To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.T...To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.展开更多
The performances of a dual-pump parametric and Raman amplification process and the wavelength conversion in silicon waveguides are investigated. By setting the Raman contribution fraction f to be 0.043 in our analytic...The performances of a dual-pump parametric and Raman amplification process and the wavelength conversion in silicon waveguides are investigated. By setting the Raman contribution fraction f to be 0.043 in our analytical model, the amplification gain of the probe signal can be obtained to be over 10 dB. The pump transfer noise （PTN）, the quantum noise （QN）, and the total noise figure （TNF） are discussed, and the TNF has a constant value of about 4 dB in the gain bandwidth. An idler signal generated during the parametric amplification （PA） process can be used to realize the wavelength conversion in wavelength division multiplexing （WDM） systems. In addition, the pump signal parameters, the generated free carrier lifetime and effective mode area （EMA） of the waveguide are analysed for the optimization of signal gain and noise characteristics.展开更多
An all-optical analog-to-digital converter （ADC） based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integra...An all-optical analog-to-digital converter （ADC） based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift （SSFS） module within a wavelength range of 1550 nm-1580 nm. A dispersion coefficient as high as -19800 ps/（km.nm） with ＋0.5 ps/（km.nm） variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate （MSSR） is 50.45 GSa/s with full width at half maximum （FWHM） variation less than 2.52 ps, along with the 2-bit effective- number-of-bit and Gray code output.展开更多
In this paper, an analytical model to investigate the parametric amplification （PA） and the PA ＋ stimulated Raman scattering （SRS） in silicon waveguides is put forward. When two pump signals are employed, the PA ...In this paper, an analytical model to investigate the parametric amplification （PA） and the PA ＋ stimulated Raman scattering （SRS） in silicon waveguides is put forward. When two pump signals are employed, the PA bandwidth of the probe signal is so large that the Raman contribution has to be considered. When Raman contribution fraction f is set to be 0, only the PA occurs to amplify the probe signal, and when f is set to be 0.043, the PA and the SRS amplify the probe signal at the same time. The signal amplifications of both single and dual pump schemes are investigated by using this model. With this model, three main affecting factors, i.e., zero dispersion wavelength （ZDWL）, third-order dispersion （TOD）, and fourth-order dispersion （FOD）, are discussed in detail.展开更多
A quasi-two-dimensional layer of MoS2 was placed on top of a silicon optical waveguide to form a MoS2–silicon hybrid structure. Chirped pulse self-phase modulation measurements were carried out to determine the optic...A quasi-two-dimensional layer of MoS2 was placed on top of a silicon optical waveguide to form a MoS2–silicon hybrid structure. Chirped pulse self-phase modulation measurements were carried out to determine the optica Kerr nonlinearity of the structure. The observed increase in the spectral broadening of the optical pulses in the MoS2–silicon waveguide compared with the silicon waveguides indicated that the third-order nonlinear effect in MoS2 is about 2 orders of magnitude larger than that in silicon. The measurements show that MoS2 has an effective optical Kerr coefficient of about 1.1 × 10-16m2∕W. This work reveals the potential application of MoS2 to enhance the nonlinearity of hybrid silicon optical devices.展开更多
All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit/s polarization multiplexing(Pol-MUX) non-return-to-zero quadrature phase-shift keying(QPSK) signal to Pol-MUX binary...All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit/s polarization multiplexing(Pol-MUX) non-return-to-zero quadrature phase-shift keying(QPSK) signal to Pol-MUX binary phase-shift keying(BPSK) signals by using phase-doubled four-wave mixing effects with two polarization-angled pumps in a silicon waveguide. The eye diagrams and constellation diagrams of the original QPSK sequences and the converted BPSK sequences of each channel are clearly observed on the two polarization states. Moreover,the bit error rates(BERs) of the two converted idlers are measured. The power penalties of all these converted BPSK sequences on both X and Y polarization states are less than 3.4 dB at a BER of 3.8 × 10^(-3).展开更多
A polarization-diversity loop with a silicon waveguide with a lateral p-i-n diode as a nonlinear medium is used to realize polarization insensitive four-wave mixing. Wavelength conversion of seven dual-polarization 16...A polarization-diversity loop with a silicon waveguide with a lateral p-i-n diode as a nonlinear medium is used to realize polarization insensitive four-wave mixing. Wavelength conversion of seven dual-polarization 16-quadrature amplitude modulation(QAM) signals at 16 GBd is demonstrated with an optical signal-to-noise ratio penalty below 0.7 dB. High-quality converted signals are generated thanks to the low polarization dependence(≤0.5 dB) and the high conversion efficiency(CE) achievable. The strong Kerr nonlinearity in silicon and the decrease of detrimental free-carrier absorption due to the reverse-biased p-i-n diode are key in ensuring high CE levels.展开更多
The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated. The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absor...The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated. The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absorption.Experimental results show that the photocurrent is enhanced by the avalanche effect.A pin silicon waveguide with an intrinsic region width of 3.4μm and a length of 2000μm achieves a responsivity of 4.6 mA/W and an avalanche multiplication factor of about five.展开更多
A novel design of a two-channel optical add-drop multiplexer based on a self-rolled-up microtube （SRM） is presented. This design consists of an SRM that has a parabolic lobe-like pattern along the tube＇s axial dire...A novel design of a two-channel optical add-drop multiplexer based on a self-rolled-up microtube （SRM） is presented. This design consists of an SRM that has a parabolic lobe-like pattern along the tube＇s axial direction, as well as straight silicon waveguides and a 180° waveguide bend. The vertical configuration of the SRM and waveguides is analyzed by the coupled mode theory for achieving the optinmm gap. In the critical coupling regime, when the device serves as an optical demultiplexer, the minimum insertion loss is 1.94 dB, and the maximunl channel crosstalk is -6.036 dB. Also, as an optical multiplexer, the maximum crosstalk becomes -11.9 dB.展开更多
With progress in fabrication technology, integrated photonics plays an increasingly important role in high-speed optical communications, from monolithic transmitters and receivers for advanced optical modulation forma...With progress in fabrication technology, integrated photonics plays an increasingly important role in high-speed optical communications, from monolithic transmitters and receivers for advanced optical modulation formats to on-chip subsystems for optical signal processing. We review our recent work on the highly tailorable physical properties of silicon waveguides for communication and signal processing applications, using slot structures. Controllable chromatic dispersion, nonlinearity, and polarization properties of the waveguides are presented, and the enabled wideband wavelength conversion, optical tunable delay, and signal processing of polarization-multiplexing data channels are discussed.展开更多
Changes in refractive index and the corresponding changes in the characteristics of an optical waveguide in enabling propagation of light are the basis for many modern silicon photonic devices. Optical properties of t...Changes in refractive index and the corresponding changes in the characteristics of an optical waveguide in enabling propagation of light are the basis for many modern silicon photonic devices. Optical properties of these active nanoscale waveguides are sensitive to the little changes in geometry, external injection/biasing, and doping profiles, and can be crucial in design and manufacturing processes. This paper brings the active silicon waveguide for complete characterization of various distinctive guiding parameters, including perturbation in real and imaginary refractive index, mode loss, group velocity dispersion, and bending loss, which can be instrumental in developing optimal design specifications for various application-centric active silicon waveguides.展开更多
To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,u...To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,utilizing the reflection of the grating to achieve the electromagnetic-like induced transparency effect at different wavelengths.The high slope characteristics of the EIT-like effect enabled a higher quality factor and sensitivity.The transmission principle of the structure was analyzed using the transmission matrix method,and the transmission spectrum and mode field distribution were simulated using the finite-difference time-domain(FDTD)method,and the device structure parameters were adjusted for optimization.Simulation results show that the proposed structure achieves an EIT-like effect with a quality factor of 59267.5.In the analysis of refractive index sensing characteristics,the structure exhibits a sensitivity of 408.57 nm/RIU and a detection limit of 6.23×10^(-5) RIU.Therefore,the proposed structure achieved both a high quality factor and refractive index sensitivity,demonstrating excellent sensing performance for applications in environmental monitoring,biomedical fields,and other areas with broad market potential.展开更多
Electron beam lithography(EBL) is a key technology in the fabrication of nanoscale silicon optical waveguide. The influence of exposure dose, the main process parameter of EBL, on the structure profile of poly-methyl ...Electron beam lithography(EBL) is a key technology in the fabrication of nanoscale silicon optical waveguide. The influence of exposure dose, the main process parameter of EBL, on the structure profile of poly-methyl methacrylate(PMMA) after development was studied using a silicon on insulator(SOI) wafer with 220 nm top silicon as the substrate. The relationship between exposure dose and structure pattern width after development was analyzed according to the measurement results. The optimum exposure dose of 220 μC/cm^(2) was found to obtain a final structure consistent with the designed mask value through subsequent processes. At the same time, according to the image segmentation curve tracking technology, the contour extraction process of the dose test results was carried out, and the relationship among mask design value, exposure dose and two-dimensional roughness of boundary contour was analyzed, which can provide reference for the subsequent electron beam lithography of the same substrate material.展开更多
We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slo...We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slot size are studied in detail. The results show that the optical field in the slot region with metallic gratings is significantly enhanced compared with the traditional slot waveguide due to the surface plasmon polaritons coupling on metallic gratings. The extraordinary optical confinement is attributed to the low effective dielectric constant of metallic gratings. The effective dielectric constant decreases with the increasing wavelength, and reaches the minimum when the width of the metal gap is about 0.01 times the wavelength.展开更多
By introducing photonic crystals with Dirac point based on valley edge states,we design heterostructure waveguides on the silicon-on-insulator platform,promising waveguides with different widths to operate in the sing...By introducing photonic crystals with Dirac point based on valley edge states,we design heterostructure waveguides on the silicon-on-insulator platform,promising waveguides with different widths to operate in the singlemode state.Benefiting from the unidirectional transmission and backscattering-immunity characteristics enabled by the topological property,there is no scattering loss induced by the mode-mismatch at the transition junction between the waveguides with different widths.Therefore,the valley-locked heterostructure waveguide possesses unique width degrees of freedom.We demonstrate it by designing and fabricating waveguides with expanding,shrinking,and Z-type configurations.Thanks to the free transition between waveguides with different widths,an interesting energy convergency is observed,which is represented from the imaging of the enhanced thirdharmonic generation of the silicon slab.Consequently,these heterostructure waveguides can be more flexibly integrated with existing on-chip devices and have the potential for high-capacity energy transmission,energy concentration,and field enhancement.展开更多
The rapid development of information technology has fueled an ever-increasing demand for ultrafast and ultralow-en-ergy-consumption computing.Existing computing instruments are pre-dominantly electronic processors,whi...The rapid development of information technology has fueled an ever-increasing demand for ultrafast and ultralow-en-ergy-consumption computing.Existing computing instruments are pre-dominantly electronic processors,which use elec-trons as information carriers and possess von Neumann architecture featured by physical separation of storage and pro-cessing.The scaling of computing speed is limited not only by data transfer between memory and processing units,but also by RC delay associated with integrated circuits.Moreover,excessive heating due to Ohmic losses is becoming a severe bottleneck for both speed and power consumption scaling.Using photons as information carriers is a promising alternative.Owing to the weak third-order optical nonlinearity of conventional materials,building integrated photonic com-puting chips under traditional von Neumann architecture has been a challenge.Here,we report a new all-optical comput-ing framework to realize ultrafast and ultralow-energy-consumption all-optical computing based on convolutional neural networks.The device is constructed from cascaded silicon Y-shaped waveguides with side-coupled silicon waveguide segments which we termed“weight modulators”to enable complete phase and amplitude control in each waveguide branch.The generic device concept can be used for equation solving,multifunctional logic operations as well as many other mathematical operations.Multiple computing functions including transcendental equation solvers,multifarious logic gate operators,and half-adders were experimentally demonstrated to validate the all-optical computing performances.The time-of-flight of light through the network structure corresponds to an ultrafast computing time of the order of several picoseconds with an ultralow energy consumption of dozens of femtojoules per bit.Our approach can be further expan-ded to fulfill other complex computing tasks based on non-von Neumann architectures and thus paves a new way for on-chip all-optical computing.展开更多
To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes ...To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes to form an FP cavity and a microring resonator.The two different optical modes generated by the micro-ring resonator were destructively interfered to form a Fano line shape,which improved the system sensitivity while obtaining a higher quality factor and extinction ratio.The transmission principle of the structure was analyzed by the transfer matrix method.The transmission spectrum and mode field distribution of the proposed structure were simulated by the finite difference time domain(FDTD)method,and the key structural parameters affecting the Fano line shape in the device were optimized.The simulation results show that the quality factor of the device reached 22037.1,and the extinction ratio was 23.9 dB.By analyzing the refractive index sensing characteristics,the sensitivity of the structure was 354 nm·RIU−1,and the detection limit of the sensitivity was 2×10−4 RIU.Thus,the proposed compact asymmetric FP cavity slot micro-ring resonator has obvious advantages in sensing applications owing to its excellent performance.展开更多
Microring resonators have been widely used in passive optical devices such as wavelength division multiplexers,differentiators,and integrators.Research on terahertz(THz)components has been accelerated by these photoni...Microring resonators have been widely used in passive optical devices such as wavelength division multiplexers,differentiators,and integrators.Research on terahertz(THz)components has been accelerated by these photonics technologies.Compact and integrated time-domain differentiators that enable low-loss,high-speed THz signal processing are necessary for THz applications.In this study,an on-chip THz temporal differentiator based on all-silicon photonic technology was developed.This device primarily consisted of a microring waveguide resonator and was packaged with standard waveguide compatibility.It performed time-domain differentiation on input signals at a frequency of 405.45 GHz with an insertion loss of 2.5 dB and a working bandwidth of 0.36 GHz.Various periodic waveforms could be handled by this differentiator.This device could work as an edge detector,which detected step-like edges in high-speed input signals through differential effects.This development holds significant promise for future THz data processing technologies and THz communication systems.展开更多
The realization of high responsivity,high sensitivity,fast response,and wide operation band photodetection in silicon photonics is currently a critical challenge for emerging applications such as on-chip optical sensi...The realization of high responsivity,high sensitivity,fast response,and wide operation band photodetection in silicon photonics is currently a critical challenge for emerging applications such as on-chip optical sensing and spectroscopy.In this work,we present a promising solution by integrating a graphene–colloidal-quantum-dot(CQD)heterostructure onto a silicon waveguide platform to construct photodetectors with large photogating gain,without needing complex layered structures.Waveguide integration confines light and CQDs within a compact active region featuring short channel length and absorption length.Leveraging graphene’s low density of states and high mobility,the device simultaneously achieves high-responsivity,high-sensitivity,and high-speed performance.The device achieved a responsivity of 1.1×10^(5) AW^(−1) to 4 AW^(−1) and a noise equivalent power(NEP)of 1.27×10^(−4) to 2.03 pWHz−0.5 when subjected to input optical power ranging from 56 pW to 3μW at 1.55μm.Notably,a substantial bandwidth of 2.7 MHz was reached,outperforming the high-gain counterparts based on the photogating effect.By adjusting the energy band of the graphene–CQD heterostructure,the manipulation of the photogating response is realized,offering valuable insights for further optimization of the high-gain photodetectors.Furthermore,we demonstrate dynamic tuning of the graphene–CQD heterostructure band alignment via an integrated gate electrode,enabling the modulation of the photogating response while elucidating the underlying mechanism.This approach provides a good pathway for performance improvement of similar photogating devices.In the future,this platform can be readily extended to longer wavelengths(e.g.,midinfrared)through straightforward adjustments to CQD synthesis parameters or material composition,complemented by protective-layer passivation for enhanced operational stability.With its compatibility with scalable fabrication processes,this architecture holds significant promise for broadband,high-sensitivity,high-speed,onchip photodetection applications.展开更多
Silicon-based waveguide-integrated photodetectors,leveraging their distinct advantages,have become crucial components in integrated photonic circuits.Despite achieving combined designs of two-dimensional materials and...Silicon-based waveguide-integrated photodetectors,leveraging their distinct advantages,have become crucial components in integrated photonic circuits.Despite achieving combined designs of two-dimensional materials and silicon waveguides,understanding the underlying mechanisms and optimizing structural designs remains challenging.In this study,we systematically investigated the impact of electrode distances on the optical loss and photoelectric response of PdSe_(2)-based strip,rib,and slot waveguide-integrated photodetectors.Optimal electrode distances were determined,leading to significant enhancements in responsivity.Specifically,our devices demonstrated high responsivity values of 9.24 A/W(strip),3.34 A/W(rib),and 4.52 A/W(slot)at 1550 nm.These results represent remarkable enhancements of 481%,237%,and 267%,respectively,compared to the initial unoptimized electrode configurations.Additionally,we found the slot waveguide-integrated photodetector achieves 34%of absorption saturation with PdSe_(2)coverage of approximately 10μm,while the rib waveguide enables 70%absorption(not yet saturated)with PdSe_(2)coverage of 50μm.Furthermore,we explored the effect of input power on the performance of these photodetectors,finding that lower input optical power yields higher responsivity and external quantum efficiency(EQE),especially for slot waveguide-integrated photodetectors.Additionally,these detectors exhibit fast optical response rates across the optical communication O to U bands,with strip,rib and slot waveguide-integrated photodetectors demonstrating 3 dB bandwidths of 23.10,14.49,and 14.86 GHz,respectively.展开更多
基金supported by the Quantum Science and Technology-National Science and Technology Major Project (Grant No.2024ZD0302502 for WZ)the National Natural Science Foundation of China(Grant No.92365210 for WZ)+1 种基金Tsinghua Initiative Scientific Research Program (for WZ)the project of Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies (JIAOT,for YH)。
文摘To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.
基金supported by the State Key Development Program for Basic Research of China (Grant No. 2010CB327605)the Discipline Co-construction Project of Beijing Municipal Commission of Education, China (Grant No. YB20081001301)the Fundamental Research Funds for Central Universities, China (Grant Nos. 2011RC008 and 2009RC0314)
文摘The performances of a dual-pump parametric and Raman amplification process and the wavelength conversion in silicon waveguides are investigated. By setting the Raman contribution fraction f to be 0.043 in our analytical model, the amplification gain of the probe signal can be obtained to be over 10 dB. The pump transfer noise （PTN）, the quantum noise （QN）, and the total noise figure （TNF） are discussed, and the TNF has a constant value of about 4 dB in the gain bandwidth. An idler signal generated during the parametric amplification （PA） process can be used to realize the wavelength conversion in wavelength division multiplexing （WDM） systems. In addition, the pump signal parameters, the generated free carrier lifetime and effective mode area （EMA） of the waveguide are analysed for the optimization of signal gain and noise characteristics.
基金supported by the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-030A1)China Postdoctoral Science Foundation(Grant No.2015M580978)
文摘An all-optical analog-to-digital converter （ADC） based on the nonlinear effect in a silicon waveguide is a promising candidate for overcoming the limitation of electronic devices and is suitable for photonic integration. In this paper, a lumped time-delay compensation scheme with 2-bit quantization resolution is proposed. A strip silicon waveguide is designed and used to compensate for the entire time-delays of the optical pulses after a soliton self-frequency shift （SSFS） module within a wavelength range of 1550 nm-1580 nm. A dispersion coefficient as high as -19800 ps/（km.nm） with ＋0.5 ps/（km.nm） variation is predicted for the strip waveguide. The simulation results show that the maximum supportable sampling rate （MSSR） is 50.45 GSa/s with full width at half maximum （FWHM） variation less than 2.52 ps, along with the 2-bit effective- number-of-bit and Gray code output.
基金Project supported by the National Basic Research Program of China (Grant No. 2010CB327605)the Discipline Co-construction Project of Beijing Municipal Commission of Education, China (Grant No. YB20081001301)the Fundamental Research Funds for Central Universities, China (Grant No. 2011RC008)
文摘In this paper, an analytical model to investigate the parametric amplification （PA） and the PA ＋ stimulated Raman scattering （SRS） in silicon waveguides is put forward. When two pump signals are employed, the PA bandwidth of the probe signal is so large that the Raman contribution has to be considered. When Raman contribution fraction f is set to be 0, only the PA occurs to amplify the probe signal, and when f is set to be 0.043, the PA and the SRS amplify the probe signal at the same time. The signal amplifications of both single and dual pump schemes are investigated by using this model. With this model, three main affecting factors, i.e., zero dispersion wavelength （ZDWL）, third-order dispersion （TOD）, and fourth-order dispersion （FOD）, are discussed in detail.
基金funded by Hong Kong Research Grants Council research project nos. GRF416913, N_CUHK405/12, Ao E/P-02/12, CUHK1/CRF/12G
文摘A quasi-two-dimensional layer of MoS2 was placed on top of a silicon optical waveguide to form a MoS2–silicon hybrid structure. Chirped pulse self-phase modulation measurements were carried out to determine the optica Kerr nonlinearity of the structure. The observed increase in the spectral broadening of the optical pulses in the MoS2–silicon waveguide compared with the silicon waveguides indicated that the third-order nonlinear effect in MoS2 is about 2 orders of magnitude larger than that in silicon. The measurements show that MoS2 has an effective optical Kerr coefficient of about 1.1 × 10-16m2∕W. This work reveals the potential application of MoS2 to enhance the nonlinearity of hybrid silicon optical devices.
基金National Natural Science Foundation of China(NSFC)(61475138,61675177)Specialized Research Fund for the Doctoral Program of Higher Education of China(20130101110089)Natural Science Foundation of Zhejiang Province(LY14F050006)
文摘All-optical two-channel format conversion is proposed and experimentally demonstrated from a 40 Gbit/s polarization multiplexing(Pol-MUX) non-return-to-zero quadrature phase-shift keying(QPSK) signal to Pol-MUX binary phase-shift keying(BPSK) signals by using phase-doubled four-wave mixing effects with two polarization-angled pumps in a silicon waveguide. The eye diagrams and constellation diagrams of the original QPSK sequences and the converted BPSK sequences of each channel are clearly observed on the two polarization states. Moreover,the bit error rates(BERs) of the two converted idlers are measured. The power penalties of all these converted BPSK sequences on both X and Y polarization states are less than 3.4 dB at a BER of 3.8 × 10^(-3).
文摘A polarization-diversity loop with a silicon waveguide with a lateral p-i-n diode as a nonlinear medium is used to realize polarization insensitive four-wave mixing. Wavelength conversion of seven dual-polarization 16-quadrature amplitude modulation(QAM) signals at 16 GBd is demonstrated with an optical signal-to-noise ratio penalty below 0.7 dB. High-quality converted signals are generated thanks to the low polarization dependence(≤0.5 dB) and the high conversion efficiency(CE) achievable. The strong Kerr nonlinearity in silicon and the decrease of detrimental free-carrier absorption due to the reverse-biased p-i-n diode are key in ensuring high CE levels.
基金supported by the Natural Basic Research Program of China(No.2013CB632105)the National Natural Science Foundation of China(No.61177055)
文摘The photocurrent effect in pin silicon waveguides at 1550 nm wavelength is experimentally investigated. The photocurrent is mainly attributed to surface-state absorption,defect-state absorption and/or two-photon absorption.Experimental results show that the photocurrent is enhanced by the avalanche effect.A pin silicon waveguide with an intrinsic region width of 3.4μm and a length of 2000μm achieves a responsivity of 4.6 mA/W and an avalanche multiplication factor of about five.
文摘A novel design of a two-channel optical add-drop multiplexer based on a self-rolled-up microtube （SRM） is presented. This design consists of an SRM that has a parabolic lobe-like pattern along the tube＇s axial direction, as well as straight silicon waveguides and a 180° waveguide bend. The vertical configuration of the SRM and waveguides is analyzed by the coupled mode theory for achieving the optinmm gap. In the critical coupling regime, when the device serves as an optical demultiplexer, the minimum insertion loss is 1.94 dB, and the maximunl channel crosstalk is -6.036 dB. Also, as an optical multiplexer, the maximum crosstalk becomes -11.9 dB.
基金research work sponsored by DARPA (under contract number HR0011-09-C-0124)and HP Laboratories
文摘With progress in fabrication technology, integrated photonics plays an increasingly important role in high-speed optical communications, from monolithic transmitters and receivers for advanced optical modulation formats to on-chip subsystems for optical signal processing. We review our recent work on the highly tailorable physical properties of silicon waveguides for communication and signal processing applications, using slot structures. Controllable chromatic dispersion, nonlinearity, and polarization properties of the waveguides are presented, and the enabled wideband wavelength conversion, optical tunable delay, and signal processing of polarization-multiplexing data channels are discussed.
文摘Changes in refractive index and the corresponding changes in the characteristics of an optical waveguide in enabling propagation of light are the basis for many modern silicon photonic devices. Optical properties of these active nanoscale waveguides are sensitive to the little changes in geometry, external injection/biasing, and doping profiles, and can be crucial in design and manufacturing processes. This paper brings the active silicon waveguide for complete characterization of various distinctive guiding parameters, including perturbation in real and imaginary refractive index, mode loss, group velocity dispersion, and bending loss, which can be instrumental in developing optimal design specifications for various application-centric active silicon waveguides.
基金supported by Natural Science Foundation of Gansu Province(NO.21JR7RA289)。
文摘To enhance the quality factor and sensitivity of refractive index sensors,a feedback waveguide slot grating micro-ring resonator was proposed.An air-hole grating structure was introduced based on the slot micro-ring,utilizing the reflection of the grating to achieve the electromagnetic-like induced transparency effect at different wavelengths.The high slope characteristics of the EIT-like effect enabled a higher quality factor and sensitivity.The transmission principle of the structure was analyzed using the transmission matrix method,and the transmission spectrum and mode field distribution were simulated using the finite-difference time-domain(FDTD)method,and the device structure parameters were adjusted for optimization.Simulation results show that the proposed structure achieves an EIT-like effect with a quality factor of 59267.5.In the analysis of refractive index sensing characteristics,the structure exhibits a sensitivity of 408.57 nm/RIU and a detection limit of 6.23×10^(-5) RIU.Therefore,the proposed structure achieved both a high quality factor and refractive index sensitivity,demonstrating excellent sensing performance for applications in environmental monitoring,biomedical fields,and other areas with broad market potential.
基金Project(52175445) supported by the National Natural Science Foundation of ChinaProject(ZZYJKT2020-09) supported by the State Key Laboratory of High Performance Complex Manufacturing (Central South University),China+1 种基金Projects(2020JJ4247, 2022JJ30743) supported by the Natural Foundation of Hunan Province,ChinaProject(1053320190337) supported by the Fundamental Research Funds for the Central University,China。
文摘Electron beam lithography(EBL) is a key technology in the fabrication of nanoscale silicon optical waveguide. The influence of exposure dose, the main process parameter of EBL, on the structure profile of poly-methyl methacrylate(PMMA) after development was studied using a silicon on insulator(SOI) wafer with 220 nm top silicon as the substrate. The relationship between exposure dose and structure pattern width after development was analyzed according to the measurement results. The optimum exposure dose of 220 μC/cm^(2) was found to obtain a final structure consistent with the designed mask value through subsequent processes. At the same time, according to the image segmentation curve tracking technology, the contour extraction process of the dose test results was carried out, and the relationship among mask design value, exposure dose and two-dimensional roughness of boundary contour was analyzed, which can provide reference for the subsequent electron beam lithography of the same substrate material.
基金Supported by the Key Grant Project of the Ministry of Education of China under Grant No 313007
文摘We present a silicon slot waveguide with metallic gratings embedded on the silicon surface in the slot region. The dependence of the optical coupling between two silicon wires on the width of the metal gap and the slot size are studied in detail. The results show that the optical field in the slot region with metallic gratings is significantly enhanced compared with the traditional slot waveguide due to the surface plasmon polaritons coupling on metallic gratings. The extraordinary optical confinement is attributed to the low effective dielectric constant of metallic gratings. The effective dielectric constant decreases with the increasing wavelength, and reaches the minimum when the width of the metal gap is about 0.01 times the wavelength.
基金National Key Research and Development Program of China(2022YFA1404800)National Natural Science Foundation of China(62305270,12374359,62375225)+2 种基金Shaanxi Fundamental Science Research Project for Mathematics and Physics(22JSY004,22JSQ039)Xi’an Science and Technology Plan Project(2023JH-ZCGJ-0023)Key R&D Program of Shaanxi Province(2023-JC-YB-502).
文摘By introducing photonic crystals with Dirac point based on valley edge states,we design heterostructure waveguides on the silicon-on-insulator platform,promising waveguides with different widths to operate in the singlemode state.Benefiting from the unidirectional transmission and backscattering-immunity characteristics enabled by the topological property,there is no scattering loss induced by the mode-mismatch at the transition junction between the waveguides with different widths.Therefore,the valley-locked heterostructure waveguide possesses unique width degrees of freedom.We demonstrate it by designing and fabricating waveguides with expanding,shrinking,and Z-type configurations.Thanks to the free transition between waveguides with different widths,an interesting energy convergency is observed,which is represented from the imaging of the enhanced thirdharmonic generation of the silicon slab.Consequently,these heterostructure waveguides can be more flexibly integrated with existing on-chip devices and have the potential for high-capacity energy transmission,energy concentration,and field enhancement.
基金financial supports from the National Key Research and Development Program of China(2018YFB2200403)National Natural Sci-ence Foundation of China(NSFC)(61775003,11734001,91950204,11527901,11604378,91850117).
文摘The rapid development of information technology has fueled an ever-increasing demand for ultrafast and ultralow-en-ergy-consumption computing.Existing computing instruments are pre-dominantly electronic processors,which use elec-trons as information carriers and possess von Neumann architecture featured by physical separation of storage and pro-cessing.The scaling of computing speed is limited not only by data transfer between memory and processing units,but also by RC delay associated with integrated circuits.Moreover,excessive heating due to Ohmic losses is becoming a severe bottleneck for both speed and power consumption scaling.Using photons as information carriers is a promising alternative.Owing to the weak third-order optical nonlinearity of conventional materials,building integrated photonic com-puting chips under traditional von Neumann architecture has been a challenge.Here,we report a new all-optical comput-ing framework to realize ultrafast and ultralow-energy-consumption all-optical computing based on convolutional neural networks.The device is constructed from cascaded silicon Y-shaped waveguides with side-coupled silicon waveguide segments which we termed“weight modulators”to enable complete phase and amplitude control in each waveguide branch.The generic device concept can be used for equation solving,multifunctional logic operations as well as many other mathematical operations.Multiple computing functions including transcendental equation solvers,multifarious logic gate operators,and half-adders were experimentally demonstrated to validate the all-optical computing performances.The time-of-flight of light through the network structure corresponds to an ultrafast computing time of the order of several picoseconds with an ultralow energy consumption of dozens of femtojoules per bit.Our approach can be further expan-ded to fulfill other complex computing tasks based on non-von Neumann architectures and thus paves a new way for on-chip all-optical computing.
基金supported by Natural Science Foundation of Gansu Province(No.22JR5RA320).
文摘To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes to form an FP cavity and a microring resonator.The two different optical modes generated by the micro-ring resonator were destructively interfered to form a Fano line shape,which improved the system sensitivity while obtaining a higher quality factor and extinction ratio.The transmission principle of the structure was analyzed by the transfer matrix method.The transmission spectrum and mode field distribution of the proposed structure were simulated by the finite difference time domain(FDTD)method,and the key structural parameters affecting the Fano line shape in the device were optimized.The simulation results show that the quality factor of the device reached 22037.1,and the extinction ratio was 23.9 dB.By analyzing the refractive index sensing characteristics,the sensitivity of the structure was 354 nm·RIU−1,and the detection limit of the sensitivity was 2×10−4 RIU.Thus,the proposed compact asymmetric FP cavity slot micro-ring resonator has obvious advantages in sensing applications owing to its excellent performance.
基金support from the Innovation Program for Quantum Science and Technology(No.2021ZD0303401)Fundamental Research Funds for the Central Universities,National Natural Science Foundation of China(Grant Nos.62271245,62227820,62271242,62071214,62004093,12033002,62035014,62288101,and 11227904)+2 种基金National Key R&D Program of China(Grant No.2018YFB1801504)Excellent Youth Natural Science Foundation of Jiangsu Province(Grant No.BK20200060)Priority Academic Program Development of Jiangsu Higher Education Institutions,Key Lab of Optoelectronic Devices and Systems with Extreme Performance,and Jiangsu Key Laboratory of Advanced Techniques for Manipulating Electromagnetic Waves.
文摘Microring resonators have been widely used in passive optical devices such as wavelength division multiplexers,differentiators,and integrators.Research on terahertz(THz)components has been accelerated by these photonics technologies.Compact and integrated time-domain differentiators that enable low-loss,high-speed THz signal processing are necessary for THz applications.In this study,an on-chip THz temporal differentiator based on all-silicon photonic technology was developed.This device primarily consisted of a microring waveguide resonator and was packaged with standard waveguide compatibility.It performed time-domain differentiation on input signals at a frequency of 405.45 GHz with an insertion loss of 2.5 dB and a working bandwidth of 0.36 GHz.Various periodic waveforms could be handled by this differentiator.This device could work as an edge detector,which detected step-like edges in high-speed input signals through differential effects.This development holds significant promise for future THz data processing technologies and THz communication systems.
基金National Key Research and Development Program of China(2022YFA1204900,2024YFA1211200)National Ten Thousand Talent Program(Young Talents)+4 种基金National Natural Science Foundation of China(62475233,U24A20510,62374068)Natural Science Foundation of Zhejiang Province(LR22F050001,LD22F040004,LY23F040005)Innovation Project of Optics Valley Laboratory(OVL2023ZD002)State Key Laboratory of Pulsed Power Laser Technology(SKL2023KF02)Major Program(JD)of Hubei Province(2023BAA017).
文摘The realization of high responsivity,high sensitivity,fast response,and wide operation band photodetection in silicon photonics is currently a critical challenge for emerging applications such as on-chip optical sensing and spectroscopy.In this work,we present a promising solution by integrating a graphene–colloidal-quantum-dot(CQD)heterostructure onto a silicon waveguide platform to construct photodetectors with large photogating gain,without needing complex layered structures.Waveguide integration confines light and CQDs within a compact active region featuring short channel length and absorption length.Leveraging graphene’s low density of states and high mobility,the device simultaneously achieves high-responsivity,high-sensitivity,and high-speed performance.The device achieved a responsivity of 1.1×10^(5) AW^(−1) to 4 AW^(−1) and a noise equivalent power(NEP)of 1.27×10^(−4) to 2.03 pWHz−0.5 when subjected to input optical power ranging from 56 pW to 3μW at 1.55μm.Notably,a substantial bandwidth of 2.7 MHz was reached,outperforming the high-gain counterparts based on the photogating effect.By adjusting the energy band of the graphene–CQD heterostructure,the manipulation of the photogating response is realized,offering valuable insights for further optimization of the high-gain photodetectors.Furthermore,we demonstrate dynamic tuning of the graphene–CQD heterostructure band alignment via an integrated gate electrode,enabling the modulation of the photogating response while elucidating the underlying mechanism.This approach provides a good pathway for performance improvement of similar photogating devices.In the future,this platform can be readily extended to longer wavelengths(e.g.,midinfrared)through straightforward adjustments to CQD synthesis parameters or material composition,complemented by protective-layer passivation for enhanced operational stability.With its compatibility with scalable fabrication processes,this architecture holds significant promise for broadband,high-sensitivity,high-speed,onchip photodetection applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.61905035,62371095,62074029)the National Key Research and Development Program of China(Grant No.2022YFB3206100)the Natural Science Foundation of Sichuan Province(Grant Nos.2022NSFSC0652,2022JDTD0020)。
文摘Silicon-based waveguide-integrated photodetectors,leveraging their distinct advantages,have become crucial components in integrated photonic circuits.Despite achieving combined designs of two-dimensional materials and silicon waveguides,understanding the underlying mechanisms and optimizing structural designs remains challenging.In this study,we systematically investigated the impact of electrode distances on the optical loss and photoelectric response of PdSe_(2)-based strip,rib,and slot waveguide-integrated photodetectors.Optimal electrode distances were determined,leading to significant enhancements in responsivity.Specifically,our devices demonstrated high responsivity values of 9.24 A/W(strip),3.34 A/W(rib),and 4.52 A/W(slot)at 1550 nm.These results represent remarkable enhancements of 481%,237%,and 267%,respectively,compared to the initial unoptimized electrode configurations.Additionally,we found the slot waveguide-integrated photodetector achieves 34%of absorption saturation with PdSe_(2)coverage of approximately 10μm,while the rib waveguide enables 70%absorption(not yet saturated)with PdSe_(2)coverage of 50μm.Furthermore,we explored the effect of input power on the performance of these photodetectors,finding that lower input optical power yields higher responsivity and external quantum efficiency(EQE),especially for slot waveguide-integrated photodetectors.Additionally,these detectors exhibit fast optical response rates across the optical communication O to U bands,with strip,rib and slot waveguide-integrated photodetectors demonstrating 3 dB bandwidths of 23.10,14.49,and 14.86 GHz,respectively.
