Excimer drills multiple holes

17 Jun 2002

An excimer laser that drills 100 holes in parallel has been developed by researchers in The Netherlands.

From Opto & Laser Europe magazine magazine

Jet-engine maker Pratt & Whittle, US, has awarded a contract to develop a multiple-hole-drilling excimer laser to Netherlands-based Nederlands Centrum voor Laser Research (NCLR). The system will be used to make jet engines for the F35 Joint Strike Fighter (JSF).

NCLR, a University of Twente spin-off, initially developed the 308 nm XeCl source under the Eureka project Eurolaser Hipulse.

The excimer laser emits 1 J per pulse at a repetition rate of 1 kHz, enough to generate an average power of 1 kW. It was the first excimer laser to reach 1 kW, and this high beam power makes multiple hole-drilling possible.

To generate an array of beams, the NCLR team uses a lens array or a hologram. Kees Biesheuvel, who is working on the project at NCLR, explained: "To have equal energy in each beamlet using a lens array, a top-hat profile of the initial beam is required. However, a hologram will copy the original beam into multiple beams that all have the same energy."

Both methods are being considered, he adds. "It is easily possible to generate more than 100 beams - the application determines the number of beams."

High beam quality is also required for precise drilling of the holes. NCLR says that the XeCl laser spot is 1.5 times the diffraction limit, which is achieved by using a relatively long pulse length of 150 ns. The laser-drilled holes are required to keep components at a low temperature, while a high temperature is maintained in the engine.

Bieshevel says that the excimer laser is also being investigated for a variety of other micromachining applications. According to Pratt & Whittle, the F35 jet engine is in development and is scheduled for manufacture in 2007.

Author
Michael Hatcher is technology editor of Opto & Laser Europe magazine.