Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userPhotonic Crystal-Based Compact High-Power Vacuum Electronic Devices
88
0
0.0
(
0
)
Added by
Alexandra Gurinovich
Publication date
2018
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
This paper considers how the finite dimensions of a photonic crystal placed inside a resonator or waveguide affect the law of electron beam instability. The dispersion equations describing e-beam instability in the finite photonic crystal placed inside the resonator or waveguide (a bounded photonic crystal) are obtained. Two cases are considered: the conventionally considered case, when diffraction is suppressed, and the case of direct and diffracted waves having almost equal amplitudes. The instability law is shown to be responsible for increase of increment of instability and decrease of length, at which instability develops, for the case when amplitude of diffracted wave is comparable with that of direct one, that happens in the vicinity of $pi$-point of dispersion curve. Application of photonic crystals for development of THz sources at electron beam current densities available at modern accelerators is discussed.
rate research
Read More
Since the first vacuum tube (X-ray tube) was invented by Wilhelm Rontgen in Germany, after more than one hundred years of development, the average power density of the vacuum tube microwave source has reached the order of 108 [MW][GHz]2. In the high-power microwave field, the vacuum devices are still the mainstream microwave sources for applications such as scientific instruments, communications, radars, magnetic confinement fusion heating, microwave weapons, etc. The principles of microwave generation by vacuum tube microwave sources include Cherenkov or Smith-Purcell radiation, transition radiation, and Bremsstrahlung. In this paper, the vacuum tube microwave sources based on Cherenkov radiation were reviewed. Among them, the multi-wave Cherenkov generators can produce 15 GW output power in X-band. Cherenkov radiation vacuum tubes that can achieve continuous-wave operation include Traveling Wave Tubes and Magnetrons, with output power up to 1MW. Cherenkov radiation vacuum tubes that can generate frequencies of the order of 100 GHz and above include Traveling Wave Tubes, Backward Wave Oscillators, Magnetrons, Surface Wave Oscillators, Orotrons, etc.
Interest in photonic crystal nanocavities is fueled by advances in device performance, particularly in the development of low-threshold laser sources. Effective electrical control of high performance photonic crystal lasers has thus far remained elusive due to the complexities associated with current injection into cavities. A fabrication procedure for electrically pumping photonic crystal membrane devices using a lateral p-i-n junction has been developed and is described in this work. We have demonstrated electrically pumped lasing in our junctions with a threshold of 181 nA at 50K - the lowest threshold ever demonstrated in an electrically pumped laser. At room temperature we find that our devices behave as single-mode light-emitting diodes (LEDs), which when directly modulated, have an ultrafast electrical response up to 10 GHz corresponding to less than 1 fJ/bit energy operation - the lowest for any optical transmitter. In addition, we have demonstrated electrical pumping of photonic crystal nanobeam LEDs, and have built fiber taper coupled electro-optic modulators. Fiber-coupled photodetectors based on two-photon absorption are also demonstrated as well as multiply integrated components that can be independently electrically controlled. The presented electrical injection platform is a major step forward in providing practical low power and integrable devices for on-chip photonics.
Initial test results of an L-band multi-beam klystron with parameters relevant for ILC are presented. The chief distinction of this tube from MBKs already developed for ILC is its low operating voltage of 60 kV, a virtue that implies considerable technological simplifications in the accelerator complex. To demonstrate the concept underlying the tubes design, a six-beamlet quadrant (a 54 inch high one-quarter portion of the full 1.3 GHz tube) was built and recently underwent initial tests, with main goals of demonstrating rated gun perveance, rated gain, and at least one-quarter of the full 10-MW rated power. Our initial three-day conditioning campaign without RF drive (140 microsec pulses @ 60 Hz) was stopped at 53% of full rated duty because of time-limits at the test-site; no signs appeared that would seem to prevent achieving full duty operation (i.e., 1.6 msec pulses @ 10 Hz). The subsequent tests with 10-15 microsec RF pulses confirmed the rated gain, produced output powers of up to 2.86 MW at 60 kV with high efficiency and 56 dB gain, and showed acceptable beam interception. These results suggest that a full version of the tube should be able to produce up to 11.5 MW. Follow-on tests are planned for later in 2015.
Graphene and related materials can lead to disruptive advances in next generation photonics and optoelectronics. The challenge is to devise growth, transfer and fabrication protocols providing high (>5,000 cm2 V-1 s-1) mobility devices with reliable performance at the wafer scale. Here, we present a flow for the integration of graphene in photonics circuits. This relies on chemical vapour deposition (CVD) of single layer graphene (SLG) matrices comprising up to ~12000 individual single crystals (SCs), grown to match the geometrical configuration of the devices in the photonic circuit. This is followed by a transfer approach which guarantees coverage over ~80% of the device area, and integrity for up to 150 mm wafers, with room temperature mobility ~5000 cm2 V-1 s-1. We use this process flow to demonstrate double SLG electro-absorption modulators with modulation efficiency ~0.25, 0.45, 0.75, 1 dB V-1 for device lengths ~30, 60, 90, 120 {mu}m. The data rate is up to 20 Gbps. Encapsulation with single-layer hBN is used to protected SLG during plasma-enhanced CVD of Si3N4, ensuring reproducible device performance. Our full process flow (from growth to device fabrication) enables the commercial implementation of graphene-based photonic devices.
When exposed to intense electromagnetic fields, the quantum vacuum is expected to exhibit properties of a polarisable medium akin to a weakly nonlinear dielectric material. Various schemes have been proposed to measure such vacuum polarisation effects using a combination of high power lasers. Motivated by several planned experiments, we provide an overview of experimental signatures that have been suggested to confirm this prediction of quantum electrodynamics of real photon-photon scattering.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
