Circularly polarized light(CPL)has been given great attention because of its extensive application.While several devices for CPL detection have been studied,their performance is affected by the magnitude of photocurre...Circularly polarized light(CPL)has been given great attention because of its extensive application.While several devices for CPL detection have been studied,their performance is affected by the magnitude of photocurrent.In this paper,a self-powered photodetector based on hot electrons in chiral metamaterials is proposed and optimized.CPL can be distinguished by the direction of photocurrent without external bias owing to the interdigital electrodes with asymmetric chiral metamaterials.Distinguished by the direction of photocurrent,the device can easily detect the rotation direction of the CPL electric field,even if it only has a very weak responsivity.The responsivity of the proposed detector is near 1.9 mA/W at the wavelength of 1322 nm,which is enough to distinguish CPL.The detector we proposed has the potential for application in optical communication.展开更多
Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range....Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range.In this paper,two methods are adopted to increase the peak current of RTD for enhancing its output power.First,different metal contact systems(including Pt/Ti/Pt/Au and Au Ge/Ni/Au)for RTD contact are introduced,and a higher current of RTD with Pt/Ti/Pt/Au contact demonstrates the superior contact characteristic of Pt/Ti/Pt/Au contact system.Second,the double barrier structure(DBS)of RTD is well designed to further improve the characteristic of RTD,and a high peak current of 154 kA/cm^2 is achieved at room temperature.The improved peak current is very beneficial for increasing the output power of RTD oscillator.展开更多
This paper studies the flexibility of a tracking control method originally proposed by the authors for air-breathing hypersonic vehicles (AHVs). The main feature of this method is to design the tracking controller w...This paper studies the flexibility of a tracking control method originally proposed by the authors for air-breathing hypersonic vehicles (AHVs). The main feature of this method is to design the tracking controller without canceling but using aero-propulsive, as well as elevator-to-lift couplings. By introducing a virtual input, the tracking controller and external reference trajectories are simultaneously obtained by solving a system of linear algebraic equations. This system of linear algebraic equations is always solvable and the solution space of the corresponding homogeneous system is of dimension 3, which leads to much freedom in choosing or defining the free variables. The flexibility is reflected by the fact that the flight requirements of AHVs are involved in the definition of the free variables. Three case studies on different maneuvers, i.e., flight at constant dynamic pressure, flight at variant dynamic pressure and flight with fast climb rate are considered to verify the flexibility of this method. Simulation results show its effectiveness and flexibility.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.61705065)Hunan Provincial Natural Science Foundation of China(No.2017JJ3034)+1 种基金Technology Program of Changsha(No.kq1804001)National Training Program of Innovation and Entrepreneurship for undergraduates(No.S201910532166).
文摘Circularly polarized light(CPL)has been given great attention because of its extensive application.While several devices for CPL detection have been studied,their performance is affected by the magnitude of photocurrent.In this paper,a self-powered photodetector based on hot electrons in chiral metamaterials is proposed and optimized.CPL can be distinguished by the direction of photocurrent without external bias owing to the interdigital electrodes with asymmetric chiral metamaterials.Distinguished by the direction of photocurrent,the device can easily detect the rotation direction of the CPL electric field,even if it only has a very weak responsivity.The responsivity of the proposed detector is near 1.9 mA/W at the wavelength of 1322 nm,which is enough to distinguish CPL.The detector we proposed has the potential for application in optical communication.
文摘Resonant tunneling diodes(RTD)have the potential for compact and coherent terahertz(THz)sources operating at room temperature,but their low output power severely restricts their application in THz frequency range.In this paper,two methods are adopted to increase the peak current of RTD for enhancing its output power.First,different metal contact systems(including Pt/Ti/Pt/Au and Au Ge/Ni/Au)for RTD contact are introduced,and a higher current of RTD with Pt/Ti/Pt/Au contact demonstrates the superior contact characteristic of Pt/Ti/Pt/Au contact system.Second,the double barrier structure(DBS)of RTD is well designed to further improve the characteristic of RTD,and a high peak current of 154 kA/cm^2 is achieved at room temperature.The improved peak current is very beneficial for increasing the output power of RTD oscillator.
基金supported by the National Natural Science Foundation of China(No.61273153)partially by the Scientifc Research Foundation for the Returned Overseas Chinese Scholars(2009-8),Ministry of Education,Chinaby the National Laboratory of Space Intelligent Control,Beijing Institute of Control Engineering(No.XDHT2011238A)
文摘This paper studies the flexibility of a tracking control method originally proposed by the authors for air-breathing hypersonic vehicles (AHVs). The main feature of this method is to design the tracking controller without canceling but using aero-propulsive, as well as elevator-to-lift couplings. By introducing a virtual input, the tracking controller and external reference trajectories are simultaneously obtained by solving a system of linear algebraic equations. This system of linear algebraic equations is always solvable and the solution space of the corresponding homogeneous system is of dimension 3, which leads to much freedom in choosing or defining the free variables. The flexibility is reflected by the fact that the flight requirements of AHVs are involved in the definition of the free variables. Three case studies on different maneuvers, i.e., flight at constant dynamic pressure, flight at variant dynamic pressure and flight with fast climb rate are considered to verify the flexibility of this method. Simulation results show its effectiveness and flexibility.