ANDERSONStevens Leônidas Gomes

The activities of the Laboratory of Optoelectronics and Photonics, as part of the Optics Group at the Physics Department of UFPE, started back in 1987, and the first laboratory was established in 1988, based on a Q-switched and mode-locked Nd:YAG laser, performing research in nonlinearities in optical fibers.

The present research activities are in the areas Nanophotonics, Biophotonics, Nonlinear Optics and Optical Communications.


NANOPHOTONICS


Nanophotonics deals with the light-matter interaction at the nanoscale. Our present work focus on (a) studies of optically enhanced nonlinearities in nanostructured glasses containing silver, gold or rare earth doped ions; (b) studies and applications of random lasers exploiting dye embedded nanoparticles or nanostructured semiconductor materials and (c) fabrication and characterization of MOCVD grown semiconductor nanostructures.

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Pictorial description of conventional lasers vs random lasers.

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TiO2- based nanomembrane Random Laser
(Dominguez et al, Opt Express, 2012)




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Colloidal RL emission.
Top image: below threshold.
Bottom: above threshold.
(from Lawandy, Gomes, 1994)






BIOPHOTONICS


Biophotonics research is a multidisciplinary theme and our work exploits imaging technologies applied to dentistry and dermatology, as well as Nonlinear optical methods, such as multiphoton induced absorption has also been used to study biomaterials. Detection of earlier caries is being evaluated using laser induced fluorescence, NIR transillumination and a major emphasis in optical coherence tomography (OCT) for non-invasive imaging. OCT is the main technique currently employed for dental materials characterization, besides clinical trials. The research has also been extended to nanobiophotonics, whereby the methods mentioned above are used in conjunction with nanoparticles to, for enhance, provide imaging enhancement.

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OCT image sequence of caries
Evaluation in human tooth
(Mota, DF/UFPE, 2009)

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In figure we show an OCT image of the adhesion process on dentin using DBAs prepared with gold nano particles. The adhesion process regions are identified: adhesive layer (AL), hybrid layer (HL), and resin tags (arrows).
(Braz, et al, JBO 2012)




NONLINEAR OPTICS

Nonlinear Optics is a well-established field of research, and a subject that has been the flagship of the optics group in Recife since the late 70’s. Presently, our laboratory is geared to perform characterization of optical nonlinearities in photonicsmaterials such as polymer based nonlinear photonic crystals, hybrid quantum dot polymer nanocomposites and rare earth doped glasses. Available techniques include Z-scan, femtosecond resolved Kerr gate, upconversion spectroscopy, etc. The research includes development of new nonlinear optics characterization methods as well as the characterization of novel photonics materials e nanomaterials.


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Thermally Managed eclipse Z-scan technique
used to characterize nanomaterials
(Gomes et al, Opt. Express 2007)

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TM EZ-scan characterization of 15 nm
Size gold nanoparticles.
(Romani et al. Opt. Express 2011)




PHOTONICS DEVICES FOR OPTICAL COMMUNICATIONS

Optical communications are the basis for all the information technology developed so far. Several photonics devices, such as optical amplifiers, diode lasers, optical switches, etc., are key elements for such development. We have carried out research in S/C/L band optical amplifiers, with emphasis is on S-band(1400 nm - 1530 nm) amplifiers. TDFA, Raman, Parametric Amplifiers and Hybrid Amplifiers were developed and characterized. Presently, our focus has been on femtosecond laser written channel waveguides for optical amplification and other applications.

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Profile of a fs laser written waveguide
In an Er-doped germanate glass.
(da Silva et al, Opt Materials, 2011)




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Spatial profile of a waveguide written with fs-laser in sol-gel activated Er3+: SiO2-Ta2O5 glass ceramics






Research Facilities


Our research facilities comprises of a number of lasers sources and modern equipment for sources characterization and data acquisition, in the spatial, spectral and temporal domain.

Presently the Lab occupies three rooms with 30 m2, and is equipped with laser sources covering the UV-NIR spectrum (discretely or continuously using a OPA), from nano- to femtosecond regime (fs Ti-sapphire laser, ps QS&ML Nd:YAG, ns Nd:YAG laser with infrared, second and third harmonic output, cw semiconductor lasers covering the near-infrared range (800 nm – 1600 nm), diode pumped Yt-lasers, diode pumped Raman lasers and dye lasers). Microwave generators (up to 20 GHz) for optoelectronics are also available.
Data acquisition equipment includes optical spectrum analysers, CCD coupled spectrometer (visible and NIR), ocean optics spectrometers, electrical spectrum analyzer (up to 44GHz), lock'ins, box-cars, real time autocorrelator, laser beam profile diagnostics and other diagnostics tools, all computer controlled. Other common facilities include absorption spectrometers (200nm to 3µm), waveguide characterization, SEM and AFM.

The laboratory also hosts a multiuser facility, the NanofemtoLab, consisting of a Coherent LIBRA regenerative amplifier delivering up to 1 mJ, 1 kHz, 80 fs pulses at 800 nm and a continuously tunable fs OPA. This is an open facility to researchers from Brazil or abroad.
Among the linear and nonlinear optical techniques available, we have exploited upconversion spectroscopy set up, Z-scan (and some varieties, such as thermally managed Eclipse Z-scan), Kerr gate, optical coherence tomography (at 800 nm and 1300 nm, home made and Thorlabs equipment), infrared transillumination, femtosecond writing, multiphoton fluorescence microscopy and facilities for setting up optical amplifiers for optical communications in the S, C and L bands.

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Partial view of the multiuser femtosecond facility, showing the
Regenerative amplifier and OPA system.