We describe a technique for generating tunable narrow-band terahertz radiation via optical rectification in periodically-poled lithium niobate. Frequency tuning is accomplished by spatially chirping the domain width laterally to the beam propagation direction, and adjusting the temperature of the sample. We demonstrate tuning over a continuous range from 0.8 to 2.5 THz. The bandwidth of the ter...

By performing two-beam coupling experiments in a liquid crystal light-valve, optical beam amplification is obtained as a strongly resonant process to which a narrow frequency bandwidth is associated. By exploiting this property, we realize an adaptive holographic interferometric system that is able to efficiently sensing displacements as small as fraction of picometers. The adaptive interferome...

highest-priority project for the future. Research and development toward the design of such a machine has occurred at KEK for more than a decade. Two major areas of current accelerator R&D at KEK include the technologies needed to generate high-quality beams in an injector complex and high-power microwave technology required for the main linear accelerators. Because its particle bunches encount...

We present methods and results of the testing of an inexpensive home-made diffraction limited lens system, the design of which was proposed in [1] and which has since been used (with slight alterations) by several research groups (e.g. [2, 3, 4]). Our system will be used for both: focussing a collimated laser beam at a wavelength of λ = 830 nm down to a narrow spot and for collimating fluoresce...

A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequencychirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to ampl...

This paper introduces a new application of genetic algorithm (GA) in dynamic sector synthesis of antenna array for mobile base transceiver station (BTS). The basic objective is to have narrow beam widths in heavy handoff areas and wider beam widths in areas with low traffic density. By predefining the beam widths and thus the beams of each sector, optimal sectoring can be achieved using GA at d...

In this paper, an optical beam jitter control method for the Naval Postgraduate School HEL beam control testbed is presented. Additional hardware is developed and integrated on the testbed to realize the strap-down IRU jitter compensation architectures. Feedforward control design of the strap-down IRU design is studied and tested on the testbed. An adaptive filtering method for narrow-field-of-...

The asymptotic form of the beam break-up instability is computed up to quadrature for an arbitrary wakefield, in the presence of a linear variation in betatron tune from head to tail along the beam. For illustration, the result is applied to a broadband impedance (resistive wall) and a narrow-band impedance (single resonator), and benchmarked against simulation, for parameters of interest in in...

Received Jan 16, 2017 Revised Mar 18, 2017 Accepted Mar 30, 2017 5G technology is using millimeter-wave band to improve the wireless communication system. However, narrow transmitter and receiver beams have caused the beam coverage area to be limited. Due to propagation limitations of mm wave band, beam forming technology with multi-beam based communication system, has been focused to overcome ...