Generation of ultrafast user defined multi-micro-pulse burst structure from a femtosecond mode-locked fiber oscillator by using semiconductor optical amplifier for photoinjector.

We demonstrate and present detailed technical insights into the generation of a user-defined multi-micro-pulse burst structure from an in-house developed femtosecond mode-locked fiber oscillator using a standard semiconductor optical amplifier (SOA), which acts as an excellent candidate for an ultrafast fiber-based pulse-picker. An in-house developed 130 MHz mode-locked fiber oscillator followed by a 500 m long optical fiber as the pulse stretcher along with polarization control units was used to achieve a highly stable multi-micro-pulse structure at variable repetition rates by using and adapting a fiber coupled SOA. The timing system with a synchronous trigger setup has been explained in detail to achieve the multi-micro-pulse structure from the fiber laser system, which is being used to generate multi-micro-electron bunches in a photoinjector based free electron laser facility at IUAC named as Delhi Light Source.

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.