Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Analysis and design equations for phase matching using Bragg reflector waveguides

Abstract: In this paper, we introduce and analyze a novel wave-guide design to provide phase matching for nonlinear optical processes. Phase matching is achieved by designing the structure to guide the fundamental frequency by total internal reflection and the second harmonic (SH) frequency by transverse Bragg reflection. By forcing the SH mode to operate in the middle of the Bragg stopband, we solve for the waveguide dimensions for arbitrary waveguide materials, given the material dispersion between the fundamental and SH frequencies. Using GaAs-AlGaAs as an example, we analytically investigate and quantify properties such as nonlinear coupling efficiency, bandwidth, tunability, and limitations due to dispersion. The technique shows tremendous promise when compared to alternate technologies, where it is particularly attractive as an effective means to obtain ultralow-loss nonlinear optical elements for monolithic integration with coherent light sources and other active devices.

Fast Amplitude Estimation of Harmonics Using Undecimated Wavelet Packet Transform and Its Hardware Implementation

Abstract: Accurate and fast estimation of time-varying harmonics are essential requirements for online monitoring, analysis, and control of electrical power system. This paper presents a fast algorithm based on the undecimated wavelet packet transform (UWPT) to estimate the amplitude of fundamental and harmonic components of stationary as well as a time-varying power signal. The UWPT uses only one cycle of the fundamental frequency for precise measurement of time-varying harmonics while their amplitude has been determined accurately utilizing the time-invariant property of the UWPT. The robustness and accuracy of the proposed technique have been investigated on synthetic as well as experimental test signals using MATLAB tool. Further, the UWPT algorithm has also been implemented on the Xilinx Virtex-6 FPGA ML-605 board, using XSG/ISE design suite 14.2 and its performance, in terms of hardware accuracy, resource utilization as well as timing requirements have been tested using the experimental test signal.

Self-trapping of magnetic oscillation modes in Landau flux-closure structures.

Abstract: We investigated the magnetodynamics in rectangular Permalloy platelets by means of time-resolved x-ray photoemission microscopy. 10 nm thick platelets of size 16 x 32 microm were excited by an oscillatory field along the short side of the sample with a fundamental frequency of 500 MHz and considerable contributions of higher harmonics. Under the influence of the oscillatory field, the Neel wall in the initial classical Landau pattern shifts away from the center, corresponding to an induced magnetic moment perpendicular to the exciting field. This phenomenon is explained by a self-trapping effect of the dominating spin-wave mode when the system is excited just below the resonance frequency. The basic driving mechanism is the maximization of entropy.