Swinburne Joint Experimental Cosmology Laboratory
Prof. Karl Glazebrook (Centre for Astrophysics and Supercomputing),
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.