Surveying on MIMO Technology for Future Wireless Communication

Massive MIMO is an extension of traditional MIMO with the exception that the BSs in massive MIMO are equipped with large number of antennas, usually hundred or more. This large number of antennas provide several positive advantages towards wireless communication with respect to increasing volume of data traffic. Each antenna is capable of serving multiple users simultaneously leading to reduction in power consumption as well as data rate amplification. Additionally, narrow and more focused beams are pointed to individual user devices located at the cell edge thereby upgrading of downlink signal quality. Using massive MIMO technique also increases reliability of the links, reduces noise effects, and mitigates and interference. With increasing number of users gets service, the throughput of the system also increases.

Shrinking multiplexed orbital angular momentum to the nanoscale

Orbital angular momentum interactions at the nanoscale have remained elusive because the phase structure becomes unresolved. Now researchers have shown how to overcome this with tightly focused beams, demonstrating a record-high six-dimensional encoding in an ultra-dense nanoscale volume.

Methodology of optimisation for a nanostructured two-photon absorption photodetector

We introduce a 3-step method to optimise a nanostructured photodetector for infrared sensing through non degenerated two-photon absorption (NDTPA). First, the nanostructure is designed to tailor the distribution and concentration of both pump and signal intensities within the absorbing layer, thus leading to a gain in two-photon absorption. Second, the issue of the competition between NDTPA and other sub-bandgap transitions is tackled with a new figure of merit to favor as much as possible NDTPA while minimising other absorption processes. Third, a refined computation of the gain and the figure of merit is done to consider focused beams. Finally, two scenarios based on low power infrared photodetection are investigated to illustrate the flexibility and adaptibility of the method. It is shown that the gain is up to 7 times higher and the figure of merit is up to 20 times higher compared to the literature.

A multipurpose end-station for atomic, molecular and optical sciences and coherent diffractive imaging at ELI beamlines

We report on the status of a users’ end-station, MAC: a Multipurpose station for Atomic, molecular and optical sciences and Coherent diffractive imaging, designed for studies of structure and dynamics of matter in the femtosecond time-domain. MAC is located in the E1 experimental hall on the high harmonic generation (HHG) beamline of the ELI Beamlines facility. The extreme ultraviolet beam from the HHG beamline can be used at the MAC end-station together with a synchronized pump beam (which will cover the NIR/Vis/UV or THz range) for time-resolved experiments on different samples. Sample delivery systems at the MAC end-station include a molecular beam, a source for pure or doped clusters, ultrathin cylindrical or flat liquid jets, and focused beams of substrate-free nanoparticles produced by an electrospray or a gas dynamic virtual nozzle combined with an aerodynamic lens stack. We further present the available detectors: electron/ion time-of-flight and velocity map imaging spectrometers and an X-ray camera, and discuss future upgrades: a magnetic bottle electron spectrometer, production of doped nanodroplets and the planned developments of beam capabilities at the MAC end-station.

Light-emitting metalenses and meta-axicons for focusing and beaming of spontaneous emission

Phased-array metasurfaces have been extensively used for wavefront shaping of coherent incident light. Due to the incoherent nature of spontaneous emission, the ability to similarly tailor photoluminescence remains largely unexplored. Recently, unidirectional photoluminescence from InGaN/GaN quantum-well metasurfaces incorporating one-dimensional phase profiles has been shown. However, the possibility of generating arbitrary two-dimensional waveforms—such as focused beams—is not yet realized. Here, we demonstrate two-dimensional metasurface axicons and lenses that emit collimated and focused beams, respectively. First, we develop off-axis meta-axicon/metalens equations designed to redirect surface-guided waves that dominate the natural emission pattern of quantum wells. Next, we show that photoluminescence properties are well predicted by passive transmission results using suitably engineered incident light sources. Finally, we compare collimating and focusing performances across a variety of different light-emitting metasurface axicons and lenses. These generated two-dimensional phased-array photoluminescence waveforms facilitate future development of light sources with arbitrary functionalities.

Ultrafast Light Targeting for High-Throughput Precise Control of Neuronal Networks

Understanding how specific sets of neurons fire and wire together during cognitive-relevant activity is one of the most pressing questions in neuroscience. Two-photon, single-cell resolution optogenetics based on holographic light-targeting approaches enables accurate spatio-temporal control of individual or multiple neurons. Yet, currently, the ability to drive asynchronous activity in distinct cells is critically limited to a few milliseconds and the achievable number of targets to several dozens. In order to expand the capability of single-cell optogenetics, we introduce an approach capable of ultra-fast sequential light targeting (FLiT), based on switching temporally focused beams between holograms at kHz rates. We demonstrate serial-parallel photostimulation strategies capable of multi-cell sub-millisecond temporal control and many-fold expansion of the number of activated cells. This approach will be important for experiments that require rapid and precise cell stimulation with defined spatio-temporal activity patterns and optical control of large neuronal ensembles.

A treatment planning study comparison between supine and prone position for different lung tumour locations using CyberKnife TPS

Aim: CyberKnife is the most advanced form of stereotactic body radiotherapy (SBRT) system that uses a robotic arm to deliver highly focused beams of radiation; however, a limitation is that it only irradiates from ceiling to floor direction. In patients with posterior lungs tumour who are positioned supine, normal lung tissue may suffer undesirable radiation injuries. This study compares the treatment planning between the prone set-up and the supine set-up for lung cancer in CyberKnife SBRT to decrease normal lung dose to avoid radiation side effects. Materials and methods: A human phantom was used to generate 108 plans (54 for prone and 54 for supine) using the CyberKnife planning platform. The supine and prone plans were compared in terms of the dosimetric characteristics, delivery efficiency and plan efficiency. Results: For posterior targets, the area of low-dose exposure to normal lungs was smaller in the prone set-up than in the supine set-up. V10 of the lungs was 7·53% and 10·47% (p < 0·001) in the anterior region, and 10·78% and 8·03% (p < 0·001) in the posterior region in the supine and prone set-up plans, respectively. Conclusions: The comparison between the prone set-up and the supine set-up was investigated with regard to target coverage and dose to organs at risk. Our results may be deployed in CyberKnife treatment planning to monitor normal tissue dose by considering patient positioning. This may assist in the design of better treatment plans and prevention of symptomatic radiation pneumonitis in lung cancer patients.

Methodology of optimisation for a nanostructured two-photon absorption photodetector

We introduce a 3-step method to optimise a nanostructured photodetector for infrared sensing through non degenerated two-photon absorption (NDTPA). First, the nanostructure is designed to tailor the distribution and concentration of both pump and signal intensities within the absorbing layer, thus leading to a gain in two-photon absorption. Second, the issue of the competition between NDTPA and other sub-bandgap transitions is tackled with a new figure of merit to favor as much as possible NDTPA while minimising other absorption processes. Third, a refined computation of the gain and the figure of merit is done to consider focused beams. Finally, two scenarios based on low power infrared photodetection are investigated to illustrate the flexibility and adaptibility of the method. It is shown that the gain is up to 7 times higher and the figure of merit is up to 20 times higher compared to the literature.