The National Institute of Standards and Technology’s Physical Measurement Laboratory have come up with a “near-perfect” super-continuum solar simulator to be used to test photovoltaic materials.

Until now, solar engineers have relied on xenon arc lamps to stand in for the sun, which have their own strengths but are not quite perfect at imitating sunlight. For one, they emit dispersed light, making focusing difficult. And two, the solar technology being developed is outpacing them.

The new apparatus mimics the solar spectrum with wavelengths from 450 to 1750nm that are readily focused into an adaptable beam to test the performance of a range of photovoltaic configurations.

It works like this: Light is generated in a laser that emits pulses of several hundred femtoseconds duration at a rate that is controllable between 1 MHz and 80 MHz. Then, that light is amplified and sent into a photonic-crystal fiber, which broadens the spectrum over a wavelength of about 2000 nanometers. All the component frequencies form one ray, which is then directed into a prism and directs them at a mirror. The reflected light is then recombined into a single beam and focused onto PV samples.

If the system becomes a standard solar simulator, Tasshi Dennis of the Quantum Electronics and Photonics Division at NIST’s Boulder, Colo., campus says it could alleviate a number of difficulties that arise in studying the newest high-tech PV materials. For one thing, its collimated beam can be tightly focused to selectively probe and excite very small features such as nanowires and carbon nanotubes.

The technology, however, is not perfect: The system doesn’t include UV rays in the 330nm to 450nm wavelengths. Not to worry, though – researchers are already looking into ways to fill them in.

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