Integrated optics is a well established technology that finds its main applications in the fields of optical communication
and sensing. However, it is expanding into new areas, and in the last decade application in astronomical interferometry
has been explored. In particular, several examples have been demonstrated in the areas of beam control and combination.
In this paper, different examples of application integrated optics devices for fabrication of beam combiners for
astronomical interferometry 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 fabricated in hybrid sol-gel were validated using an
interferometric set-up. These results demonstrate that hybrid sol-gel technology can produce quality devices, opening the
possibility of rapid prototyping of new designs and concepts.
Hybrid sol-gel technology was used for fabrication of prototypes of coaxial two, three and four telescopes beam
combiners for astronomical applications. These devices were designed for the astronomical J-band and have been
characterized using an optical source with emission centered at 1265 nm and with a spectral FWHM of 50 nm.
Interferometric characterization of the two, three and four beam combiners, showed average contrasts respectively
higher than 98%, 96% and 95%. Interferometric spectral analysis of the beam combiners revealed that the chromatic
differential dispersion is the main contributor to the observed contrast decay in the latter cases. The laser direct writing
technique was used for fabrication of a coaxial two beam combiner on sol-gel material; it showed a contrast of 95%. The
measured high contrast fringes confirm that the procedures used lead to performant IO beam combiners. These results
demonstrate the capabilities of the hybrid sol-gel technology for fast prototyping of complex chip designs for astronomical applications.
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.
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.
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