In this paper, for the first time up to where we know, an explicit expression for the maximum detection range of an entangled quantum two-mode squeezed (QTMS) radar, in which a two-mode squeezed vacuum state of microwave electromagnetic fields is used, have been derived by considering both the quantum properties of the entangled microwave fields and radar parameters. By comparing this equation with that of traditional radars, we showed that one can though a QTMS radar as a traditional radar with a reduced threshold signal-to-noise ratio. By discussing the current limitations, it has been shown that the critical parameter to have both simultaneous quantum advantage and substantial radar range is increasing the bandwidth of the generated output signal in the quantum entangled source. It has been shown that by considering the current feasible system parameters, it is possible to implement a QTMS radar with maximum detection range up to the order of 2km, which is suitable for recognizing small unmanned aerial vehicles in urban distances. Moreover, based on the false alarm rate, we introduce two classes of early alarm and track QTMS radars. The present approach can be generalized to other quantum radars with different types of quantum sources like electro-opto-mechanical sources, and also may shed new light on investigating the quantum radar system toward practical applications, for example, in far-distance ultrasensitive contactless vital sign detection as well as in the counter Drone technology. Finally, we have discussed the potential outlooks to improve and develop the quantum entangled radar systems to be practical from the engineering point of view.
This paper details an experiment utilizing ESP8266 modules as servers to wirelessly control diverse electrical appliances in home automation. The experiment showcased the modules' capability to respond to commands via a web interface on both mobile and desktop platforms or even tablets. While most of the experiment ran smoothly, occasional freezing and connectivity disruptions were observed. The abstract encapsulates the experiment's successes, discusses encountered challenges, and outlines a forward-looking perspective, including the integration of a custom PCB for enhanced system stability.
We present studies of a novel plastic scintillator branded M600, which was developed and provided by Target Systemelektronik. This new material is, in contrast to other solid organic scintillators offered by commercial providers, based on a polyurethane matrix complemented with scintillating and wavelength-shifting additives. This paper covers measurements of absolute light output, LO, (photons per 1 MeV-ɣ, ɣ-non-proportionality (NP), light pulse shapes, and neutron-gamma (n/ɣ) discrimination. The measurements were carried out either using standard calibration gamma sources (LO, NP) or in a mixed field of neutron and ɣ radiation from an intense (~4 × 105 neutrons/s/4π) AmBe source (n/ɣ discrimination). The measured light output was 9650±1000 ph/MeV, and the PSD's figure of merit (FoM) was found as 2.2±0.1 at 1000 keVee for Ø1" × 1" M600 sample. The bigger sample (Ø2" × 2") exhibits about 25% lower LO and poorer FoM when compared to the Ø1" × 1" M600, due to self-absorption.
The performance of intensity modulation (IM) with direct detection (DD) transmission systems is enhanced through a novel combination of multidimensional coding, Nyquist pulse shaping, and electronic dispersion compensation (EDC) at the transmitter using a finite impulse response (FIR) filter. A 24dimensional (24D) extended Golay binary code effectively transforms each incoming 12-bit message into a 24-bit codeword, achieving a coding efficiency of 0.5 bits per symbol for a 56 Gb/s on-off keying (OOK) transmission over 80 km of single mode fiber. While this encoding process introduces a 50% overhead, the required bandwidth is maintained at 56 GHz through doubling the symbol rate and the application of Nyquist pulse shaping with a raised cosine (RC) profile and a roll-off factor of zero, resulting in a flat power spectral density. This flat distribution contrasts with standard OOK transmission at 56 Gb/s with a roll-off factor of 1.0, where signal power is predominantly concentrated in the lower frequency range. One of the key advantages of the 24D Golay code is its substantial error correction capability. However, the benefits of this multidimensional coding and Nyquist pulse shaping extend beyond error correction. It is shown that, while both the proposed and standard OOK methods exhibit comparable performance in a white Gaussian noise channel at back-to-back, they differ significantly under frequency selective power fading conditions caused by the interplay of chromatic dispersion (CD) and direct detection. The misalignment between the frequency notches introduced by the FIR pre-EDC and those inherent in the channel response, especially severe at lower frequencies, favors transmission schemes with a flat power spectral density, like the 24D Golay-coded Nyquist pulses.
We propose and experimentally demonstrate the design of a compact source for DAS systems using a mini-EYDFA commonly used in CATV networks together with an integrated, low-phase-noise Direct Digital Synthesis (DDS) device that can generate readily programmable probe waveforms with a bandwidth of up to 1.4 GHz. The DDS module is synchronized with a NI-PXIe system for real-time acquisition of traces at a rate of up to 200MS/s and, thanks to the low phase noise DDS characteristics as well as high gain and stability of the EYDFA and jitter-suppressed acquisition of traces, the scheme enables measurements of representative vibration signatures with a bandwidth of up to 4 kHz at a distance of 9.71 km, with an SNR of ~24 dB without trace averaging, offering a performance near the Nyquist limit set by round-trip-time of trace acquisition. Analyzes of the spatial, temporal, and spectral responses of extracted vibrations confirm the distributed dynamic sensing capability of the technique. The proposed configuration enables the simplification of sources used in DAS systems, paving the way toward further miniaturization of the interrogation units and their scalable commercialization for wider use in several safety and integrity monitoring applications.
We report enhanced nonlinear optics in integrated nanophotonic chips through the use of integrated with 2D graphene oxide (GO) films. We investigate nanophotonic platforms including silicon, silicon nitride and high index doped silica. Due to the high Kerr nonlinearity of GO films and low nonlinear absorption we observe significant enhancement of thirdorder nonlinear processes. In particular, in silicon we observe an increase in both the Kerr nonlinearity and nonlinear figure of merit of up to 20 times. These results show the strong capability of GO films for improving the nonlinear optical performance of integrated photonic devices.
The effect of incoherent optical feedback to a semiconductor diode laser is numerically investigated and the time delay signature of the external cavity is found to exhibit regimentation corresponding to the incoherent feedback. The occurrence of time delay signature and its characteristics such as area of time delay signature distribution and its temporal spread (FWHM) exhibit a definite relation to the regimes of incoherent optical feedback. Turn-on-delay characteristics also exhibit concurring regimentation of incoherent optical feedback to a semiconductor diode laser.
Weber-Maxwell electrodynamics is a modernized, compressed, cleansed and, in many respects, advantageous representation of classical electrodynamics that results from the Liénard-Wiechert potentials. In the non-relativistic domain, it is compatible with both Maxwell's electrodynamics and Weber electrodynamics. It is suitable for all electrical engineering tasks, ranging from electrical machines to radar and high-frequency technologies. Weber-Maxwell electrodynamics also simplifies access to quantum physics and other areas of modern physics, such as optics and atomic physics. Particular advantages of Weber-Maxwell electrodynamics are its simple and fast computability in computer calculations and, as it is based on point charges, in the simulation of plasmas. The latter is particularly important for fusion research. Moreover, Weber-Maxwell electrodynamics is also highly suited to academic and post-primary education, as it allows an easy comprehension of both magnetism and electromagnetic waves. Due to the novelty of Weber-Maxwell electrodynamics, there are currently no articles that summarize its most important aspects. The present article aims to achieve this.
Feedback control plays a crucial role in improving system accuracy and stability for a variety of scientific and engineering applications. Here, we theoretically and experimentally investigate the implementation of feedback control in microwave photonic (MWP) transversal filter systems based on optical microcomb sources, which offer advantages in achieving highly reconfigurable processing functions without requiring changes to hardware. We propose four different feedback control methods including (1) one-stage spectral power reshaping, (2) one-stage impulse response reshaping, (3) twostage spectral power reshaping, and (4) two-stage synergic spectral power reshaping and impulse response reshaping. We experimentally implement these feedback control methods and compare their performance. The results show that the feedback control can significantly improve not only the accuracy of comb line shaping as well as temporal signal processing and spectral filtering, but also the system's long-term stability. Finally, we discuss the current limitations and future prospects for optimizing feedback control in microcomb-based MWP transversal filter systems implemented by both discrete components and integrated chips. Our results provide a comprehensive guide for the implementation of feedback control in microcomb-based MWP filter systems in order to improve their performance for practical applications.
In this paper, we propose two different methods for time-domain finite-difference analysis of uniform temporally and spatially dispersive metasurfaces using their zero thickness sheet representations using the Generalized Sheet Transition Conditions (GSTCs). Metasurfaces are described here using their effective surface susceptibilities which are assumed to exhibit Lorentzian temporal dispersion characteristics. For both methods, the spatial dispersion of the, the surface susceptibilities (i.e., their dependence on angle of incidence) are represented using the extended GSTCs presented in -. However, the first method takes advantage of a polynomial expansion of the angle-dependent surface susceptibilities in terms of the transverse wavevector to implement spatial derivatives of the electric and magnetic polarization as well as the average field on the surface, leading to a coupled set of field equations encompassing the entire surface. Limitations for this method are presented in terms of poor conditioning for a coupled system of equations and an inconvenient extension to the higher-order expansion of the susceptibility terms. The second method lifts these limitations by solving the spatial dispersion problem in the spatial frequency domain at every time step. Both methods are validated for custom Lorentzian models and two canonical physical cells while comparing their transmission and reflection coefficients with analytical results.
This study presents a novel technique for generating terahertz (THz) waves with frequency modulation capabilities ranging from linear sweeping to random hopping. Departing from conventional methods that utilize wavelength-tunable lasers to produce optical waves with variable frequency differences, this approach harnesses an optical frequency comb to generate optical wave frequencies at fixed intervals. Crucially, it employs a uniquely configured optical filter with adjustable dual passbands, allowing for the selection of optical beats with frequency variances that are multiples of the comb's interval. These beats are subsequently converted into THz waves using a THz photomixer, aligning the THz frequency with the adjustable interval between the filter's passbands. This innovation significantly enhances the versatility and scope of THz wave frequency modulation, offering substantial potential for advancements in high-speed communication, precision imaging, and spectroscopy.
The foundations of nonlinear optics are revisited, and the formalism is applied to waveguide modes. The effect of loss and dispersion are included rigorously along with the vectorial nature of the modes, and a new version of the nonlinear Schrödinger (NLS) equation is derived. This leads to more general expressions for the group index, for the group-index dispersion (GVD), and for the Kerr coefficient. These quantities are essential for the design of waveguides suitable for e.g. the generation of optical frequency combs and all-optical switches. Examples are given using the silicon nitride material platform. Specifically, values are extracted for the coefficients of the chi-3 tensor based on measurements of Kerr coefficients and mode simulations.
We explore essential factors pertaining to the spatial directivity of quantum radiating source systems (QSSs), encompassing quantum antennas and quantum sensors. Our primary focus is on their capacity to control the emission of photons in specific spatial directions. We present a comprehensive definition of quantum directivity, drawing inspiration from Glauberâ\euro™s photon detection theory. This definition closely parallels the framework of analogous concepts in classical antenna theory. By conducting thorough conceptual and mathematical analysis, we address the challenge of characterizing the directive properties of a general QSS. Essentially, our approach presents a computational model that relies solely on the radiation field operatorâ\euro™s density as input.
In our manuscript, we present a detailed multi-domain modeling approach for the numerical study of free-running harmonic frequency comb (HFC) formation in terahertz quantum cascade lasers (QCLs). We investigate the influence of the chosen eigenstate basis on the gain spectrum and present self-consistent simulation results of stable HFC operation in a double metal terahertz QCL. In our simulations, the studied QCL gain medium shows self-starting harmonic mode-locking for different bias and waveguide configurations, resulting in a mode spacing of up to eight times the cavity round trip frequency. Furthermore, we characterize the spectral time evolution of the coherent HFC formation process, yielding the spontaneous build-up of a dense multimode state which is gradually transferred into a broad and clear HFC state.
We integrate the differential signaling technique from OWC systems into our work, suggesting a practical autoencoder-based architecture that accommodates negative encoder output elements. This Â capability affords us a greater degree of freedom in shaping the signal constellation space when compared to traditional AEs.
This paper reports a novel design of compact tuneable resonance filter with a highly extinguished and ultra-broad out-of-band rejection in CMOS compatible silicon photonics technology platform. The proposed device is designed with two identically apodized distributed grating structures for guided Fabry-PÃ©rot resonant transmissions in a silicon on insulator rib waveguide structure. The device design parameters are optimized by theoretical simulation for a low insertion loss singly-resonant transmission peak at a desired wavelength. Â However, the devices were fabricated (using in-house facilities) to demonstrate multiple resonant transmission peaks along with a singly-resonant one. Â We observed that a device length of as low as âˆ¼35 ð?œ‡m exhibits a rejection band as large as âˆ¼60 nm with an extinction of âˆ¼40 dB with respect to the resonant wavelength peak at ð?œ†ð?‘Ÿâˆ¼1550 nm (FWHM âˆ¼80 pm, ILâˆ¼2 dB). The experimental results have been shown to be closely matching to our theoretical simulation and modelling results. As expected from the theoretical prediction, the trend pertaining to the trade-off between passive insertion loss and Q-value of the resonances has been observed depending on the device parameters. The thermo-optic tuning characteristics of resonant wavelengths have been obtained by integrating microheaters in the cavity. The resonance peak has been tuned at a rate of 96 pm per mW of consumed thermal power. The thermo-optic switching response has been measured to be in the order of ~5 ð?œ‡s. As a potential application, noise associated with an amplified pump wavelength (ð?œ†ð?‘ƒâˆ¼1550 nm) has been shown to be suppressed by âˆ¼15 dB (up to the detector noise floor) which can be investigated further for large-scale integrated quantum photonic circuits. The demonstrated device can also be explored further for many other applications such as modulation, add-drop multiplexing, sensing etc.Â