Showing papers by "Xinliang Zhang published in 2015"
TL;DR: This work provides a promising solution for on-chip passive nonreciprocal device with the advantages of simple structure, low power consumption and large operating bandwidth.
Abstract: We propose an all-optical integrated nonreciprocal device on the optomechanical platform with a large nonreciprocal bandwidth and low operating power. The device is based on an asymmetric silicon coupler consisting of two branches. One of them is a conventional strip waveguide fixed on the substrate and the other is a freestanding nanostring suspended above a groove in the substrate. When light is launched into the coupler, the optical gradient force between the freestanding nanostring and the underlying substrate leads to the deflection of the nanostring and finally results in destruction of the initial phase-matching condition between the two branches. The suspended branch would achieve distinct deflections when light is incident from different ports. The simulation results show a nonreciprocal bandwidth of 13.1 nm with operating power of 390 μW. With the advantages of simple structure, low power consumption and large operating bandwidth, our work provides a promising solution for on-chip passive nonreciprocal device.
57 citations
TL;DR: This study experimentally demonstrate a feasible integrated scheme to solve first-order linear ordinary differential equation with constant-coefficient tunable based on a single silicon microring resonator with impact of the chirp and pulse-width of input signals on the computing deviation.
Abstract: Photonic integrated circuits for photonic computing open up the possibility for the realization of ultrahigh-speed and ultra wide-band signal processing with compact size and low power consumption. Differential equations model and govern fundamental physical phenomena and engineering systems in virtually any field of science and engineering, such as temperature diffusion processes, physical problems of motion subject to acceleration inputs and frictional forces, and the response of different resistor-capacitor circuits, etc. In this study, we experimentally demonstrate a feasible integrated scheme to solve first-order linear ordinary differential equation with constant-coefficient tunable based on a single silicon microring resonator. Besides, we analyze the impact of the chirp and pulse-width of input signals on the computing deviation. This device can be compatible with the electronic technology (typically complementary metal-oxide semiconductor technology), which may motivate the development of integrated photonic circuits for optical computing.
53 citations
TL;DR: A wavelength-division-multiplexing (WDM) compatible and multi-functional mode-division (MDM) integrated circuit, which can perform the mode conversion and multiplexing for the incoming multipath WDM signals, avoiding the wavelength conflict is proposed.
Abstract: We propose and fabricate a wavelength-division-multiplexing (WDM) compatible and multi-functional mode-division-multiplexing (MDM) integrated circuit, which can perform the mode conversion and multiplexing for the incoming multipath WDM signals, avoiding the wavelength conflict. An phase-to-intensity demodulation function can be optionally applied within the circuit while performing the mode multiplexing. For demonstration, 4 × 10 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) signals are successfully processed, with open and clear eye diagrams. Measured bit error ratio (BER) results show less than 1 dB receive sensitivity variation for three modes and four wavelengths with demodulation. In the case without demodulation, the average power penalties at 4 wavelengths are -1.5, -3 and -3.5 dB for TE₀-TE₀, TE₀-TE₁ and TE₀-TE₂ mode conversions, respectively. The proposed flexible scheme can be used at the interface of long-haul and on-chip communication systems.
41 citations
TL;DR: The proposed 2D GC is designed and demonstrated based on the silicon-on-insulator (SOI) platform using subwavelength cylinders, realizing a fabrication simplification without performance degradation.
Abstract: We design and demonstrate a single step etched two dimensional grating coupler (2D GC) based on the silicon-on-insulator (SOI) platform using subwavelength cylinders. Taking the lag effect into consideration, the 2D GC is manufactured in the same lithography and etching processes with the strip waveguide. The measured coupling loss of the proposed 2D GC is -6.0 dB, which is comparable with conventional shallowly etched 2D GC, realizing a fabrication simplification without performance degradation.
37 citations
TL;DR: A feasible integrated scheme is demonstrated which can simultaneously function as first-order optical differentiation and optical Hilbert transformation based on a single microdisk resonator and may motivate the development of integrated optical signal processors.
Abstract: Optical differentiation and optical Hilbert transformation play important roles in communications, computing, information processing and signal analysis in optical domain offering huge bandwidth. Meanwhile, silicon-based photonic integrated circuit is one of the most promising candidates for all-optical signal processing due to its intrinsic advantages of low power consumption, compact footprint, ultra-high speed and compatibility with electronic integrated circuits. In this study, we analyze the interrelation between first-order optical differentiation and optical Hilbert transformation and then experimentally demonstrate a feasible integrated scheme which can simultaneously function as first-order optical differentiation and optical Hilbert transformation based on a single microdisk resonator. This finding may motivate the development of integrated optical signal processors.
37 citations
TL;DR: A bottom Si grating reflector with comparable reflectivity is utilized to improve the coupling efficiency and can be easily fabricated by single step of patterning and etching, simplifying the fabrication processes.
Abstract: We theoretically propose a silicon nitride (Si3N4) grating coupler (GC) with both ultrahigh efficiency and simplified fabrication processes. Instead of using a bottom distributed Bragg reflector (DBR) or metal reflector, a bottom Si grating reflector (GR) with comparable reflectivity is utilized to improve the coupling efficiency. The fully etched Si GR is designed based on an industrially standard silicon-on-insulator (SOI) wafer with 220 nm top Si layer. By properly adjusting the trench width and period length of the Si GR, a high reflectivity over 90% is obtained. The Si3N4 GC is optimized based on a common 400 nm Si3N4 layer sitting on the Si GR with a SiO2 separation layer. With an appropriate distance between the Si3N4 GC and bottom Si GR, a low coupling loss of −1.47 dB is theoretically obtained using uniform GC structure. A further record ultralow loss of −0.88 dB is predicted by apodizing the Si3N4 GC. The specific fabrication processes and tolerance are also investigated. Compared with DBR, the bottom Si GR can be easily fabricated by single step of patterning and etching, simplifying the fabrication processes.
34 citations
TL;DR: This work proposes and demonstrates an optical arbitrary waveform generator and high-order photonic differentiator based on a four-tap finite impulse response (FIR) silicon-on-insulator (SOI) on-chip circuit that can switch the differentiator patterns from first- to third-order freely.
Abstract: We propose and demonstrate an optical arbitrary waveform generator and high-order photonic differentiator based on a four-tap finite impulse response (FIR) silicon-on-insulator (SOI) on-chip circuit. Based on amplitude and phase modulation of each tap controlled by thermal heaters, we obtain several typical waveforms such as triangular waveform, sawtooth waveform, square waveform and Gaussian waveform, etc., assisted by an optical frequency comb injection. Unlike other proposed schemes, our scheme does not require a spectral disperser which is difficult to fabricate on chip with high resolution. In addition, we demonstrate first-, second- and third-order differentiators based on the optical pulse shaper. Our scheme can switch the differentiator patterns from first- to third-order freely. In addition, our scheme has distinct advantages of compactness, capability for integration with electronics.
32 citations
TL;DR: By combining two independent resonant wavelengths of two MRRs and adjusting their powers in a certain order, all-optical 4-bit Gray code generation has been successfully demonstrated and the proposed integrated device is competent in on-chip all- optical communication and optical interconnection systems with significant advantages.
Abstract: We propose and experimentally demonstrate a 4-port passive encoder for 4-bit Gray code on pure silicon platform. The operation principle for this device is the thermo-optic (TO) effect in silicon microring resonator (MRR) whose transmission spectrum could be shifted by injecting strong light power. Therefore, the output powers of both the through-port and drop-port of the MRR could be controllable and switchable. Two threshold powers are defined to decide the port output code of bit “0” or “1”. By combining two independent resonant wavelengths of two MRRs and adjusting their powers in a certain order, all-optical 4-bit Gray code generation has been successfully demonstrated. The proposed integrated device is competent in on-chip all-optical communication and optical interconnection systems with significant advantages, such as simple operation, compact size, economical fabrication process and great scalability.
28 citations
TL;DR: The proposed PDM phase-modulated PR scheme based on the vector dual-pump nondegenerate phase sensitive amplification (PSA) can be useful and promising in current PDM based coherent fiber-optic communication.
Abstract: The polarization-division multiplexing (PDM) technology is a practical method to double the transmission capacity, and the corresponding phase regeneration (PR) for PDM signals is meaningful and necessary to extend the transmission distance and increase the transparency for the phase-encoded PDM system. Those reported PDM PR schemes either utilized polarization-diversity technique or required special PDM format. In order to overcome these issues, the PR for the PDM phase-modulated signals is proposed and theoretically demonstrated in this paper, based on the vector dual-pump nondegenerate phase sensitive amplification (PSA). The theoretical model is established and the detailed characteristics are investigated to optimize the PR performance. Results show an obvious phase squeezing for the degraded 80 Gbit/s PDM differential phase-shift keying (DPSK) signals, and the error vector magnitude (EVM) of the regenerated signals on dual polarization states can be improved from 22.58% and 21.39% to 4.57% and 4.63%, respectively. Furthermore, the applicability of the proposed scheme for PDM quaternary-phase shift keying (QPSK) signals is investigated. The proposed scheme can be useful and promising in current PDM based coherent fiber-optic communication.
22 citations
TL;DR: An ultrahigh speed germanium photodetector is demonstrated by introducing gold wires into the discrete ground electrodes with standard wire bonding technology and the bandwidth can be effectively extended from less than 30 GHz to over 60 GHz.
Abstract: We demonstrate an ultrahigh speed germanium photodetector by introducing gold wires into the discrete ground electrodes with standard wire bonding technology. To engineer the parasitic parameter, the physical dimension of the gold wire used for wire bonding is specially designed with an inductance of about 450 pH. Simulation and experimental results show that the bandwidth of the photodetector can be effectively extended from less than 30 GHz to over 60 GHz.
22 citations
TL;DR: In this article, a specific plasmonic vortex lens (PVL) structure was proposed to focus the surface plasmor polariton wave on an arbitrary spatial position. But, the structure of the PVL can focus the input beam into a zeroth-order Bessel beam with a central peak.
Abstract: A plasmonic vortex lens (PVL), which enables to focus the spin or orbital angular momentum to a specific spatial position in the form of a plasmonic vortex, has been widely studied Here, we present a specific PVL structure to focus the surface plasmon polariton wave on an arbitrary spatial position Both analytical and numerical analyses are presented The plasmonic field of our PVL is an approximate Bessel beam In particular, the PVL can focus the input beam into a zeroth-order Bessel beam with a central peak Based on this principle, multiple focuses by combining multiple different PVLs are designed We can freely control the focuses just by changing the input modes Owing to the tuning ability of the focuses, these findings can motivate the applications for optical trapping, optical data, and digital display on chip
TL;DR: The FP-SOAs based all-optical differential-equation solvers can be easily integrated with other optical components based on InP/InGaAsP materials, such as laser, modulator, photodetector and waveguide, which can motivate the realization of the complicated optical computing on a single integrated chip.
Abstract: We experimentally demonstrate an all-optical temporal computation scheme for solving 1st- and 2nd-order linear ordinary differential equations (ODEs) with tunable constant coefficients by using Fabry-Perot semiconductor optical amplifiers (FP-SOAs). By changing the injection currents of FP-SOAs, the constant coefficients of the differential equations are practically tuned. A quite large constant coefficient tunable range from 0.0026/ps to 0.085/ps is achieved for the 1st-order differential equation. Moreover, the constant coefficient p of the 2nd-order ODE solver can be continuously tuned from 0.0216/ps to 0.158/ps, correspondingly with the constant coefficient q varying from 0.0000494/ps2 to 0.006205/ps2. Additionally, a theoretical model that combining the carrier density rate equation of the semiconductor optical amplifier (SOA) with the transfer function of the Fabry-Perot (FP) cavity is exploited to analyze the solving processes. For both 1st- and 2nd-order solvers, excellent agreements between the numerical simulations and the experimental results are obtained. The FP-SOAs based all-optical differential-equation solvers can be easily integrated with other optical components based on InP/InGaAsP materials, such as laser, modulator, photodetector and waveguide, which can motivate the realization of the complicated optical computing on a single integrated chip.
TL;DR: In this paper, a feasible integrated scheme based on a single all-passive micro-ring resonator is proposed to realize the optical power limitation which has a similar function of current limiting circuit in electronics.
Abstract: Recent progress in silicon nanophotonics has dramatically advanced the possible realization of large-scale on-chip optical interconnects integration. Adopting photons as information carriers can break the performance bottleneck of electronic integrated circuit such as serious thermal losses and poor process rates. However, in integrated photonics circuits, few reported work can impose an upper limit of optical power therefore prevent the optical device from harm caused by high power. In this study, we experimentally demonstrate a feasible integrated scheme based on a single all-passive micro-ring resonator to realize the optical power limitation which has a similar function of current limiting circuit in electronics. Besides, we analyze the performance of optical power limiter at various signal bit rates. The results show that the proposed device can limit the signal power effectively at a bit rate up to 20 Gbit/s without deteriorating the signal. Meanwhile, this ultra-compact silicon device can be completely compatible with the electronic technology (typically complementary metal-oxide semiconductor technology), which may pave the way of very large scale integrated photonic circuits for all-optical information processors and artificial intelligence systems.
TL;DR: The results show that the proposed scheme has a 10-dB nonreciprocal transmission bandwidth (NTB) as large as about 66 nm corresponding to 80-mW operating power, which indicates over two orders of magnitude enhancement compared to previous on-chip passive schemes.
Abstract: On-chip broadband optical nonreciprocal transmission based on asymmetric hybrid slot waveguide (HSW) coupler is proposed. Filled with flint glass LaSF-010 and organic material DDMEBT in slots, respectively, two branches of an asymmetric HSW coupler have very distinct nonlinear coefficients, yet very close effective indexes. Since asymmetric coupler with low linear mismatch has a large free spectral range, the results show that our device has a 10-dB nonreciprocal transmission bandwidth (NTB) as large as about 66 nm corresponding to 80-mW operating power. The NTB could be even larger when the incident power is raised. This indicates over two orders of magnitude enhancement compared to previous on-chip passive schemes. Owing to the large NTB, the device also functions properly for sub-picosecond pulses. Our scheme paves a path toward practical all-optical nonreciprocal applications.
TL;DR: In this paper, the optical phase erasure and wavelength conversion based on the nontransparency four-wave mixing simultaneously using the integrated silicon waveguide with reverse biased PIN junction was demonstrated, and the phase information of the phase-shift keying signal at 10 Gb/s was erased.
Abstract: We demonstrate the optical phase erasure and wavelength conversion based on the nontransparency four-wave mixing simultaneously using the integrated silicon waveguide with reverse biased PIN junction. By optimizing the design of the waveguide, a conversion efficiency of $-$ 12 dB can be achieved with 3-dB conversion bandwidth of 15 nm. For demonstration, the phase information of the phase-shift keying signal at 10 Gb/s is erased. The simulated and measured constellations and eye diagrams validate the successful operation.
TL;DR: For the first time, it is experimentally demonstrated that the lower limitation of the operation bandwidth does exist and differentiators with different bandwidths have significantly different acceptable pulse width range of input signals, which is consistent to the theoretical prediction.
Abstract: We theoretically investigate the operation bandwidth limitation of the photonic differentiator including the upper limitation, which is restrained by the device operation bandwidth and the lower limitation, which is restrained by the energy efficiency (EE) and detecting noise level Taking the silicon photonic crystal L3 nano-cavity (PCN) as an example, for the first time, we experimentally demonstrate that the lower limitation of the operation bandwidth does exist and differentiators with different bandwidths have significantly different acceptable pulse width range of input signals, which are consistent to the theoretical prediction Furthermore, we put forward a novel photonic differentiator scheme employing cascaded PCNs with different Q factors, which is likely to expand the operation bandwidth range of photonic differentiator dramatically
TL;DR: In this paper, all-optical canonical logic units at 40Gb/s using bidirectional four-wave mixing (FWM) in highly nonlinear fiber are proposed and experimentally demonstrated.
Abstract: All-optical canonical logic units at 40 Gb/s using bidirectional four-wave mixing (FWM) in highly nonlinear fiber are proposed and experimentally demonstrated. Clear temporal waveforms and correct pattern streams are successfully observed in the experiment. This scheme can reduce the amount of nonlinear devices and enlarge the computing capacity compared with general ones. The numerical simulations are made to analyze the relationship between the FWM efficiency and the position of two interactional signals.
TL;DR: In this article, the characteristics of dual-pump degenerate phase-sensitive amplification in the SOA were theoretically analyzed and experimentally investigated, providing the absolute possibility of the on-chip all-optical signal processing based on PSA in the optic communication system.
Abstract: The phase-sensitive amplification (PSA) has attracted intensive attention due to its ability to amplify the in-phase component and attenuate the out-of-phase component of an optical signal. This ability leads to several applications in the all-optical signal processing and fiber optic communication, such as the low-noise amplification, the phase regeneration, and so on. The phase-sensitive functionality can be performed with different nonlinear devices, including the high-nonlinear fiber (HNLF), the periodically poled lithium niobate, the semiconductor optical amplifier (SOA), and so on. Most reported schemes are based on the HNLF, while SOA-based PSA research works are rarely reported. In this paper, the characteristics of dual-pump degenerate PSA in the SOA are theoretically analyzed and experimentally investigated. The input power, injection current, and internal loss of the SOA correlated to the PSA are examined. The influence of the involved wavelengths is also considered. Experimental results show good agreement with the numerical calculations. A gain extinction ratio of ∼25 dB is experimentally obtained, providing the absolute possibility of the on-chip all-optical signal processing based on PSA in the optic communication system.
22 Mar 2015
TL;DR: A novel four-port polarization diversity coupler for vertical coupling with an ultralow coupling loss of -4.8dB is experimentally measured with polarization insensitivity.
Abstract: We propose and fabricate a novel four-port polarization diversity coupler for vertical coupling With the help of 45° reflectors and improved 2×1 couplers, an ultralow coupling loss of −48dB is experimentally measured with polarization insensitivity
03 Dec 2015
TL;DR: In this paper, a novel optical sensor based on a one-dimensional photonic crystal slot nanobeam cavity is presented, which possesses an estimated very high sensitivity of 851 nm/RIU.
Abstract: We present a novel optical sensor based on a one-dimensional photonic crystal slot nanobeam cavity. An ultra-high quality factor of 174,000 is obtained. The sensor possesses an estimated very high sensitivity of 851 nm/RIU.
16 Jun 2015
TL;DR: In this article, all-optical canonical logic units (CLUs) were demonstrated at 40 Gb/s using bidirectional FWM in a single highly nonlinear fiber (HNLF).
Abstract: We propose and experimentally demonstrate all-optical canonical logic units (CLUs) at 40 Gb/s using bidirectional FWM in a single highly nonlinear fiber (HNLF). The XOR, XNOR and maxterms are further demonstrated based on these minterms.
19 Nov 2015
TL;DR: In this paper, the optical phase erasure and wavelength conversion of 10 Gb/s phase shift keying signal based on the non-transparency four-wave mixing (FWM) simultaneously using the integrated silicon waveguide with reverse biased PIN junction was demonstrated.
Abstract: We demonstrate the optical phase erasure and wavelength conversion of 10 Gb/s phase shift keying signal based on the non-transparency four-wave-mixing (FWM) simultaneously using the integrated silicon waveguide with reverse biased PIN junction.
10 May 2015
TL;DR: In this article, an efficient polarization beam splitter based on a silica microcapillary is proposed and experimentally demonstrated, which relies on the inherent geometry-induced birefringence.
Abstract: An efficient polarization beam splitter (PBS) based on a silica microcapillary is proposed and experimentally demonstrated. This PBS relies on the inherent-geometry-induced birefringence. A maximum extinction ratio of up to 25 dB is achieved.
10 May 2015
TL;DR: In this article, a specific plasmonic vortex lens (PVL) structure was proposed to focus the surface polariton wave on an arbitrary spatial position, which was used to obtain a better resolution of the image.
Abstract: We present a specific plasmonic vortex lens (PVL) structure to focus the surface plasmon polariton wave on an arbitrary spatial position.
19 Nov 2015
TL;DR: In this paper, a broadband and polarization insensitive 3 dB coupler based on a tapered three-guide structure on the silicon-on-insulator platform is proposed, which has a wide bandwidth (~100nm) for both polarizations and has a large fabrication tolerance.
Abstract: We propose a broadband and polarization insensitive 3 dB coupler based on tapered three-guide structure on the silicon-on-insulator platform. The coupler has a wide bandwidth (~100nm) for both polarizations and has a large fabrication tolerance.
22 Mar 2015
TL;DR: An on-chip polarization insensitive interconnection is proposed and fabricated based on SOI platform and experimentally demonstrated in fiber-optic communication system utilizing wavelength, polarization and mode multiplexing techniques with power penalty of 3.2dB.
Abstract: An on-chip polarization insensitive interconnection is proposed and fabricated based on SOI platform. The proposed circuit is experimentally demonstrated in fiber-optic communication system utilizing wavelength, polarization and mode multiplexing techniques with power penalty of 3.2dB.
10 May 2015
TL;DR: In this paper, the orbital angular momentum (OAM) beam is incident on a 90 degree arc slit, a focus will be generated and have a displacement which is nearly linear with the topological charge of the incoming OAM beam.
Abstract: When the orbital angular momentum (OAM) beam is incident on a 90 degree arc slit, a focus will be generated and have a displacement which is nearly linear with the topological charge of the incoming OAM beam. It can detect the OAM beams with a very simple structure.
10 May 2015
TL;DR: In this article, an on-chip thermal-tuned optical pulse shaper based on the four-path finite impose response (FIR) was demonstrated by tuning the phase and amplitude of each path.
Abstract: We demonstrate an on-chip thermal-tuned optical pulse shaper based on the four-path finite impose response (FIR) Four typical waveform are demonstrated by tuning the phase and amplitude of each path
10 May 2015
TL;DR: An on-chip WDM-compatible mode multiplexing system with function of phase demodulation is demonstrated and can be useful at the interface of long-haul and on- chip communication systems, which prefer phase and intensity modulated formats respectively.
Abstract: We demonstrate an on-chip WDM-compatible mode multiplexing system with function of phase demodulation The proposed scheme can be useful at the interface of long-haul and on-chip communication systems, which prefer phase and intensity modulated formats respectively
17 Dec 2015
TL;DR: In this paper, a simple photonic approach to achieving tunable and reconfigurable bandpass microwave photonic filters (MPFs) based on cascaded microring resonators (CMRRs) was proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate a simple photonic approach to achieving tunable and reconfigurable bandpass microwave photonic filters (MPFs) based on cascaded microring resonators (CMRRs). The optical spectrum of the silicon CMRRs could offer two bandpass responses to separately filter the optical carrier and one of the sidebands generated by the phase modulation. Thus we could achieve a bandpass MPF. Moreover, as the central frequencies and bandwidths of the two bandpass responses can be tuned by simply adjusting the voltages applied on one MRR, tunable and reconfigurable MPFs could be successfully achieved. A proof-of-concept experiment illustrates a central frequency tuning range from 19 GHz to 40 GHz, and a wide bandwidth tuning range from 5.5 GHz to 17.5 GHz.