James W. Beletic (TELEDYNE Imaging Sensors, USA)

The Fantastical Discoveries of Astronomy made possible by the Wonderful Properties of II-VI Materials
When May 08, 2012 from 11:00 AM to 12:00 PM
  • Special Seminar
Where SH, Lecture hall
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The universe is an amazingly huge place. While humankind has directly explored Earth’s sister planets with space probes, we don’t have the means to venture beyond the solar system, and so almost all information about the universe comes from sensing light that happens our way. Astronomy is constantly striving to find better ways to sense the feeble amount of energy from distant stars and galaxies. This quest has led to a new generation of very large telescopes (up to 10-meter diameter) on the ground and the deployment of the 2.4-meter Hubble telescope in space.

Ground-based astronomy will soon begin construction on an even more ambitious generation of 30-meter class extremely large telescopes (ELTs), and the James Webb Space Telescope’s 6.5-meter mirror will launch by the end of the decade. Possibly more important than the development of bigger telescopes is the rapid advancement in solid state detector technology.

The detector revolution was led by silicon CCDs (IV material) starting in the 1970’s for sensing visible light, but the II-VI materials (HgCdTe) that were developed during the past two decades for sensing infrared light have made the most significant difference in astronomy. Long before the CCD, astronomers could detect visible light with the human eye and photographic plates, but until recently, infrared astronomy was not possible.

Infrared light is the only way to study a wide range of astronomical phenomena. As known from terrestrial applications, infrared light propagates through dust and infrared light is required for sensing cooler objects. More important for astronomy, the universe has been expanding since the Big Bang and the expansion of the universe has redshifted the ultraviolet and visible light of distant objects into the infrared. The distant universe is an infrared universe and several of the next generation facilities (JWST, dark energy missions, the ELTs) will rely mainly, if not entirely, on infrared detectors made from the II-VI materials whose features enable modern astronomy. This talk will present the cutting edge astronomy that is made possible by the wonderful properties of II-VI materials, including:

  • ability to tune the cutoff wavelength to optimize instrument performance
  • substrate removal that enables simultaneous detection of visible and infrared light
  • extremely low dark current (0.01 electrons per pixel per sec for 5 micron cutoff)
  • high quantum efficiency (>80%)
  • very low noise readout (3 electrons rms, after multiple sampling)
  • large format arrays (2K×2K is standard today, and 4K×4K is in development)
  • high operability (>99%)