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A simple photonic scheme for generation of linear frequency modulated (LFM) THz pulses with large bandwidth is experimentally demonstrated based on an optical interferometer. We successfully generate linearly chirped THz pulses centered at 350 GHz, and featuring a bandwidth in excess of 40 GHz. The tunability of the THz center frequency is also investigated in the experiment. The time bandwidth product...
In this paper, we discuss the impact of finite extinction ratio of modulator on the photonic time stretch (PTS) system and address concise expressions of all harmonics for modulation with a single arm Mach-Zehnder modulator (MZM) and a push pull MZM separately. The 3dB bandwidth of the system is investigated based on the theoretical analysis. Both experimental and numerical results are presented to...
We propose a method to design and implement the microwave photonic filter with rectangular response by using the frequency comb, spatial light modulator-based spectrum shaper and dispersive element. Numerical results are presented to verify the proposed scheme.
An x-cut millimeter-size lithium niobate whispering gallery mode disk resonator is demonstrated, which is fabricated based on commercially available lithium niobate disk with diameter of 12 mm and thickness of 1 mm. The Q factor is measured using the linewidth method, which is found to be Q=1.2×107, suggesting a very good condition of the WGM disk resonator. In addition, the transmission behaviors...
In this study, we propose a practical method, in which a single grid image is utilized, to realize the calibration of an optical microscopic. This method mainly comprises four steps, including 1) Automatic detection of line features and point features from the grid image; 2) Correction of the lens Distortion utilizing the straightness of the line feature; 3) Estimation of the homograph using the corrected...
Dielectric elastomer (DE) known as the electromechanical transducers has been widely discovered and used in sensors, generators and actuators decades earlier. Number of DE actuators including the linear actuator, bending actuator and rotational actuator has been designed utilizing concept design method. This paper proposes a novel method for the design of DE actuator by using topology optimization...
The flexure hinge is a key component for designing compliant mechanisms that have been widely used in precision engineering which high positioning accuracy is demanded. This paper presents a systematic method for designing flexure hinges by using the topology optimization method. An optimization model is developed by equally considering the following three objectives: (I) maximizing the compliance...
A temperature insensitive load sensor based on a dual loop optoelectronic oscillator is proposed. The two loops, with one subjected to a load, have different oscillation frequencies but same temperature sensitivity so that load sensing can be achieved by interrogating their mixing frequency.
We overview recent trend in developing high speed wireless communication systems by exploring large bandwidth available in the THz band, and we also present our recent experimental achievements on 400 GHz wireless transmission with a data rate of up to 60 Gbit/s by using a uni-travelling carrier photodiode (UTC-PD) as emitter and a Schottky diode as receiver. This system is foreseen to be capable...
Piezoelectric actuators with their high stiffness, fast response and nearly unlimited displacement resolution have been widely used in precision positioning systems. But, the existence of the inherent hysteretic behavior considerably degrades the accuracy of the actuators. To compensate for hysteresis, one of the suggested ways is to have a feedforward controller with an inverse model to linearize...
A novel asperity model is proposed by mixing two types of classical asperity model. The novel asperity is capable of describing both the tangential and vertical asperity behaviors reasonably. Based on this novel asperity model, a novel friction model is proposed, which is a Maxwell like model, and can describe both the tangential and vertical friction characteristics with a simple structure.
In the compact micro-grasping system, the combination of precisely orthogonal movement transformation, displacement amplification and simple structure is important. The typical solution of the combination issue requires bidirectional symmetric input forces/displacements. However, under a certain driving condition, numerous actuators used in micro-manipulation only supply unidirectional input froce/displacement...
This paper presents a compact design, modeling and analysis of strain-based output/input sensing cell integrated within a compliant bridge-type amplifier. Through extending the length of the leaf hinges, the output displacement sensor, input displacement sensor and input force sensor are embedded in the new amplifier in a same strain-gauges configuration. Based on the symmetric configuration of the...
In this paper, we designed a new underactuated multi-finger robotic hand. First, we designed the number of fingers, the layout and the driving method. And then, we built the static force model of the multi-finger robotic hand, and analyzed the relationship between the grasping force of the finger, the joint angle and the size of grasped object, especial in grasping some classical objects. Finally,...
A series of novel organic spin valve devices with a Fe3O4/Al-O)/organic semiconductors (OSs)/Co/Al stacking structure was fabricated. Here, four kinds of OSs, Poly(vinylidene fluoride) (PVDF), rubrene, C60 and Alq3 were tested in the devices. The spin-dependent transport properties and magnetoresistance (MR) effect were systemically studied. Giant MR ratio over 8% was observed at 300 K in C60-based...
Poly(vinylidene fluoride) (PVDF) was used as an organic spacer to fabricate spin-valve devices for the first time. Their magnetoresistance (MR) effects with different layer numbers of PVDF were investigated at both room and low temperatures. The device resistances and MR ratios increase with decreasing measurement temperature. It is noted that the MR ratios at room temperature are over 2% and 0.5%...
The structural properties and pressure-induced phase transitions of BaTe are theoretically studied using the first-principles pseudopotential method Our calculations show the phase transition pressure point between B1 and B2 structure is 4.8 GPa, and the metallization pressure for BaTe with B2 phase occurs at 20 GPa The electronic band structures and the density of states for BaTe were further investigated...
A traveling wave circular loop antenna (CLA) model was demonstrated to generate the OAM carrying wave. Three different structures of the antennas based on this model are proposed to verify the generation of OAM waves, and its features are discussed.
In this paper, we analyze the nonlinearity in the photonic time stretch (PTS) system and present exact expressions for the intermodulation products and harmonics at the system output. Based on the nonlinearity analysis of the PTS system, the spurious-free dynamic range of the PTS system is also investigated.
An orbital angular momentum (OAM) multiplexed radio data link with the novel partial arc sampling receiving (PASR) scheme is experimentally demonstrated. These four coaxially propagating OAM waves with modes of l = −6, −2, +2 and +6 are generated by a Cassegrain antenna based on the dual ring-slot radiators. Over 10 m free-space transmission, four identical horn antennas uniformly located at the π/2...
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