Aharon Friedman

It has been shown that the spontaneous emission rate of photons by free electrons, unlike stimulated emission, is independent of the shape or modulation of the quantum electron wavefunction (QEW). Nevertheless, here we show that the quantum state of the emitted photons is non-classical and does depend on the QEW shape. This non-classicality originates from the shape dependent off-diagonal terms of the photon density matrix. This is manifested in the Wigner distribution function and would be observable experimentally through homodyne detection techniques as a squeezing effect. Considering a scheme of electrons interaction with a single microcavity mode, we present a QED formulation of spontaneous emission by multiple modulated QEWs through a build-up process. Our findings indicate that in the case of a density modulated QEWs beam, the phase of the off-diagonal terms of the photon state emitted by the modulated QEWs is the harbinger of bunched beam superradiance, where the spontaneous emission is proportional to N e 2 . This observation offers a potential for enhancement of other quantum electron interactions with quantum systems by a modulated QEWs beam carrying coherence and quantum properties of the modulation.

We present a numerical platform for 3D imaging and general analysis of multidimensional complex THz fields. A special 3D visualization is obtained by converting electromagnetic (EM) radiation to a light field via the Wigner distribution function, which is known for discovering (revealing) hidden details. This allows for 3D diagnostics using the simple techniques of geometrical optics, which significantly facilitates the whole analysis. This simulation was applied to a complex field composed of complex beams emitted as ultra-narrow femtosecond pulses. A method was developed for the generation of phase–amplitude and spectral characteristics of complex multimode radiation in a free-electron laser (FEL) operating under various parameters. The tool was successful at diagnosing an early design of the transmission line (TL) of an innovative accelerator at the Schlesinger Family Center for Compact Accelerators, Radiation Sources, and Applications.

This paper presents a diagnostic method for THz pulses produced by EA-FEL. Experimental results present a comparison between ZnTe and GaAs crystals for the detection of a single terahertz pulse using electro-optic sampling. In order to match an electro-optic detector for the EA-FEL radiation, the THz pulse from a source was simultaneously detected by ZnTe and GaAs electro-optic detectors. The GaAs detection system was found to have a shorter response time but low signal-to-noise ratio (SNR) compared to the ZnTe system. The GaAs crystal is suitable for the detection of short THz pulses due to fiber coupling, and the SNR of the GaAs system can be improved using a faster and more sensitive photodetector.

This article establishes a very important part of the transmission line (TL) design of the novel 6 MeV compact particle accelerator. Practically, the entire new array of particle accelerators has been designed and is in the final stages of construction at the Ariel University. Except for a novel hybrid photo-cathode electron gun, which has been developed and built in University of California, Los Angeles's Laboratory, it was commissioned at The Schlesinger Family Center for Compact Accelerators, Radiation Sources and Applications (free electron laser) as a part of an ongoing collaboration between the two universities. In this work, we have built a complete simulator for the analysis and propagation of terahertz pulses through the TL, which meets our specific requirements with a high level of flexibility. To simulate the propagation of an output wave packet of the source through the TL quasi-optical system, the original wave packet is decomposed in terms of free-space Hermite–Gaussian basis while the following transformations of the wave packet is described by the transfer matrices technique. Total radiation losses and spectral properties of the TL transfer are analyzed.

Tera Hertz radiation is currently the most researched and useful area in almost all fields of science and industry. The additional challenge is expressed in the form of radiation, pulses of femto-seconds in length are supposed to pass through a transmission line (TL) most efficiently, at a wide range of frequencies. These are complex beams, which make up the electromagnetic (EM) field, represented in the frequency domain in terms of cavity eigenmodes. A simulation allows to describe of the phase-amplitude and spectral characteristics of multimode radiation free-electron laser (FEL) operating in various operational parameters. The analysis is performed through the transmission of optical rays accurately, with each ray being characterized by amplitude, position, and angle in 3D space. A light field representation of a complex EM field is obtained via Wigner Distribution Function, which allows to describe of the dynamics of field evolution in future propagation by a ray tracing (RT) method. The final diagnostics will determine the design of the TL to be assembled in an innovative accelerator under construction at the Schlesinger Family Center for Compact Accelerators, Radiation Sources, and Applications.

We present a comprehensive theory for interrogation of the quantum state of a two-level system (TLS) based on a free-electron–bound-electron resonant interaction scheme. The scheme is based on free electrons, whose quantum electron wavefunction is preshaped or optically modulated by lasers in an electron microscope setup and then inelastically scattered by a quantum TLS target (e.g., atom, quantum dot, and crystal defect center) upon traversing in proximity to the target. Measurement of the postinteraction energy spectrum of the electrons probes and quantifies the full Bloch sphere parameters of a pre-excited TLS and enables coherent control of the qubit states. The exceptional advantage of this scheme over laser-based ones is atomic-scale spatial resolution of addressing individual TLS targets. Thus, this scheme opens horizons for electron microscopy in material interrogation and quantum information technology.

The electro-optical process is a popular method for terahertz radiation detection. Detectors based on the electro-optical process have large bandwidth, and the signal-to-noise ratio (SNR) is relatively high. Further, this detector can be applied to detect high-power signals without using radiation attenuation. This paper presents a method to improve the electro-optic process to THz radiation detection based on GaAs crystals by coupling the optical output signal into fiber. Results demonstrated an improvement in the signal-to-noise ratio that means an increase in the dynamic range of the electro-optical detector.

We present a comprehensive relativistic quantum-mechanical theory for interaction of a free electron with a bound electron in a model, where the free electron is represented as a finite-size quantum electron wave packet (QEW) and the bound electron is modeled by a quantum two-level system (TLS). The analysis reveals the wave-particle duality nature of the QEW, delineating the point-particle-like and wavelike interaction regimes and manifesting the physical reality of the wave function dimensions when interacting with matter. This QEW size dependence may be used for interrogation and coherent control of superposition states in a TLS and for enhancement of cathodoluminescence and electron energy-loss spectroscopy in electron microscopy.