Amplification and phase regeneration can be realized using a phase-sensitive amplifier （PSA）. The phase regeneration of differential phase-shift keying （DPSK） signals based on PSA is analyzed theoretically. We rea...Amplification and phase regeneration can be realized using a phase-sensitive amplifier （PSA）. The phase regeneration of differential phase-shift keying （DPSK） signals based on PSA is analyzed theoretically. We realize the phase regeneration of differential quadrature phase-shift keying （DQPSK） signals based on a structure using two balanced PSAs. Simulations show that nearly ideal phase regeneration can be achieved for the DPSK/DQPSK signals.展开更多
Electroabsorption modulators（EAMs） with negative chirp and very low insertion loss are numerically designed with asymmetric intra-step-barrier coupled double strained quantum wells（AICD-SQWs） based on InGaAlAs mat...Electroabsorption modulators（EAMs） with negative chirp and very low insertion loss are numerically designed with asymmetric intra-step-barrier coupled double strained quantum wells（AICD-SQWs） based on InGaAlAs material.For this purpose,the electroabsorption coefficient is calculated over a range of wells layer strain from compressive（CS） to tensile（TS）.The chirp parameter and insertion loss for TE input light polarization are evaluated from the calculated electroabsorption spectra,and their Kramers-Kronig transformed refractive index changes.The results of the numerical simulation show that the best range of left and right wells strain for EAMs based on AICD-SQWs with negative chirp and very low insertion loss are from 0.032%to 0.05%（TS） and-0.52% to-0.50%（CS）,respectively.展开更多
A stable 10 GHz ultrashort pulse generator consisted of an electroabsorption modulator （EAM） and a welldesigned fibre-based pulse compressor is proposed and demonstrated experimentally. The obtained short pulse has ...A stable 10 GHz ultrashort pulse generator consisted of an electroabsorption modulator （EAM） and a welldesigned fibre-based pulse compressor is proposed and demonstrated experimentally. The obtained short pulse has high extinction ratio, no pedestal, low timing jitter, and FWHM of only 2.4ps. The excellent performance of multiplexing from 10 GHz to 160 GHz confirms the potential of the generator for applications in 160 Gbit/s optical time-division-multiplexing （OTDM） systems.展开更多
The sensitivity of diffuse optical tomography （DOT） imaging exponentially decreases with the increase of photon penetration depth, which leads to a poor depth resolution for DOT. In this letter, an exponential adjus...The sensitivity of diffuse optical tomography （DOT） imaging exponentially decreases with the increase of photon penetration depth, which leads to a poor depth resolution for DOT. In this letter, an exponential adjustment method （EAM） based on maximum singular value of layered sensitivity is proposed. Optimal depth resolution can be achieved by compensating the reduced sensitivity in the deep medium. Simulations are performed using a semi-infinite model and the simulation results show that the EAM method can substantially improve the depth resolution of deeply embedded objects in the medium. Consequently, the image quality and the reconstruction accuracy for these objects have been largely improved.展开更多
A number of active elements have been demonstrated using the hybrid silicon evanescent platform, including lasers, amplifiers, and detectors. In this letter, two types of hybrid silicon modulators, flflfilling the bui...A number of active elements have been demonstrated using the hybrid silicon evanescent platform, including lasers, amplifiers, and detectors. In this letter, two types of hybrid silicon modulators, flflfilling the building blocks in optical communication on this platform, are presented. A hybrid silicon electroabsorp- tion modulator, suitable for high speed interconnects, with 10-dB extinction ratio at -5 V and 16-GHz modulation bandwidth is demonstrated. In addition, a hybrid silicon Mach-Zehnder modulator utilizing carrier depletion in multiple quantum wells is proved with 2 V.mm voltage-length product, 150-nm optical bandwidth, and a large signal modulation up to 10 Gb/s.展开更多
We study the effects of electron-phonon interaction on the electron ground state in a symmetric triangular quantum well, and calculate the ground state energy of an electron in the GaAs/Al0.96Ga0.04As triangular quant...We study the effects of electron-phonon interaction on the electron ground state in a symmetric triangular quantum well, and calculate the ground state energy of an electron in the GaAs/Al0.96Ga0.04As triangular quantum well including the effects of the interaction between electrons and confined LO phonons by using a modified Lee-Low-Pines variational method. The electron wavefunction in the triangular well is chosen as the Airy function. The numerical results are given and discussed.展开更多
A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators （EAMs） at very low bias voltage of -0.8 V in conjunction with atunable ...A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators （EAMs） at very low bias voltage of -0.8 V in conjunction with atunable distributed feedback （DFB） semiconductor laser. An approximate transform-limited optical pulse, with the pulse width less than 7 ps, the spectral width of 0.3 nm, and the side-mode suppression ratio （SMSR） above 20 dB, is obtained by tuning the optical delay line.展开更多
A 100-μm-long electroabsorption modulator monolithically integrated with passive waveguides at the input and output ports is fabricated through ion implantation induced quantum well intermixing, using only a twostep ...A 100-μm-long electroabsorption modulator monolithically integrated with passive waveguides at the input and output ports is fabricated through ion implantation induced quantum well intermixing, using only a twostep low-pressure metal-organic vapor phase epitaxial process. An InGaAsP/InGaAsP intra-step quantum well is introduced to the active region to improve the modulation properties. In the experiment high modulation speed and high extinction ratio are obtained simultaneously, the electrical-to-optical frequency response （E/O response） without any load termination reaches to 22 GHz, and extinction ration is as high as 16 dB.展开更多
We have proposed a new model for the calculation of excitonic electroabsorption based on modified previously reported models for bulk structure. The excitonic absorption spectra in high purity GaAs have been theoretic...We have proposed a new model for the calculation of excitonic electroabsorption based on modified previously reported models for bulk structure. The excitonic absorption spectra in high purity GaAs have been theoretically studied in the presence of electric field at room temperature (RT). The Stark shift, linewidth broadening of exciton and extinction ratio have been calculated as a function of electric field. For the validity of our model we have compared with experimental result.展开更多
Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well in...Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.展开更多
This paper reports a detailed theoretical investigation of strain effects on the performance of electroabsorption optical modulators based on the asym- metric intra-step-barrier coupled double strained quantum wells ...This paper reports a detailed theoretical investigation of strain effects on the performance of electroabsorption optical modulators based on the asym- metric intra-step-barrier coupled double strained quantum wells （AICD-SQWs） active layer. For this purpose, the electroabsorption coefficient was calculated over a range of AICD-SQWs strain from compressive to tensile strain. Then, the extinction ratio （ER） and insertion loss parameters were evaluated from calculated electroabsorp- tion coefficient for transverse electric （TE） input light polarization. The results of the simulation suggest that the tensile strain from 0.05% to 0.2% strain in the wide quantum well has a significant impact on the ER and insertion loss as compared with compressive strain, whereas the compressive strain of the narrow quantum well from -0.5% to -0.7% strain has a more pronounced impact on the improvement of the ER and insertion loss as compared with tensile strain.展开更多
We focus on the optimization of SiGe material deposition, the minimization of the parasitic capacitance of the probe pads for high speed, low voltage and high contrast ratio operation. The device fabrication is based ...We focus on the optimization of SiGe material deposition, the minimization of the parasitic capacitance of the probe pads for high speed, low voltage and high contrast ratio operation. The device fabrication is based on processes for standard Si electronics and is suitable for mass-production. We present observations of quantum confinement and quantum-confined Stark effect （QCSE） electroabsorption in Ge quantum wells （QWs） with SiGe barriers grown on Si substrates. Though Ge is an indirect gap semiconductor, the resulting effects are at least as clear and strong as seen in typical III-V QW structures at similar wavelengths. We also demonstrated a modulator, with eye diagrams of up to 3.5 GHz, a small driving voltage of 2.5 V and a modulation bandwidth at about 10 GHz. Finally, carrier dynamics under ultra-fast laser excitation and high- speed photocurrent response are investigated.展开更多
We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photo- diodes （EC-UTC-PDs） and intra-step quantum well electroabsorption modulators （IQW-EAMs） on n-InP s...We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photo- diodes （EC-UTC-PDs） and intra-step quantum well electroabsorption modulators （IQW-EAMs） on n-InP substrates. These devices exhibit simultaneously 2.1 GHz and -16.2 dB RF-gain at 21 GHz with a 450 t2 thin-film resistor and a bypass capacitor integrated on a chip.展开更多
基金supported by the Beijing Education Committee Common Build Foundation (No.XK100130637)the National "863" Program of China(No.2009AA01Z224)
文摘Amplification and phase regeneration can be realized using a phase-sensitive amplifier （PSA）. The phase regeneration of differential phase-shift keying （DPSK） signals based on PSA is analyzed theoretically. We realize the phase regeneration of differential quadrature phase-shift keying （DQPSK） signals based on a structure using two balanced PSAs. Simulations show that nearly ideal phase regeneration can be achieved for the DPSK/DQPSK signals.
文摘Electroabsorption modulators（EAMs） with negative chirp and very low insertion loss are numerically designed with asymmetric intra-step-barrier coupled double strained quantum wells（AICD-SQWs） based on InGaAlAs material.For this purpose,the electroabsorption coefficient is calculated over a range of wells layer strain from compressive（CS） to tensile（TS）.The chirp parameter and insertion loss for TE input light polarization are evaluated from the calculated electroabsorption spectra,and their Kramers-Kronig transformed refractive index changes.The results of the numerical simulation show that the best range of left and right wells strain for EAMs based on AICD-SQWs with negative chirp and very low insertion loss are from 0.032%to 0.05%（TS） and-0.52% to-0.50%（CS）,respectively.
基金Support by the National Natural Science Foundation of China under Grant No 60577033, and the Specialized Research Fund for the Doctoral Program of Higher Education （SRFDP） under Grant No 20050003010.
文摘A stable 10 GHz ultrashort pulse generator consisted of an electroabsorption modulator （EAM） and a welldesigned fibre-based pulse compressor is proposed and demonstrated experimentally. The obtained short pulse has high extinction ratio, no pedestal, low timing jitter, and FWHM of only 2.4ps. The excellent performance of multiplexing from 10 GHz to 160 GHz confirms the potential of the generator for applications in 160 Gbit/s optical time-division-multiplexing （OTDM） systems.
基金supported by the National Natural Science Foundation of China(No.60675011 and 30425004)the National"973"Program of China(No.2003CB716100)the National"863"Program of China(No.2006AA01Z132)
文摘The sensitivity of diffuse optical tomography （DOT） imaging exponentially decreases with the increase of photon penetration depth, which leads to a poor depth resolution for DOT. In this letter, an exponential adjustment method （EAM） based on maximum singular value of layered sensitivity is proposed. Optimal depth resolution can be achieved by compensating the reduced sensitivity in the deep medium. Simulations are performed using a semi-infinite model and the simulation results show that the EAM method can substantially improve the depth resolution of deeply embedded objects in the medium. Consequently, the image quality and the reconstruction accuracy for these objects have been largely improved.
基金the financial support from DARPA/MTO and ARL, USA.
文摘A number of active elements have been demonstrated using the hybrid silicon evanescent platform, including lasers, amplifiers, and detectors. In this letter, two types of hybrid silicon modulators, flflfilling the building blocks in optical communication on this platform, are presented. A hybrid silicon electroabsorp- tion modulator, suitable for high speed interconnects, with 10-dB extinction ratio at -5 V and 16-GHz modulation bandwidth is demonstrated. In addition, a hybrid silicon Mach-Zehnder modulator utilizing carrier depletion in multiple quantum wells is proved with 2 V.mm voltage-length product, 150-nm optical bandwidth, and a large signal modulation up to 10 Gb/s.
基金Supported by the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20040126003, and the Natural Science Foundation of Inner Mongol of China under Grant No 200408020101.
文摘We study the effects of electron-phonon interaction on the electron ground state in a symmetric triangular quantum well, and calculate the ground state energy of an electron in the GaAs/Al0.96Ga0.04As triangular quantum well including the effects of the interaction between electrons and confined LO phonons by using a modified Lee-Low-Pines variational method. The electron wavefunction in the triangular well is chosen as the Airy function. The numerical results are given and discussed.
基金This work was supported by Hundreds of Talents Plan of CAS.
文摘A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators （EAMs） at very low bias voltage of -0.8 V in conjunction with atunable distributed feedback （DFB） semiconductor laser. An approximate transform-limited optical pulse, with the pulse width less than 7 ps, the spectral width of 0.3 nm, and the side-mode suppression ratio （SMSR） above 20 dB, is obtained by tuning the optical delay line.
基金Project supported by the National High Technology Research and Development Program of China (No.2006AA01Z256)the State Key Development Program for Basic Research of China (Nos.2006CB604901,2006CB604902)the National Natural Science Foundationof China (No.90401025)
文摘A 100-μm-long electroabsorption modulator monolithically integrated with passive waveguides at the input and output ports is fabricated through ion implantation induced quantum well intermixing, using only a twostep low-pressure metal-organic vapor phase epitaxial process. An InGaAsP/InGaAsP intra-step quantum well is introduced to the active region to improve the modulation properties. In the experiment high modulation speed and high extinction ratio are obtained simultaneously, the electrical-to-optical frequency response （E/O response） without any load termination reaches to 22 GHz, and extinction ration is as high as 16 dB.
文摘We have proposed a new model for the calculation of excitonic electroabsorption based on modified previously reported models for bulk structure. The excitonic absorption spectra in high purity GaAs have been theoretically studied in the presence of electric field at room temperature (RT). The Stark shift, linewidth broadening of exciton and extinction ratio have been calculated as a function of electric field. For the validity of our model we have compared with experimental result.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60736036,60706009,60777021 and 60702006)the National Basic Research Program of China (Grant Nos. 2006CB604901 and 2006CB604902)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z419,2007AA03Z417 and 2009AA03Z442)
文摘Electroabsorption modulators combining Franz-Keldysh effect and quantum confined Stark effect have been mono-lithically integrated with tunnel-injection quantum-well distributed feedback lasers using a quantum well intermixing method. Superior characteristics such as extinction ratio and temperature insensitivity have been demonstrated at wide temperature ranges.
文摘This paper reports a detailed theoretical investigation of strain effects on the performance of electroabsorption optical modulators based on the asym- metric intra-step-barrier coupled double strained quantum wells （AICD-SQWs） active layer. For this purpose, the electroabsorption coefficient was calculated over a range of AICD-SQWs strain from compressive to tensile strain. Then, the extinction ratio （ER） and insertion loss parameters were evaluated from calculated electroabsorp- tion coefficient for transverse electric （TE） input light polarization. The results of the simulation suggest that the tensile strain from 0.05% to 0.2% strain in the wide quantum well has a significant impact on the ER and insertion loss as compared with compressive strain, whereas the compressive strain of the narrow quantum well from -0.5% to -0.7% strain has a more pronounced impact on the improvement of the ER and insertion loss as compared with tensile strain.
文摘We focus on the optimization of SiGe material deposition, the minimization of the parasitic capacitance of the probe pads for high speed, low voltage and high contrast ratio operation. The device fabrication is based on processes for standard Si electronics and is suitable for mass-production. We present observations of quantum confinement and quantum-confined Stark effect （QCSE） electroabsorption in Ge quantum wells （QWs） with SiGe barriers grown on Si substrates. Though Ge is an indirect gap semiconductor, the resulting effects are at least as clear and strong as seen in typical III-V QW structures at similar wavelengths. We also demonstrated a modulator, with eye diagrams of up to 3.5 GHz, a small driving voltage of 2.5 V and a modulation bandwidth at about 10 GHz. Finally, carrier dynamics under ultra-fast laser excitation and high- speed photocurrent response are investigated.
基金supported by the National High Technology Research and Development of China (Grant Nos. 2006AA01Z256,2007AA03Z419 and 2007AA03Z417)the State Key Development Program for Basic Research of China (Grant Nos. 2006CB604901and 2006CB604902)the National Natural Science Foundation of China (Grant Nos. 90401025,60736036,60706009 and 60777021)
文摘We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photo- diodes （EC-UTC-PDs） and intra-step quantum well electroabsorption modulators （IQW-EAMs） on n-InP substrates. These devices exhibit simultaneously 2.1 GHz and -16.2 dB RF-gain at 21 GHz with a 450 t2 thin-film resistor and a bypass capacitor integrated on a chip.
