Latest Laser Developments in Berlin

The focus is on semiconductor lasers at this year’s Laser Optics Berlin, held from March 22 to 24, 2010.

The Ferdinand-Braun-Institut (FBH) will present the latest developments in laser technology at the event, as well as during the accompanying technical conference.

Compact laser systems for displays

The FBH’s scientists are developing compact high-power visible light sources, and have made progress towards their real application in commercial systems, such as laser televisions or even flight simulators and displays for planetariums.

Compact laser module for display technology. (Photos: Copyright FBH/Immerz)

Recent prototype units used hybrid –micro-bench technology to reliably produce more than 1 W of continuous wave blue light in a high quality beam at 488 nm. The hybrid micro-bench used frequency conversion to transform infrared laser light with a wavelength of 976 nm into blue light by means of a non-linear crystal – the frequency is doubled (wavelength halved) to 488 nm.

Previously, such powers could only be produced using an experimental set up on an optical table, which occupied more than one square meter of laboratory space. Using FBH’s micro-bench technology, this has been miniaturized to a unit the size of a matchbox (25x10x50 mm). These micro-bench designs can be flexibly adapted to all other required wavelengths.

The next development step will be to transfer the concept to lasers emitting blue light at a wavelength of 460 nm and green light at 530 nm – these are the optimum wavelengths for display technology. The necessary pump sources with 920 nm for blue and 1060 nm for green lasers have already been developed.

Pulse picker for ultra-short light impulses

Another development from the FBH is the pulse picker technology that allows FBH to pick out single pulses from the high-frequency pulse chain generated by a semiconductor laser operating as an unstable resonator.

Pulse picker for precise selection of single laser impulses.

Laser systems with pulse pickers can be used, for example, in laser material processing as seed lasers for fiber lasers, in biomedical analytics based on fluorescence spectroscopy, and in laser light detection and range finding.

The pulse picker technology, a compact module completely based on semiconductor technology, is now available for the first time. It can deliver ultrashort light impulses of less than ten picoseconds with almost any desired pulse repetition rate from the kilohertz to the 100 megahertz range. Demonstrator modules combine high-power pulse generators with a pulse picker and the associated drive electronics into a compact unit. The modules are constructed using a tailored optical design to efficiently couple light between the optical elements. The radio frequency (RF) control electronics were developed at the FBH using their in-house gallium nitride technology.

Highly efficient diode lasers with an extremely narrow spectrum

Additionally, the FBH is presenting new broad area diode lasers with built-in gratings for narrow line width operation at Laser Optics Berlin. According to FBH, for the first time world-wide more than 10 Watt could be delivered from a 100 µm laser stripe in a spectral range of significantly smaller than one nanometer. This laser operates with a high power conversion efficiency: the ratio of electrical energy transformed into light adds up to 58 percent and is therefore scarcely below conventional high-power diode lasers, which however have a significantly broader spectral width of 2 to 3 nm.

These diode lasers are a cost-saving option for laser sources, as no external grating is needed for operation within a narrow spectral line. Such narrow line width sources are required for new high-performance industrial laser systems, where wavelength-multiplexing can be used to combine the output of many lasers into a single spot (the input of a 100 µm core fiber) via a wavelength selective element. Such systems lead to an increase in the delivered power density, enabling high-speed cutting and welding. A further application field for these devices is their use as pump source for fiber and solid-state lasers in materials processing, where they enable narrow absorption lines to be pumped, for higher overall system performance.

For more information, visit: www.fbh-berlin.de