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Swinburne Joint Experimental Cosmology Laboratory

Prof. Karl Glazebrook (Centre for Astrophysics and Supercomputing), Paul Stoddart, Peter Hannaford
Collaborators: Prof. Abraham (University of Toronto), Barr Associates Inc., CSIRO-Australian Centre for Precision Optics

An experimental prototype of a close to ideal 'OH suppressing imaging multinotch filter' is under development for ground based astronomy in the 1-2 µm bands. This complex photonic device requires up to one million refractive index layers in a piece of glass only 3 mm thick. Development of such a device represents a serious technical challenge, as the narrow notch bandwidths required to filter the sky in this way represents a factor of ten improvement on current techniques. The investigators have formed a partnership with Barr Associates Inc, the worlds leading specialist manufacturer of thin film glass filters, to achieve these aims.

One of the most important things that advanced ground-based telescopes do is take deep images of the sky to reveal the faintest, most distant objects. Longer exposures go deeper but are limited by the glow of the Earth’s own atmosphere. Achievement of a filter to block atmospheric OH emission would increase the imaging performance of large ground-based telescopes by factors of 20-25 and would have numerous scientific applications, including discovery of the first galaxies to form in our Universe. The device, if viable, may also open new applications in optical broadband communications photonics technology.

Simulation of the effect of an OH filter on a deep image of the near-IR sky. The left panel shows a noisy image without the OH filter, while the right panel shows how it would look with the filter after the same exposure time. Every little blob is a faint galaxy at cosmological distances.