OSA TOPS 56, Conf. on Lasers and Electro-Optics, Tech. Digest (OSA, Wash DC, 2001), pp. 574-577. F 2 -Lasers: High-Resolution Micromachining System for Shaping Photonic Components Peter R. Herman, Kevin P. Chen, Midori Wei, and Jie Zhang Department of Electrical and Computer Engineering, University of Toronto, 10 King’s College Rd., Toronto, ON, M5S 3G4, Canada; Tel: 416-978-7722 Fax: 416-971-3020; hermanp@ecf.utoronto.ca Jurgen Ihlemann, Dirk Schäfer, and Gerd Marowsky Laser Laboratorium Göttingen, Hans-Adolf-Krebs-Weg 1, 37077 Göttingen, Germany Peter Oesterlin and Berthold Burghardt MicroLas Lasersystem GMBH, Robert-Bosch-Breite 10, 37079 Göttingen, Germany Abstract: We describe a new high-resolution 157-nm optical processing system for micromachining optical materials with record short-wavelength F 2 laser radiation. © 2001 Optical Society of America CIS codes: (060.2340) Fiber optics components 1. Introduction The F 2 -laser defines the short-wavelength forefront of today’s commercial laser systems. The 157-nm light supports high resolution patterning of ~100 nm features [1] while a large 7.9-eV photon energy drives strong absorption mechanisms for processing our most difficult materials. The F 2 -laser photons can access near-bandedge states in fused silica, germanosilicate [2-4], and other [5] glasses to smoothly microsculpt surfaces and to imprint refractive index structures with ∆n > 3 x 10 -3 [3,4] for a broad range of new applications in photonics processing and trimming. Microfabrication also extends to weakly absorbing polymers like polyethylene, PMMA, and PTFE [6-10] for potential biomedical, electronic, and MEMs applications. The recent addition of the F 2 -laser onto the International Technology Roadmap for Semiconductors by Sematech [11] is promising to expedite the development of 157-nm nanofabrication technology. Efficient and robust optical materials are now becoming available and new gas-flow techniques offer to overcome the 157-nm air absorption problem. To this end, our groups are collaborating to develop the first high-resolution optical processing system for high-fluence machining and refractive-index structuring of optical glasses. This paper offers a progress report of the performance of this novel 157-nm processing system and examines the prospects for F 2 -laser microfabrication of photonic components in the telecommunication and general optics manufacturing fields. 2. F 2 -Laser Optical Processing System The 157-nm optical processing system, jointly developed by MicroLas and the University of Toronto, is shown in Figure 1. A F 2 laser (Lambda Physik LPF 220i) provides ~25-mJ pulses of ~15-ns duration at 1-200 Hz repetition rate. A non-uniform beam of 5 mm x 22 mm area enters a dielectric coated attenuator to control the on-target fluence. The beam is expanded by a prism telescope to improve the symmetry of the laser beam before entering four sets of 9x9 cylindrical lens arrays for beam homogenization. The homogenizer lens then folds all 81 elements of the laser beam onto a common 6 mm x 6 mm aperture for uniform illumination (< ± 5%) at the mask plane. A three- position stage is used to deflect the beam to a fluorescent-plate beam profiler to monitor the homogenizer optics performance in situ. The illuminated mask is imaged by a 25X Schwarzschild lens to provide on-target fluence of up to ~2.5 J/cm 2 – more than sufficient for ablating glass and other robust materials. The field lens and prism expander serve to redistribute the laser light to overcome zeroth-order occlusion in the Schwarzschild optics and uniformly illuminate a 240 μm x 240 μm field at the target surface. Target alignment is facilitated by a CCD camera and light source system offering ~ 3-μm resolution of target features. Vacuum-ultraviolet transparency is obtained by flushing the 3- m long chamber with high purity argon gas from a liquid dewar. A gas-flow nozzle is applied near the Schwarzschild optic to provide a stream of transparent gas to the target surface. In this way, the target can be located external to the surface to speed set-up time and protect optics from ablation debris. The sample is located on precision 3-axis stages for dual purposes of optical alignment and computer-controlled surface structuring. All