unitary transformation numerical method. The present formalism is based on the k&oarr;·P&oarr; perturbation theory as done to date but contains two significant improvements: 1) a more efficient treatment of band structures, optical matrix elements, and absorption coefficients; and 2) the avoidance of zero-order Bloch function approximation for calculating the intervalence subband optical matrix elements and absorption spectra in favour of correcting the first-order perturbation theory in order to take the remote band effects into account. Both of the requirements, especially the latter, play a very important role in gaining qualitative insight and obtaining quantitative calculation of optical selection rules. A systematical study of the subband structures, intervalence subband optical matrix elements, and absorption spectra is made for p-doped In0.49Ga 0.51P-GaAs quantum wells, and a design guideline for near 10 μm infrared absorption is also discussed View full abstract»

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  • Off-plane angle dependence of photonic band gap in a two-dimensional photonic crystal

    Page(s): 535 - 542
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    We present an analysis of off-plane angle dependence of the photonic band gap in a two-dimensional triangular lattice with circular air rods embedded in a dielectric background. The plane-wave expansion theory is used to calculate band structures within the first Brillouin zone, and an effective refractive index approach is introduced to derive the off-plane angle dependence. The off-plane angle at which the in-plane band gap decreases to half of its gap width has been obtained, which can be increased significantly by increasing the filling fraction of the air rods. For a typical semiconductor material with a refractive index of 3.6 as the background, this angle reaches 26° at a high filling fraction of 0.84 (where the normalized in-plane band gap width is 24%). The corresponding solid angle of 1.75π could cover about 60 of the spontaneous emission from a linear-polarized dipole along the air rods View full abstract»

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  • Fundamental thermodynamic limit of laser efficiency

    Page(s): 567 - 573
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    The thermodynamic limits on the efficiency of different types of lasers are calculated both classically and quantum mechanically. In the classical case, the limit is derived from the inequality provided by the population inversion. In the quantum mechanical case, the limit is derived from the inequality of the change of entropy. The Shannon and von Neuman entropies of different light states are worked out View full abstract»

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  • Characteristics of multistack multiquantum barrier and its application to graded-index separate confinement heterostructure lasers

    Page(s): 442 - 447
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    The enhancement of electron barrier height by multistack multiquantum barrier structure is simulated using the transfer matrix method. The validity and feasibility of this concept is verified by the experimental results on GaAs-AlAs multistack multiquantum barriers. Based on the simulated results, both 0.78 and 1.3 μm graded-index separate confinement heterostructure (GRIN-SCH) lasers with predicted enhanced carrier and optical confinements using graded multistack multiquantum barriers are designed. Lower threshold current, higher modulation bandwidth as well as higher characteristic temperature are expected for these lasers View full abstract»

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  • Characteristics of a class of new opto-coupler amplifiers with positive feedback

    Page(s): 502 - 506
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    This paper discusses a new method of optoelectronic amplification that utilizes an array of one or more series connected light emitters (LED's or laser diodes) from which the light is collected by closely coupled PIN diode detectors with high quantum efficiency. Positive current feedback is applied to the opto-coupler in order to increase the current gain of the system. It is shown that the gain-bandwidth product of the system is proportional to the number of light emitters used. Current, voltage, and power gains of the opto-amplifier are derived and typical results shown. The system noise becomes very small if devices of high current transfer efficiency are used. Further, the noise figure is found to be independent of the positive feedback applied. For a given system, there is a minimum noise figure, and it is independent of the number of light emitters used in the array. With a transfer efficiency of 0.95, a single light emitter opto-amplifier can provide a current gain of 14.7 dB with a noise figure of about 1.5 dB View full abstract»

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  • Incomplete inversion and double-valued fundamental linewidth of infrared HeNe and HeXe lasers

    Page(s): 383 - 387
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    We have measured the quantum-limited linewidths of small HeNe 3.39 μm and HeXe 3.51 μm lasers. In contrast to the expected Schawlow-Townes behaviour strong deviations from the inverse power dependence are observed, leading to a double-valued relation between the linewidth and the output power. This phenomenon is analyzed in terms of the increase of spontaneous emission, by a factor Nsp, due to incompleteness of the inversion. Our analysis shows that typically Nsp has a value ranging from 1-10. Combining existing models for the pump power dependence of the level populations with measurements of the small signal gain, we are able to explain the observed double-valued linewidth behaviour in a quantitative way View full abstract»

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  • Travelling wave model of a multimode Fabry-Perot laser in free running and external cavity configurations

    Page(s): 553 - 566
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    We report the results of a numerical study of multimode behaviour of a Fabry-Perot laser. The model is based on travelling-wave equations for the slowly varying amplitudes of the counterpropagating waves in the cavity, coupled to equations for spatially dependent population inversion and polarization of a two-level active medium. Variations in the material variables on the scale of a wavelength are taken into account by means of an expansion in a Fourier series. Results are given for typical semiconductor laser parameters. Spatially distributed spontaneous emission noise and carrier diffusion are taken into account. The competing roles of spatial hole burning (SHE), spontaneous emission noise, and carrier diffusion in determining multimode behaviour are elucidated; with no carrier diffusion, spontaneous emission noise excites a large number of modes close to threshold, while SHE leads to a fixed number of significant lasing modes well above threshold. Carrier diffusion washes out the gratings in the material variables, and the resulting strengthening of the inter-mode coupling (cross-saturation) restores dominant single-mode emission well above threshold. We have also studied the effects of optical feedback and opportunities for mode selection with short external cavities; for an external cavity much shorter than the laser cavity length and a small field amplitude reflectivity coefficient, a single mode can be selected. For a large reflectivity coefficient, two groups of intracavity modes separated by the external cavity mode interspacing are selected. For an external cavity with a round trip time half that of the laser cavity, the laser can be forced with modest feedback to operate on two modes that are both quasiresonant with the external cavity. Mode selection is not found, even for weak feedback, when the external mode spacing is about 90% of the laser mode spacing View full abstract»

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  • An energy band-pass filter using superlattice structures

    Page(s): 507 - 512
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    A novel quantum mechanical energy band-pass filter (EBPF) using semiconductor superlattices is proposed. Such structures with a Gaussian superlattice potential profile allow the incident electrons to be nearly totally transmitted when the impinging electron energy is in the passband. On the other hand, a complete reflection occurs when the impinging energy is in the stopband. By adjusting the parameters of the potential profile and the superlattice, the desired passband and stopband of such filter can be obtained. Time evolution of an electron wave packet moving through such a structure is calculated by numerically solving the time-dependent Schrodinger equation. The numerical simulation clearly demonstrates the characteristics of total transmission and total reflection. The generalized concept of matched quantum-mechanical wave impedance (QMWI) analogous to that used in the transmission line theory is presented to explain the occurrence of total transmission of the proposed structures View full abstract»

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  • Multipulse operation of a high average power, good beam quality zig-zag dye laser

    Page(s): 378 - 382
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    A laser pumped zig-zag dye laser operating at 568 nm with a pulse length ~2 μs has been sealed to high power using a MOPA configuration. Pulse energies in excess of 7 J with beam quality <2 XDL have been achieved under repetitively pulsed, 10 Hz operation. RMS jitter was measured as 0.12 of a 1 XDL spot. The device has operated with over 70 W output for runs up to 5 s. Substantially longer run times and output powers are possible. This device represents an advance in dye laser capabilities. Improvement in pointing accuracy of better than an order of magnitude have been demonstrated. In addition, an improvement in beam quality by about an order of magnitude has been achieved compared to other dye lasers operating in this power range View full abstract»

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  • Interband-resonant light modulation by intersubband-resonant light in undoped quantum wells

    Page(s): 448 - 455
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    Interband-resonant light modulation by intersubband-resonant light in undoped quantum wells is investigated. Theoretical calculation for the modulation is carried out by considering not only the excitonic interband-transition but also the continuous level transition between the conduction and valence bands. The modulation characteristics are compared with those of the modulation using n-doped quantum wells. The possibility of the modulation using undoped quantum well is successfully shown by real-time single-shot experiment using Ti-Al2O3 and CO2 lasers for interband- and intersubband-resonant lights at room temperature View full abstract»

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  • Tuning of mid-infrared diode lasers for spectroscopy operated in sub-μs-pulses

    Page(s): 456 - 462
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    Near room temperature operation and hence Peltier cooling for lead chalcogenide diode lasers can be achieved by using sub-μs-pulses. At present, the typical CW low operation temperatures of these lasers limit their commercial gas analysis applications. We experimentally investigated the spectral characteristics concerning tuning width, temporal and current tuning rate, and mode behaviour of short pulsed diode lasers. For understanding of the pulse tuning, we present a qualitative thermodynamic model calculation. We observed for the first time a temporary negative tuning, that is opposite to the common mechanisms of temperature and current tuning View full abstract»

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  • Propagation characteristics of coherent array beams from carbon dioxide waveguide lasers

    Page(s): 400 - 407
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    The characteristics of coherent array beams generated by waveguide carbon dioxide laser structures have been investigated, with particular emphasis on their propagation and transformation properties. Methods of array beam generation are presented, and measurements of array beam quality are given through the use of the M2 parameter. Efficient transformation of an array beam from the antisymmetric to symmetric pattern is achieved through the use of a binary phase plate, and spatial filtering is shown to improve the beam quality at the expense of only a moderate loss of total beam power. Coherence effects in the near-field propagation of array beams are also explored 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