Phys.org June 3, 2024 Photonic lantern (PL) spatial multiplexers enable efficient conversion between multiple single-mode (SM) sources and a multimode (MM) waveguide of the same dimension. PL multiplexers operate by facilitating adiabatic transitions between the SM arrayed space and the single MM space. However, current fabrication methods are forcing the size of these devices to multi-millimeters, making integration with micro-scale photonic systems quite challenging. A team of researchers (Israel, USA – industry) presented the design, fabrication, and characterization of a 6-mode mixing, 375 µm long PL that enabled the conversion between six single-mode inputs and a single six-mode waveguide. The PL […]
Category Archives: Communications technology
Physicists create optical component for 6G
Phys.org May 16, 2024 A new generation of diffractive components integrating specific geometry with additional features (flexibility, stretchability, rotation, and other approaches for tuning properties) extends the functionality of wavefront control. Researchers in Russia demonstrated an innovative approach to control the THz wavefront via a layered composition of spiral zone plates (SZPs) with tunable mutual orientation and scaling. As a proof of concept, they designed the SZP with experimental characterization of the resultant vortex beams. For each single SZP, a flexible element was proposed based on thin film of single-walled carbon nanotubes deposited on a stretchable substrate. The diffraction element […]
Physicists demonstrate first metro-area quantum computer network in Boston
Phys.org May 15, 2024 A team of researchers in the US (MIT, Harvard University, industry) demonstrated a two-node quantum network composed of multi-qubit registers based on silicon-vacancy (SiV) centres in nanophotonic diamond cavities integrated with a telecommunication fibre network. Remote entanglement was generated by the cavity-enhanced interactions between the electron spin qubits of the SiVs and optical photons. Serial spin-photon entangling gate operations with time-bin qubits were used for robust entanglement of separated nodes. Long-lived nuclear spin qubits were used to provide second-long entanglement storage and integrated error detection. By integrating efficient bidirectional quantum frequency conversion of photonic communication qubits […]
Physicists reach atomic-scale telegraphy with light
Phys.org May 8, 2024 By exploiting linear interaction with tip-confined evanescent light fields, near-field microscopy has reached even higher resolution, prompting a vibrant research field by exploring the nanocosm in motion. Yet the finite radius of the nanometre-sized tip apex has prevented access to atomic resolution. Researchers in Germany leveraged extreme atomic nonlinearities within tip-confined evanescent fields to push all-optical microscopy to picometric spatial and femtosecond temporal resolution. They discovered an unprecedented and efficient non-classical near-field response, in phase with the vector potential of light and strictly confined to atomic dimensions. This ultrafast signal was characterized by an optical phase […]
Combating disruptive ‘noise’ in quantum communication
Phys.org April 15, 2024 Nonlocality is crucial for device-independent technologies like quantum key distribution and randomness generation. It quickly deteriorates in the presence of noise, and restoring nonlocal correlations requires additional resources incurring a significant resource overhead. An international team of researchers (Australia, France, USA – NIST, Boulder, CO) experimentally demonstrated that single copies of Bell-local states, incapable of violating any standard Bell inequality, could give rise to nonlocality after being embedded into a quantum network of multiple parties. They subjected the initial entangled state to a quantum channel that broadcast part of the state to two independent receivers and […]
The world is one step closer to secure quantum communication on a global scale
Phys.org March 25, 2024 An on-demand source of bright entangled photon pairs is needed for quantum key distribution (QKD) and quantum repeaters. The generation of such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, SPDC pair extraction efficiency is very limited when operating at near-unity fidelity. In principle quantum dots in photonic nanostructures can overcome this limit, but the devices with high entanglement fidelity have low pair extraction efficiency. An international team of researchers (Canada, the Netherlands, Sweden) has demonstrated a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP […]
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 […]