International study reveals exceptional property of next generation optical fibers

EurekAlert  February 15, 2021 The elastic backscattering of light in optical fiber is a fundamental phenomenon that sets the ultimate performance of several fiber systems such as gyroscopes and bidirectional transfer links. Until now, efforts to reduce the backscattering coefficient have yielded limited results. An international team of researchers (Canada, UK) measured backscattering from a low-loss antiresonant hollow-core fiber and showed that it is more than 40 dB below reported values in silica-core fiber and hollow-core photonic bandgap fiber. The record-low level of −118dB/m measured with their optical frequency-domain reflectometer is in good agreement with simulations in which they assumed […]

A performance leap for graphene modulators in next generation datacom and telecom

Nanowerk  February 16, 2021 Electro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration, and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. An international team of researchers (Spain, Italy, Belgium) overcame this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. They integrated hafnium oxide and two-dimensional hexagonal boron nitride within the insulating section of a double-layer graphene EA modulator. This combination of materials […]

Wafer-scale production of graphene-based photonic devices

Science Daily  February 11, 2021 Graphene has been recently proposed to be integrated with silicon photonics to meet the challenges of next generation optical communication to increase the available bandwidth while reducing the size, cost, and power consumption of photonic integrated circuits. An international team of researchers (Italy, UK) focused on graphene photodetectors for high speed datacom and telecom applications based on the photo-thermo-electric effect, allowing for direct optical power to voltage conversion, zero dark current, and ultra-fast operation. They reported on a chemical vapour deposition graphene photodetector based on the photo-thermoelectric effect, integrated on a silicon waveguide, providing frequency […]

Capturing Free-Space Optical Light for High-Speed WiFi

Duke University  February 9, 2021 Visible and infrared light can carry more data than radio waves, but has always been confined to a hard-wired, fiber-optic cable. A team of researchers in the US (Duke University, industry) has demonstrated a low-loss plasmonic metasurface that can collect fast-modulated light with a 3 dB bandwidth exceeding 14 GHz and a 120º acceptance angle and convert it to a directional source with an overall efficiency of ∼30%. This exhibits a 910-fold increase in the overall fluorescence and a 133-fold emission rate enhancement. The metasurface was created over macroscopic areas with scalable techniques and the […]

Quantum effects help minimize communication flaws

EurekAlert  February 10, 2021 Both quantum computation and quantum communication are strongly deteriorated because quantum superposition state can be destroyed, or entanglement between two or more quantum particles can be lost. An international team of researchers (Austria, UK, Hong Kong, Switzerland, France, Canada) experimentally and numerically compare different ways in which two trajectories through a pair of noisy channels can be superposed. They observed that, within the framework of quantum interferometry, the use of channels in series with quantum-controlled operations generally yields the largest advantages. The results contribute to clarify the nature of these advantages in experimental quantum-optical scenarios and […]

Quantum tunneling in graphene advances the age of terahertz wireless communications

EurekAlert  February 3, 2021 As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. An international team of researchers (Russia, UK) address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG’s electrically tunable band structure, they created a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation was then down-converted by the tunnel junction nonlinearity, resulting in high responsivity and low-noise detection. They demonstrated how switching from intraband Ohmic to interband tunneling regime can […]

Terahertz accelerates beyond 5G towards 6G

TechXplore  February 1, 2021 Researchers in Japan configured a two-channel terahertz transmitter (Tx) by modulating the output of a laser pair with wavelengths in the 1.55-micron band, which was set so that the frequency difference was in the 300-GHz band, with an 8K video signal source using an intensity modulator and converting it into terahertz waves using an ultrafast photodiode. After the wirelessly transmitted terahertz waves were detected by sensitive terahertz coherent receivers (Rxs) using resonant tunnel diodes (RTDs) they were split from the two channels into four channels and connected to an 8K monitor via HDMI cable. Using this […]

Long-distance and secure quantum key distribution (QKD) over a free-space channel

Phys.org  January 25, 2021 Measurement-device-independent quantum key distribution (MDI-QKD) protocol can help in closing all loopholes on detection at once. It has only been successfully implemented using fiber optics. To implement the protocol across free-space channels two main challenges need to be addressed. One is to reduce the gap between theory and practice of QKD, and the other one is to extend the distance of QKD. Researchers in China have developed a robust adaptive optics system – high-precision time synchronization and frequency locking between independent photon sources located far apart to realize free-space MDI-QKD over a 19.2-km urban atmospheric channel. […]

Record-breaking laser link could help us test whether Einstein was right

Science Daily  January 22, 2021 An international team of researchers (Australia, France) combined phase stabilisation technology with advanced self-guiding optical terminals that allowed laser signals to be sent from one point to another without interference from the atmosphere. They demonstrated phase-stabilized optical frequency transfer over a 265 m horizontal point-to-point free-space link between optical terminals with active tip-tilt mirrors to suppress beam wander, in a compact, human-portable set-up. They could correct for atmospheric turbulence in 3D, that is, left-right, up-down and, critically, along the line of flight. According to the researchers if you have one of these optical terminals on the […]

Using graphene, researchers increase optical data transmission speed by a factor of at least 10,000.

Nanowerk  January 19, 2021 Conventional optical-fiber-based pulsed lasers have limits to increasing the number of pulses per second above the MHz level. Researchers in South Korea inserted an additional resonator containing graphene into a fiber-optic pulsed-laser oscillator that operates in the domain of femtoseconds (10-15 seconds). This increased data transmission and processing speeds significantly. They synthesized graphene, which has the characteristics of absorbing and eliminating weak light and amplifying the intensity by passing only strong light into the resonator. This allows the laser intensity change to be accurately controlled at a high rate, and thus the repetition rate of pulses […]