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Time-domain nature of group delay

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Chinese Physics B 2015年第10期24卷 36-40页

作者：王建武冯正和 Department of Electronic Engineering Tsinghua University Air-force Air-born Academy

The characteristic of group delay is analyzed based on an electronic circuit, and its time-domain nature is studied with time-domain simulation and experiment. The time-domain simulations and experimental results show that group delay is the delay of the energy center of the amplitude-modulated pulse, rather than the propagation delay of the electromagnetic field. As group velocity originates from the definition of group delay and group delay is different from the propagation delay, the superluminaiity or negativity of group velocity does not mean the supeduminal or negative propagation of the electromagnetic field.

关键词： energy center group delay time domain superluminality

A 3-5GHz CMOS UWB power amplifier with±8ps group delay ripple

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Journal of Semiconductors 2010年第4期31卷 76-79页

作者：席天佐黄鲁郑重冯立松 Department of Electronic Science and Technology University of Science and Technology of China

A differential power amplifier （PA）, designed using the linear-phase filter model, for a BPSK modulated ultra-wideband （UWB） system operating in the 3-5 GHz frequency range is presented. The proposed PA was fabricated using 0.18μm SMIC CMOS technology. To achieve sufficient linearity and efficiency, this PA operates in the class-AB region, delivering an output power of 8.5 dBm at an input-1 dB compression point of-0.5 dBm. It consumes 28.8 mW, realizing a fiat gain of 9.11± 0.39 dB and a very low group delay ripple of ±8 ps across the whole band of operation.

关键词： PA UWB group delay linearity

Optical soliton with group delay in microring coupled-resonator optical waveguides

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Chinese Physics B 2009年第1期18卷 221-224页

作者：田赫掌蕴东王号欧阳秋云王楠袁萍 National Key Laboratory of Tunable Laser Technology Institute of Opto-ElectronicsHarbin Institute of Technology

This paper derives the dispersion relation of microring coupled-resonator optical waveguides （CROWs） without any approximation by using the transfer matrix method. Based on the established dispersion relation of CROWs it obtains the slow group velocity and dispersion coefficient. It finds that the effect Of dispersion on optical pulses can be adjusted to balance the effect of nonlinearity by changing coupling coefficient or loss, so optical soliton with group delay can be obtained in microring CROWs. The optical soliton with group delay is of great significance for applications of microring CROWs in delay lines and optical buffers of future all-optical communication systems.

关键词： optical waveguide optical soliton group delay

Enhancement of the group delay in quadratic coupling optomechanical systems subjected to an external force

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Chinese Physics B 2023年第12期32卷 325-331页

作者： Jimmi HervéTalla Mbé Ulrich Chancelin Tiofack Demanou Christian Kenfack-Sadem Martin Tchoffo Research Unit of Condensed Matter Electronics and Signal ProcessingDepartment of PhysicsUniversity of DschangP.O.Box 67DschangCameroon African Institute for Mathematical Sciences P.O.Box 608LimbeCameroon

We theoretically study the effect of the quadratic coupling strength on optomechanical systems subjected to a continuous external force. Quadratic coupling strength originates from strong coupling between the optical and the mechanical degrees of freedom. We show that the quadratic coupling strength reduces the amplitude of the dispersion spectra at the resonance in both blue-and red-sideband regimes. However, it increases(decreases) the amplitude of the absorption spectrum in the blue-(red-)sideband regime. Furthermore, in both sideband regimes, the effective detuning between the pump and the cavity deviates with the quadratic coupling strength. Thereby, appropriate selection of the quadratic coupling strength results in an important magnification(in absolute value) of the group delay for both slow and fast light exiting from the optomechanical cavity.

关键词： slow and fast light optomechanical systems group delay quadratic coupling

Enhanced and controllable reflected group delay based on Tamm surface plasmons with Dirac semimetals

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Chinese Physics B 2023年第7期32卷 404-408页

作者：郑棋文卢文广胥加青叶云洋赵新民蒋乐勇 School of Physics and Electronics Hunan Normal UniversityChangsha 410081China School of Intelligent Manufacturing and Electronic Engineering Wenzhou University of TechnologyWenzhou 325035China School of Electronic Science and Engineering National University of Defense TechnologyChangsha 410073China

The reflected group delay from a multilayer structure comprising a one-dimensional photonic crystal coated with a bulk Dirac semimetal(BDS)separated by a spacer layer is investigated *** is shown that the group delay of the reflected beam in this structure can be significantly negatively enhanced and switched from negative to *** enhanced group delay originates from the steep phase change caused by the excitation of the optical Tamm state at the interface between the BDS and spacer ***,positive and negative group delays can be actively tuned through the Fermi energy and the relaxation time of the *** believe that this enhanced and tunable delay scheme has important research significance for the fabrication of optical delay devices.

关键词： group delay Tamm plasmons Dirac semimetals

An optical rotation sensor based on dispersive slow-light medium

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Chinese Physics B 2011年第7期20卷 210-215页

作者：王楠掌蕴东袁萍 Institute of Opto-electronics Harbin Institute of Technology Engineering Research Center of Optoelectronic Materials & Devices School of Materials Science and EngineeringDalian Jiaotong University

Slow light supported by electromagnetically induced transparency effect in dispersive medium is extremely susceptible with respect to Doppler detuning. In this paper, the Doppler effect induced by rotating dispersive medium was considered and the effect of the velocity of rotating dispersive medium on the group velocity was studied. Based on a dispersive slow-light medium, a high sensitive optical rotation sensor for measuring absolute rotation is proposed and analysed. The sensitivity of the rotation sensor is the group delay between the counterpropagationed wave packets in the device, and scales directly with square of the group index which can reach 102-10s orders of magnitude by selecting a proper dispersive medium.

关键词： slow light dispersive medium absolute rotation group delay

A large bandwidth photonic delay line using passive cascaded silicon-on-insulator microring resonators

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Chinese Physics B 2011年第7期20卷 216-222页

作者：胡应涛肖希李智勇李运涛樊中朝韩伟华俞育德余金中 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences Engineering Research Center for Semiconductor Integrated Technology Institute of SemiconductorsChinese Academy of Sciences

This paper investigated the design and the characterization of a photonic delay line based on passive cascaded silicon-on-insulator （SOI） microrings. We considered the compromise of group delay, bandwidth and insertion loss. A 3-stage double channel side-coupled integrated spaced sequence of resonator （SCISSOR） device was optimized by shifting the resonance of each microring and fabricated with electron beam lithography and dry etching. The group delay was measured to be 17 ps for non-return-to-zero signals at different bit rates and the bandwidth of 78 GHz was achieved. The experiment result agreed well with our simulation.

关键词： group delay delay line slow light microring resonator

Investigation of Helical Pulse Forming Line

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Plasma Science and Technology 2006年第5期8卷 596-599页

作者：刘振祥张建德 College of Opto-electronic Science and Engineering National University of Defense Technology Changsha 410073 China

To investigate the feasibility for a helical line to be used as a pulse forming line （PFL）, the transmission characteristics of the helical transmission line is studied both theoretically and experimentally. The results indicate that it is feasible to employ a helical line as a long-pulse PFL, and the influence of its dispersion is negligible. Compared with a conventional coaxial PFL, the helical PFL with the same size can produce a longer pulse.

关键词： helical pulse forming line long pulse group delay dispersion

An eighth order channel selection filter for low-IF and zero-IF DVB tuner applications

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Journal of Semiconductors 2009年第11期30卷 79-87页

作者：邹亮廖友春唐长文 ASIC & System State Key Laboratory Fudan University Ratio Microelectronics Technology Co Ltd

An eighth order active-RC filter for low-IF and zero-IF DVB tuner applications is presented, which is implemented in Butterworth biquad structure. An automatic frequency tuning circuit is introduced to compensate the cut-off frequency variation using a 6-bit switched-capacitor array. Switched-resistor arrays are adopted to cover different cut-off frequencies in low-IF and zero-IF modes. Measurement results show that precise cut-off frequencies at 2.5, 3, 3.5 and 4 MHz in zero-IF mode, 5, 6, 7 and 8 MHz in low-IF mode can be achieved, 60 dB frequency attenuation can be obtained at 20 MHz, and the in-band group delay agrees well with the simulation. Two-tone testing shows the in-band IM3 achieves -52 dB and the out-band IM3 achieves -55 dB with -11 dBm input power. This proposed filter circuit, fabricated in a SMIC 0.18μm CMOS process, consumes 4 mA current with 1.8 V power supply.

关键词： active-RC filter Butterworth frequency tuning group delay noise linearity