Volume 18 Issue 12, December 2024

Daniel Mittleman spoke with Nature Photonics about promising applications using terahertz waves, including spectroscopy, imaging, wireless communications, and quality control in industry.

Picosecond pulses of terahertz light used for rapid and reversible switching of charged excitons (trions) into neutral excitons in a two-dimensional semiconductor open perspectives for high-speed optoelectronic devices and fundamental studies of new electronic phases of matter.

Oscillators for tunable terahertz waves with ultra-high spectral purity may pave the way for precise molecular clocks and extremely high-data-rate wireless communications.

A new attosecond metrology technique for studying light–molecule interactions in liquids may open the door for variety of attosecond applications in chemistry and biology.

Implementing stable lasers often requires complex packaging of multiple devices, such as stand-alone external cavities and isolators. Now, stabilizing and isolating lasers can be realized in a single silicon chip thanks to the Kerr nonlinear effect in a resonator.

Light upconversion and bistable optical switching is achieved via positive photonic feedback by integrating a photoactive layer with a tandem OLED.

Light-based processing and machine learning featured heavily in San Diego at the 2024 SPIE Optics + Photonics conference. Enthusiasm was coupled with questions related to the real-world applicability and the merits of linear vs non-linear, and all-optical vs hybrid, approaches.

The authors review recent advances in inverted perovskite solar cells, with a focus on non-radiative recombination processes and how to reduce them for highly efficient and stable devices.

Cr³⁺-sensitized lanthanide-doped nanoparticles afford high-brightness luminescence in the near-infrared region for applications in in vivo non-invasive bioimaging.

A Brillouin laser-driven terahertz oscillator is developed. The phase noise level of the generated terahertz waves is less than –100 dBc Hz^–1, translating to timing noise below 10 as Hz^–1/2 at 10 kHz Fourier frequency, over a carrier frequency range from 300 GHz to 3 THz.

Amorphous phases of self-assembling molecules employed as a hole-transporting layer in inverted perovskite solar cells contribute to homogeneous perovskite film growth, resulting in a power conversion efficiency of 25.20% (certified 24.35%) for one-square-centimetre area cells.

Two chiral enantiomers, R- and S-BBTI, are found to efficiently emit near-infrared circularly polarized phosphorescence with a large dissymmetry factor of 0.013 in dilute solutions.

A nonlinear nanophotonic resonator is used to spectrally translate an electro-optic frequency comb to a controllable set of wavelengths between 600 nm and 1,050 nm, with comb properties that are advantageous for high-resolution spectroscopy preserved.

Using the European XFEL free-electron laser, researchers demonstrate terawatt-scale, attosecond hard X-ray pulses. Ten pulse trains per second, each containing hundreds of pulses at megahertz repetition rates, are achieved. Such short and intense pulses at high repetition rate enable unprecedented damage-free X-ray measurements with attosecond temporal resolution.

Integrating an organic photodiode with a tandem OLED enables positive photonic feedback that results in bistable behaviour. Devices show giant hysteresis in their current–voltage–luminance characteristic and upconversion of near-infrared to visible light with 100-fold photon-to-photon gain.

Both laser stabilization and isolation are demonstrated simultaneously by using Kerr nonlinearity in a high-Q silicon nitride ring resonator to self-injection lock a distributed-feedback laser, bringing on-chip lasers closer to real-world fully integrated applications.

By incorporating time-programmable frequency combs, free-form dual-comb spectroscopy enables compressive sensing at factors of up to 155, with a corresponding reduction in acquisition time without sacrificing spectral resolution.

Near-petahertz electric field detection of few-femtosecond pulses with a temporal resolution of 200 attoseconds and subfemtojoule sensitivity is experimentally demonstrated, paving the path towards high-resolution biological spectro-microscopy.

A diamond storage medium that uses fluorescent vacancy centres as robust storage units provides a high storage density of 14.8 Tbit cm⁻³.

Researchers experimentally demonstrate a fully integrated coherent optical neural network. The system, with six neurons and three layers, operates with a latency of 410 ps.

Using short pulses in the terahertz spectral range following optical injection, ultrafast excitation of trions to excitons and free carriers in monolayer MoSe₂ can be realized within picoseconds, advancing nanoscale optoelectronics devices.