Articles in 2021

Waveforms of mid-infrared few-cycle optical pulses are captured in a single shot by measuring nonlinear photocurrents in a Si-based image sensor chip. The temporal resolution of waveforms is determined by the spatial resolution of the image sensor.

A four-port programmable interferometer based on aluminium nitride piezo-optomechanical actuators coupled to silicon nitride waveguides is reported. Its low-power mechanism, which can be fabricated in a complementary metal–oxide–semiconductor foundry, facilitates operation at cryogenic temperatures.

Near-infrared emission at around 2 µm is observed from HgTe nanocrystals. LEDs based on this material platform could prove to be a useful low-cost, convenient light source for applications in gas sensing and other tasks.

Absorption lineshape of H₂ is coherently controlled by using intense near-infrared laser pulses. Depending on the time delay between the near-infrared and extreme ultraviolet pulses, the profiles display a Lorentzian or an asymmetric Fano lineshape.

Measurement of the arrival times of annihilation photons in a detector with greater precision is opening the way to new direct forms of tomographic positron emission imaging that do not require back-projection-based reconstruction techniques.

For 20 years, nanoscale 3D printing has been based on two-photon absorption, requiring expensive pulsed lasers. Now, via a two-step absorption process, such printing has been demonstrated using a low-cost, low-power continuous-wave laser diode, showing the potential for dramatic cost reductions in 3D nanoprinting.

The National Ignition Facility at Lawrence Livermore National Laboratory reported over 1.3 MJ output, representing 70% of both input laser energy and official ‘fusion ignition’. Operations manager, Bruno Van Wonterghem, delves into the optics and what to expect next.

As an alternative to high-resolution fabrication by two-photon absorption, researchers demonstrate a two-step absorption process that employs inexpensive light sources.

Progress on Landau level lasers—based on external magnetic field splitting of electronic states—is reviewed, with particular attention paid to the potential for tunable terahertz lasers.

The three-dimensional images generated by digital holography are usually limited to a single color. A new technique exploiting frequency combs generates holograms with hundreds of colors at once.

The direct generation of femtosecond pulses from an 8-μm quantum cascade laser could prove transformative for sensing and spectroscopy.

Near-transform-limited 630 fs pulses with 4.5 W of peak power are generated by compensating the dispersion of a quantum cascade laser emitting around 8 μm. Their temporal nature is assessed by a new method called asynchronous upconversion sampling.

Dual-comb digital holography based on an interferometer composed of two frequency combs of slightly different repetition frequencies and a lensless camera sensor allows highly frequency-multiplexed holography with high temporal coherence.

Visible-spectrum silicon nitride thermo-optic phase modulators based on adiabatic micro-ring resonators with a small device footprint and low power consumption, of potential use for applications like augmented-/virtual-reality goggles, quantum information processing circuits and optogenetics, are presented.

The demonstration of a germanium-based photodiode with a 3 dB bandwidth of 265 GHz and compatibility with silicon photonics and CMOS fabrication offers a cost-effective route to faster channel data rates for optical communications.

Highly efficient upconversion of light by organic semiconductor heterojunction interfaces is demonstrated. This process is enabled by charge separation- and recombination-mediated charge transfer states at the interface.

By sandwiching a germanium fin between complementary in situ-doped silicon layers, a waveguide-coupled germanium photodiode with a 3-dB bandwidth of 265 GHz, accompanied by high responsivity and low dark current, is realized.