D. Alexandre

High-speed integrated optical logic based on the protein bacteriorhodopsin

The principle of all-optical logical operations utilizing the unique nonlinear optical properties of a protein was demonstrated by a logic gate constructed from an integrated optical Mach-Zehnder interferometer as a passive structure, covered by a bacteriorhodopsin (bR) adlayer as the active element. Logical operations were based on a reversible change of the refractive index of the bR adlayer over one or both arms of the interferometer. Depending on the operating point of the interferometer, we demonstrated binary and ternary logical modes of operation. Using an ultrafast transition of the bR photocycle (BR-K), we achieved high-speed (nanosecond) logical switching. This is the fastest operation of a protein-based integrated optical logic gate that has been demonstrated so far. The results are expected to have important implications for finding novel, alternative solutions in all-optical data processing research.

Hybrid sol-gel planar optics for astronomy.

Hybrid sol-gel planar optics devices for astronomy are produced for the first time. This material system can operate from the visible (0.5 microm) up to the edge of astronomical J-band (1.4 microm). The design, fabrication and characterization results of a coaxial three beam combiner are given as an example. Fringe contrasts above 94% are obtained with a source with spectral bandwidth of 50 nm. These results demonstrate that hybrid sol-gel technology can produce devices with high quality, opening the possibility of rapid prototyping of new designs and concepts for astronomical applications.

Performance of astronomical beam combiner prototypes fabricated by hybrid sol-gel technology.

Integrated optics coaxial two, three and four telescope beam combiners have been fabricated by hybrid sol-gel technology for astronomical applications. Temporal and spectral analyses of the output interferometric signal have been performed, and their results are in mutual good agreement. The results of the characterization method employed are cross-checked using contrast measurements obtained independently, demonstrating that the chromatic differential dispersion is the main contributer to contrast reduction. The mean visibility of the fabricated devices is always higher than 95 %, obtained using a source with spectral bandwidth of 50 nm. These results show the capability of hybrid sol-gel technology for fast prototyping of complex chip designs used in astronomical applications.

Fabrication and test of an integrated optical sensor with high sensitivity and high dynamic range based on a Mach-Zehnder interferometric configuration

Integrated optics (IO) technology has been primarily used in optical communication applications but it is expanding fast into the field of optical sensing. In this work we report the fabrication of integrated devices using hybrid sol-gel technology and in particular its application in the fabrication of a refractive index integrated sensor based in a Mach-Zehnder interferometric configuration. In one of the interferometer arms, a analysis chamber is created by exposing the waveguide through the removal of the device cladding. On the same arm, two Bragg gratings with the same period are fabricated: one in the unprotected waveguide area and another in close proximity (cladded area); because of the different effective index in the two grating regions, two peaks are observed in reflection if the device is tested with a broadband source. Any change of the refractive index of the material filling the analysis chamber can be detected in two ways: by measuring the intensity of the interferometric output (at a wavelength different from the Bragg wavelength of the two gratings) or by measuring the spectrum of the reflected signal. The high sensitivity is obtained by measuring the interferometric output, while the high dynamic range can be achieved by measuring the reflected signal from the grating structures.

Integrated hybrid sol-gel devices for astronomical interferometry

Astronomical interferometry is an active area of research and an increasing number of new conceptual ideas and designs are being proposed to achieve optimum astronomical instruments. In particular, integrated optics has a lot to offer in what concerns beam combination and control. In this paper, different examples of application of hybrid sol-gel integrated optics devices for fabrication of beam combiners for astronomical applications is given. For the multiaxial beam combiners, a UV laser direct writing unit is used for mask fabrication. The operation principles of the coaxial combiners were validated using an interferometric set-up. Differential polarization and differential dispersion effects were minimized in this set-up to avoid any error in the characterization of the beam combiners. In all the devices, fringe contrasts above 90% were obtained with a source with spectral bandwidth of 50 nm. These results demonstrate that hybrid sol-gel technology can produce devices with high quality, opening the possibility of rapid prototyping of new designs and concepts for astronomical applications.

Rapid prototyping of integrated sol-gel devices for astronomical interferometry

Integrated optics is a mature technology with standard applications to telecommunications. Since the pioneering work of Berger et al. 1999 beam combiners for optical interferometry have been built using this technology. Classical integrated optics device production is very expensive and time consuming. The rapid production of devices using hybrid sol-gel materials in conjunction with UV laser direct writing techniques allows overcoming these limitations. In this paper this technology is tested for astronomical applications. We report on the design, fabrication and characterization of multiaxial two beam combiners and a coaxial beam combiner for astronomical interferometry. Different multiaxial two beam combiner designs were tested and high contrast (better than 90%) was obtained with a 1.3 μm laser diode and with an SLD ( λ0 = 1.26 μm, FWHM of 60 nm). High contrast fringes were produced with 1.3 μm laser diode using the coaxial two beam combiner. These results show that hybrid sol-gel techniques produce devices with high quality, allowing the rapid prototyping of new designs and concepts for astronomy.

Photosensitive Materials for Integrated Optic Applications

Abstract This article presents results of device fabrication using UV processing of materials and integrated optic components produced by flame hydrolysis deposition and hybrid sol-gel technology. Photosensitive materials were employed in the fabrication of channel waveguides and channel photo-imprinted waveguides incorporating Bragg gratings through single and double-step exposure.

Fabrication of Microfluidic Channels by Femtosecond Laser Micromachining and Application in Optofluidics

Micromachining with femtosecond laser can be exploited to fabricate optical components and microfluidic channels in fused silica, due to internal modification of the glass properties that is induced by the laser beam. In this paper, we refer to the formation of microfluidic channels, where an optimization of the fabrication procedure was conducted by examining etch rate and surface roughness as a function of the irradiation conditions. Microfluidic channels with high and uniform aspect ratio and with smooth sidewalls were obtained, and such structures were successfully integrated with optical components. The obtained results set the foundations towards the development of new optofluidic devices.

Integrated Optical Devices - Fabrication of Multimode Interference Devices in Fused Silica by Femtosecond Laser Direct Writing

1xN (N=2, 3, 4) MMI power splitters were fabricated in a fused silica substrate by laser direct writing, using a focused 515 nm amplified femtosecond laser beam, and characterized at 1550 nm. To accomplish this, several low loss waveguides were fabricated side by side to form a multimode waveguide with the output in a polished facet of the substrate, while a single low loss waveguide was fabricated to inject light in the centre of the multimode waveguide. The performance of the fabricated devices was optimized by testing three different designs.

High Speed All Optical Logic Operations Utilizing the Protein Bacteriorhodopsin

In data-processing applications requiring high speed and wide bandwidth, photonic devices - where logic operations are processed on an all-optical basis - represent a promising alternative of their electronic counterparts. Besides in/organic active optical crystals, dyes and polymers, molecules of biological origin with suitable nonlinear optical properties can also find applications in integrated optical - biophotonic - devices.The principle of all-optical logical operations utilizing the unique nonlinear optical properties of a protein was demonstrated by a logic gate constructed from an integrated optical Mach-Zehnder interferometer as a passive structure, covered by a bacteriorhodopsin (bR) adlayer as the active element. Logical operations were based on a reversible change of the refractive index of the bR adlayer over one or both arms of the interferometer. Depending on the operating point of the interferometer, we demonstrated binary and ternary logical modes of operation. Using an ultrafast transition of the bR photocycle (BR-K), we achieved high-speed (nanosecond) logical switching. This is the fastest operation of a protein-based integrated optical logic gate that has been demonstrated so far. The results are expected to have important implications for finding novel, alternative solutions in all-optical data processing research.