The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contr...The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contradiction between the noncontextuality hidden variable predictions and those of quantum mechanics or by the violation of noncontextual inequality. We propose an experimental scheme of state-independent contextual inequality derived from the Mermin proof of the Kochen–Specker(KS) theorem in eight-dimensional Hilbert space, which could be observed either in an individual system or in a composite system. We also show how to resolve the compatibility problems. Our scheme can be implemented in optical systems with current experiment techniques.展开更多
The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The propertie...The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The properties of the propagation of MBG beam traveling through this misaligned ABCD optical system are discussed. A special case of misaligned circular thin lens is illustrated analytically and numerically. The shape of the MBG beam at the exit of the misaligned optical system is unchanged;however the center of the beam is shifted from the propagation axis in correlated manner with the design parameters of the optical system.展开更多
Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided ...Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided media with light.This system requires multi-carrier modulation such as Orthogonal Frequency Division Multiplexing(OFDM).This paper studies optical OFDM performance based on Intensity Modulation with Direct Detection(IM/DD)system.This system requires a non-negativity constraint.The paper presents a framework for wireless optical OFDM system that comprises(IM/DD)with different forms,Direct Current biased Optical OFDM(DCO-OFDM),Asymmetrically Clipped Optical OFDM(ACO-OFDM),Asymmetrically DC-biased Optical OFDM(ADO-OFDM),and Flip-OFDM.It also considers channel coding as a tool for error control,channel equalization for reducing deterioration due to channel effects,and investigation of the turbulence effects.The evaluation results of the proposed framework reveal enhancement of performance.The performance of the IM/DD-OFDM system is investigated over different channel models such as AWGN,log-normal turbulence channel model,and ceiling bounce channel model.The simulation results show that the BER performance of the IM/DD-OFDM communication system is enhanced while the fading strength is decreased.The results reveal also that Hamming codes,BCH codes,and convolutional codes achieve better BER performance.Also,two algorithms of channel estimation and equalization are considered and compared.These algorithms include the Least Squares(LS)and the Minimum Mean Square Error(MMSE).The simulation results show that the MMSE algorithm gives better BER performance than the LS algorithm.展开更多
A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability ...A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability of the demodulator, a phase-lock device is designed, and it is composed of a symmetric 3 × 3 coupler and a feedback circuit. For further estab- lishing a differential polarization-shift keying (DPolSK) transmission system, we successfully carry out the demodulation experiments on 10-Gb/s DPolSK optical signals for the first time. Due to the all-optical structure with phase-lock, our scheme is available to realize the DPolSK optical communication in practical optical fiber systems.展开更多
A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the syst...A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the system precision in building and maintenance of a satellite optical communication system.In this paper,vibration influence is consciously discussed by acquisition time for intersatellite optical communications.Analytical expression of acquisition possibility is derived,taking the scan parameters and platform vibration into account,and vibration influence on the multi-scan acquisition time is also presented.The theoretical result calculated by the proposed analytical expression is approximate to the result by the Monte Carlo simulation.展开更多
Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerabl...Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.展开更多
In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials are used to describe the wavefront error ...In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials are used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between the distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show that the pointing jitter is strongly related to the wavefront error. Furthermore, when the jitter decreases 10 times from 100 nrad to 10 nrad, the wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with the wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, the wavefront error is not monotonic and has oscillation.Nevertheless, the wavefront error almost remains constant with the arm length increasing from 10-1Mkm to 10~3Mkm.When the arm length decreases for three orders of magnitude from 10-1Mkm to 10-4Mkm, the wavefront error has only an order of magnitude increasing. In the range of 10-4Mkm to 10~3Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm at Z[5,3] Zernike and 10 nrad jitter.展开更多
Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd:YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 ...Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd:YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 nm. The reorientation rate of azo polymer films is enhanced in the presence of Ag nanoparticles, and the rate of the azo polymer film with Ag concentration of 2.2 μg/ml is larger than that of the azo polymer films with Ag concentrations of 1.1 μg/ml and 4.4 μg/ml. The third-order nonlinear optical properties of the Ag/azo composite film are obtained by the Z-scan technique at a wavelength of 532 nm, and the measured nonlinear refractive index is 9.258×10-9 esu. It is shown that the main mechanisms involved in the large nonlinear optical responses come from the local field enhancement of Ag nanoparticles and the nonlinear effect of the azo polymer matrix.展开更多
This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the rece...This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence-induced fading,mis alignment fading and pass-loss is presented.Under given weather and mis alignment conditions,a closed-form analytical expression for the end-to-end outage probability of serial Decode-and-Forward(DF) multi-hop FSO communications is derived.Numerical results show that the serial DF multi-hop transmission is a promising technology to enhance the performance of FSO communications.Moreover,the derived analytical expression can provide close approximations to the simulation results.展开更多
In this paper, a new kind of light beam called off-axial elliptical cosine-Gaussian beam (ECosGBs) is defined by using the tensor method. An analytical propagation expression for the ECosGBs passing through axially ...In this paper, a new kind of light beam called off-axial elliptical cosine-Gaussian beam (ECosGBs) is defined by using the tensor method. An analytical propagation expression for the ECosGBs passing through axially nonsymmetrical optical systems is derived by using vector integration. The intensity distributions of ECosGBs on the input plane, on the output plane with the equivalent Fresnel number being equal to 0.1 and on the focal plane are respectively illustrated for the propagation properties. The results indicate that an ECosGB is eventually transformed into an elliptical cosh- Gaussian beam. In other words, ECosGBs and cosh-Gaussian beams act in a reciprocal manner after propagation.展开更多
In order to decrease dispersion penalty and increase the optical bandwidth efficiency,an optical single-side-band modulation(SSBM) scheme in sub-carrier multiplexing(SCM) is proposed.The principle of the SSBM is analy...In order to decrease dispersion penalty and increase the optical bandwidth efficiency,an optical single-side-band modulation(SSBM) scheme in sub-carrier multiplexing(SCM) is proposed.The principle of the SSBM is analytically presented,and a configuration for generating optical SSB signal is proposed using a balanced Mach-Zehnder electro-optic modulator.展开更多
The properties of ultra-short dense dispersion-managed soliton (DBMS) in optical fiber links are investigated. They show some excellent characters, such as, reducing pulse's breathing extent greatly, facing fewer ...The properties of ultra-short dense dispersion-managed soliton (DBMS) in optical fiber links are investigated. They show some excellent characters, such as, reducing pulse's breathing extent greatly, facing fewer mutual interactions and tolerating larger local dispersion. In general, DBMS is more stable than a conventional dispersion-managed soliton in high-capacity systems. Excessively dense dispersion compensation is more suitable for systems with weak nonlinear effect.展开更多
We experimentally demonstrate a Faraday laser at Rb 1529 nm transition by using a performance-improved Rb electrodeless-discharge-lamp-based excited-state Faraday anomalous dispersion optical filter as the frequency- ...We experimentally demonstrate a Faraday laser at Rb 1529 nm transition by using a performance-improved Rb electrodeless-discharge-lamp-based excited-state Faraday anomalous dispersion optical filter as the frequency- selective element. Neither the electrical locking scheme nor the additional frequency-stabilized pump laser are used. The frequency of the external-cavity diode laser is stabilized to the Rb 1529 nm transition, and the Allan deviation of the Faraday laser is measured by converting the optical intensity into frequency. The Faraday laser can be used as a frequency standard in the telecom C band for further research on metrology, microwave photonics, and optical communication systems.展开更多
We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigoro...We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigorous noise model of the receiver has been developed for this purpose.We calculate the total noise and sensitivity of the receiver.The front-end of the receiver exhibits a sensitivity of -45 dBm at a bit rate of 1 Gb/s and -30 dBm at a bit rate of 10 Gb/s,and the total mean-square noise curren t〈i2n〉=5×10-15 A2 at a bit rate of 1 Gb/s an d〈i2n〉 =10-12 A2 at a bit rate of 10 Gb/s,and a 3-dB bandwidth of 10 GHz.展开更多
Based on the tight-binding approximation, analytical solutions of the energy dispersion and band gap of armchair-edge graphene nanoribbons (AGNRs) under uniaxial strains are derived. Subsequent numerical results on ...Based on the tight-binding approximation, analytical solutions of the energy dispersion and band gap of armchair-edge graphene nanoribbons (AGNRs) under uniaxial strains are derived. Subsequent numerical results on band gap are found to be consistent with the analytical solutions. It is shown that the energy gap of AGNRs is sensitive to the uniaxial strains and is predicted to change with a V shape as a function of the applied uniaxial strain. It is interesting to find that the uniaxial strain could induce metal-semiconductor transition for the AGNRs with a width of n=3m+2 ((3m + 2)-AGNRs) and semiconductor-metal-semiconductor phase transition for the (3m + 1)-AGNRs, but no phase transition is induced for the 3m-AGNRs.展开更多
Calcium fluoride is widely used in optical lithography lenses and causes retardation that cannot be ignored. However, few studies have been conducted to compensate for the retardation caused by calcium fluoride in opt...Calcium fluoride is widely used in optical lithography lenses and causes retardation that cannot be ignored. However, few studies have been conducted to compensate for the retardation caused by calcium fluoride in optical lithography systems. In this Letter, a new index based on orientation Zernike polynomials is established to describe the value of retardation. Then, a method of retardation compensation is described. The method is implemented by clocking calcium fluoride lens elements, and the optimal rotation angles are calculated using a population-based stochastic optimization algorithm. Finally, an example is provided to validate the method.展开更多
We propose simple and practical approaches to upgrade electronic-repeated systems by using optical amplifiers and zero-dispersion wavelength transmission. Possibility of increasing data rate from 560 Mbit/s to 80 Gbit...We propose simple and practical approaches to upgrade electronic-repeated systems by using optical amplifiers and zero-dispersion wavelength transmission. Possibility of increasing data rate from 560 Mbit/s to 80 Gbit/s in 1,318-km-long Thai-Malaysia system is demonstrated.展开更多
In order to realize reliable and fast simulation of FWM power evaluation, USSD (Uniform Step-Size Distribution) method is modified and its corresponding simulation results of FWM efficiency and computational time are ...In order to realize reliable and fast simulation of FWM power evaluation, USSD (Uniform Step-Size Distribution) method is modified and its corresponding simulation results of FWM efficiency and computational time are presented.展开更多
Various optical fiber connectors have been developed during the 20 years since optical fiber communications systems were first put into practical use. This paper describes the technical background and recent issues re...Various optical fiber connectors have been developed during the 20 years since optical fiber communications systems were first put into practical use. This paper describes the technical background and recent issues related to photonic connection technologies.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. U1930402)support from the Project Funded by China Postdoctoral Science Foundation (Grant Nos. 2020M680006 and 2021T140045)+1 种基金support from the National Natural Science Foundation of China (Grant No. 12004184)the Natural Science Foundation of Jiangsu Province, China (Grants No. BK20190428)。
文摘The contradiction between classical and quantum physics can be identified through quantum contextuality, which does not need composite systems or spacelike separation. Contextuality is proven either by a logical contradiction between the noncontextuality hidden variable predictions and those of quantum mechanics or by the violation of noncontextual inequality. We propose an experimental scheme of state-independent contextual inequality derived from the Mermin proof of the Kochen–Specker(KS) theorem in eight-dimensional Hilbert space, which could be observed either in an individual system or in a composite system. We also show how to resolve the compatibility problems. Our scheme can be implemented in optical systems with current experiment techniques.
文摘The formalism of generalized diffraction integral for paraxial misaligned optical systems is used to investigate the propagation of the Modified Bessel-Gaussian (MBG) beam through a misaligned thin lens. The properties of the propagation of MBG beam traveling through this misaligned ABCD optical system are discussed. A special case of misaligned circular thin lens is illustrated analytically and numerically. The shape of the MBG beam at the exit of the misaligned optical system is unchanged;however the center of the beam is shifted from the propagation axis in correlated manner with the design parameters of the optical system.
文摘Optical Wireless Communication(OWC)is a new trend in communication systems to achieve large bandwidth,high bit rate,high security,fast deployment,and low cost.The basic idea of the OWC is to transmit data on unguided media with light.This system requires multi-carrier modulation such as Orthogonal Frequency Division Multiplexing(OFDM).This paper studies optical OFDM performance based on Intensity Modulation with Direct Detection(IM/DD)system.This system requires a non-negativity constraint.The paper presents a framework for wireless optical OFDM system that comprises(IM/DD)with different forms,Direct Current biased Optical OFDM(DCO-OFDM),Asymmetrically Clipped Optical OFDM(ACO-OFDM),Asymmetrically DC-biased Optical OFDM(ADO-OFDM),and Flip-OFDM.It also considers channel coding as a tool for error control,channel equalization for reducing deterioration due to channel effects,and investigation of the turbulence effects.The evaluation results of the proposed framework reveal enhancement of performance.The performance of the IM/DD-OFDM system is investigated over different channel models such as AWGN,log-normal turbulence channel model,and ceiling bounce channel model.The simulation results show that the BER performance of the IM/DD-OFDM communication system is enhanced while the fading strength is decreased.The results reveal also that Hamming codes,BCH codes,and convolutional codes achieve better BER performance.Also,two algorithms of channel estimation and equalization are considered and compared.These algorithms include the Least Squares(LS)and the Minimum Mean Square Error(MMSE).The simulation results show that the MMSE algorithm gives better BER performance than the LS algorithm.
基金supported by the National Natural Science Foundation of China(Grant Nos.11274037 and 61275075)the Program for New Century Excellent Talents in University,Ministry of Education of China(Grant No.NCET-12-0765)the Foundation for the Author of National Excellent Doctoral Dissertation,China(Grant No.201236)
文摘A novel scheme of differential polarization demodulation is presented and demonstrated based on a polarized asym- metrical Mach-Zehnder interferometer configuration with polarization control. To enhance the stability of the demodulator, a phase-lock device is designed, and it is composed of a symmetric 3 × 3 coupler and a feedback circuit. For further estab- lishing a differential polarization-shift keying (DPolSK) transmission system, we successfully carry out the demodulation experiments on 10-Gb/s DPolSK optical signals for the first time. Due to the all-optical structure with phase-lock, our scheme is available to realize the DPolSK optical communication in practical optical fiber systems.
基金Project supported by the Program of Excellent Team in Harbin Institute of Technology,China
文摘A stable and accurate pointing,acquisition system is an important part of initially building intersatellite optical communication links.Satellite platform vibration can cause the system instability and reduce the system precision in building and maintenance of a satellite optical communication system.In this paper,vibration influence is consciously discussed by acquisition time for intersatellite optical communications.Analytical expression of acquisition possibility is derived,taking the scan parameters and platform vibration into account,and vibration influence on the multi-scan acquisition time is also presented.The theoretical result calculated by the proposed analytical expression is approximate to the result by the Monte Carlo simulation.
基金supported by 973 Program of China under Grant No.2006CB302900part by the National Natural Science Foundation of China under Grant No.60825405 and No.60778018
文摘Several approaches to fabricate micro optical elements by use of half tone masks are studied and compared. It is shown that half tone masks employed in filtering image systems can obtain gray patterns with considerably high precision, but it is hard to operate from the viewpoint of operation. The method using contacting lithography technology or laser ablation can be easily operated with the cost of reducing fabrication precision and the trouble of choosing appropriate materials. For all of these methods, the coding of half tone masks with corrections for the nonlinear characteristics of coding, imaging and photoresist is recommended.
基金supported in part by the National Key Research and Development Program of China (Grant No. 2020YFC2201501)the National Natural Science Foundation of China (Grant No. 12147103, special fund to the center for quanta-to-cosmos theoretical physics) (Grant No. 11821505)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB23030100)the Chinese Academy of Sciences (CAS)。
文摘In space-based gravitational wave detection, the estimation of far-field wavefront error of the distorted beam is the precondition for the noise reduction. Zernike polynomials are used to describe the wavefront error of the transmitted distorted beam. The propagation of a laser beam between two telescope apertures is calculated numerically. Far-field wavefront error is estimated with the absolute height of the peak-to-valley phase deviation between the distorted Gaussian beam and a reference distortion-free Gaussian beam. The results show that the pointing jitter is strongly related to the wavefront error. Furthermore, when the jitter decreases 10 times from 100 nrad to 10 nrad, the wavefront error reduces for more than an order of magnitude. In the analysis of multi-parameter minimization, the minimum of wavefront error tends to Z[5,3] Zernike in some parameter ranges. Some Zernikes have a strong correlation with the wavefront error of the received beam. When the aperture diameter increases at Z[5,3] Zernike, the wavefront error is not monotonic and has oscillation.Nevertheless, the wavefront error almost remains constant with the arm length increasing from 10-1Mkm to 10~3Mkm.When the arm length decreases for three orders of magnitude from 10-1Mkm to 10-4Mkm, the wavefront error has only an order of magnitude increasing. In the range of 10-4Mkm to 10~3Mkm, the lowest limit of the wavefront error is from 0.5 fm to 0.015 fm at Z[5,3] Zernike and 10 nrad jitter.
文摘Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd:YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 nm. The reorientation rate of azo polymer films is enhanced in the presence of Ag nanoparticles, and the rate of the azo polymer film with Ag concentration of 2.2 μg/ml is larger than that of the azo polymer films with Ag concentrations of 1.1 μg/ml and 4.4 μg/ml. The third-order nonlinear optical properties of the Ag/azo composite film are obtained by the Z-scan technique at a wavelength of 532 nm, and the measured nonlinear refractive index is 9.258×10-9 esu. It is shown that the main mechanisms involved in the large nonlinear optical responses come from the local field enhancement of Ag nanoparticles and the nonlinear effect of the azo polymer matrix.
基金supported by National Key Basic Research Program of China(973 Program)under Grant No.2010CB328000National Natural Science Foundation of China under Grant No.61073168,60972023,61102068+7 种基金China Postdoctoral Science Foundation funded project under Grant No.20110490389Research Fund of National Mobile Communications Research Laboratory,Southeast University under Grant No.2010A06the Open Research Fund of National Mobile Communication Research Laboratory,Southeast University under Grant No.2010D01National Science and Technology Important Special Project under Grant No.2010ZX03003-002,2010ZX03003-004the Open research fund of the State Key Laboratory of Integrated Services Networks,Xidian University under Grant No.ISN12-11NUAA Research Funding under Grant No.NS2011013the Open Research Fund of State Key Laboratory of Advance Optical Communication Systems and Networks under Grant No.2008SH06the Startup Fund of Nanjing University of Aeronautics and Astronautics and Fundation of Graduate Innovation Center in NUAA
文摘This paper investigates the performance of multi-hop Free Space Optical(FSO) communications using serial Decode-and-Forward(DF) relay transmissions.A statistical model for the optical intensity fluctuation at the receiver due to the combined effects of atmospheric turbulence-induced fading,mis alignment fading and pass-loss is presented.Under given weather and mis alignment conditions,a closed-form analytical expression for the end-to-end outage probability of serial Decode-and-Forward(DF) multi-hop FSO communications is derived.Numerical results show that the serial DF multi-hop transmission is a promising technology to enhance the performance of FSO communications.Moreover,the derived analytical expression can provide close approximations to the simulation results.
文摘In this paper, a new kind of light beam called off-axial elliptical cosine-Gaussian beam (ECosGBs) is defined by using the tensor method. An analytical propagation expression for the ECosGBs passing through axially nonsymmetrical optical systems is derived by using vector integration. The intensity distributions of ECosGBs on the input plane, on the output plane with the equivalent Fresnel number being equal to 0.1 and on the focal plane are respectively illustrated for the propagation properties. The results indicate that an ECosGB is eventually transformed into an elliptical cosh- Gaussian beam. In other words, ECosGBs and cosh-Gaussian beams act in a reciprocal manner after propagation.
基金supported by Science Foundation for Youthful Teachers of Anhui University (Grant No.2007jql104)
文摘In order to decrease dispersion penalty and increase the optical bandwidth efficiency,an optical single-side-band modulation(SSBM) scheme in sub-carrier multiplexing(SCM) is proposed.The principle of the SSBM is analytically presented,and a configuration for generating optical SSB signal is proposed using a balanced Mach-Zehnder electro-optic modulator.
基金This work was partly supported by the Doctoral Research Fund of Shanxi University and the Youth Science Fund of Shanxi Province.
文摘The properties of ultra-short dense dispersion-managed soliton (DBMS) in optical fiber links are investigated. They show some excellent characters, such as, reducing pulse's breathing extent greatly, facing fewer mutual interactions and tolerating larger local dispersion. In general, DBMS is more stable than a conventional dispersion-managed soliton in high-capacity systems. Excessively dense dispersion compensation is more suitable for systems with weak nonlinear effect.
基金supported by the National Natural Science Foundation of China under Grant No.91436210
文摘We experimentally demonstrate a Faraday laser at Rb 1529 nm transition by using a performance-improved Rb electrodeless-discharge-lamp-based excited-state Faraday anomalous dispersion optical filter as the frequency- selective element. Neither the electrical locking scheme nor the additional frequency-stabilized pump laser are used. The frequency of the external-cavity diode laser is stabilized to the Rb 1529 nm transition, and the Allan deviation of the Faraday laser is measured by converting the optical intensity into frequency. The Faraday laser can be used as a frequency standard in the telecom C band for further research on metrology, microwave photonics, and optical communication systems.
文摘We examine theoretically the performance of an Hg0.77Cd0.23Te based p-n photodetector/HFET optical receiver due to its possible application at 10.6 μm free space optical communication system at high bit rate.A rigorous noise model of the receiver has been developed for this purpose.We calculate the total noise and sensitivity of the receiver.The front-end of the receiver exhibits a sensitivity of -45 dBm at a bit rate of 1 Gb/s and -30 dBm at a bit rate of 10 Gb/s,and the total mean-square noise curren t〈i2n〉=5×10-15 A2 at a bit rate of 1 Gb/s an d〈i2n〉 =10-12 A2 at a bit rate of 10 Gb/s,and a 3-dB bandwidth of 10 GHz.
基金Supported by the National Natural Science Foundation of China under Grant No 10804051, and by the Subject Foundation of Nanjing University of Technology.
文摘Based on the tight-binding approximation, analytical solutions of the energy dispersion and band gap of armchair-edge graphene nanoribbons (AGNRs) under uniaxial strains are derived. Subsequent numerical results on band gap are found to be consistent with the analytical solutions. It is shown that the energy gap of AGNRs is sensitive to the uniaxial strains and is predicted to change with a V shape as a function of the applied uniaxial strain. It is interesting to find that the uniaxial strain could induce metal-semiconductor transition for the AGNRs with a width of n=3m+2 ((3m + 2)-AGNRs) and semiconductor-metal-semiconductor phase transition for the (3m + 1)-AGNRs, but no phase transition is induced for the 3m-AGNRs.
文摘Calcium fluoride is widely used in optical lithography lenses and causes retardation that cannot be ignored. However, few studies have been conducted to compensate for the retardation caused by calcium fluoride in optical lithography systems. In this Letter, a new index based on orientation Zernike polynomials is established to describe the value of retardation. Then, a method of retardation compensation is described. The method is implemented by clocking calcium fluoride lens elements, and the optimal rotation angles are calculated using a population-based stochastic optimization algorithm. Finally, an example is provided to validate the method.
文摘We propose simple and practical approaches to upgrade electronic-repeated systems by using optical amplifiers and zero-dispersion wavelength transmission. Possibility of increasing data rate from 560 Mbit/s to 80 Gbit/s in 1,318-km-long Thai-Malaysia system is demonstrated.
文摘In order to realize reliable and fast simulation of FWM power evaluation, USSD (Uniform Step-Size Distribution) method is modified and its corresponding simulation results of FWM efficiency and computational time are presented.
文摘Various optical fiber connectors have been developed during the 20 years since optical fiber communications systems were first put into practical use. This paper describes the technical background and recent issues related to photonic connection technologies.