Revealing advantages and applications of ultrashort pulsed lasers



Technological advances in picosecond and sub-picosecond lasers are opening the possibility of machining materials previously thought to be too hard or too brittle for processing by the current generation of lasers. At the same time, there is a trend towards higher average power to increase throughput. These advancements were featured at the LASER World of PHOTONICS trade fair in May. Shorter bursts with higher energy Contemporary lasers deliver extremely precise, concentrated energy and are ideally suited for many delicate tasks. However, the pulse also generates heat which can damage the target material or tissue, limiting the laser's usefulness on certain materials. The next-generation ultrashort pulse laser with bursts of just a few picoseconds or less can cut into or remove material before enough heat is generated to damage it. Separating composite materials without delamination According to Dr. Gyu C. Cho, Executive Vice President of ultrashort pulse fiber-laser pioneer IMRA, ultrashort pulse lasers will soon be used for precision processing of transparent materials and extremely hard, brittle materials. Dr. Cho also anticipates cutting composite materials which would burn or delaminate at the edges if cut with classic lasers or other methods. Dr. Cho believes that the first industries that will profit from ultrashort pulse lasers include display manufacturing and the semiconductor and microelectronics industry. Increasingly thinner and harder glass touchscreens on Smartphones are a good example: "Picosecond lasers such as the TruMicro Series 5000 are ideal for cutting the glass plates. This technique avoids microcracks that appear when diamond saws or continuous or long-pulse lasers are used", says Christof Siebert, Senior Manager for Microprocessing Applications at Trumpf Laser- und Systemtechnik. "The products on the market - at least those in the picosecond-laser range - are now suitable for industrial use and are being used in three-shift manufacturing," explained Trumpf expert Christof Siebert. He will chair an Application Panel on the "Latest Applications for Shortpulse Laser Systems". Trend: shorter pulses and higher average power According to Mr. Siebert, "the current trend is toward increasing average power as a way to optimize productivity and efficiency. The second is toward lasers that are suitable for industrial use with increasingly shorter pulse durations in order to expand the range of materials in cold processing to include more sensitive materials than in the past." For Dr. Arnold Gillner, Head of the Department for Material Removal and Joining at the Fraunhofer Institute for Laser Technology, the trend is toward higher average power in the 500W range. "At the Fraunhofer ILT, a prototype of a 1kW femtosecond laser has already been demonstrated," adds Gillner, who will lead the panel on ultrashort pulse lasers with Siebert. For the scientists, the key question is how to apply the higher average power of USP lasers to the workpiece and achieve high ablation quality." The Fraunhofer ILT will introduce two approaches to doing so at the fair: An ultra-fast scanning system with beam-deflection speeds greater than 300m/s, and a multiple-beam optics system to parallelize processing by more than two orders of magnitude. Besides technical feasibility, costs play a large role in these recent developments. Experts at Jenoptik plan to use higher power lasers to increase productivity, offsetting the costs of femtosecond lasers. When it comes to performance reliability, femtosecond lasers are now delivering "very good application results in full-time, 24/7 operation." Jenoptik, for example, increased the pulse-repetition rate of its D2.fs femtosecond disk laser to more than 500 kHz and improved its output power by 25 percent. USP lasers in medicine also on the rise USP lasers also offers great advantages in medical technology. The most rapidly growing application over the past two years "is the use of ultrashort pulse lasers in laser refractive cataract surgery (LRCS)", explains Dr. Matthias Schulze, Marketing Director at Coherent. The technology permits "even better vision when replacing the intra-ocular lens (IOL) in cataract surgery," says Schulze. For example, it makes it possible to better prepare the eye for the use of premium IOLs by using precision cuts to correct astigmatism. He predicts that "compact lasers will make it possible to use smaller treatment stations, and higher pulse rates will make operation times even shorter." LASER World of PHOTONICS