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Quantum Electronics, IEEE Journal of

Issue 8 • Date Aug. 1997

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Displaying Results 1 - 25 of 25
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  • Second-harmonic generation from CuInSe2 thin films: influence of the substrate-epilayer lattice mismatch

    Page(s): 1294 - 1298
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    We investigate the second-order nonlinear optical (NLO) properties of tetragonal chalcopyrite-structure CuInSe2 thin films using optical second-harmonic generation at a fundamental wavelength of 790 nm. An approximate doubling of the second-order optical nonlinearity of the CuInSe2 thin films is achieved through changing the substrate from GaAs(001) to In0.29Ga0.71As(001), thereby reducing the lattice mismatch from 2.2% to 0.2%. This observation suggests that minimizing the lattice mismatch is a key requirement for the growth of high-quality NLO active chalcopyrite structure thin films and is in contrast to some other NLO active thin-film systems View full abstract»

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  • Exact modal analysis and optimization of N×N×1 cascaded waveguide structures with multimode guiding sections

    Page(s): 1299 - 1307
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    Cascaded multimode interference waveguide devices are analyzed to predict their switching properties. The results obtained using an exact modal analysis of an infinite slab model of these structures are compared to those found using simple approximations. Using this model, design parameters for both 2×2×1 and 8×8×1 switching structures are optimized; robustness of the numerical optimization algorithm is discussed. Sensitivity of device transmission performance to lengths and widths of each of the multimode regions, phase shifts in the interconnect regions, and wavelength are presented for the optimized devices. The deviations of the multimode region lengths found using simple approximations from those found by optimizing the model are also presented View full abstract»

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  • A differential photoconductive AND gate with Be-doped low-temperature-grown InGaAs-InAlAs MQW MSM-PD's

    Page(s): 1308 - 1315
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    A novel photoconductive AND gate that overcomes the problems of: 1) the long tail of photoconductive switches and 2) signal leakage via switch capacitance (signal feedthrough) is proposed. We use Be-doped low-temperature (LT)-grown InGaAs-InAlAs MQW metal-semiconductor-metal photodetectors (MSM-PD's) to get a shorter turn-off time and propose a differential AND gate to cancel the signal feedthrough. A comparison between LT-grown MSM-PD's and those fabricated by ion implantation shows that the LT-grown ones are ultrafast with a full width at half maximum of 5.3 ps and are suitable for low-bias operation. It is experimentally confirmed that the differential AND gate completely cancels the signal feedthrough in the picosecond region. The differential AND gate: with the LT MSM-PD's achieves return-to-zero (RZ) 20 Gb/s AND operation View full abstract»

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  • Bandwidth improvement of a homojunction p-i-n photodiode

    Page(s): 1333 - 1337
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    This paper presents an analytical study of the impact of doping profile in the p and n regions on the improvement of the bandwidth of a homo-junction p-i-n photodiode. In this study, nonuniformly doped p and n regions are considered. Thus, due to the nonuniformity in the doping, an electric field is established in both the p and n regions. Thereby, if the field is in the right direction, it will aid the diffusion of electrons and holes from p and n regions into the i region. Through these results, it is found that the bandwidth of the nonuniform photodiode is improved from 7 GHz, for uniformly doped p and n regions, to over 30 GHz. Whereas in this proposed structure, the bandwidth is comparable to that obtained for a double heterostructure photodiode, with the advantage of higher quantum efficiency View full abstract»

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  • Recent advances in Sb-based midwave-infrared lasers

    Page(s): 1403 - 1406
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    Several midwave-infrared (MWIR) lasers have been demonstrated, including 2.8-, 3.1-, 3.2-, 3.4-, 4.1-, and 4.3-μm diodes. The devices utilize multiple-quantum-well (MQW) active regions in which the quantum wells (QW's) consist of InAs-GaInSb broken-gap superlattices (BGSL's). InGaAsSb barrier layers separate the BGSL wells, and InAs-AlSb superlattices are employed as cladding layers. We have observed pulsed laser operation up to 255 K with 3.2-μm devices. Typical pulsed output powers for these devices at 200 K are over 50 mW View full abstract»

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  • Optoelectronic InP-InGaAs smart pixels for optical interconnections and computing

    Page(s): 1407 - 1416
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    We describe InP-InGaAs optoelectronic smart pixels for applications in optical interconnection and computing. These circuits consist of monolithically integrated p-i-n photodiodes, heterojunction bipolar transistor (HBT) receivers and transmitters, and surface-bonded folded-cavity surface-emitting lasers (FCSEL's). Design, fabrication, and performance of two different circuits: a high-sensitivity pixel, and a high-bandwidth pixel with logic functions are discussed. We achieve a minimum switching energy of 6 fJ, a maximum pixel bandwidth of 800 MHz, and an optoelectronic gain of 3. To our knowledge, these are the best overall performance characteristics of any optoelectronic smart pixel technology and are competitive or superior to that achieved using all-electronic interconnects View full abstract»

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  • Tunable single- and double-frequency diode-pumped Nd:YAG lasers

    Page(s): 1417 - 1423
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    An Nd:YAG 1-cm-long crystal has been used as the active medium for tunable single- and double-frequency lasers with a metallic absorbing thin-film selector. Cobalt and chromium thin films (210-nm thickness) were used for mode number and frequency control. The laser with a short cavity (25 mm) provided slow smooth tuning up to 6 GHz, the frequency chirp up to 4 GHz with repetition rate about 0.5 kHz and hop tuning over 150 GHz at a maximum pump power of 1.8 W. 520 mW of single-frequency output power was achieved. Double-frequency operation with a space of 1.5-2.5 GHz was realized in a laser with cavity length up to 100 mm View full abstract»

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  • A quantitative comparison of the classical rate-equation model with the carrier heating model on dynamics of the quantum-well laser: the role of carrier energy relaxation, electron-hole interaction, and Auger effect

    Page(s): 1350 - 1359
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    In this paper, a quantitative theoretical comparison of the classical rate-equation model with the carrier heating model for large signal dynamic response of 1.5-μm InGaAs-InGaAsP single-mode quantum-well (QW) lasers Is performed. The contributions of carrier energy relaxation, electron-hole interaction, and Auger effect to the nonlinear gain are inspected in detail by a numerical comparison of the two models at room temperature (293 K) and low temperature (50 K). It can be shown that contribution of the carrier heating to the nonlinear gain coefficient is proportional to an effective carrier energy relaxation time, and the contribution of the electron-hole energy exchange time shows a nonlinear relation. Furthermore, the influence of Auger heating on the modulation dynamics is also considered and is found to be indescribable by a single phenomenological nonlinear gain coefficient. The dependence of the nonlinear gain coefficient on the laser emission wavelength of distributed feedback lasers is also demonstrated quantitatively for the first time View full abstract»

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  • A unified Green's function analysis of complicated DFB lasers

    Page(s): 1253 - 1259
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    An efficient full-wave analysis technique for one-dimensional optical domains, known as the recursive Green's function method (RGFM), is presented for evaluation of distributed feedback (DFB) laser cavities with arbitrary material profiles. The method first constructs the Green's function of an inhomogeneous domain and subsequently uses Green's theorem to determine the laser optical field, lasing wavelength, and threshold gain. The technique is applied to investigate the performance of three DFB laser structures: a chirped-grating configuration, a modulated stripe width design, and a reduced duty cycle complex-coupled device. These structures are evaluated in terms of their single-mode lasing behavior and the uniformity of the optical field within the cavity View full abstract»

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  • Optimization in scaling fiber-coupled laser-diode end-pumped lasers to higher power: influence of thermal effect

    Page(s): 1424 - 1429
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    The optimum mode-to-pump ratio in scaling fiber-coupled laser-diode end-pumped lasers to higher power has been investigated by including the thermal effect into the space-dependent rate equation analysis. The optical path difference (OPD) distribution has been derived as a function of the pump-beam quality, focus position of pumping light, and pump radius at the focal plane under the assumption that the end faces of the crystal are thermally insulated. The diffraction losses arising from thermally induced spherical aberration have been estimated by the Strehl intensity ratio. The present results for the optimum mode-to-pump ratio are markedly different from previous analyses in which thermal effects are neglected. Here, the optimum mode-to-pump ratio is a decreasing function of input pump power, and is less than unity in the case of a slightly high pump power. The practical example of a Nd:YAG laser pumped by a 13-W fiber-coupled laser diode is considered to confirm our physical analysis View full abstract»

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  • Dynamic behavior of double-tapered-waveguide distributed feedback lasers

    Page(s): 1260 - 1267
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    Dynamic behavior of a double-tapered-waveguide (DTWG) distributed feedback (DFB) semiconductor laser is analyzed theoretically. It is found that the relaxation oscillation frequency can he enhanced by the DTWG structure especially for DFB lasers with large coupling-length product View full abstract»

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  • Design and analysis of double-fused 1.55-μm vertical-cavity lasers

    Page(s): 1369 - 1383
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    Detailed design and experimental characterization of three generations of double-fused vertical-cavity lasers are described. The result of this design evolution is the first above-room-temperature continuous-wave operation of long-wavelength vertical-cavity lasers. Threshold currents of 2.3 mA and yields greater than 90% have been obtained View full abstract»

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  • Raman shifting in the absence of multiple Stokes orders with a Nd:YAG laser in hydrogen: evidence of coupling between the forward and backward Stokes processes

    Page(s): 1288 - 1293
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    By Raman shifting the output of a 1.319-μm Nd:YAG laser in hydrogen, up to 24.5 mJ of Stokes light at 2.918 μm has been generated. Due to the low energy of the 2.918-μm Stokes photons, the first Stokes is the only Stokes line for this system. The effect of pressure on the conversion is notably simpler in this regime, but the gain saturates unusually slowly. An unexpected pump linewidth sensitivity in the forward Stokes conversion is observed. Coupling of the forward and backward Stokes processes is suggested as an explanation for these effects and is supported by a simple model View full abstract»

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  • Controlling chaotic behavior of heavy to light hole mixing tunneling by external electric fields

    Page(s): 1345 - 1349
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    Oscillatory and chaotic motion of heavy to light hole mixing tunneling in asymmetric coupled quantum-well structures can be controlled by an external electric field. Chaotic behavior occurs if the heavy-hole state in the first well is aligned with the light-hole state in the second well under a significant in-plane vector k||. Oscillatory motion is recovered if the external electric field disrupts the alignment between the heavy-hole state in the first well and the light-hole state in the second well View full abstract»

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  • Photoluminescence investigation of the carrier confining properties of multiquantum barriers

    Page(s): 1338 - 1344
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    A comparative luminescence study of two Ga0.52In0.48P-(Al0.5Ga0.5) 0.52In0.48P single-quantum-well (SQW) samples with bulk and multiquantum barrier (MQB) barriers is presented. When excess carriers are only created in the quantum wells (QW's) of the samples by resonant excitation using a dye laser, the luminescence efficiency of both samples as a function of temperature is found to be essentially identical. We find, therefore, no evidence for any enhancement in the confining potential of the MQB sample over the bulk barrier sample. From Arrhenius plots of the integrated luminescence intensity, it is found that carrier loss from the QW is dominated by a nonradiative loss mechanism with an activation energy considerably smaller than that expected from direct thermal loss of electrons and holes into the barriers. We suggest that the improved device characteristics reported for lasers containing MQB's is due to effects other than the quantum interference of electrons View full abstract»

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  • Polarization-insensitive electroabsorptive modulation using interdiffused InGaAs(P)-InP quantum wells

    Page(s): 1316 - 1322
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    This is a theoretical study to demonstrate the use of interdiffusion in the realization of polarization insensitivity at the band-edge. Two InGaAs-InP quantum well as-grown structures have been investigated: one with lattice-matched condition and the other with small as-grown tensile strain (0.15%). The interdiffusion is considered to take place on the Group V (As and P) sublattice only. As a result, a tensile strain is produced which merges the heavy- and light-hole states in order to achieve polarization insensitivity. Criteria to develop polarization-insensitive quantum wells (QW's) using interdiffusion are presented here. When the two-phase interdiffusion mechanism is modeled, the results show that the well barrier interfaces of the QW maintain an abrupt profile while the well width remains constant after interdiffusion. The two interdiffused QW structures considered here can produce polarization insensitive electroabsorption at operation wavelengths around 1.55 μm. The one with lattice-matched condition Is particularly attractive since it only requires an easy (high-yield) fabrication process with a simple postprocessing thermal annealing to achieve polarization insensitivity View full abstract»

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  • Self-consistent modeling of beam instabilities in 980-nm fiber pump-lasers

    Page(s): 1384 - 1395
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    Emission nonlinearities such as kinks in the L-I characteristic and beam steering have often been observed in semiconductor power lasers that were designed for single-mode operation. A physical model of these phenomena is presented in which they are attributed to effects of the lasing and coherent coupling of multiple lateral modes. This model has been implemented self-consistently in a finite-element scheme. Simulation results for a typical 980-nm fiber pump laser are described and are found to be in good qualitative agreement with experimental observations. This agreement includes bilateral steering of the peak field, nonsymmetric emission field intensity in a symmetric device, nonlinearity and kinks in the L-I characteristics, and beating patterns in the back plane image View full abstract»

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  • Higher order soliton pulse compression in dispersion-decreasing optical fibers

    Page(s): 1430 - 1439
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    Compression of higher order optical solitons in fibers with anomalous dispersion decreasing along their length is investigated. We demonstrate high-quality compression of pulses with initial soliton order 1<N<2 achieving compression factors over 50, using a fiber length equal to approximately one soliton period. This pulse compression technique has significant advantages over the widely reported adiabatic and soliton-effect compression techniques View full abstract»

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  • Resonant cavity-enhanced InGaAs-AlGaAs heterojunction phototransistors with an optical design for high uniformity and yield

    Page(s): 1323 - 1332
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    We present uniformity data on resonant cavity-enhanced InGaAs-AlGaAs heterojunction phototransistors (HPT's) with an optical design that promotes high uniformity and yield. The HPT's operate in the wavelength region where the GaAs substrate is transparent and the data show the HPT's to be suitable for vertical integration with optical emitters or modulators to form two-dimensional arrays of smart pixels operating in transmission mode. The absorbing region of the HPT consists of an InGaAs multiple-quantum-well structure where the quantum wells (QW's) have been distributed to make the total absorption in the cavity insensitive to growth variations as well as the spatial matching of the standing wave and absorbing QW's. Theoretically, we estimate the absorption to be 39%±1% of the incident optical power, even at wafer nonuniformities of 12.5%. With these nonuniformities, the resonant wavelength moves ±25 nm, making postgrowth tuning of the wavelength necessary. Experimentally, we show postgrowth tuning of the resonance wavelength without loss in uniformity. The arrays have good uniformity as well as very high responsivities. The average responsivity is 160 A/W ±15% from 927-955 nm. The standard deviation of a typical array is 0.5 nm in resonant wavelength and about 5% of the average responsivity. The difference between maximum and minimum values for an array is typically 3 nm in resonant wavelength and ±10% of the average responsivity View full abstract»

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  • Well number, length, and temperature dependence of efficiency and loss in InGaAsP-InP compressively strained MQW ridge waveguide lasers at 1.3 μm

    Page(s): 1360 - 1368
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    Experimental measurements of external differential efficiency on 0.7% compressively strained multiquantum-well (MQW) ridge waveguide lasers operating at 1.3 μm are presented. The lasers have the number of quantum wells (QW's) varying from 5 to 14 and cavity lengths ranging from 250 to 1000 μm and were measured over a temperature range of -50°C to 90°C. A phenomenological model is introduced which shows that over a range of design and operating conditions, the behavior of the external differential quantum efficiency can be entirely explained by intervalence band absorption (IVBA) It is also shown that outside this range IVBA alone is not sufficient to describe the behavior, indicating that current leakage becomes a significant factor. Ramifications of the IVBA contribution to the external differential quantum efficiency are investigated View full abstract»

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  • CO2 laser stabilization to 0.1-Hz level using external electrooptic modulation

    Page(s): 1282 - 1287
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    We have developed a frequency stabilization scheme for CO2 lasers using only external modulation via an electrooptic modulator (EOM). One of the two laser sidebands which are generated by the EOM and frequency-modulated is set in resonance with a Fabry-Perot cavity, itself filled with OsO4 as an absorber. The saturation signal of an OsO4 line detected in transmission of the Fabry-Perot cavity is used for stabilization. We obtained a stability of 0.1 Hz (Δν/ν=3.5 10-15) on a 100-s time scale, and a reproducibility up to 10 Hz with the strongest OsO4 reference lines. These results largely improve the performance of our previous setup for which modulation was applied through piezoelectric transducers. Further, the stabilized laser is not frequency-modulated and is easily tunable View full abstract»

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  • Optical gain and saturation intensity in a transverse-flow CW CO 2 laser

    Page(s): 1278 - 1281
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    Simple expressions for the small-signal gain and the saturation intensity in a transverse-flow CW CO2 laser have been derived considering the effect of gas flow and the finite time required for N 2 molecule to transfer its energy to CO2 molecules. These expressions provide estimates of these parameters fairly close to the experimentally measured values in high-power transverse-flow CW CO2 lasers View full abstract»

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  • Broad-band absolute frequency synthesis of pulsed coherent lightwaves by use of a phase-modulation amplified optical ring

    Page(s): 1268 - 1277
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    Broad-band absolute frequency synthesis of over 1.4 THz with a 10-GHz spacing is demonstrated for pulsed lightwaves. It is based on the recirculation of a rectangular pulse around an amplified fiber-optic ring containing a phase modulator, an acoustooptic (AO) frequency shifter, and a high-finesse Fabry-Perot etalon (FPE). The modulation frequency FM and the AO frequency shift FAO are designed so that FM±FAO is the same as the peak interval of the FPE. If one of the peak frequencies is tuned to the frequency of the initial pulse from a master laser, the frequency of the recirculating pulse jumps to the next peak for each round trip while the unwanted frequency components are eliminated by the FPE. We confirmed 70 circulations both for plus and minus frequency shift directions and a covering span was 1.4 THz (140×10 GHz) View full abstract»

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  • Wavelength chirp and dependence of carrier temperature on current in MQW InGaAsP-InP lasers

    Page(s): 1396 - 1402
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    In this paper, we derive a relation between the wavelength chirp and carrier temperature in semiconductor lasers. The coefficient relating the change in carrier temperature and chirp is expressed in terms of the temperature derivative of the optical gain, and two parameters describing the variation of refractive index produced by the variation of optical gain due to change of carrier quasi-Fermi level separation or carrier temperature. We have measured these parameters for MQW InGaAsP lasers, Using this data, we estimated the rate of the temperature increase with current above threshold in these devices, which is 0.13 K/mA 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