Volume 14 Issue 1, January 2020

Time-of-flight 3D imaging is an invaluable remote sensing tool, but raster speeds are currently limited by pulsed-laser scanning rates. By adapting techniques from ultrafast time-stretch imaging, a new LiDAR platform scans orders of magnitude faster than today’s commercial line-scanning pulsed-LiDAR systems.

The realization of ultrafast integrated opto-optical switches with ultra-low switching energies remains an ongoing challenge. Broadband, silicon-compatible devices relying on gap plasmons and saturable absorption in graphene could pave the way forward.

A high-intensity attosecond X-ray free-electron laser, meeting the demands of attosecond science for research on the sub-femtosecond-timescale quantum-mechanical motion of electrons in molecules and solids, is now available for attosecond pump–attosecond probe experiments in the soft X-ray region.

By driving ultrafast soliton molecules with an all-optical external perturbation and monitoring their response in real time, a form of spectroscopy of soliton molecules akin to optical spectroscopy of chemical bonds is introduced.

A wavelength-scanned LiDAR offers high spatial resolution and can dynamically adapt to fast moving scenes.

An amplitude squeezed light source that operates down to 1 kHz frequencies—the lowest squeezing frequency—is generated in nonlinear crystal-based systems. By injecting the squeezed light into a microresonator, the quantum radiation pressure noise is reduced by 1.2 dB.

By exploiting the electro-optic properties of thin-film lithium niobate, an integrated single-waveguide Fourier transform spectrometer with a footprint of <10 mm² and an operational bandwidth of 500 nm in the near- and short-wavelength infrared is demonstrated.

The generation of ultrashort X-ray pulses with a peak power exceeding 100 GW offers new opportunities for studying electron dynamics with nonlinear spectroscopy and single-particle imaging.

All-optical switching with a switching energy of 35 fJ and a switching time of 260 fs is reported in a nanoscale integrated optical circuit.

By employing a Doppler cancellation technique, optical frequency synthesis is achieved with stability and accuracy in the 10⁻²⁰ range within 100 s. An offset between two optical frequency combs phase-locked at 1,542 nm is obtained as 5.4 × 10⁻²¹ at 1,063 nm within 10⁵ s.

Semiconductor nanocrystals with efficient tunable emission in the 1,000–1,700 nm window could prove useful for applications in deep biological imaging and sensing.

A scalable solution involving direct wafer-bonding of high-quality, epitaxially grown gallium phosphide to low-index substrates is introduced. The promise of this platform for integrated nonlinear photonics is demonstrated with low-threshold frequency comb generation, frequency-doubled combs and Raman lasing.