Intense and ESA to develop high power diode arrays

30 Aug 2007

Intense's QWI technology will be used to boost efficiency at 808 nm to record levels for applications in space.

laser diode

An R&D contract between Intense and the European Space Agency will lead to the development of high-power, high-efficiency laser diode arrays for solid-state laser pumping applications in space.

The PULSAR (PUmp Laser Stacks with Aerospace Reliability) program is focused on improving reliability and efficiency of laser diode stacks at 808 nm wavelength. The aim is to achieve 1.2 kW power under pulsed operations with an electro-optical efficiency of 65%. The diodes will also be required to meet the demanding lifetime specification of 12 billion shots in space.

Arrays with these characteristics will save a considerable amount of power once deployed on space vehicles and will reduce heat removal requirements, since a smaller fraction of the input energy will be converted to heat.

Key to success will be Intense's quantum well intermixing (QWI) process, an integration technology that allows the properties of a semiconductor's quantum well structure to be modified after growth to include passive and active sections in the same laser cavity.

"QWI is particularly suited to space-borne applications, as it produces laser diodes with increased radiation hardness," said John Marsh of Intense.

The QWI technology involves passive waveguides located at the laser facets to form non-absorbing mirrors (NAMs), passivating the facet regions of the laser. Semiconductor lasers with NAMs have been shown to operate at much higher powers than conventional devices, and avoid catastrophic optical mirror damage.

Further improvements in pumping efficiency will be investigated, including the use of volume Bragg gratings to narrow and stabilize the array's emission spectrum. Their integration with the diode arrays will be assessed in cooperation with a US manufacturer.

"We are optimistic we can achieve these ambitious targets based on the success of the DARPA-funded SHEDS (super-high efficiency diode sources) initiative where laser efficiency was improved by over 20% at longer wavelengths," said Marsh.

The PULSAR program will run for 2.5 years, with research results to be published in industry journals and at technical conferences.