A cost-effective and high-throughput material named perovskite has proven to be capable of converting 15.9% of the solar energy to electricity, compared to an efficiency of 3.8% that was obtained only four years ago. It has already outperformed most of the thin-film solar cell technologies that researchers have been studying for decades. Currently, the architecture of perovskite solar cells has been simplified from the traditional dye-sensitized solar cells to planar-heterojunction solar cells. Recently, the performance of perovskite in solar cells has attracted intensive attention and studies. Foreseeably, many transformative steps will be put forward over the coming few years. In this review, we summarize the recent exciting development in perovskite solar cells, and discuss the fundamental mechanisms of perovskite materials in solar cells and their structural evolution. In addition, future directions and prospects are proposed toward high-efficiency perovskite solar cells for practical applications.

We theoretically investigate the electromagnetic response of a novel class of multilayered metamaterials obtained by alternating graphene sheets and dielectric layers, the whole structure not exhibiting a plane of reflection symmetry along the stacking direction. We show that the electromagnetic response of the structure is characterized by a magneto-electric coupling described by an effective chiral parameter. Exploiting the intrinsic tunability of graphene–light coupling, we prove that one can tune both the dielectric and the chiral electromagnetic response by varying the graphene chemical potential through external voltage gating.

Asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) has been a promising candidate in visible light communications (VLC) due to its improvement in power efficiency and reduction of nonlinearity based on previous simulation analysis. In this paper, for the first time as far as we know, we experimentally verify that ACO-OFDM would be an efficient scheme to improve the performance of a gigabit wavelength division multiplexing VLC system. Our theoretical investigations reveal that the advantages of ACO-OFDM can be attributed to the reduction of inter-carrier interference caused by signal–signal beating noise. An aggregate data rate of 1.05 Gb∕s is successfully achieved over 30 cm transmission below the 7% forwarderror-correction threshold of 3.8 × 10 -3. The experimental results show that ACO-OFDM can outperform DC-biased optical OFDM by BER performance of 1.5 dB at the same data rate and 4 dB at the same bandwidth, which clearly demonstrates the benefit and feasibility of ACO-OFDM.

We propose an efficient and low-power second harmonic generation (SHG) process in a silicon-compatible hybrid plasmonic microring resonator. By making the microring resonator doubly resonant at the fundamental wavelength of 3.1 μm and second harmonic wavelength of 1.55 μm, the SHG efficiency is enhanced by almost two orders of magnitude when compared to the previous result induced in a straight plasmonic waveguide. A SHG efficiency of 13.71% is predicted for a low pump power of 20 mW in a ring with radius of 2.325 μm. This device provides a potential route for realizing efficient frequency conversion between mid-infrared and near-infrared wavebands on a chip.

In this paper, a new approach for wireless data transmission within an aircraft cabin is presented. The proposed application enables the transmission of data to a passenger’s user device. As wireless in-flight applications are subject to strict frequency and electromagnetic compatibility (EMC) regulations, the data is transferred by optical wireless transmission, specifically by two-dimensional visual codes. To this end, black-and-white or colored visual code sequences are displayed on the in-flight entertainment screen. These visual codes are captured by the built-in camera of the passenger’s mobile device and are decoded to reconstruct the transmitted data. In order to compensate for frame losses caused by effects like occlusion and motion blur, a temporal forward error correction coding scheme is applied. Transmission experiments within an Airbus A330 cabin mock-up demonstrate the functionality of the implemented system under realistic conditions such as ambient illumination and geometric configuration. Representative user devices are used for evaluation; specifically, a low-cost and a high-end smartphone are employed as receivers. Performance evaluations show that the proposed transmission system achieves data rates of up to 120 kbit/s per individual passenger seat with these user devices. As the user device has no physical connection to the sensitive on-board system, the proposed transmission system provides an intrinsic safety feature.

Spurious-free dynamic range (SFDR) limited by intermodulation distortions is a usually accepted measure for dynamic performance of a photonic time-stretched analog-to-digital converter (ADC). In this paper, SFDR improvement in a photonic time-stretched ADC based on third-order predistortion is proposed. The third-order predistortion is achieved optically within an integrated dual-parallel Mach–Zehnder modulator (DPMZM). The mechanism of SFDR improvement with third-order predistortion in the DPMZM is theoretically analyzed. Compared with a conventional scheme without predistortion, the experimental results show that the SFDR improvement of ～26 dB in the proposed scheme is proved.

New designs are proposed for 2×2 electro-optical switching in the 1.3–12 μm wavelength range. Directional couplers are analyzed using a two-dimensional effective-index approximation. It is shown that three or four side-coupled Si or Ge channel waveguides can provide complete crossbar broad-spectrum switching when the central waveguides are injected with electrons and holes to modify the waveguides’ core index by an amount Δn+iΔk. The four-waveguide device is found to have a required active length L that is 50% shorter than L for the three-waveguide switch. A rule of ΔβL>28 for 3w and ΔβL>14 for 4w is deduced to promise insertion loss 1.5 dB and crosstalk ?15 dB at the bar state. At an injection of ΔNe=ΔNh=5×1017 cm?3, the predicted L decreased from ～2 to ～0.5 mm as λ increased from 1.32 to 12 μm. Because of Ge’s large Δk, the Ge bar loss is high in 4w but is acceptable in 3w.

The most general model of elliptical birefringence in an optical fiber has been developed for a steady-state and transient stimulated Brillouin scattering interaction. The impact of the elliptical birefringence is to induce a Brillouin frequency shift and distort the Brillouin spectrum—which varies with different light polarizations and pulsewidths. The model investigates the effects of birefringence and the corresponding evolution of spectral distortion effects along the fiber, providing a valuable prediction tool for distributed sensing applications.