Showing papers in "IEEE Journal of Selected Topics in Quantum Electronics in 2004"
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TL;DR: In this paper, a review of permeation-barrier technologies as well as the current status of thin-film permeation barriers for organic light-emitting devices (OLEDs) is provided.
Abstract: One of the advantages of organic light-emitting devices (OLEDs) over other display technologies is the ability to fabricate them on flexible substrates. As polymer substrates do not offer the same barrier performance as glass, OLEDs on polymer substrates will require thin-film barriers on both the bottom and top side of the device layers for sufficient lifetimes. This article provides a review of permeation-barrier technologies as well as the current status of thin-film permeation barriers for OLEDs. Topics include the implications of various device structures, permeation rate measurement, background and state-of-the-art of barrier technology, and mechanical and optical considerations for effective barriers.
528Â citations
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TL;DR: In this paper, the first passively mode-locked fiber laser based on carbon nanotubes (SAINT) is presented, which offers several key advantages such as: ultrafast recovery time (<1 ps), high-optical damage threshold, mechanical and environmental robustness, chemical stability, and the ability to operate in transmission, reflection, and bidirectional modes.
Abstract: We present the first passively mode-locked fiber lasers based on a novel saturable absorber incorporating carbon nanotubes (SAINT). This device offers several key advantages such as: ultrafast recovery time (<1 ps), high-optical damage threshold, mechanical and environmental robustness, chemical stability, and the ability to operate in transmission, reflection, and bidirectional modes. Moreover, the fabrication cost and complexity of SAINT devices are potentially lower than that of conventional semiconductor saturable absorber mirror devices. Therefore, it is expected that SAINT will greatly impact future pulsed laser design and development.
372Â citations
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TL;DR: The unitraveling-carrier photodiode (UTC-PD) as mentioned in this paper utilizes only electrons as the active carriers, which is the key for its ability to achieve excellent high-speed and high-output characteristics simultaneously.
Abstract: The unitraveling-carrier photodiode (UTC-PD) is a novel photodiode that utilizes only electrons as the active carriers. This unique feature is the key for its ability to achieve excellent high-speed and high-output characteristics simultaneously. To date, a record 3-dB bandwidth of 310 GHz and a millimeter-wave output power of over 20 mW at 100 GHz have been achieved. The superior capability of the UTC-PD for generating very large high-bit-rate electrical signals as well as a very high RF output power in millimeter/submillimeter ranges can lead to innovations in various systems, such as broadband optical communications systems, wireless communications systems, and high-frequency measurement systems. Accomplishments include photoreceivers of up to 160 Gb/s, error-free DEMUX operations using an integrated UTC-PD driven optical gate of up to 320 Gb/s, a 10-Gb/s millimeter-wave wireless link at 120 GHz, submillimeter-wave generation at frequencies of up to 1.5 THz, and photonic frequency conversion with an efficiency of -8 dB at 60 GHz. For the practical use, various types of modules, such as a 1-mm coaxial connector module, a rectangular-waveguide output module, and a quasi-optic module, have been developed. The superior reliability and stability are also confirmed demonstrating usefulness of the UTC-PD for the system applications.
369Â citations
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TL;DR: In this paper, the spectral efficiency of DWDM transmission systems is compared in terms of their spectral efficiencies and signal-to-noise ratio requirements, assuming amplified spontaneous emission is the dominant noise source.
Abstract: Information-theoretic limits to spectral efficiency in dense wavelength-division-multiplexed (DWDM) transmission systems are reviewed, considering various modulation techniques (unconstrained, constant-intensity, binary), detection techniques (coherent, direct), and propagation regimes (linear, nonlinear). Spontaneous emission from inline optical amplifiers is assumed to be the dominant noise source in all cases. Coherent detection allows use of two degrees of freedom per polarization, and its spectral efficiency limits are several b/s/Hz in typical terrestrial systems, even considering nonlinear effects. Using either constant-intensity modulation or direct detection, only one degree of freedom per polarization can be used, significantly reducing spectral efficiency. Using binary modulation, regardless of detection technique, spectral efficiency cannot exceed 1 b/s/Hz per polarization. When the number of signal and/or noise photons is small, the particle nature of photons must be considered. The quantum-limited spectral efficiency for coherent detection is slightly smaller than the classical capacity, but that for direct detection is 0.3 b/s/Hz higher than its classical counterpart. Various binary and nonbinary modulation techniques, in conjunction with appropriate detection techniques, are compared in terms of their spectral efficiencies and signal-to-noise ratio requirements, assuming amplified spontaneous emission is the dominant noise source. These include a) pulse-amplitude modulation with direct detection, b) differential phase-shift keying with interferometric detection, c) phase-shift keying with coherent detection, and d) quadrature-amplitude modulation with coherent detection.
322Â citations
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TL;DR: An overview of DPSK for high spectral efficiency optical transmission and methods for further enhancing performance of phase-shift keying in long-haul transmissions, specifically the compensation of nonlinear phase jitter are presented.
Abstract: Differential phase-shift keying (DPSK) has attracted significant attentions in research and development during the last several years. An overview of DPSK for high spectral efficiency optical transmission is presented in this paper. The advantages of DPSK in terms of receiver sensitivity and tolerance to fiber nonlinearity will be discussed in detail. A simplified method for estimating the performance of phase-shift keying in numerical simulations is explained. Results of experimental and numerical investigations of several phase shift keying formats, including polarization division multiplexing and multilevel encoding, will be reviewed. Finally, methods for further enhancing performance of phase-shift keying in long-haul transmissions, specifically the compensation of nonlinear phase jitter, are presented.
264Â citations
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TL;DR: In this paper, the authors developed a barrier film on a plastic substrate and a passivation film on the OLED device itself, which showed good emission characteristics after storage, and its characteristics were almost the same as those of a device fabricated on a glass substrate.
Abstract: Organic light-emitting diodes (OLEDs) displays using plastic substrate have many attractive features. They are ultrathin and light, in addition, it will be realized the flexible display to utilize the flexibility of the substrate. The key issue in achieving such displays is how to protect OLEDs from moisture and oxygen. We developed a barrier film on a plastic substrate and a passivation film on the OLED device itself. As a result, the device showed good emission characteristics after storage, and its characteristics were almost the same as those of a device fabricated on a glass substrate. We also developed a 3-in full-color flexible OLED display.
251Â citations
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TL;DR: In this paper, degraded GaN-based laser diodes were investigated in terms of dislocations and degradation is governed by a diffusion process, and a detailed degradation mechanism was proposed.
Abstract: We investigate degraded GaN-based laser diodes (LDs) on epitaxial lateral overgrown GaN layers in terms of dislocations. Almost all of the threading dislocations that appear in the wing regions are a-type dislocations. Their origins are the lateral extension of dislocations from the seed regions that contingently bend upwards to the episurface. Comparing short-lived LDs and long-lived LDs that have almost the same power consumption, we find that the relative levels of dislocation densities in their respective active layers are different. In the degraded LDs, neither dislocation multiplication from the threading dislocations nor any structural changes of the threading dislocations are observed. This indicates that degradation is not caused by dislocation multiplication at the active layers, which is usually observed in LDs featuring zincblende-based structures. The degradation rate is almost proportional to the square root of the aging time. Our results indicate that degradation is governed by a diffusion process, and a detailed degradation mechanism is proposed.
224Â citations
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TL;DR: In this article, the authors demonstrate a fully monolithic silicon optical scanner with large static optical beam deflection, which can be used for both one-and two-axis rotation and pistoning of a micromirror.
Abstract: In this paper, fully monolithic silicon optical scanners are demonstrated with large static optical beam deflection. The main advantage of the scanners is their high speed of operation for both axes: namely, the actuators allow static two-axis rotation in addition to pistoning of a micromirror without the need for gimbals or specialized isolation technologies. The basic device is actuated by four orthogonally arranged vertical comb-drive rotators etched in the device layer of an silicon-on-insulator wafer, which are coupled by mechanical linkages and mechanical rotation transformers to a central micromirror. The transformers allow larger static rotations of the micromirror from the comb-drive stroke limited rotation of the actuators, with a magnification of up to 3/spl times/ angle demonstrated. A variety of one-axis and two-axis devices have been successfully fabricated and tested, in all cases with 600-/spl mu/m-diameter micromirrors. One-axis micromirrors achieve static optical beam deflections of >20/spl deg/ and peak-to-peak resonant scanning of >50/spl deg/ in one example at a resonant frequency of 4447 Hz. Many two-axis devices utilizing four rotators were tested, and exhibit >18/spl deg/ of static optical deflection at <150 V, while their lowest resonant frequencies are above 4.5 kHz for both axes. A device which utilizes only three bidirectional rotators for tip-tilt-piston actuation achieves -10/spl deg/ to 10/spl deg/ of optical deflection in all axes, and exhibits minimum resonant frequencies of 4096 and 1890 Hz for rotation and pistoning, respectively. Finally, we discuss the preliminary results in scaling tip-tilt-piston devices down to 0.4 /spl times/ 0.4 mm on a side for high fill-factor optical phased arrays. These array elements include bonded low-inertia micromirrors which fully cover the actuators to achieve high fill-factor.
211Â citations
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TL;DR: By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra.
Abstract: By suitably choosing the fiber properties, and by tuning the pump wavelength near the fiber zero-dispersion wavelength, one can in principle generate a wide variety of one-pump fiber optical parametric amplifier gain spectra These can range from a very wide single region to two symmetric narrow gain regions far away from the pump We have experimentally verified these predictions With a highly nonlinear fiber, we have inferred the existence of gain over a single 400-nm region and measured a maximum on-off gain of 65 dB With a common dispersion-shifted fiber, we have obtained tunable gain regions less than 1 nm wide, up to 200 nm from the pump; we have also shifted these by several nanometers by lowering the fiber temperature to 0/spl deg/C
206Â citations
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TL;DR: A review of the recent progress in APD technology can be found in this paper, where the authors present a survey of the most recent developments in III-V compound avalanche photodiodes (APDs).
Abstract: The development of high-performance optical receivers has been a primary driving force for research on III-V compound avalanche photodiodes (APDs). The evolution of fiber optic systems toward higher bit rates has pushed APD performance toward higher bandwidths, lower noise, and higher gain-bandwidth products. Utilizing thin multiplication regions has reduced the excess noise. Further noise reduction has been demonstrated by incorporating new materials and impact ionization engineering with beneficially designed heterostructures. High gain-bandwidth products have been achieved waveguide structures. Recently, imaging and sensing applications have spurred interest in low noise APDs in the infrared and the UV as well as large area APDs and arrays. This paper reviews some of the recent progress in APD technology.
181Â citations
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TL;DR: The first experimental demonstration of a forward error correction (FEC) for 10-Gb/s optical communication systems based on a block turbo code (BTC) is reported and the ability of the proposed FEC system to achieve a receiver sensitivity of seven photons per information bit when combined with return-to-zero differential phase-shift keying modulation is demonstrated.
Abstract: The first experimental demonstration of a forward error correction (FEC) for 10-Gb/s optical communication systems based on a block turbo code (BTC) is reported. Key algorithms, e.g., extrinsic information, log-likelihood ratio, and soft decision reliability, are optimized to improve the correction capability. The optimum thresholds for a 3-bit soft decider are investigated analytically. A theoretical prediction is verified by experiment using a novel 3-bit soft decision large scale integrated circuit (LSI) and a BTC encoder/decoder evaluation circuit incorporating a 10-Gb/s return-to-zero on-off keying optical transceiver. A net coding gain of 10.1 dB was achieved with only 24.6% redundancy for an input bit error rate of 1.98/spl times/10/sup -2/. This is only 0.9 dB away from the Shannon limit for a code rate of 0.8 for a binary symmetric channel. Superior tolerance to error bursts given by the adoption of 64-depth interleaving is demonstrated. The ability of the proposed FEC system to achieve a receiver sensitivity of seven photons per information bit when combined with return-to-zero differential phase-shift keying modulation is demonstrated.
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TL;DR: In this paper, a chaotic lidar (CLIDAR) system that utilizes a chaotic laser as the light source is proposed and studied, where the detection and ranging are realized by correlating the signal waveform reflected back from the target with a delayed reference waveform.
Abstract: A novel chaotic lidar (CLIDAR) system that utilizes a chaotic laser as the light source is proposed and studied. In CLIDAR, the detection and ranging are realized by correlating the signal waveform reflected back from the target with a delayed reference waveform. Benefiting from the very broad bandwidth of the chaotic waveform that can be easily generated by a semiconductor laser, a centimeter-range resolution is readily achieved. The correlation performance of CLIDAR is studied both numerically and experimentally. The power spectra, phase portraits, time series, and correlation traces of the chaotic waveforms obtained at different operating conditions are compared. The relation between the complexity of the attractor and the correlation property is examined. The correlation dimension and the largest positive Lyapunov exponent of each waveform are calculated. To compare the correlation performance of the waveforms quantitatively, peak sidelobe levels of the correlation traces with different correlation lengths and relative noise levels are investigated. Preliminary experiments show a subcentimeter accuracy in ranging with a 3-cm-range resolution, which currently is limited by the bandwidth of the oscilloscope used.
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TL;DR: In this article, a microelectromechanical variable optical attenuator (VOA) was proposed for large optical attenuation (40 dB), corresponding to mirror angle of 0.3/spl deg.
Abstract: We report the design, fabrication, and successful demonstration of microelectromechanical variable optical attenuator (VOA) using an electrostatic microtorsion mirror (0.6 mm in diameter) combined with a fiber-optic collimator. The VOA operates at low voltages (dc 5 V or less) for large optical attenuation (40 dB, corresponding to mirror angle of 0.3/spl deg/) and a fast response time (5 ms or faster). The mirror made of a bulk-micromachined silicon-on-insulator wafer has been designed to be shock resistant up to 500 G without any mechanical failure. We also have suppressed temperature dependence of optical performance to be less than /spl plusmn/0.5 dB at 10-dB attenuation in the range of -5/spl deg/C-70/spl deg/C by mechanically decoupling the parasitic bimorph effect from the electrostatic operation.
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TL;DR: In this paper, a self-starting mode locking of a ytterbium (Yb) fiber laser tunable over 125 nm was achieved by optimization of nonlinear reflection and bandgap characteristics of the multiple-quantum-well saturable absorber and proper engineering of the laser cavity.
Abstract: Using semiconductor saturable absorber mirrors and a grating-pair dispersion compensator, we obtain reliable self-starting mode locking of a ytterbium (Yb) fiber laser tunable over 125 nm. The 980-1105-nm tuning range is achieved by optimization of nonlinear reflection and bandgap characteristics of the multiple-quantum-well saturable absorber and by proper engineering of the laser cavity. A short-length Yb-doped double-clad amplifier seeded with mode-locked Yb-fiber laser produces picosecond pulses with energy of 30 nJ (700 mW of average power). A compact version of the fiber laser was built using a Gires-Tournois compensator and short length (1-cm long) of highly doped Yb fiber. Using a novel semiconductor saturable abserver mirror based on GaInNAs structure, self-started 1.5-ps pulse mode-locked operation was obtained at 1023 nm with a repetition rate of 95 MHz. A mode-locked Yb-doped fiber laser was also developed without using any dispersion compensation technique. Overall group-velocity dispersion was minimized by using highly doped Yb fiber in a compact amplifying loop cavity. Self-started mode-locked operation was obtained in 980-1030-nm wavelength range with a fundamental repetition rate of 140 MHz. Without using dispersion compensation, the lasers produced pulses in a range from 15 to 26 ps.
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TL;DR: In this paper, a 1-mm/sup 2/2/2 2/3/2-axis, single-crystalline-silicon (SCS)-based aluminum-coated scanning micromirror with large rotation angle (up to 40/spl deg/), which can be used in an endoscopic optical coherence tomography imaging system is presented.
Abstract: This paper reports a 1-mm/sup 2/, two-axis, single-crystalline-silicon (SCS)-based aluminum-coated scanning micromirror with large rotation angle (up to 40/spl deg/), which can be used in an endoscopic optical coherence tomography imaging system. The micromirror is fabricated using a deep reactive ion etch post-CMOS micromachining process. The static response, frequency response, resonance frequency shift, and thermal imaging of the device are presented. A 4/spl times/4 pixel display using this two-dimensional micromirror device has been demonstrated.
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TL;DR: In this article, the authors report on the theory and experiments of scanning micromirrors with angular vertical comb-drive (AVC) actuators and show that the fringe fields play an important role in the estimation of maximum continuous rotation angles, particularly for combs with thin fingers.
Abstract: We report on the theory and experiments of scanning micromirrors with angular vertical comb-drive (AVC) actuators. Parametric analyses of rotational vertical comb-drive actuators using a hybrid model that combines two-dimensional finite-element solutions with analytic formulations are described. The model is applied to both AVC and staggered vertical comb-drive (SVC) actuators. Detailed design tradeoffs and conditions for pull-in-free operations are discussed. Our simulation results show that the fringe fields play an important role in the estimation of maximum continuous rotation angles, particularly for combs with thin fingers, and that the maximum scan angle of the AVC is up to 60% larger than that of the SVC. Experimentally, a large dc continuous scan angle of 28.8/spl deg/ (optical) has been achieved with a moderate voltage (65 V) for a 1-mm-diameter scanning micromirror with AVC actuators. Excellent agreement between the experimental data and the theoretical simulations has been obtained.
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TL;DR: In this paper, the effects of simulated Raman scattering (SRS) in ultra-high-Q (UHQ) surface-tension-induced spherical and chip-based toroid microcavities is considered both theoretically and experimentally.
Abstract: Stimulated Raman scattering (SRS) in ultrahigh-Q (UHQ) surface-tension-induced spherical and chip-based toroid microcavities is considered both theoretically and experimentally. These microcavities are fabricated from silica, exhibit small mode volume (typically 1000 /spl mu/m/sup 3/) and possess whispering-gallery type modes with long photon storage times (in the range of 100 ns), significantly reducing the threshold for stimulated nonlinear optical phenomena. Oscillation threshold levels of less than 100 /spl mu/W of launched fiber pump power, in microcavities with quality factors of 100 million are observed. Using a steady-state analysis of the coupled-mode equations for the pump and Raman whispering-gallery modes, the threshold, efficiencies and cascading properties of SRS in UHQ devices are derived. The results are experimentally confirmed in the telecommunication band (1550 nm) using tapered optical fibers as highly efficient waveguide coupling elements for both pumping and signal extraction. The device performance dependence on coupling, quality factor and modal volume are measured and found to be in good agreement with theory. This includes analysis of the threshold and efficiency for cascaded Raman scattering. The side-by-side study of nonlinear oscillation in both spherical microcavities and toroid microcavities on-a-chip also allows for comparison of their properties. In addition to the benefits of a wafer-scale geometry, including integration with optical, electrical, or mechanical functionality, microtoroids on-a-chip exhibit single mode Raman oscillation over a wide range of pump powers.
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TL;DR: Frozen-in viscoelasticity was only recently found to be an important draw-induced inelastic strain that can significantly perturb the refractive index profile and hence the waveguiding properties of optical fibers as mentioned in this paper.
Abstract: Frozen-in stresses and strains can significantly impact both the optical and mechanical performance of optical fibers, enabling unique functionalities or leading to serious impairments. Frozen-in strains can be grouped into two general categories: those directly inducing strong birefringence, which are associated with residual elastic stresses; and those inducing a substantially isotropic index perturbation, which can be described as inelastic frozen-in strains. Both types of frozen-in strains can be simultaneously present in the same optical fiber. Frozen-in viscoelasticity was only recently found to be an important draw-induced inelastic strain that can significantly perturb the refractive index profile and hence the waveguiding properties of optical fibers. The optical and mechanical effects of both types of frozen-in stresses and strains are reviewed. Both practical applications as well as impairments are discussed.
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TL;DR: The development of organic materials to conduct electricity and emit light should provide the basis for the economic manufacture of active matrix displays built upon organic light emitting diode technology, beginning in 2003 as mentioned in this paper.
Abstract: Recent advances in the development of organic materials to conduct electricity and emit light should provide the basis for the economic manufacture of active matrix displays built upon organic light emitting diode technology, beginning in 2003. The steps leading from laboratory science and prototype demonstrations to high-volume low-cost fabrication in the years 2003 to 2010 are outlined, and the major processing challenges are identified.
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TL;DR: In this article, a broadly tunable narrow-linewidth microwave subcarrier on an optical wave by exploiting the nonlinear dynamics of a semiconductor laser through a proper combination of optical injection and optoelectronic feedback is experimentally demonstrated.
Abstract: Generation of a broadly tunable narrow-linewidth microwave subcarrier on an optical wave by exploiting the nonlinear dynamics of a semiconductor laser through a proper combination of optical injection and optoelectronic feedback is experimentally demonstrated. The microwave frequency is generated by the period-one oscillation of an optically injected semiconductor laser. It is tuned in the range from 10 to 23 GHz by varying the optical injection strength, and its linewidth can be narrowed by optoelectronic feedback alone. The linewidth is reduced from the range of 40-120 MHz without stabilization by three orders of magnitude to the range of 10-160 kHz with stabilization through optoelectronic feedback alone. The effect of a small microwave modulation is also investigated. It reduces the linewidth to below the 1-kHz resolution limit of our instrument.
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TL;DR: In this article, the relative dependence of the frequency and the magnitude between the principal oscillation and the first sideband in period-one oscillations as a function of the detuning frequency and injection strength of the injection signal was investigated.
Abstract: The characteristics of period-one oscillations in semiconductor lasers subject to optical injection are experimentally and theoretically investigated. Attention is mainly paid to the relative dependence of the frequency and the magnitude between the principal oscillation and the first sideband in period-one oscillations as a function of the detuning frequency and the injection strength of the injection signal. The frequency separation between the two signals is found to decrease as the injection strength and the detuning frequency reduce. The magnitude of the principal oscillation decreases with the decreasing injection strength and the increasing detuning frequency, while that of the first sideband grows at the same time. At some operating conditions, the magnitude of the first sideband dominates that of the original principal oscillation, resulting in a frequency shift of the principal oscillation from the injection frequency to the first sideband. Similar studies are also done for the stable injection locking to explore the transition of the frequency and the magnitude characteristics across the Hopf bifurcation line. The effects of different bias current levels of the injected laser on the frequency and the magnitude characteristics of period-one oscillations are also investigated.
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TL;DR: In this article, the authors discuss unique light localizations in photonic crystal line defect waveguides based on two different concepts: an additional defect doping that breaks the symmetry of the line defect and chirping of the waveguide structure.
Abstract: In this paper, we discuss unique light localizations in photonic crystal line defect waveguides based on two different concepts. The first concept is an additional defect doping that breaks the symmetry of the line defect. Even though such a defect is open to the line defect, the optical field is well confined around the defect at cutoff frequencies of the line defect. This expands the design flexibility of microcavities and allows effective mode controls such as the single-mode operation. The lasing action of such cavities in a GaInAsP photonic crystal slab was experimentally observed by photopumping at room temperature. The second concept is a chirping of the waveguide structure. The photonic band of a waveguide mode has a band edge, at which the group velocity becomes zero. The band-edge condition shifts in a chirped line defect waveguide, so guided light reaches a zero group velocity point and is localized. A macroscopic behavior of this phenomenon was experimentally observed in a waveguide fabricated into a silicon-on-insulator substrate. In addition, a microscopic behavior was theoretically investigated, which suggested its applicability to a group delay device.
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TL;DR: In this article, an imaging spectrograph is used to measure the angular dispersion of a laser beam by an accuracy of 0.2 /spl mu/rad/nm using this technique.
Abstract: A misaligned stretcher or compressor in a chirped pulse amplification laser introduces residual angular dispersion into the beam, resulting in temporal distortion of the pulse. We demonstrate that an imaging spectrograph is capable for measuring the angular dispersion of a laser beam by an accuracy of 0.2 /spl mu/rad/nm. Using this technique, the analytical expressions of residual angular dispersion of misaligned prism and grating compressors are experimentally proved. Temporal degradations of short pulses due to angular dispersion are studied by measuring the temporal stretch of 16-fs pulses, while the issues of contrast deterioration are also discussed. It is proved that the simultaneous measurement of angular dispersion and pulse duration offers the most precise alignment procedure of prismatic and grating compressors.
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TL;DR: In this paper, the authors investigated nonlinear carrier dynamics in a multiquantum-well semiconductor optical amplifier (SOA) in the context of ultrafast all-optical logic and presented a rate-equation model that accounts for two-photon absorption, free-carrier absorption, self-and cross phase modulation, carrier heating, spectral, spatial hole burning, and self- and cross polarization modulation.
Abstract: We investigate nonlinear carrier dynamics in a multiquantum-well semiconductor optical amplifier (SOA) in the context of ultrafast all-optical logic. A rate-equation model is presented that accounts for two-photon absorption, free-carrier absorption, self- and cross phase modulation, carrier heating, spectral, spatial hole burning, and self- and cross polarization modulation. The nonlinear refractive index dynamics is investigated theoretically and experimentally. We find nonlinear phase changes larger than /spl pi/ radians, which recovers on a timescale in the order of 1 ps. We also investigate a nonlinear AND gate that consists of an SOA that is placed in an asymmetric Mach-Zehnder interferometer. We show that the gate can be operated using 800-fJ optical pulses with duration of 200 fs while having a contrast ratio larger than 11 dB.
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TL;DR: In this article, a waveguide-integrated photodetector is presented, exhibiting a bandwidth of 100 GHz with a responsivity of 0.66 A/W and the PDL below 0.09 dB.
Abstract: A waveguide-integrated photodetector is presented, exhibiting a bandwidth of 100 GHz The responsivity amounts to 066 A/W and the PDL is below 09 dB The detector chip is designed to obtain a Bessel filter-shaped transfer characteristic when packaged in a module comprising a 1-mm connector
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TL;DR: In this article, a direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric waveguide substrates to form flexile optical integrated devices is demonstrated.
Abstract: Direct fabrication of organic light-emitting diodes (OLEDs) and organic photodetectors (OPDs) on polymeric substrates, i.e., polymeric waveguide substrates to form flexile optical integrated devices is demonstrated. The OELD and OPD were fabricated by organic molecular beam deposition (OMBD) technique on a polymeric or a glass substrate, for comparison. The device fabricated on a polymeric substrate shows similar device characteristics to that on a glass substrate. Optical signals of faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing diamine derivative, or rubrene or porphine doped in 8-hydoxyquinolinum aluminum derivatives, as an emissive layer. Electrical signals are successively converted to optical signals for optical transmission of moving picture signals with OLED fabricated on a polymeric waveguide. OPDs utilizing phthalocyanines derivatives with superlattice structure provide increased pulse response with input optical signals, and the OPD with the cutoff frequency of more than 5 MHz has been realized.
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TL;DR: In this paper, the effects of monochromatic illumination on the electrical performance of organic polymer thin-film transistors (OP-TFTs) and the use of these devices as photosensors were investigated.
Abstract: We present our study of the effects of monochromatic illumination on the electrical performance of organic polymer thin-film transistors (OP-TFTs) and the use of these devices as photosensors. In the case of monochromatic illumination that is strongly absorbed by the polymer, the drain current of a device biased in the OFF-state is significantly increased and the threshold voltage is reduced. Light that is not strongly absorbed by the polymer has little effect on the electrical performance of the OP-TFTs. We explain these effects in terms of the photogeneration of excitons in the polymer channel region of the device. The density of excitons generated in the polymer depends on the energy of the incident photons, as well as on the irradiance level of the incident illumination. The photogenerated excitons subsequently dissociate into electrons and holes. The electrons can be trapped by positively charged states, thereby reducing the threshold voltage, while the photogenerated holes contribute to the excess photocurrent measured at the drain. To demonstrate the possible use of OP-TFTs as photosensors, we also present the responsivity, photosensitivity (signal-to-noise ratio), external quantum efficiency, noise-equivalent power, and specific detectivity of these devices. The dependence of these parameters on the incident photon energy and irradiance level is described.
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TL;DR: In this article, the authors studied the nonlinearities in silicon-on-insulator (SOI) optical waveguides, which include two-photon absorption, free-carrier absorption, and spontaneous and stimulated Raman scattering (SRS).
Abstract: We study the nonlinearities in silicon-on-insulator (SOI) optical waveguides, which include two-photon absorption (TPA), free-carrier absorption, and spontaneous and stimulated Raman scattering (SRS). We show experimentally that free carriers generated by TPA in the SOI waveguides produce large optical loss at room temperature. The experimental results confirmed the presence of relative optical signal amplification from SRS, but it was found that net gain was hardly achieved because the stimulated Raman gain was less than the induced loss from TPA-generated free carriers at room temperature with continuous-wave pumping source in a SOI rib waveguide. We also experimentally investigated the temperature dependence of Raman scattering in the SOI waveguide and observed the Raman gain to be greater than TPA-generated free-carrier absorption loss at 77 K.
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TL;DR: A novel family of structured low-density parity-check codes with block-circulant parity- check matrices that consist of permutation blocks is proposed, which tend to outperform many other known structured LDPCs of comparable rate and length.
Abstract: A novel family of structured low-density parity-check (LDPC) codes with block-circulant parity-check matrices that consist of permutation blocks is proposed. The codes from this family are based on new combinatorial objects termed cycle-invariant difference sets, and they have low storage requirements, fast encoding algorithms, and girth of at least six. Most importantly, they tend to outperform many other known structured LDPCs of comparable rate and length.
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TL;DR: In this article, the authors describe the design and performance of two widebandwidth photodiode structures, which achieve saturation currents (bandwidths) of >430mA (300 MHz) and 199 mA (1 GHz) for 100-spl mu/m/sup 2/ area devices.
Abstract: This paper describes the design and performance of two wide-bandwidth photodiode structures. The partially depleted absorber photodiode utilizes an absorbing layer consisting of both depleted and undepleted In/sub 0.53/Ga/sub 0.47/As layers. These photodiodes have achieved saturation currents (bandwidths) of >430 mA (300 MHz) and 199 mA (1 GHz) for 100-/spl mu/m-diameter devices and 24 mA (48 GHz) for 100-/spl mu/m/sup 2/ area devices. Charge compensation has also been utilized in a similar, but modified In/sub 0.53/Ga/sub 0.47/As-InP unitraveling-carrier photodiode design to predistort the electric field in the depletion region in order to mitigate space charge effects. For 20-/spl mu/m-diameter photodiodes the large-signal 1-dB compression current and bandwidth were /spl sim/90 mA and 25 GHz, respectively.