Through theoretical analysis and experiments, the viscoelastic mechanical model of optical fiber coupler in the process of fused biconical taper was established, and the numerical analysis in non-uniform temperature f...Through theoretical analysis and experiments, the viscoelastic mechanical model of optical fiber coupler in the process of fused biconical taper was established, and the numerical analysis in non-uniform temperature field was made. The results show that the rheological parameters, such as drawing speed and fused temperature, have a tremendous influence on stress distribution and performance of optical fiber coupler, especially the influence of fused temperature. The change of fused temperature by 5℃ can lead to the change of the maximum stress by 30% and stress difference by 20% in the same cross section. The change of temperature gradient by 3% can result in the change of stress difference by 90%. In the present condition of rheological technology, rheological defects such as crystallizations and microcracks are easy to generate in the optical fiber coupler.展开更多
To find out the effect of the shape of fused taper region on the optical fiber coupler, the fiber couplers were fabricated at different drawing speeds with a six-axes fiber coupler machine. The results, which were obt...To find out the effect of the shape of fused taper region on the optical fiber coupler, the fiber couplers were fabricated at different drawing speeds with a six-axes fiber coupler machine. The results, which were obtained fi'om the shape of fused taper region measured with microscope, show that there is a close correlation between the cone angle and optical performance of fiber coupler. High-performance fiber coupler cannot be obtained until rheological shape is controlled accurately. The numerical analysis model, which was built based on generalized Maxwell viscoelastic theory, is resolved with ANSYS software. The calculated results accord with the experimental data. It can apply a theoretic basis for forecasting the shape of fiber coupler fabricated under the conditions of different technological parameters.展开更多
Based on the coupling mode theory that the coupling ratio of fiber coupler changes periodically with center distance of two optical fibers, a novel manufacturing method of optical fiber couplers was developed with fus...Based on the coupling mode theory that the coupling ratio of fiber coupler changes periodically with center distance of two optical fibers, a novel manufacturing method of optical fiber couplers was developed with fused biconical taper experimental system. Its fabrication process is that the fiber is fused but not stretched when light begins to split, and the reduction of diameter of fiber is dependent on the theological characteristic of the fused fiberglass. The performance of the coupler was tested. The results show that the performance of the novel optical fiber coupler meets the performance expectations, and its diameter of coupling region (about 30 μm) is twice as long as that of classical fused biconical taper coupler (about 16 μm), so the default, that is, the device is easy to fracture, is restrained and the reliability is greatly improved.展开更多
Nanodevices using the photovoltaic effect of a single nanowire have attracted growing interest. In this paper, we consider potential applications of the photovoltaic effect to optical signal coupling and optical power...Nanodevices using the photovoltaic effect of a single nanowire have attracted growing interest. In this paper, we consider potential applications of the photovoltaic effect to optical signal coupling and optical power transmission, and report on the realization of a heterojunction formed between WO2 and WO3 in a fine-wire having a diameter on the micrometer scale. Using a laser beam of 514.5 nm as a signal source, the WO2-WO3 heterojunction yields a maximum output power of up to 37.4 pico watt per heterojunction. Fast responses (less than a second) of both photovoltaic voltage and current are also observed. In addition, we demonstrate that it is a simple and effective way to adapt a commercial Raman spectrometer for the combined functions of fabrication, material characterization and photovottaic measurement of an optical signal coupler and optical power transmitter based on a fine-wire. Our results show an attractive perspective of developing nanowire or fine-wire elements for coupling optical signals into and for powering a nanoelectronic or nano-optoelectronic integrated circuit that works under the condition of preventing it from directly electrically connecting with the optical coupler.展开更多
In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler(CM-LPGC).Temporal rectangular waveform with 2-ps full width at half maximum(FWHM) is obtained by tran...In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler(CM-LPGC).Temporal rectangular waveform with 2-ps full width at half maximum(FWHM) is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.展开更多
In this paper, we present the results of numerical analysis of optical solitons in dual core couplers. We studied the optical couplers as an application for the non-linear Schrödinger equation in the case of ...In this paper, we present the results of numerical analysis of optical solitons in dual core couplers. We studied the optical couplers as an application for the non-linear Schrödinger equation in the case of Kerr law for non-linear and clarify the exact solution in this case. Then we have provided a numerical study of the effect of changing the constants in the form of the three types of solitons: bright soliton and dark solitons and singular soliton.展开更多
To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experime...To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experimental setup. Fused fiber coupler's optical performances such as insertion loss, excess loss, directivity and uniformity were tested with the optical test system that was constituted of tunable laser and optical spectrum analyzer. Especially the relationship between optical performance and drawing speed was investigated. The experimental results show that the optical performance is closely related to process conditions. At fused temperature of 1 200 ℃, there exists a drawing speed of 150 μms, which makes the device's performance optimum. Out of this speed region, the optical performance drops quickly. At drawing speed of 200 μms, the excess loss is relatively small when the fused temperature is above 1 200 ℃. So the technological parameters have close relationship with optical performance of the coupler, and the good performance coupler can't get until the drawing speed and fused temperature match accurately.展开更多
To obtain excellent performance optical fiber couplers, the structural difference of SiO2 in couplers with different manufacturing techniques was investigated. With 740-FT-IR infrared spectrometric analyzer, the infra...To obtain excellent performance optical fiber couplers, the structural difference of SiO2 in couplers with different manufacturing techniques was investigated. With 740-FT-IR infrared spectrometric analyzer, the infrared absorption spectrum of SiO2 in couplers at different drawing velocities was measured, and two characteristic peaks in the wavenumber range of 6502000 cm-1 were observed. One characteristic peak is at about 943 cm-1, which is (attributed) to Si—O—Si bond asymmetric stretching vibration, the other is at about 773 cm-1, which is attributed to (Si—O—Si) bond symmetric stretching vibration. From the infrared spectrum, it is found that the intensity and wavenumber of the characteristic peaks are related to the manufacturing technique of couplers. The characteristic peak at (about) 943 cm-1 becomes steeper when increasing the drawing velocity. At the drawing velocity of 150 μm/s, the distance between the two characteristic peaks is maximum, and then the optical fiber coupler has excellent performance, indicating that the performance of the optical fiber coupler has a close relationship with the wavenumber of the two characteristic peaks.展开更多
An optical code generating device has been developed based on a 1×2 asymmetric plastic optical fiber (POF) coupler. The code generating device provides a unique series of output power which are successively use...An optical code generating device has been developed based on a 1×2 asymmetric plastic optical fiber (POF) coupler. The code generating device provides a unique series of output power which are successively used as an optical code in a portable optical access-card system. The device utilizing a tap-off ratio (TOFR) technique based on a simple variation of the tap width of an asymmetric Y-branch splitter, allows various ratios of optical power to be generated. The POF coupler has been fabricated using low cost acrylic material and computer numerical control (CNC) machining technique. The simulated and fabricated results show the same linear characteristics between the TOFR and the tap width. The fabricated device enables a variation of the TOFR from 10% up to 50% for a tap width of 500 um to 1 mm.展开更多
Coupling plane wave into a single-mode fiber (SMF) with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fibe...Coupling plane wave into a single-mode fiber (SMF) with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler (AFC) which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent (SPGD) algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error (MSE) of coupling efficiency drops from 7.43% to 1.75%.展开更多
A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to o...A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.展开更多
Utilizing hybrid integration model.the integrated model optocouplers have successfully developed.The design,fabrication and characteristic parameters of the devices are presented.
Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor(CMOS) process com...Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor(CMOS) process compatible grating coupler is proposed.The poly-Si layer used as a gate in the CMOS metal-oxide-semiconductor field effect transistor(MOSFET) is combined with a normal fully etched grating coupler,which greatly enhances its coupling efficiency.With optimal structure parameters,a coupling efficiency can reach as high as ~ 70% at a wavelength of 1550 nm as indicated by simulation.From the angle of fabrication,all masks and etching steps are shared between MOSFETs and grating couplers,thereby making the high performance grating couplers easily integrated with CMOS circuits.Fabrication errors such as alignment shift are also simulated,showing that the device is quite tolerant in fabrication.展开更多
We propose an identical geometrical representation scheme for both Landau-Zener (LZ) tunneling process in two-waveguide coupler with a cubically bent structure and stimulated Raman adiabatic passage (STIRAP) in th...We propose an identical geometrical representation scheme for both Landau-Zener (LZ) tunneling process in two-waveguide coupler with a cubically bent structure and stimulated Raman adiabatic passage (STIRAP) in three-waveguide coupler, similar to the geometrical representation of sum frequency process. The results show that although the two-waveguide coupler with a cubically bent axis has not aperiodic structure, it acts as a chirped quasi-phase-matching (QPM) grating and corrects the relative phase between the two supermodes in the curved coupler system. We present a scheme about how to choose the parameters to design the curved beam splitter.展开更多
SOI zero-gap directional couplers are studied by using large cross-section single-mode rib waveguide theory and dual-mode interference principle in silicon direct bonding SOI by back-polishing. And they are fabricated...SOI zero-gap directional couplers are studied by using large cross-section single-mode rib waveguide theory and dual-mode interference principle in silicon direct bonding SOI by back-polishing. And they are fabricated by using KOH anistropic etching. The insertion loss is measured to 4.81 dB, and the crosstalk is below —18.6 dB at a wavelength of 1.3μm.展开更多
An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler ...An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector.We investigate the general phase principle of output light image.The complete proof of nonoverlapping-image MMI coupler’s optical unitarity along with the phase analysis of matrix element is provided.Based on a two-dimensional finite-difference time-domain(2 D-FDTD)simulation,the unitary transformation is obtained for a 4×4 nonoverlapping-image MMI coupler within a deviation of 4×10-2 for orthogonal invariance and 8×10-2 for transvection invariance in the C-band spectral range.A compact 1×4 splitter based on cascaded MMI coupler is proposed,showing a phase deviation less than 5.4°while maintaining a low-loss performance in C-band spectra.展开更多
Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32- and 36-wavelengths o...Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32- and 36-wavelengths optical waveguide wavelength-interleave coupler(i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8 nm at 1 550 nm.The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%,while the least through coupling ratios are respectively greater than 98.2% and 96.5%.The output differences due to polarization fluctuation are less than ±1.7% and ±3.2%.展开更多
In this work, we develop a simulation method based on supermode theory and transfer matrix formalism, and then apply it to the analysis and design of taper couplers for vertically integrated As2S3 and Ti: LiNbO3 hybri...In this work, we develop a simulation method based on supermode theory and transfer matrix formalism, and then apply it to the analysis and design of taper couplers for vertically integrated As2S3 and Ti: LiNbO3 hybrid waveguides. Test structures based on taper couplers are fabricated and characterized. The experimental results confirm the validity of the modeling method, which in turn, is used to analyze the fabricated couplers.展开更多
The temperature dependence of characteristics for multimode interference(MMI) based 3-dB coupler in silicon-on-insulator is analyzed, which originates from the relatively high thermo-optic coefficient of silicon. For ...The temperature dependence of characteristics for multimode interference(MMI) based 3-dB coupler in silicon-on-insulator is analyzed, which originates from the relatively high thermo-optic coefficient of silicon. For restricted interference 3-dB MMI coupler, the output power uniformity is ideally 0 at room temperature and becomes 0.32 dB when temperature rises up to 550 K.For symmetric interference 3-dB MMI coupler, the power uniformity keeps ideally 0 due to its intrinsic symmetric interference mechanism. With the temperature rising, the excess loss of the both devices increases. The performance deterioration due to temperature variety is more obvious to restricted interference MMI 3-dB coupler, comparing with that of symmetric interference MMI 3-dB coupler.展开更多
基金Project (50235040) supported by the National Natural Science Foundation of China project( NCET-040753) supportedby the New Century Excellent Talent in University project(20050533037) supported by the Doctoral Programof Higher Education
文摘Through theoretical analysis and experiments, the viscoelastic mechanical model of optical fiber coupler in the process of fused biconical taper was established, and the numerical analysis in non-uniform temperature field was made. The results show that the rheological parameters, such as drawing speed and fused temperature, have a tremendous influence on stress distribution and performance of optical fiber coupler, especially the influence of fused temperature. The change of fused temperature by 5℃ can lead to the change of the maximum stress by 30% and stress difference by 20% in the same cross section. The change of temperature gradient by 3% can result in the change of stress difference by 90%. In the present condition of rheological technology, rheological defects such as crystallizations and microcracks are easy to generate in the optical fiber coupler.
基金Project (50605063) supported by the National Natural Science Foundation of ChinaProject(NCET-040753) supported by New Century Excellent Talents in University, ChinaProject (20050533037) supported by the Doctoral Program of Higher Education, China
文摘To find out the effect of the shape of fused taper region on the optical fiber coupler, the fiber couplers were fabricated at different drawing speeds with a six-axes fiber coupler machine. The results, which were obtained fi'om the shape of fused taper region measured with microscope, show that there is a close correlation between the cone angle and optical performance of fiber coupler. High-performance fiber coupler cannot be obtained until rheological shape is controlled accurately. The numerical analysis model, which was built based on generalized Maxwell viscoelastic theory, is resolved with ANSYS software. The calculated results accord with the experimental data. It can apply a theoretic basis for forecasting the shape of fiber coupler fabricated under the conditions of different technological parameters.
基金Project(50235040) supported by the National Natural Science Foundation of China projected(NCET-040753) supporteby the Programof New Century Excellent Talents in University project(20050533037) supported by the Research Fund for the DoctoraProgramof Higher Education
文摘Based on the coupling mode theory that the coupling ratio of fiber coupler changes periodically with center distance of two optical fibers, a novel manufacturing method of optical fiber couplers was developed with fused biconical taper experimental system. Its fabrication process is that the fiber is fused but not stretched when light begins to split, and the reduction of diameter of fiber is dependent on the theological characteristic of the fused fiberglass. The performance of the coupler was tested. The results show that the performance of the novel optical fiber coupler meets the performance expectations, and its diameter of coupling region (about 30 μm) is twice as long as that of classical fused biconical taper coupler (about 16 μm), so the default, that is, the device is easy to fracture, is restrained and the reliability is greatly improved.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. U0634002,50725206 and 50672135)the National Basic Research Program of China (Grant Nos. 2003CB314701,2007CB935501 and 2008AA03A314)the Department of Information Industry of Guangdong Province,China
文摘Nanodevices using the photovoltaic effect of a single nanowire have attracted growing interest. In this paper, we consider potential applications of the photovoltaic effect to optical signal coupling and optical power transmission, and report on the realization of a heterojunction formed between WO2 and WO3 in a fine-wire having a diameter on the micrometer scale. Using a laser beam of 514.5 nm as a signal source, the WO2-WO3 heterojunction yields a maximum output power of up to 37.4 pico watt per heterojunction. Fast responses (less than a second) of both photovoltaic voltage and current are also observed. In addition, we demonstrate that it is a simple and effective way to adapt a commercial Raman spectrometer for the combined functions of fabrication, material characterization and photovottaic measurement of an optical signal coupler and optical power transmitter based on a fine-wire. Our results show an attractive perspective of developing nanowire or fine-wire elements for coupling optical signals into and for powering a nanoelectronic or nano-optoelectronic integrated circuit that works under the condition of preventing it from directly electrically connecting with the optical coupler.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61007007 and 61101110)the Foundation of Beijing Municipal Committee of CPC Organization Department (Grant No. 2012D005002000001)
文摘In this paper,we present a novel ultrashort pulse shaper based on complex-modulated long-period-grating coupler(CM-LPGC).Temporal rectangular waveform with 2-ps full width at half maximum(FWHM) is obtained by transforming the input Gaussian pulse.Tolerances of the CM-LPGC-based shaper to various non-ideal excitation conditions and fabricating errors are investigated.Results confirm that CM-LPGC is stable and suitable for optical pulse shaping operation.
文摘In this paper, we present the results of numerical analysis of optical solitons in dual core couplers. We studied the optical couplers as an application for the non-linear Schrödinger equation in the case of Kerr law for non-linear and clarify the exact solution in this case. Then we have provided a numerical study of the effect of changing the constants in the form of the three types of solitons: bright soliton and dark solitons and singular soliton.
基金Project (50605063) supported by the National Natural Science Foundation of ChinaProject(NCET-040753) supported by New Century Excellent Talents in University of ChinaProject (20050533037) supported by the Doctoral Program of Higher Education of China
文摘To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experimental setup. Fused fiber coupler's optical performances such as insertion loss, excess loss, directivity and uniformity were tested with the optical test system that was constituted of tunable laser and optical spectrum analyzer. Especially the relationship between optical performance and drawing speed was investigated. The experimental results show that the optical performance is closely related to process conditions. At fused temperature of 1 200 ℃, there exists a drawing speed of 150 μms, which makes the device's performance optimum. Out of this speed region, the optical performance drops quickly. At drawing speed of 200 μms, the excess loss is relatively small when the fused temperature is above 1 200 ℃. So the technological parameters have close relationship with optical performance of the coupler, and the good performance coupler can't get until the drawing speed and fused temperature match accurately.
文摘To obtain excellent performance optical fiber couplers, the structural difference of SiO2 in couplers with different manufacturing techniques was investigated. With 740-FT-IR infrared spectrometric analyzer, the infrared absorption spectrum of SiO2 in couplers at different drawing velocities was measured, and two characteristic peaks in the wavenumber range of 6502000 cm-1 were observed. One characteristic peak is at about 943 cm-1, which is (attributed) to Si—O—Si bond asymmetric stretching vibration, the other is at about 773 cm-1, which is attributed to (Si—O—Si) bond symmetric stretching vibration. From the infrared spectrum, it is found that the intensity and wavenumber of the characteristic peaks are related to the manufacturing technique of couplers. The characteristic peak at (about) 943 cm-1 becomes steeper when increasing the drawing velocity. At the drawing velocity of 150 μm/s, the distance between the two characteristic peaks is maximum, and then the optical fiber coupler has excellent performance, indicating that the performance of the optical fiber coupler has a close relationship with the wavenumber of the two characteristic peaks.
基金supported by the Malaysian E-Science Fund under Grant No 01-01-01-SF0197
文摘An optical code generating device has been developed based on a 1×2 asymmetric plastic optical fiber (POF) coupler. The code generating device provides a unique series of output power which are successively used as an optical code in a portable optical access-card system. The device utilizing a tap-off ratio (TOFR) technique based on a simple variation of the tap width of an asymmetric Y-branch splitter, allows various ratios of optical power to be generated. The POF coupler has been fabricated using low cost acrylic material and computer numerical control (CNC) machining technique. The simulated and fabricated results show the same linear characteristics between the TOFR and the tap width. The fabricated device enables a variation of the TOFR from 10% up to 50% for a tap width of 500 um to 1 mm.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61205069).
文摘Coupling plane wave into a single-mode fiber (SMF) with high and steady coupling efficiency is crucial for fiber- based free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler (AFC) which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent (SPGD) algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80/3tad. The compensation bandwidth is 35 Hz at sine-jitter of 15 ~rad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error (MSE) of coupling efficiency drops from 7.43% to 1.75%.
基金Project supported by the National Natural Science Foundation of China (Grant No.60877036)the National Basic Research Program of China (Grant Nos.2006CB302803 and 2011CB301701)+1 种基金the State Key Laboratory of Advanced Optical Communication Systems and Networks,China (Grant No.2008SH02)the Knowledge Innovation Program of Institute of Semiconductors,Chinese Academy of Sciences (Grant No.ISCAS2008T10)
文摘A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.
文摘Utilizing hybrid integration model.the integrated model optocouplers have successfully developed.The design,fabrication and characteristic parameters of the devices are presented.
基金Project supported by the Natural Science Foundation of Shanghai,China (Grant No. 11ZR1443700)the Funds from the Science and Technology Commission of Shanghai Municipality,China (Grant Nos. 10DJ1400400 and 10706200500)the National Natural Science Foundation of China (Grant No. 61106051)
文摘Grating couplers are widely investigated as coupling interfaces between silicon-on-insulator waveguides and optical fibers.In this work,a high-efficiency and complementary metal-oxide-semiconductor(CMOS) process compatible grating coupler is proposed.The poly-Si layer used as a gate in the CMOS metal-oxide-semiconductor field effect transistor(MOSFET) is combined with a normal fully etched grating coupler,which greatly enhances its coupling efficiency.With optimal structure parameters,a coupling efficiency can reach as high as ~ 70% at a wavelength of 1550 nm as indicated by simulation.From the angle of fabrication,all masks and etching steps are shared between MOSFETs and grating couplers,thereby making the high performance grating couplers easily integrated with CMOS circuits.Fabrication errors such as alignment shift are also simulated,showing that the device is quite tolerant in fabrication.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11304247 and 61505161)the Shaanxi Provincial Research Plan for Young Scientific and Technological New Stars,China(Grant No.2015KJXX-40)
文摘We propose an identical geometrical representation scheme for both Landau-Zener (LZ) tunneling process in two-waveguide coupler with a cubically bent structure and stimulated Raman adiabatic passage (STIRAP) in three-waveguide coupler, similar to the geometrical representation of sum frequency process. The results show that although the two-waveguide coupler with a cubically bent axis has not aperiodic structure, it acts as a chirped quasi-phase-matching (QPM) grating and corrects the relative phase between the two supermodes in the curved coupler system. We present a scheme about how to choose the parameters to design the curved beam splitter.
基金the High Technology Research and Development Programme of China
文摘SOI zero-gap directional couplers are studied by using large cross-section single-mode rib waveguide theory and dual-mode interference principle in silicon direct bonding SOI by back-polishing. And they are fabricated by using KOH anistropic etching. The insertion loss is measured to 4.81 dB, and the crosstalk is below —18.6 dB at a wavelength of 1.3μm.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB2200202)the National Natural Science Foundation of China(Grant No.61804148)
文摘An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector.We investigate the general phase principle of output light image.The complete proof of nonoverlapping-image MMI coupler’s optical unitarity along with the phase analysis of matrix element is provided.Based on a two-dimensional finite-difference time-domain(2 D-FDTD)simulation,the unitary transformation is obtained for a 4×4 nonoverlapping-image MMI coupler within a deviation of 4×10-2 for orthogonal invariance and 8×10-2 for transvection invariance in the C-band spectral range.A compact 1×4 splitter based on cascaded MMI coupler is proposed,showing a phase deviation less than 5.4°while maintaining a low-loss performance in C-band spectra.
文摘Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32- and 36-wavelengths optical waveguide wavelength-interleave coupler(i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8 nm at 1 550 nm.The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%,while the least through coupling ratios are respectively greater than 98.2% and 96.5%.The output differences due to polarization fluctuation are less than ±1.7% and ±3.2%.
文摘In this work, we develop a simulation method based on supermode theory and transfer matrix formalism, and then apply it to the analysis and design of taper couplers for vertically integrated As2S3 and Ti: LiNbO3 hybrid waveguides. Test structures based on taper couplers are fabricated and characterized. The experimental results confirm the validity of the modeling method, which in turn, is used to analyze the fabricated couplers.
文摘The temperature dependence of characteristics for multimode interference(MMI) based 3-dB coupler in silicon-on-insulator is analyzed, which originates from the relatively high thermo-optic coefficient of silicon. For restricted interference 3-dB MMI coupler, the output power uniformity is ideally 0 at room temperature and becomes 0.32 dB when temperature rises up to 550 K.For symmetric interference 3-dB MMI coupler, the power uniformity keeps ideally 0 due to its intrinsic symmetric interference mechanism. With the temperature rising, the excess loss of the both devices increases. The performance deterioration due to temperature variety is more obvious to restricted interference MMI 3-dB coupler, comparing with that of symmetric interference MMI 3-dB coupler.