Sun powers tellurium gas amplifier

17 Jun 2002

Scientists in Israel have taken a big step towards building a solar-powered laser that operates in the visible.

Idit Pe'er and colleagues from the Weizmann Institute of Science have demonstrated a broadband laser amplifier based on tellurium gas molecules (Te₂) pumped by the Sun (Opt. Letts 26 1332).

The group believes that this is the first time molecular energy-level transitions have been used as an active medium for a solar-powered laser (SPL).

The researchers passed a modulated 3 mW HeNe laser beam through the Te₂ gas medium and measured its intensity with and without solar pumping. With the Sun's input, they saw a gain of 42%. Pe'er said: "This amplifier could be the basis of a new type of high-power laser with a broad gain in the visible range."

SPLs have applications both on Earth and in space. Terrestrial applications include laser photochemistry, while in space SPLs are used for satellite-to-satellite optical communication, wireless power transmission and remote sensing. They are mainly based on solid-state lasers or photodissociation gas lasers (the former being the more common).

Solid-state SPLs, however, suffer from three disadvantages: they operate in the near-infrared only; their size is limited; and the laser beam suffers from thermal lensing that distorts its shape. Visible-range SPLs should open up new opportunities in photochemistry that were not economical until now.

SPLs based on dimers could prove to be promising sources, for three reasons. First, a number of dimers have absorption and emission bands in the visible range. Second, they also permit the use of large volumes of the active media - important for achieving high output power - and third, the active medium has a very low refractive index, so no significant thermal lensing will occur.

The group is currently building a laser based on the Te₂ amplifier.