Tiny terahertz laser is the first to reach three key performance goals at once

Nanowerk  December 30, 2020 A photonic wire laser (PWL) is a type of laser built on a semiconductor chip that has nanometer-sized bore and a millimeter length cavity. Coupling multiple adjacent PWLs can synchronize the light beams to emit at the same or multiple wavelengths and combine their power. A team of researchers in the US (MIT, Sandia National Laboratory) proposed and demonstrated a scheme to form a coupled cavity by taking advantage of this unique feature of photonic wire lasers. They used quantum cascade lasers with antenna-coupled third-order distributed feedback grating as the platform. Inspired by the chemistry of […]

Researchers invent broad-band tunable terahertz absorber

Phys.org  November 24, 2020 THz absorbers with strong absorption, broad-band absorption bandwidth and tunable characteristics have attracted the attention of many researchers with extensive application prospects in THz wave shielding, THz imaging, and THz sensitive thermal detecting. Researchers in China introduced strongly correlated electron material VO2 as a functional layer and realized the broad-band tunable THz spectrum properties in the device. The conductivity, dielectric constant, as well as optical properties got a dramatic switching during the insulator-metal transition at TC = 340 K, and the transition could be tuned by temperature, electric field, and light. The device had a 74% […]

Researchers develop a high-power, portable terahertz laser

MIT News  November 2, 2020 Until now, generation of terahertz radiation powerful enough to perform real-time imaging and fast spectral measurements required temperatures far below 200 kelvins (-100 degrees Fahrenheit) or lower. An international team of researchers (USA – MIT, Canada) has developed THz QCLs (at ~4 THz) with a maximum operating temperature of 250 K. The high operating temperature enables portable THz systems to perform real-time imaging with a room-temperature THz camera, as well as fast spectral measurements with a room-temperature detector…read more. TECHNICAL ARTICLE

Paving the way for tunable graphene plasmonic THz amplifiers

Nanowerk  September 8, 2020 An international team of researchers (Japan, Poland, France, Russia) has demonstrated room-temperature coherent amplification of terahertz radiation in graphene, electrically driven by a dry cell battery. They designed a series of monolayer-graphene channel transistor structures that worked as a highly efficient antenna to couple the THz radiations and graphene plasmons. They demonstrated THz radiation amplification gain of up to 9% in the monolayer graphene–far beyond the well-known landmark level of 2.3% that is the maximum available when photons directly interact with electrons without excitation of graphene plasmons. Because all results were obtained at room temperature, the […]

Music goes terahertz: Scientists achieve breakthrough for pulsed terahertz lasers

Nanowerk  August 27, 2020 If ultrashort pulses could be directly generated in quantum cascade lasers terahertz radiation could be used for many more applications. An international team of researchers (Germany, Italy, UK) has developed a new class of saturable absorbers operating at much lower saturation intensities to change the ultrashort pulses generated in quantum cascade lasers into pulsed operation. They designed a microstructured assembly of a gold mirror and a gold grating that jointly work like a resonating body for terahertz radiation. The strong coupling between the electrons and the terahertz microcavity results in an excitation that is half electron, […]

NTU Singapore scientists build ultra-high-speed Terahertz wireless chip

EurekAlert  August 5, 2020 Conventional approaches to terahertz waveguiding suffer from sensitivity to defects and sharp bends. Building on the topological phase of light, an international team of researchers (Singapore, Japan) experimentally demonstrated robust terahertz topological valley transport through several sharp bends on the all-silicon chip. The valley kink states are excellent information carriers owing to their robustness, single-mode propagation, and linear dispersion. They have demonstrated error-free communication through a highly twisted domain wall at an unprecedented data transfer rate (exceeding ten gigabits per second) that enables real-time transmission of uncompressed 4K high-definition video. The research opens a route towards […]

Underused part of the electromagnetic spectrum gets optics boost from metamaterial

Phys.org  July 14, 2020 Terahertz radiation potentially has applications in next-generation wireless communications (6G/7G), security systems, biomedicine, etc. because of the lack of appropriate materials and sophisticated optical components for flexible control of terahertz waves. Researchers in Japan have engineered a 2.28-µm ultra-thin terahertz metasurface collimator with a high directivity of 4.6 times consisting of 339 pairs of meta-atoms compared with a single terahertz continuous-wave source. The metasurface exhibits an extremely high refractive index of 15.0 and a low reflectance of 15.5% at 3.0 THz. It should facilitate ground-breaking applications such as arbitrary phase converters, solid immersion lenses, and cloaking…read more. […]

Research team presents novel transmitter for terahertz waves

Phys.org  March 16, 2020 If you irradiate pure germanium with a short laser pulse, it takes several microseconds before the electrical charge in the semiconductor disappears. Only then can the crystals absorb the next laser pulse. Gallium-arsenide crystals only deliver relatively narrowband terahertz pulses and thus a restricted frequency range. Researchers in Germany used gold implanted germanium to present ultrabroadband (extending up to 70 THz) THz emission that is compatible with mode-locked fibre lasers operating at wavelengths of 1.1 and 1.55 μm with pulse repetition rates of 10 and 20 MHz, respectively. This result opens the possibility for the development of compact THz […]

New graphene amplifier unlocks hidden frequencies in the electromagnetic spectrum

Nanowerk  February 3, 2020 An international team of researchers (South Korea, Russia, UK) propose a new type of optical transistor for broadband amplification of THz radiation. It is made of a graphene–superconductor hybrid, where electrons and Cooper pairs couple via Coulomb forces. The transistor operates via the propagation of surface plasmons in both layers, and the origin of amplification is the quantum capacitance of graphene. It leads to THz waves amplification, the negative power absorption, and as a result, the system yields positive gain, and the hybrid acts like an optical transistor, operating with the terahertz light. It can, in […]

Record-breaking terahertz laser beam

Phys.org  January 20, 2020 An international team of researchers (Greece, Austria, Qatar, Russia, Lithuania) has experimentally demonstrated that two-color filamentation of femtosecond mid-infrared laser pulses at 3.9 μm allows one to generate ultrashort sub-cycle THz pulses with sub-milijoule energy and THz conversion efficiency of 2.36%, resulting in THz field amplitudes above 100 MV cm−1. Numerical simulations predict that the observed THz yield can be significantly upscaled by further optimizing the experimental setup. They showed that the generated THz pulses are powerful enough to induce nonlinear cross-phase modulation in electro-optic crystals. The work paves the way toward free space extreme nonlinear THz optics using […]