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Dynamics of pulse amplification in tapered-waveguide quantum-dot semiconductor optical amplifiers
摘要： Tapered-waveguide quantum dot semiconductor optical amplifiers (TW-QDSOAs) have been modeled using numerical calculation of the rate and propagation equations in this article and the amplification characteristics and dynamics of pulse propagation in non-tapered QDSOA, linear, and exponential TW-QDSOA structures have been studied and compared in detail. It has been found that TW-QDSOAs apply less distortion to the amplified pulse and have greater optical gain than non-tapered QDSOA. In TW-QDSOAs, the amplified pulse becomes much less broadening and this amount is negligible, therefore the pulse bit rate can be increased. While the amplified pulse in a non-tapered QDSOA is much broadening than the TW-QDSOAs. The carrier density distribution and dependency of the amplifier gain to the output energy for both non-tapered and tapered structures have been studied. The carrier density and gain in non-tapered QDSOA decreases more than TW-QDSOAs, indicating that the tapered amplifiers are saturated at higher input energies. Our obtained results agree well with those previously obtained for conventional tapered amplifiers.
关键词： Quantum dot semiconductor optical amplifier,tapered QDSOA,gain saturation
更新于2025-09-23 15:19:57
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Ultrafast all-optical digital comparator using quantum-dot semiconductor optical amplifiers
摘要： In this investigation, three types of 160 Gb/s all-optical digital comparators using quantum-dot semiconductor optical amplifiers (QD-SOAs) are constructed. These configurations have different combination patterns of logic gates and QD-SOAs. Based on numerical simulations, we investigate and evaluate the performance of the devices in terms of the number of logic gates and QD-SOAs, and the value of the extinction ratio (ER). In addition, we demonstrate the effect of amplified spontaneous emission (ASE) noise on the ER and Q-factor. The results show that two of the three configurations are superior to the other configuration in terms of circuit complexity, value of ER, and sensitivity to injection current. Moreover, these two configurations achieve ER values over 10 dB and Q-factor over 9, even when intense ASE noise is considered. The proposed configurations have several advantages such as high quality, easy configuration, insensitivity to injection current, and strong noise robustness, which are favorable for practical applications. This investigation also facilitates the specification of the pros and cons of each configuration, and the determination of the appropriate comparator according to the desired requirements.
关键词： Logic gates,All-optical digital comparator,Amplified spontaneous emission (ASE),Quantum-dot semiconductor optical amplifier (SOA)
更新于2025-09-19 17:15:36
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A scheme for the development of a trinary logic unit (TLU) using polarization-based optical switches
摘要： Frequency-encoded optical processors based on multivalued logic (MVL) will play a significant role in future all-optical networks. In this work, basic optical logic gates are designed using a modified trinary system, exploiting the switching action of semiconductor optical amplifiers (SOAs) based on the principle of the nonlinear rotation of the polarization of a probe beam in the presence of a pump beam. A control unit capable of performing OR, AND, and XOR logic operations depending on the frequency of the control signal is then developed. Finally, a trinary logic unit is designed to execute 27 different logic operations. The feasibility of these proposals is confirmed by simulation results. In this approach, each trinary bit, i.e., 'trit,' is represented by a unique frequency, which in turn helps to address the noise margin problem that arises in intensity-encoded MVL systems. This scheme can therefore play an important role in errorless optical computing and processing.
关键词： Modified trinary number,Multivalued logic,Semiconductor optical amplifier,Trinary logic unit,Polarization switch
更新于2025-09-19 17:15:36
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Application of Judd-Ofelt Theory Upon Chlofluorophosphate Glass Doped with Erbium
摘要： A series of erbium doped glasses chlorofluorophosphates were prepared and characterized. The absorption spectra were analyzed to determine the Judd-Ofelt parameters. The optical performance of these doped glasses suggesting the relevance of these glasses for optical fiber/ wave guide lasers and optical amplifiers.
关键词： and optical amplifier,rare earth,Judd-Ofelt parameters,glass doped,laser,erbium
更新于2025-09-19 17:15:36
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Optical Fiber Vibration Sensor Using Least Mean Square Error Algorithm
摘要： In order to enhance the signal-to-noise ratio (SNR) of a distributed optical fiber vibration sensor based on coherent optical time domain reflectometry (COTDR), a high extinction ratio cascade structure of an acousto-optic modulator and semiconductor optical amplifier is applied. The prior time-frequency analysis and least mean square error algorithm are adopted in the COTDR system for amplitude demodulation and phase demodulation, in order to improve the SNR by noise elimination. The experimental results show that the adaptive filter based on the least mean square error algorithm could realize the extraction of a three-order sinusoidal harmonic signal from strong background noise along the optical fiber and the SNR improvement from 10.4 dB to 42.2 dB. The proposed demodulation algorithm is suitable for the detection of vibration signals with characteristic frequencies in the application of acoustic fault diagnosis for electromechanical devices.
关键词： least mean square error algorithm,optical fiber vibration sensor,semiconductor optical amplifier,coherent optical time domain reflectometry
更新于2025-09-19 17:13:59
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Functionalized polymer waveguide optical switching devices integrated with visible optical amplifiers based on an organic gain material
摘要： In this work, polymer waveguide based optical switching devices integrated with visible optical amplifying waveguides based on an organic gain material are designed and fabricated. The gain compound is a red emissive oligomer, with good dispersibility in organic polymer matrices. Optical characteristics and thermal stabilities of the active polymer waveguide core and cladding materials are analyzed. Optical gain of the amplifier operating at 650 nm red signal wavelength with 0.1 mW input power is found to be over 3.5 dB under only 1.6 mW pumping power with 532 nm green excitation light. The on-off response time of the integrated thermo-optic switch applied is measured to be 600 μs, with switching extinction ratio of 20 dB and electric switching power of 18.5 mW. The integrated switching device capable of optical gain will be suitable for applications to optical communications at the visible wavelength range involving plastic optical fiber systems.
关键词： Optical amplifier,Optical switch,Polymer waveguide,Fluorene-based oligomer
更新于2025-09-19 17:13:59
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Polarization-insensitive fiber-to-fiber gain of semiconductor optical amplifier using closely stacked InAs/GaAs quantum dots
摘要： The gain characteristics of a semiconductor optical amplifier (SOA) that contains forty layers of closely stacked InAs/GaAs quantum dots (QDs) were studied by employing a fiber-to-fiber measurement system. The fiber-to-fiber gain values obtained for transverse-electric (TE)- and transverse-magnetic (TM)-polarized optical input signals exhibited their maxima at a wavelength of 1100 nm, which corresponds to the excited state of the closely stacked QDs. In the wavelength range from 1060 to 1170 nm, the gain obtained for TE-polarized input signal was slightly higher than that for TM-polarized input signal and the absolute gain difference was less than 1 dB for an injection current of 80 mA. The small but non-zero difference of the gain reflects the polarization anisotropy of the optical gain provided by the closely stacked QDs. Our results suggest that closely stacked QDs are suitable for realizing polarization-insensitive SOA device with operation bandwidths of more than 100 nm.
关键词： fiber-to-fiber gain,quantum dots,polarization-insensitive,semiconductor optical amplifier
更新于2025-09-19 17:13:59
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[IEEE 2018 Photonics in Switching and Computing (PSC) - Limassol, Cyprus (2018.9.19-2018.9.21)] 2018 Photonics in Switching and Computing (PSC) - Polarization Diversity Circuit Using Photonic Crystal Waveplates for 1.2-μm Quantum Dot Semiconductor Optical Amplifiers
摘要： Silica-based polarization diversity circuit for QD-SOA operating in T-band was fabricated. By connecting polarization diversity the polarization dependent gain of less than 0.8 dB and the optical gain of 3.2 dB were achieved.
关键词： Semiconductor optical amplifier,Polarization diversity,Quantum dot
更新于2025-09-16 10:30:52
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Hybrid Integrated Semiconductor Lasers with Silicon Nitride Feedback Circuits
摘要： Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth, as well as compatibility for embedding into integrated photonic circuits, are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si3N4 in SiO2) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around a 1.55 μm wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.
关键词： low-loss Si3N4 waveguides,dual-wavelength laser,laser frequency comb,InP semiconductor optical amplifier,integrated photonic circuits,semiconductor laser,hybrid integration,narrow intrinsic linewidth
更新于2025-09-16 10:30:52
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Enhancement of Signals Characteristics with Least Effect of Optical Communication Losses for Dense Optical Communication Systems
摘要： In this paper, the major aim is to enhance the bandwidth and therefore increase the capacity of the optical fibre communication system by reducing the dispersion in the fibre. Dispersion compensation is necessary to reduce losses and cost of the system. In this paper, we are basically focusing on reducing or decreasing chromatic dispersion. Chromatic dispersion is a type of dispersion in which pulse broadening occurs due to delay in different spectral components. We here make use of dispersion compensated fibre (DCF) for reducing the dispersion in the WDM system. Here, we basically use three dispersion compensated techniques (pre-compensation, post-compensation and mix compensation). The comparison in the three models of dispersion compensated technique is made in terms of transmission power vs. Q factor and also transmission power vs. Bit Error Rate.
关键词： DCF,MMF,WDM,SMF,quality factor,BER,optical amplifier
更新于2025-09-12 10:27:22