New type of tunable filter reveals the potential for terahertz wireless communications

Phys.org   March 11, 2024 Researchers in Japan constructed a tunable Fabry–Perot interferometer (FPI) by controlling the effective refractive index of pitch-variable subwavelength gratings (PV-SWGs) that were incorporated into an FP cavity. The period of the PV-SWG could be varied to change the effective refractive index and shift the optical resonant frequency of the FPI. Compared with conventional methods that tune the optical resonance by adding fillers or deforming the cavity, the  FPI obtained a higher transmission and quality factor (Q-factor) for the transmittance peak, and its resonant frequency could be shifted by simply stretching the PV-SWG. According to the researchers […]

Single sideband modulation technique can relax the bandwidth restriction

Phys.org  September 26, 2023 The highest frequency achievable for microwave signals is limited by the bandwidths of optoelectronic devices. To maximize the microwave frequency with a limited bandwidth of a photodetector (PD) and relieve the bandwidth bottleneck, researchers in China proposed to generate microwave signals with the single sideband (SSB) format by beating a continuous wave (CW) light with an optical SSB signal. By simply adjusting the frequency difference between the CW light and the carrier of the optical SSB signal, the frequency of the generated microwave SSB signal was changed correspondingly. In the experiment, amplitude shift keying (ASK) microwave […]

Device offers long-distance, low-power underwater communication

MIT News  September 6, 2023 Researchers at MIT have designed, evaluated, and implemented Van Atta Acoustic Backscatter (VAB), a technology that enables long-range, ultra-low-power networking in underwater environments. VAB is scalable underwater backscatter architecture that bridges recent advances in RF backscatter (Van Atta architectures) with ultra-low-power underwater acoustic networks. Their design introduces multiple innovations across the networking stack to overcome unique challenges that arise from the electro-mechanical properties of underwater backscatter and the challenging nature of low-power underwater acoustic channels. They implemented and evaluated their design in over 1,500 real-world experimental trials in a river and the ocean. In stationary […]

Researchers demonstrate high-fidelity transmission of information via novel electronic-optical system

Phys.org  August 29, 2023 Free-space optical information transfer through diffusive media is critical in many applications but remains challenging due to random, unknown perturbations in the optical path. Researchers at UCLA demonstrated an optical diffractive decoder with electronic encoding to accurately transfer the optical information of interest through unknown random phase diffusers along the optical path. The model comprised a convolutional neural network-based electronic encoder and successive passive diffractive layers that were jointly optimized. After their joint training using deep learning, their hybrid model could transfer optical information through unknown phase diffusers, demonstrating generalization to new random diffusers. The model […]

New technique measures structured light in a single shot

Phys.org  August 8, 2023 Orbital angular momentum (OAM) spectrum diagnosis is a fundamental building block for diverse OAM-based systems. Among others, the simple on-axis interferometric measurement can retrieve the amplitude and phase information of complex OAM spectra in a few shots. Yet, its single-shot retrieval remains elusive, due to the signal–signal beat interference inherent in the measurement. Researchers in Switzerland have introduced the concept of Kramers–Kronig (KK) receiver in coherent communications to the OAM domain, enabling rigorous, single-shot OAM spectrum measurement. They explained in detail the working principle and the requirement of the KK method and applied the technique to […]

Lights could be the future of the internet and data transmission

Phys.org  July 25, 2023 The modulation characteristics of perovskite LEDs are not clear. An international team of researchers (UK, Switzerland) has developed a new approach for realizing fast perovskite photonic sources on silicon based on tailoring alkylammonium cations in perovskite systems. They showed the recombination behaviour of charged species at various carrier density regimes relevant for their modulation performance. By integrating a Fabry–Pérot microcavity on silicon, they demonstrated perovskite devices with efficient light outcoupling and achieved device modulation bandwidths of up to 42.6 MHz and data rates above 50 Mbps, with further analysis suggesting that the bandwidth may exceed gigahertz levels. According […]

Protecting light communication with random objects

Phys.org  July 17, 2023 Researchers in the Netherlands have developed an optical communication system with two scattering layers to hide both the sender and receiver, by measuring the correlation of the intermediate speckle generated between the two layers. The binary message is modulated as spatially shaped wavefronts, and the high number of transmission modes of the scattering layers allowed for many uncorrelated incident wavefronts to send the same message, making it difficult for an attacker to intercept or decode the message and thus increasing secrecy. They collected 50,000 intermediate speckle patterns and analyzed their correlation distribution using the Kolmogorov-Smirnov (K-S) […]

China has begun launching its own satellite internet network

Phys.org  July 17, 2023 On Sunday, July 9, launched a prototype internet satellite from China’s Jiuquan Satellite Launch Center in Inner Mongolia. The satellite will conduct several tests to validate the broadband satellite technology. The long-term aim of the project is to create a constellation of 13,000 satellites code-named “Guo Wang”. They intend to create two constellations (GW-A59 and GW-2) with a coverage of 37.5 to 42.5 GHz (space-to-Earth) and 47.2 to 51.4 GHz (Earth-to-space). According to multiple sources, this constellation is part of a wider effort by China to stake its claim to the growing satellite internet market. The […]

Photonic filter separates signals from noise to support future 6G wireless communication

Science Daily  April 11, 2023 To achieve high reconfigurability in integrated microwave photonic filters (IMPFs) previous works adopt complicated system structures and modulation formats, which put great pressure on power consumption and controlment, and, therefore, impeded the massive deployment of IMPF. Researchers in China proposed a streamlined architecture for a wideband and highly reconfigurable IMPF on the silicon photonics platform. For various practical filter responses, to avoid complex auxiliary devices and bias drift problems, a phase-modulated flexible sideband cancellation method was employed based on the intensity-consistent single-stage-adjustable cascaded-microring. The IMPF exhibited an operation band extending to millimeter-wave and other extraordinary […]

Scientists develop energy-saving, tunable meta-devices for high-precision, secure 6G communications

Nanowerk  March 16, 2023 Researchers in Hong Kong has invented a synthetic phase design of rotary doublet Airy beam and triplet Gaussian beam varifocal meta-devices to fully control the terahertz beam’s propagation direction and coverage area. The focusing spot can be delivered to arbitrary positions in a two-dimensional plane or a three-dimensional space. The highly concentrated signal can be delivered to a specific position, and the transmission direction can be adjusted freely to enable secure, flexible, and high-directivity 6G communication systems. According to the researchers this technology avoids the high costs associated with extensive use of active components. 6G communication […]