High Energy-High Repetition Rate Fiber Laser System for Precision Micromachining with Fundamental and Second Harmonic Wavelengths

Abstract

Interest in femtosecond laser micromachining has been growing for applications that require precise material removal or modification over very small features. Flat panel display manufacturing, lithography mask repair, semiconductor wafer scribing and optical waveguide writing are some ex- amples where femtosecond pulse lasers are being studied. IMRA's latest experimental prototype FCPA is based on components similar to the production FCPA µJewel D-400. The latest design concept produces 10-µJ pulses at a repetition rate of up to 100 kHz or 1-µJ pulses at 1 MHz using Yb-doped fiber amplifier technology. Frequency-doubling produces 522-nm wavelength output with pulse energies up to 4 µJ. The higher pulse energy, relatively high repetition rate, availability of efficient frequency-doubling with a compact, reliable design will enable additional industrial ap- plications. This paper describes the experimental results comparing the nonlinear optical loss through different types of transparent materials. The combination of the nonlinear absorption initi- ated by the ultrashort pulses and the heat accumulation from the high repetition rate enable some unique advantages over other lasers. The effect of the two different wavelengths (1045 nm and 522 nm) on processing of transparent materials is illustrated in several examples.