Photonics is the science of the light. “Light plays a central role in human activities. On the most fundamental level through photosynthesis, light is necessary to the existence of life itself, and the many applications have revolutionised society through medicine, communications, entertainment and culture ...” (from 2015 the International Year of Light and Light-based Technologies, United Nations proclamation). 

GROC is the Photonics Research Group at the Universitat Jaume I. Our research focuses on light manipulation. Can light filaments generated from a femtosecond Iaser source be advantageously used for cancer radiotherapy? Can disruptive imaging modalities based on compressive sensing improve early diagnosis of diseases? Can we use laser light to enhance the capabilities of solar plants through nanofluidics? To address the above questions we use computer-controlled microdisplays and computational models for smart control and delivery of light beams. 

GROC also offers a high-quality training in general aspects of photonics at postgraduate level. As a matter of fact, GOC is the OSA Student Chapter at the Universitat Jaume I managed by our Ph.D. Students. This Chapter offers many benefits including activity and travel grants, guest lecture resources, networking opportunities and much more.




News:
Through 24th to 26th of September, the first international congress of young researchers jointly organized by student groups of both Spain and Portugal was celebrated. This congress, under the OSA IONS program, received students from more than 15 different countries. It took place on the Fundación Universidad y Empresa de Valencia (ADEIT). The organization was composed by the Group of Optics Castellón (GOC-OSA), formed by GROC members and by other student chapters from the University of Aveiro (UA-OSA), University of Salamanca (OSAL), University of Santiago de Compostela (USC-OSA) and the optics institute of CSIC (IOSA).

During the three days that the congress lasted, assistants presented the last advances in their research topics. They were grouped onto several themes: signal processing, visual optics, optical fibers and communications and laser processing. On the first evening, assistants had the opportunity to visit the research labs of ITEAM and VLC Photonics, based on the scientific park of Universidad Politécnica de Valencia. Students also attended a talk about the research that NTC and DAS Photonics are carrying out, placed at the same university.


Moreover, several renowned scientists gave invited talks during the congress. Chris Dainty (University College London, England) talked about image science and mobile cameras. Susana Marcos (Instituto de Óptica, Centro Superior de Investigaciones Científicas, España), provided a talk about visual optics. Lastly, Chandrasekhar Roychoudhuri (University of Connecticut, USA) gave a presentation about the paradigms of modern optics and photon nature.

To mark the occasion of the International Year of Light, the organizers premiered the documentary “The secrets of Light”, produced by the Group of Optics and Vector Producciones.



Highlighted Publications:
In situ decoration of graphene sheets with gold nanoparticles synthetized by pulsed laser ablation in liquids (Scientific Reports 6, 30478, 2016) 

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



Single pixel camera ophthalmoscope (Optica, 3, 1056-1059, 2016) 

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



Diffraction-Based Phase Calibration of Spatial Light Modulators With Binary Phase Fresnel Lenses (Optics Letters, 41, 1062, 2016) 

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/



Computational imaging with a balanced detector (Scientific Reports 6, 29181, 2016) 

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





News:







This movie shows programmable optical filamentation from a phase-modulated IR femtosecond laser beam. Four different filaments are generated inside a fused silica crystal. The location of the filaments is controlled at video rate with a LCoS display. 
The Optics And Photonics magazine devoted its cover of May 2014 to the femtosecond laser of our photonics group (GROC·UJI) 
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