We present here the implementation of an optoelectronic oscillator (OEO) that leverages the optical comb produced by a silicon add‐drop ring resonator to directly convert signals from optical to microwave domain. The OEO comprises a CW laser, an intensity modulator, a silicon add‐drop ring, a photodetector, and radiofrequency amplifier. By using millimeter‐long silicon‐on insulator micro‐ring resonator, we generated an oscillation signal with a frequency determined by the free spectral range (FSR) of the ring. In this scheme, the sharp transmission peaks in the drop port of an add‐drop silicon resonator are used as the optical comb. The optimised ring has a length of 5.8 mm with a measured FSR of 112 pm, an extinction ratio of 20 dB and an optical quality factor of 2.2 × 10 5 . The complete OEO loop yields a 14.12 GHz signal with a phase noise level of −100 dBc/Hz at an offset of 100 kHz from the carrier. This result shows that OEOs directly based on millimeters long silicon rings are a promising path for generating low‐noise microwave signals.

Here, the authors propose and apply two novel schemes of multi‐band carrierless amplitude and phase (m‐CAP) modulation for spatial modulation (SM)‐based visible light communications (VLC) systems. In SM, both spatial and signal constellation are utilised to improve the performance of the m‐CAP system. Here, they have adopted the non‐DC m‐CAP which is a power efficient technique with no DC‐bias. The bit error rate (BER) performance and the spectral efficiency of the proposed systems are compared with single‐input single‐output (SISO) and multiplexing multiple‐input multiple‐output (MIMO) m‐CAP systems. Results demonstrate that non‐DC m‐CAP, with the same spectral efficiency as that of SISO m‐CAP, outperforms other schemes in terms of BER due to its power efficiency; however, a higher spectral efficiency can be achieved by the SM‐MIMO m‐CAP scheme.

The high optical bandwidth requirement in the mobile fronthaul link of the next generation cloud radio access network represents one of the major design constraints. In this study, a digital fronthaul link based on digital radio over fibre system that integrates the duobinary coding scheme with the optical single sideband (OSSB) transmission is proposed. This system reduces the spectral occupancy of the transmitted signals as well as the chromatic dispersion effects induced by fibre in both the electrical and optical domains. The OSSB signal is created by driving two cascaded optical modulators with a combination of a baseband digital signal and the Hilbert transform of that signal. The transmission performance of a digitised 16‐quadrature amplitude modulation 16‐QAM radio frequency signal with a bit rate of 1.25 Gb/s over a standard single mode fibre is investigated. The results show that the fronthaul transmission length can be extended by 75 and 16.6% relative to the case of transmitting the digitised signal using double sideband and single sideband (SSB) transmission formats, respectively. The power budget is improved by 10 dB compared to the SSB case with respect to the measured optical signal‐to‐noise ratio at 70 km fibre distance, while maintaining the EVM below the standardised values of the 3GPP.

Here to determine the thermal stability of buffered layer organic solar cell (BL-OSC), the effect of post anneal treatment has been studied. To investigate the effect of post annealing, the organic solar cells (OSCs) are annealed at the 120°C for different time duration. It has been observed that the BL-OSC structure exhibits the better thermal stability. Further, as the authors vary the post-annealing time duration from 0 min to 20 min, the power conversion efficiency (PCE) in the case BL-OSC drops by ~20%, whereas in conventional OSC, the PCE drops by ~35%. This annealing dependent study shows that, in conventional OSC structure an increase in phase segregation between donor and acceptor molecules reduces exciton dissociation and charge separation, this leads to sharp increase in series resistance and significant reduction in fill factor of the device. Whereas in the case of BL-OSS, there is a minimum reduction in the fill factor, which also determines the superior carrier collection and low recombination on the elevated annealing conditions. Further, the experimental results show that, in comparison with the conventional OSC structure, inserting the pure P3HT interlayer between PEDOT:PSS (hole transport layer) and P3HT:PCBM (photoactive layer) improves the PCE of the device by 34%.

To improve the bandwidth efficiency of free‐space optical systems and at the same time to reduce the impact of the background noise, a differential M ‐ary pulse‐amplitude modulation ( M ‐PAM) signalling scheme that uses two laser transmitters is proposed. The authors first consider the condition that the receiver perfectly knows the instantaneous channel coefficient and compare the performance of the proposed differential PAM with the conventional PAM signalling and show the improved performance when the background noise level is relatively high. Second , the practical situation where the receiver has to estimate the channel for signal detection is considered. The authors propose an estimation scheme based on the characteristics of the differential PAM signalling while requiring no pilot symbol transmission. The proposed data‐aided channel estimation is performed on a sequence of received PAM symbols. The authors also show that for a sufficiently large observation window, the proposed estimation method allows achieving a performance close to the perfect channel knowledge.

Copper ions are incorporated into the PbS quantum dots as dopants via a chemical method and an ion irradiation method. For irradiating the samples, a 100 MeV copper swift heavy ion beam is used with three different doses of 1 × 10 11 , 3 × 10 11 , and 1 × 10 12 ions/cm 2 . The doped and irradiated samples are characterised by different techniques and introduced as a sensitising layer in a solar cell. The current density-voltage characteristics of the solar cells are studied under white light illumination conditions and the solar cell parameters such as J sc , V oc , fill factor, and efficiency are obtained. Efficiency as high as 4.78% is obtained for irradiated quantum dots, which is significantly higher than that of pristine and doped quantum dot solar cells. However, at higher ion dosage, the solar cell efficiency degrades due to unwanted particle agglomeration in quantum dots.

Recently, a novel Photonic-Integrated Circuit (PIC) paradigm based on the use of a new kind of ultra-directive, low-loss, highly efficient and broadband silicon nanoantenna has enabled the first demonstration of an on-chip wireless interconnect, with potential applications in reconfigurable networks and lab-on-a-chip systems. Despite the fact that the far-field properties of these nanoantennas have been widely studied, their near-field behaviour stays unexplored. Here, the authors study this feature through scanning near-field optical microscopy (SNOM). For this purpose, the authors design and characterise an on-chip two-port wireless link using a tailored SNOM. The conducted near-field measurements will be useful to improve the design of these integrated photonic devices with potential impact on a variety of applications, from biosensing to optical communications.

In this work, the authors present their recent progress in the development of a platform for the mid‐infrared wavelength range, based on suspended silicon waveguides with subwavelength metamaterial cladding. The platform has some intrinsic advantages, which make it a very promising candidate for sensing applications in the molecular fingerprint region. Specifically, it can cover the full transparency window of silicon (up to a wavelength of 8 μm), only requires one lithographic etch‐step and can be designed for strong light–matter interaction. Design rules, practical aspects of the fabrication process and experimental results of a complete set of elemental building blocks operating at two very different wavelengths, 3.8 and 7.7 μm, are discussed. Propagation losses as low as 0.82 dB/cm at λ0 = 3.8 μm and 3.1 dB/cm at λ0 = 7.7 μm are attained for the interconnecting waveguides.