Articles

Near-infrared photoluminescence from carbon nanotubes makes it possible to optically image the vasculature in the brain directly through the skull.

Trapping of a terahertz wave in a photonic-crystal slab and subsequent ‘capture’ through absorption are demonstrated. Over 90% of the wave lying within 17% of the centre frequency is absorbed. Application to the stabilization of terahertz wireless communication systems is shown.

Scalable methods employing a random unitary chip and a quantum walk chip are developed to experimentally verify correct operation for large-scale boson sampling. Experimental analysis reveals that the resulting statistics of the output of a linear interferometer fed by indistinguishable single-photon states exhibits true non-classical characteristics.

A high-resolution, broadband imaging system based on coherent anti-Stokes Raman spectroscopy performs rapid, chemically specific imaging of biological tissue. It employs three-colour excitation and operates across the entire biological window.

The phase of a collection of spins is measured with a sensitivity ten times beyond the limit set by the quantum noise of an unentangled ensemble of ⁸⁷Rb atoms. A cavity-enhanced probe of an optical cycling transition is employed to mitigate back-action associated with state-changing transitions induced by the probe.

The vibrations of the chemical bonds of a single molecule are observed by employing time-resolved coherent anti-Stokes Raman scattering. A gold nanoantenna is used to enhance the signal from the molecule.

A suite of flexible, integrated, high-index-contrast chalcogenide glass photonic devices, including waveguides, microdisk resonators, add–drop filters and photonic crystals, is reported. The devices are demonstrated to survive repeated bending to a submillimetre radius without any significant degradation in their optical performance.

A photothermal imaging scheme that is analogous to optical coherence tomography can be used to construct the three-dimensional structures of bone and burn-affected skin.

Extreme-ultraviolet frequency combs have previously been used to realize spectroscopy with a megahertz level resolution, but higher resolutions are desired for precision-measurement applications. Now, a sub-hertz spectral resolution is demonstrated, which corresponds to coherence times of over 1 s at photon energies up to 20 eV; such coherence times are over six orders of magnitude longer than those previously reported.

Hybrid entanglement between a quantum single-photon qubit state and a classical one is experimentally generated by quantum-mechanically superposing non-Gaussian operations on distinct modes. Entanglement is clearly observed between the two different types of generated states. This method provides a feasible way to generate even larger hybrid entanglement.

Optical entanglement between a particle-like subsystem and a wave-like one is generated through the heralding detection of a single photon in an indistinguishable fashion at a central station. This enables information to be converted from one Hilbert space to the other via teleportation, and hence permits remote quantum processors based on different encodings to be connected.

A simple method is demonstrated for high-order harmonic generation with fully controlled (linear, elliptical and circular) polarization. Its conversion efficiency is comparable to those of conventional high-order harmonic methods. This technique potentially has a broad range of applications from ultrafast circular dichroism to attosecond quantum optics.

A cavity quantum electrodynamics system comprising a quantum emitter and an optical cavity is theoretically investigated. The outcoupling process for the N-photon state of the cavity is simulated. The numerical calculations predict the possibility of operating this system as a source of N-photon bundles with a tunable integer N.

Large-scale densely integrated optical memory on a single photonic crystal chip is demonstrated. The wavelength-division-multiplexing (WDM) capabilities of nanophotonic memories are exploited for optical addressing. This work may enable optical random-access memories and a large-scale WDM photonic network-on-chip.

Recent demonstrations of modulators, polarization rotators and isolators have indicated the potential of graphene for photonic applications. The present study investigates the fundamental limits and near-optimal design of graphene modulators and non-reciprocal devices.

Theoretical analysis reveals that spasers do not differ fundamentally from conventional semiconductor lasers; differences are mainly technical and result from loss in the metal. Spasers are shown to have significantly inferior threshold currents and linewidths to those of vertical-cavity surface-emitting lasers, but their speed can be slightly greater.

High-resolution diffuse optical tomography employing a large array of light sources and detectors arranged around the head can perform functional brain imaging. It provides an alternative to magnetic resonance imaging for monitoring activity in different areas of the brain.

By integrating a photoacoustic transmitter based on a carbon nanotube nanocomposite and an optical microring resonator as an ultrasonic sensor, a low-noise terahertz pulse detection system is demonstrated at room temperature. The response time and the noise-equivalent detectability energy are on the order of 0.1 µs and 220 pJ, respectively.

Frequency combs based on terahertz quantum cascade lasers, which combine the high power of lasers with the broadband capabilities of pulsed sources, are demonstrated. The frequency combs generate 5 mW of terahertz power covering a frequency range of almost 500 GHz and produce more than 70 lines at 3.5 THz.

An investigation of the use of nonlinear upconversion effects like second-harmonic generation and four-wave mixing within biological tissue indicates that it should be possible to perform photodynamic therapy with near-infrared laser light at greater depths than previously.