The demand for nanocomposites of graphene and carbonaceous materials decorated with metallic nanoparticles is increasing on account of their applications in science and technology. Traditionally, the production of graphene-metal assemblies is achieved by the non-environmentally friendly reduction of metallic salts in carbonaceous suspensions. However, precursor residues during nanoparticle growth may reduce their surface activity and promote cross-chemical undesired effects. In this work we present a laser-based alternative to synthesize ligand-free gold nanoparticles that are anchored onto the graphene surface in a single reaction step. Laser radiation is used to generate highly pure nanoparticles from a gold disk surrounded by a graphene oxide suspension. The produced gold nanoparticles are directly immobilized onto the graphene surface. Moreover, the presence of graphene oxide influences the size of the nanoparticles and its interaction with the laser, causes only a slight reduction of the material. This work constitutes a green alternative synthesis of graphene-metal assemblies and a practical methodology that may inspire future developments. You can follow this result at: http://www.nature.com/articles/srep30478

Ophthalmoscopes to image the retina are widely used diagnostic tools in ophthalmology and are vital for the early detection of many eye diseases. Although there are various effective optical implementations of ophthalmoscopes, new, robust systems may have a future practical importance in cases where ocular media present significant opacities. Here, we present, as a proof of concept, a novel approach for imaging the retina in real time using a single pixel detector combined with spatially coded illumination. Examples of retinal images in both artificial and real human eyes are presented for the first time to our knowledge. You can follow this result at: https://doi.org/10.1364/OPTICA.3.001056

We propose a simple and robust method to determine the calibration function of phase-only spatial light modulators (SLMs). The proposed method is based on the codification of binary phase Fresnel lenses (BPFLs) onto an SLM. At the principal focal plane of a BPFL, the focal irradiance is collected with a single device just able to measure intensity-dependent signals, e.g., CCD camera, photodiodes, power meter, etc. In accordance with the theoretical model, it is easy to extract the desired calibration function from the numerical processing of the experimental data. The lack of an interferometric optical arrangement, and the use of minimal optical components allow a fast alignment of the setup, which is in fact poorly dependent on environmental fluctuations. In addition, the effects of the zero-order, commonly presented in the diffraction-based methods, are drastically reduced because measurements are carried out only in the vicinity of the focal points, where main light contributions are coming from diffracted light at the BPFL. Furthermore, owing to the simplicity of the method, full calibration can be done, in most practical situations, without moving the SLM from the original place for a given application. You can follow this result at: http://ieeexplore.ieee.org/document/7491270/

Single-pixel cameras allow to obtain images in a wide range of challenging scenarios, including broad regions of the electromagnetic spectrum and through scattering media. However, there still exist several drawbacks that single-pixel architectures must address, such as acquisition speed and imaging in the presence of ambient light. In this work we introduce balanced detection in combination with simultaneous complementary illumination in a single-pixel camera. This approach enables to acquire information even when the power of the parasite signal is higher than the signal itself. Furthermore, this novel detection scheme increases both the frame rate and the signal-to-noise ratio of the system. By means of a fast digital micromirror device together with a low numerical aperture collecting system, we are able to produce a live-feed video with a resolution of 64 × 64 pixels at 5 Hz. With advanced undersampling techniques, such as compressive sensing, we can acquire information at rates of 25 Hz. By using this strategy, we foresee real-time biological imaging with large area detectors in conditions where array sensors are unable to operate properly, such as infrared imaging and dealing with objects embedded in turbid media. You can follow this result at: http://www.nature.com/articles/srep29181