An innovative compact - yet high resolution - cross-dispersed echelle spectrograph has been designed, built, and
deployed at TSU's 2-meter robotic telescope for initial tests and commissioning. This design is based on a single
mode fiber (SMF) and it eliminates mode noise in fiber-fed spectrographs which is important for m/s precision
exoplanet Doppler searches. The use of SMFs removes modal variation, makes the design compact and the
camera focus slow and stable at the price of lower throughput. This can be improved by using adaptive optics
or by placing it in space; the compact design is well suited for such deployment.
VISION is the next generation science camera for the Navy Optical Interferometer (NOI). In comparison to
the current beam combiner of NOI, VISION will deliver higher precision data products and better
incorporating single mode bers for spatial ltering and by using low-noise detectors. VISION can coherently
combine up to six telescope beams using an image-plane combination scheme. This results in simultaneous
measurement of 15 visibility amplitudes and 10 independent closure phases that can be used to reconstruct
multipixel images of stars.
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 ( λ<sub>0</sub> = 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.