Harmonically mode-locked laser pulse accumulation in a self-resonating optical cavity.

Optical enhancement cavities enabling laser pulses to be coherently stacked in free space are used in several applications to enhance accessible optical power. In this study, we develop an optical cavity that accumulates harmonically mode-locked laser pulses with a self-resonating mechanism for X-ray sources based on laser-Compton scattering. In particular, a Fabry-Perot cavity composed of 99% reflectance mirrors maintained the optical resonance in a feedback-free fashion for more than half an hour and automatically resumed the accumulation even if the laser oscillation was suspended.

THz Smith-Purcell and grating transition radiation from metasurface: experiment and theory.

We report the results of experimental and theoretical studies of monochromatic coherent terahertz radiation generated by a short relativistic electron bunch interacting with a metasurface. The metasurface consists of subwavelength metal elements arranged on a dielectric substrate. The constructed theory explains the experimental spectra of Smith-Purcell radiation and grating transition radiation with very high precision.

Observation of grating diffraction radiation at the KEK LUCX facility.

The development of linac-based narrow-band THz sources with sub-picosecond, [Formula: see text]-level radiation pulses is in demand from the scientific community. Intrinsically monochromatic emitters such as coherent Smith-Purcell radiation sources appear as natural candidates. However, the lack of broad spectral tunability continues to stimulate active research in this field.

Stimulated Excitation of an Optical Cavity by a Multibunch Electron Beam via Coherent-Diffraction-Radiation Process.

With a low emittance and short-bunch electron beam at a high repetition rate realized by a superconducting linac, stimulated excitation of an optical cavity at the terahertz spectrum range is shown. The electron beam passes through small holes in the cavity mirrors without being destroyed. A sharp resonance structure which indicates wideband stimulated emission via coherent diffraction radiation is observed while scanning the round-trip length of the cavity.

A Fabry-Pérot interferometer with wire-grid polarizers as beamsplitters at terahertz frequencies.

The design of a compact Fabry-Pérot interferometer (FPi) and results of the experimental studies carried out using the device are presented. Our FPi uses freestanding wire-grid polarizers (WGPs) as beamsplitters and is suitable for use at terahertz (THz) frequencies. The FPi was studied at the LUCX facility, KEK, Japan, and an 8 MeV linear electron accelerator was used to generate coherent Smith-Purcell radiation.

Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders.

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys.

First observation of the point spread function of optical transition radiation.

We represent the first experimental observation of the point spread function (PSF) of optical transition radiation (OTR) performed at KEK-Accelerator Test Facility extraction line. We have demonstrated that the PSF vertical polarization component has a central minimum with a two lobe distribution. However, the distribution width varied significantly with wavelength.