Microwave photonics

The ability to communicate research results to a non-specialist audience in a clear and concise manner is a skill that should not be overlooked.

Directly embedding single nitrogen–vacancy centres into ordered arrays of plasmonic nanostructures can enhance their radiative emission rate and thus give greater scalability over previous bottom-up approaches for the realization of on-chip quantum networks.

Using a new form of spectroscopic optical coherence tomography, researchers demonstrate three-dimensional molecular imaging of both endogenous and exogenous chromophores with high spectral fidelity. This scheme has significant implications for a range of biomedical applications, including ophthalmology, early cancer detection and understanding fundamental disease mechanisms such as hypoxia and angiogenesis.

Researchers report an all-optical signal processing architecture that enables the multilevel all-optical quantization of phase-encoded optical signals. Using four-wave-mixing and two-pump parametric processes, they experimentally demonstrate up to six levels of quantization.

Using a thin-film outcoupling enhancement method consisting of a weak optical cavity on a flexible substrate with a non-indium-tin-oxide anode, researchers demonstrate phosphorescent organic LEDs with an external quantum efficiency of up to 63% at green wavelengths, which remains as high as 60% at luminous intensities of >10,000 cd m⁻².

Scientists report the fabrication of a nonreciprocal optical resonator with a small length footprint of 290 µm on a silicon-on-insulator substrate. The device achieves unidirectional optical transmission with an isolation ratio of up to 19.5 dB near the telecommunications wavelength of 1,550 nm in a homogeneous external magnetic field.

Researchers use a pre-orienting layer to achieve nearly single-crystalline GaN pyramidal arrays on amorphous glass substrates. The polycrystalline morphology can be controlled by placing a hole-patterned SiO₂ layer on the low-temperature GaN nucleation layer. Light-emitting diodes fabricated by this technique exhibited a luminance of 600 cd m⁻².

Researcher demonstrate the line-by-line pulse shaping of frequency combs generated in silicon nitride ring resonators, and observe two distinct paths to comb formation that exhibit strikingly different time domain behaviours.

The ability to fabricate an array of GaN light emitters on an amorphous glass substrate could lead to significant improvements in the scalability and cost of blue and white LED technology.

Researchers have developed flexible thin-film OLEDs that exhibit high efficiencies at green wavelengths without the use of a high-refractive-index substrate.

The ease at which group III–V semiconductors can now be integrated with silicon suggests that the need for a pure silicon laser is rapidly fading.

The popularity and demand for data-rich wireless communication is driving the deployment of radio-over-fibre technology and the success of the firms such as Zinwave, reports Nadya Anscombe.

Photonic technology can now be used to construct miniature sources of high-frequency radio waves that have exceptional spectral purity.

Slow-light techniques originally conceived for buffering high-speed digital optical signals now look set to play an important role in providing broadband phase and true time delays for microwave signals.

The combination of microwave photonics and optics has advanced many applications in defence, wireless communications, imaging and network infrastructure. Rachel Won talks to Jianping Yao from the University of Ottawa in Canada about the importance of this growing field.

The successful growth of GaN-based LEDs on amorphous glass avoids the size and cost limitations of a sapphire substrate, says Jun Hee Choi from the Samsung Advanced Institute of Technology in South Korea.