"Artificial Star"

MPB, in partnership with Toptica Photonics AG, is developing four continuous-wave, high-power (> 25W) Narrow-Band Visible Raman Fiber Amplifier Systems for the European Southern Observatory (ESO) in Paranal, Chile.

The systems will be used to create laser guide stars for ESO's Very Large Telescopes (VLT). Laser guide stars are used as reference points for calculating adjustments necessary to the adaptive optics in order to correct the natural atmospheric distortion of light. A "star" is created by energizing sodium atoms, which exist in a layer of the mesosphere, approximately 90 km away.

MPB is providing the novel narrow-band, polarization-maintaining Raman Fiber Amplifiers used to amplify the output of a Toptica narrow-band laser diode at 1178 nm which is then converted to 589 nm by a resonantly-enhanced high-power frequency doubler from Toptica.

High power, continuous wavelength, and extremely good beam quality are needed to create the perfect star. The laser sources must also be reliable, compact, and low-maintenance - all benchmarks of MPB's Visible Fiber Laser line.

The laser architecture was first developed as a breadboard experiment at the European Southern Observatory, and the licensing technology was passed on to MPB and Toptica for product finalization and realization.

The four units will be installed in the Very Large Telescopes in September 2013.

Key Advantages of the Fiber-Optics Approach:

• No bulk mirrors to align or clean - maintenance free
• Inherently immune to gravity vector changes
• Silica-based fibers - proven technology from telecom industry
• Large surface-to-volume ratio simplifies heat removal
• Closed, all-fiber optical path
• Single-mode PM fiber – inherently true diffraction-limited, linearly polarized output
• Remote pumping capability allows mounting of compact Laser

Wendelstein Portable Laser Guide Star

The PM Raman Fiber Amplifier supplied by MPB Communications for the Wendelstein Portable Laser Guide Star

In 2011, in conjunction with ESO, the Wendelstein portable guide star, with many similarities to the Very Large Telescope units, was developed and tested for strategic field experiments.

The unit consists of a 20 W 589nm CW laser system, for which MPB Communications provided the Polarization Maintaining Raman Fiber Amplifier. The PM RFA produced up to 44 W of power during stable operation testing, meeting and exceeding the output power specification of 36 W.

In field tests, the unit was proven to provide excellent beam quality, output powers with doubling efficiencies greater than 80%, and require less than 700 W of electrical power, while being maintenance-free, reliable, efficient, and ruggedized.