Photonics

Telescopes

The technical world is abuzz with the plethora of large scale telescopes coming over the horizon in the wake of the Hubble Space Telescope’s success (once the right unit system was in use).

The Giant Magellan Telescope (GMT) is scheduled to be fully up and working in Chile’s Atacama Desert by 2024 and will be the world’s largest optical telescope.

The even larger proposed $1.4bn optical Thirty Metre Telescope (TMT) on Mauna Kea in Hawaii has yet to begin construction following protests from the local population.

These two, once built will be larger than the current Very Large Telescope from The European Space Observatory in Chile (VLT) though may face competition from the  European – Extremely Large Telescope (E-ELT) .

There is also the   the Large Binocular Telescope (LBT) in the USA.

Successor to the Hubble is the James Webb Telescope (JWT) to be launched in 2018 and will operate in the mid-infra red to long wavelength visible range. Hubble was in essence an optical telescope and sensitive to light from about 800M years after the big bang; JWT will extend back to 200M year mark (CMB is around 400,000 years after the BB). When launched JWT will live at the Lagrange point (L2) beyond the moon and will orbit the sun in a fixed position relative to the earth. JWT will be blocked from the IR emissions of the sun, moon and earth by employing its ultra-thin Kapton heat-resistant shield on one side only.

The successor to JWT has already been mooted – the HDST, High Defintion Space Telescope, pencilled in for the 2030’s and using UV light and near IR.

On the radio wavelength scale the Sqaure Kilometre Array (SKA) – based in South Africa, Australia and controlled from Jodrell Bank, UK will generate more data then the LHC at Cern – how will the computer scientists deal with that onslaught!?

One of the three precursor telescopes to SKA is Murchison Widefield Array in (MWA) Australia used in the search for the very early “seed” galaxies just after “first light”.

Five hundred meter Aperture Speherical radio telescope (FAST) is largest single aperture radio receiver in China – now part of the Breakthrough Listen programme.

And the world’s largest digital camera – the Large Synoptic Survey Telescope (LSST), nearing completion in Cerro Pahon, Chile and will be studying stellar objects that change over time and will be the most powerful survey telescope ever built – but at a cost to the Arecibo disc?

The Wide Field Infra-red survey (WFIRST)  is another survey telescope – this time in the IR range – a space telescope and will sit in geo-stationery orbit.

Other sky surveys include the  SLOAN survey (red-shift) and the parallax using GAIA project.

The neutrino telescope KM3NeT will be the next generation of neutrino searching telescopes.

The BICEP-2 experiment measures the polarization of the CMB  but steady on with those predictions of gravitational waves and hence the inflation theory of the big bang. Those claims were later to hit the dust literally as the polarisation was due to interstellar dust. Eyes peeled though on BICEP3!…

Now CMB-S4, a new blueprint for a study of, among other items, to measure the polarisation of the CMB caused by G-waves to one more order of magnitude of sensitivity.

and watch out for…

NGARI-1 telescope a new China/US colloboration (Hurrah!) – B-mode polarization of the CMB- cosmic inflation.

The Event Horizon Telescope (EHT) employs a network of millimetre wave observatories from around the world to form a giant interferometer to reveal geometrical effects around black holes – of all things with a small resolving power of only a few mm.

And associated with all things predicted from general relativity, particularly gravitational waves, two telescopes are being proposed; eLISA will be in space and the Einstein telescope somewhere underland in Europe . Both telescopes using the similar approach to the existing LIGO  interferometry techniques.

Stop Press!! February 2016 – gravitational waves detected by LIGO!! And traveling at the speed of light – does this mean the graviton has zero mass, and if so what are the implications for the cosmological constant and dark energy? And did the CHANDRA X-ray telescope pick up the aftermath of the black hole collision, or was it just noise?

The first paper from the New Horizons project details  spectacular views of Pluto and its moon system.

Adaptive optics

Software based adaptive optics:  possibilities  for eye imaging without the expensive hardware option:

Software adapative optics

Advances in cameras are being made too. Already we’ve seen the development from photosensitive chemicals to digital image capture and storage; manual to electromechanical driven hardware; CCD (charge coupled devices) and CMOS (complementary metal oxide semiconductor) convert photons to charge for image capture.

Some new techniques (computational cameras)  include taking infrared images in 2D or 3D without the need for pixellated sources (hence cheaper); imaging systems to produce video images of a light pulse and  3D imagery using just one single stationary camera.

The non-pixellated sensor camera uses a single photosensitive detector and an array of adjustable mirrors that shine the light on the detector (photodiode). In effect the camera just needs one pixel and  works well at imaging moving objects as well as detecting hidden objects behind  visible light objects.

Future applications include imaging hazardous gas leaks, peeking around corners or creating 3D cameras via a 3D printer.

Measurement

LIDAR – surveying via LASER…

LiFi

Communication via light rather than radio waves – PureLiFi here in Scotland is one leading the way…

Quantum Optics

Entanglement, teleportation, mensuration, computing…

 

A Note on Light units…

One candela is the light energy over one solid angle; the lumen is that energy over the whole sphere; lux is the energy per unit area. The candela is roughly the energy emitted by a standard candle at 1 metre’s distance. Note at 1 metre distance, candelas = lux = lumens/4π

The Moon: 1 lux on the earth at full moon so 1017 cd

The Sun: 105 on the earth in direct sunlight so 1027 cd

 

Light bulbs come in around 1000 lumens, just watch the wattage!