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
We propose a terahertz(THz)vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges.Addressing the challenge of double circular polarization superposit...We propose a terahertz(THz)vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges.Addressing the challenge of double circular polarization superposition resulting from the high refractive index contrast,we regulate the transverse spin state through a newly designed second-order grating partially etched on the waveguide’s top side.The reflected wave can be received directly by a linearly polarized antenna,simplifying the process.Benefiting from the tuning feature,a joint detection method involving positive and negative topological charges identifies and detects rotational Doppler effects amid robust micro-Doppler interference signals.This emitter can be used for the rotational velocity measurement of an on-axis spinning object,achieving an impressive maximum speed error rate of∼2%.This approach holds promise for the future development of THz vortex beam applications in radar target detection and countermeasure systems,given its low cost and potential for mass production.展开更多
Achromatic focusing is essential for broadband operation, which has recently been realised from visible to infrared wavelengths using a metasurface. Similarly, multi-terahertz functional devices can be encoded in a de...Achromatic focusing is essential for broadband operation, which has recently been realised from visible to infrared wavelengths using a metasurface. Similarly, multi-terahertz functional devices can be encoded in a desired metasurface phase profile. However, metalenses suffer from larger chromatic aberrations because of the intrinsic dispersion of each unit element. Here, we propose an achromatic metalens with C-shaped unit elements working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the centre frequency. The designed metalens possesses a high working efficiency of more than 68% at the peak and a relatively high numerical aperture of 0.385. We further demonstrate the robustness of our Cshaped metalens, considering lateral shape deformations and deviations in the etching depth. Our metalens design opens an avenue for future applications of terahertz meta-devices in spectroscopy, time-offlight tomography and hyperspectral imaging systems.展开更多
We explore all-optical wavelength conversion in a microdisk resonator integrated with interleaved p-n junctions.Numerical simulation based on temporal coupled mode theory is performed to study the free-carrier dynamic...We explore all-optical wavelength conversion in a microdisk resonator integrated with interleaved p-n junctions.Numerical simulation based on temporal coupled mode theory is performed to study the free-carrier dynamics inside the cavity.It reveals that the detuning of pump and probe frequencies and the carrier lifetime have a significant effect on the device performance.Experimental result confirms that the conversion speed can be considerably improved by applying a reverse bias on the p-n junctions.Wavelength conversion at 10 Gb/s data rate is achieved with a pump power of 5.41 dBm and a bias voltage of-6 V.展开更多
The control of spin electromagnetic(EM)waves is of great significance in optical communications.Although geometric metasurfaces have shown unprecedented capability to manipulate the wavefronts of spin EM waves,it is s...The control of spin electromagnetic(EM)waves is of great significance in optical communications.Although geometric metasurfaces have shown unprecedented capability to manipulate the wavefronts of spin EM waves,it is still challenging to independently manipulate each spin state and intensity distribution,which inevitably degrades metasurface-based devices for further applications.Here we propose and experimentally demonstrate an approach to designing spin-decoupled metalenses based on pure geometric phase,i.e.,geometric metasurfaces with predesigned phase modulation possessing functionalities of both convex lenses and concave lenses.Under the illumination of left-/right-handed circularly polarized(LCP or RCP)terahertz(THz)waves,these metalenses can generate transversely/longitudinally distributed RCP/LCP multiple focal points.Since the helicity-dependent multiple focal points are locked to the polarization state of incident THz waves,the relative intensity between two orthogonal components can be controlled with different weights of LCP and RCP THz waves,leading to the intensity-tunable functionality.This robust approach for simultaneously manipulating orthogonal spin states and energy distributions of spin EM waves will open a new avenue for designing multifunctional devices and integrated communication systems.展开更多
Asymmetric transmission,defined as the difference between the forward and backward transmission,enables a plethora of applications for on-chip integration and telecommunications.However,the traditional method for asym...Asymmetric transmission,defined as the difference between the forward and backward transmission,enables a plethora of applications for on-chip integration and telecommunications.However,the traditional method for asymmetric transmission is to control the propagation direction of the waves,hindering further applications.Metasurfaces,a kind of two-dimensional metamaterials,have shown an unprecedented ability to manipulate the propagation direction,phase,and polarization of electromagnetic waves.Here we propose and experimentally demonstrate a metasurface-based directional device consisting of a geometric metasurface with spatially rotated microrods and metallic gratings,which can simultaneously control the phase,polarization,and propagation direction of waves,resulting in asymmetric focusing in the terahertz region.These dual-layered metasurfaces for asymmetric focusing can work in a wide bandwidth ranging from 0.6 to 1.1 THz.The flexible and robust approach for designing broadband asymmetric focusing may open a new avenue for compact devices with potential applications in encryption,information processing,and communication.展开更多
Terahertz(THz)science and technology have attracted significant attention based on their unique applications in non-destructive imaging,communications,spectroscopic detection,and sensing.However,traditional THz device...Terahertz(THz)science and technology have attracted significant attention based on their unique applications in non-destructive imaging,communications,spectroscopic detection,and sensing.However,traditional THz devices must be sufficiently thick to realise the desired wave-manipulating functions,which has hindered the development of THz integrated systems and applications.Metasurfaces,which are two-dimensional metamaterials consisting of predesigned meta-atoms,can accurately tailor the amplitudes,phases,and polarisations of electromagnetic waves at subwavelength resolutions,meaning they can provide a flexible platform for designing ultra-compact and high-performance THz components.This review focuses on recent advancements in metasurfaces for the wavefront manipulation of THz waves,including the planar metalens,holograms,arbitrary polarisation control,special beam generation,and active metasurface devices.Such ultra-compact devices with unique functionality make metasurface devices very attractive for applications such as imaging,encryption,information modulation,and THz communications.This progress report aims to highlight some novel approaches for designing ultra-compact THz devices and broaden the applications of metasurfaces in THz science.展开更多
Low-loss dielectric terahertz(THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wav...Low-loss dielectric terahertz(THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wave from the metal waveguide to the dielectric waveguide. However, out-of-plane couplers are more suitable for wafer-scale testing and tolerant of alignment variation. In this work, we propose an out-of-plane THz coupler for coupling the antenna to the dielectric waveguide. The device is constructed using a grating and a compact spot-size converter. As the conventional optical spot-size converters that apply directly to THz chips are too large, we have designed a compact spot-size converter based on a tapered waveguide with a lens. The total device is 2.9 cm long and can couple a 7 mm diameter THz beam to a 500 μm wide waveguide. The device can scan the THz beam, radiate the input rectangular waveguide mode to free space, and drive the rotation angle of the fan beam through the scanning frequency. We fabricated the device using a single lithography step on a silicon wafer.The out-of-plane coupling efficiency was found to be ~5 d B at 194 GHz. The fan-beam steering range was found to be around40° in the frequency range of 170–220 GHz. The proposed out-of-plane coupling technique may provide an effective way for THz wafer-scale testing with a higher degree of freedom for on-chip integration. Also, the proposed technique being nonmechanical, beam steering using it, may therefore find applications in THz radar, communication, and sensing.展开更多
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supported in part by the National Natural Science Foundation of China(62275155,61988102,62271320).
文摘We propose a terahertz(THz)vortex emitter that utilizes a high-resistance silicon resonator to generate vortex beams with various topological charges.Addressing the challenge of double circular polarization superposition resulting from the high refractive index contrast,we regulate the transverse spin state through a newly designed second-order grating partially etched on the waveguide’s top side.The reflected wave can be received directly by a linearly polarized antenna,simplifying the process.Benefiting from the tuning feature,a joint detection method involving positive and negative topological charges identifies and detects rotational Doppler effects amid robust micro-Doppler interference signals.This emitter can be used for the rotational velocity measurement of an on-axis spinning object,achieving an impressive maximum speed error rate of∼2%.This approach holds promise for the future development of THz vortex beam applications in radar target detection and countermeasure systems,given its low cost and potential for mass production.
基金supported in part by the National Natural Science Foundation of China(11874266,11604208,61705131,and 81701745)Shanghai Science and Technology Committee of China(16ZR1445600 and 16ZR1445500)+2 种基金Chen Guang Program of China(17CG49)S.W.and T.L.thank the support from National Key R&D Program of China(2017YFA0303700,2016YFA0202103)the National Natural Science Foundation of China(11822406,11834007,11674167,11621091,11774164,and 91850204)
文摘Achromatic focusing is essential for broadband operation, which has recently been realised from visible to infrared wavelengths using a metasurface. Similarly, multi-terahertz functional devices can be encoded in a desired metasurface phase profile. However, metalenses suffer from larger chromatic aberrations because of the intrinsic dispersion of each unit element. Here, we propose an achromatic metalens with C-shaped unit elements working from 0.3 to 0.8 THz with a bandwidth of approximately 91% over the centre frequency. The designed metalens possesses a high working efficiency of more than 68% at the peak and a relatively high numerical aperture of 0.385. We further demonstrate the robustness of our Cshaped metalens, considering lateral shape deformations and deviations in the etching depth. Our metalens design opens an avenue for future applications of terahertz meta-devices in spectroscopy, time-offlight tomography and hyperspectral imaging systems.
基金supported in part by the National Basic Research Program of China (ID2011CB301700)the National High Technology Research and Development Program of China (2013AA014402)+1 种基金the National Natural Science Foundation of China (61007039, 61001074, 61127016, 61107041)the Science and Technology Commission of Shanghai Municipality (STCSM) Project (12XD1406400)
文摘We explore all-optical wavelength conversion in a microdisk resonator integrated with interleaved p-n junctions.Numerical simulation based on temporal coupled mode theory is performed to study the free-carrier dynamics inside the cavity.It reveals that the detuning of pump and probe frequencies and the carrier lifetime have a significant effect on the device performance.Experimental result confirms that the conversion speed can be considerably improved by applying a reverse bias on the p-n junctions.Wavelength conversion at 10 Gb/s data rate is achieved with a pump power of 5.41 dBm and a bias voltage of-6 V.
基金National Key Research and Development Program of China(2017YFA0701005)National Natural Science Foundation of China(61871268,61722111)+3 种基金Natural Science Foundation of Shanghai(18ZR1425600)“Shuguang”Program of Shanghai Education Commission(19SG44)Key Project Supported by Science and Technology Commission Shanghai Municipality(YDZX20193100004960)Higher Education Discipline Innovation Project(D18014).
文摘The control of spin electromagnetic(EM)waves is of great significance in optical communications.Although geometric metasurfaces have shown unprecedented capability to manipulate the wavefronts of spin EM waves,it is still challenging to independently manipulate each spin state and intensity distribution,which inevitably degrades metasurface-based devices for further applications.Here we propose and experimentally demonstrate an approach to designing spin-decoupled metalenses based on pure geometric phase,i.e.,geometric metasurfaces with predesigned phase modulation possessing functionalities of both convex lenses and concave lenses.Under the illumination of left-/right-handed circularly polarized(LCP or RCP)terahertz(THz)waves,these metalenses can generate transversely/longitudinally distributed RCP/LCP multiple focal points.Since the helicity-dependent multiple focal points are locked to the polarization state of incident THz waves,the relative intensity between two orthogonal components can be controlled with different weights of LCP and RCP THz waves,leading to the intensity-tunable functionality.This robust approach for simultaneously manipulating orthogonal spin states and energy distributions of spin EM waves will open a new avenue for designing multifunctional devices and integrated communication systems.
基金National Key Research and Development Program of China(2017YFA0701005)National Natural Science Foundation of China(61722111,61871268)+5 种基金Natural Science Foundation of Shanghai(18ZR1425600)"Shuguang"Program of Shanghai Education Commission(19SG44)Shanghai Pujiang Program(18PJD033)Shanghai International Joint Laboratory Project(17590750300)Key Project Supported by the Science:and Technology Commission Shanghai Municipality(YDZX20193100004960)Higher Education Discipline Innovation Project(D18014).
文摘Asymmetric transmission,defined as the difference between the forward and backward transmission,enables a plethora of applications for on-chip integration and telecommunications.However,the traditional method for asymmetric transmission is to control the propagation direction of the waves,hindering further applications.Metasurfaces,a kind of two-dimensional metamaterials,have shown an unprecedented ability to manipulate the propagation direction,phase,and polarization of electromagnetic waves.Here we propose and experimentally demonstrate a metasurface-based directional device consisting of a geometric metasurface with spatially rotated microrods and metallic gratings,which can simultaneously control the phase,polarization,and propagation direction of waves,resulting in asymmetric focusing in the terahertz region.These dual-layered metasurfaces for asymmetric focusing can work in a wide bandwidth ranging from 0.6 to 1.1 THz.The flexible and robust approach for designing broadband asymmetric focusing may open a new avenue for compact devices with potential applications in encryption,information processing,and communication.
基金This work is supported in part by the National Key Research and Development Program of China(2017YFA0701005)National Natural Science Foundation of China(61871268,61722111)+6 种基金Natural Science Foundation of Shanghai(18ZR1425600),Shanghai Pujiang Program(18PJD033)"Shuguang"Program of Shanghai Education Commission(19SG44)Shanghai international joint laboratory project(17590750300)111 Project(D18014)Shanghai top talent program.the Russian Foundation for Basic Research under Grant 18-29-20104 and Grant 20-21-00143the Ministry of Science and Higher Education in part within the Agreement No.075-15-2019-1950in part within the State assignment FSRC“Crystallography and Photonics”RAS.
文摘Terahertz(THz)science and technology have attracted significant attention based on their unique applications in non-destructive imaging,communications,spectroscopic detection,and sensing.However,traditional THz devices must be sufficiently thick to realise the desired wave-manipulating functions,which has hindered the development of THz integrated systems and applications.Metasurfaces,which are two-dimensional metamaterials consisting of predesigned meta-atoms,can accurately tailor the amplitudes,phases,and polarisations of electromagnetic waves at subwavelength resolutions,meaning they can provide a flexible platform for designing ultra-compact and high-performance THz components.This review focuses on recent advancements in metasurfaces for the wavefront manipulation of THz waves,including the planar metalens,holograms,arbitrary polarisation control,special beam generation,and active metasurface devices.Such ultra-compact devices with unique functionality make metasurface devices very attractive for applications such as imaging,encryption,information modulation,and THz communications.This progress report aims to highlight some novel approaches for designing ultra-compact THz devices and broaden the applications of metasurfaces in THz science.
基金This work was supported in part by the National Key Research and Development Program of China(No.2017YFA0701005)the National Natural Science Foundation of China(Nos.61705131,61671302,and 61871268)the Major National Development Project of Scientific Instrument and Equipment(No.2016YFF0100503)。
文摘Low-loss dielectric terahertz(THz) chips are efficient platforms for diverse THz applications. One of the key elements in the chip is the coupler. Most of the available THz couplers are in-plane and couple the THz wave from the metal waveguide to the dielectric waveguide. However, out-of-plane couplers are more suitable for wafer-scale testing and tolerant of alignment variation. In this work, we propose an out-of-plane THz coupler for coupling the antenna to the dielectric waveguide. The device is constructed using a grating and a compact spot-size converter. As the conventional optical spot-size converters that apply directly to THz chips are too large, we have designed a compact spot-size converter based on a tapered waveguide with a lens. The total device is 2.9 cm long and can couple a 7 mm diameter THz beam to a 500 μm wide waveguide. The device can scan the THz beam, radiate the input rectangular waveguide mode to free space, and drive the rotation angle of the fan beam through the scanning frequency. We fabricated the device using a single lithography step on a silicon wafer.The out-of-plane coupling efficiency was found to be ~5 d B at 194 GHz. The fan-beam steering range was found to be around40° in the frequency range of 170–220 GHz. The proposed out-of-plane coupling technique may provide an effective way for THz wafer-scale testing with a higher degree of freedom for on-chip integration. Also, the proposed technique being nonmechanical, beam steering using it, may therefore find applications in THz radar, communication, and sensing.
