High precision material processing using ultrashort laser pulses

Laser micromachining using femtosecond pulses, is a most promising and versatile technique, having a variety of applications. The main features are an efficient and localized energy deposition, low ablation thresholds and no thermal and mechanical damage of the substrate material. The maximum benefits are obtained when one operates just above ablation or modification threshold. Under typical focusing conditions the required energies are 10s of nJ, which is slightly above the output of standard femtosecond oscillators. Amplified laser systems on the other hand are overkill for microstructuring as the pulse energy has to be strongly attenuated, resulting in a low average output power and process speed. This limits the achievable throughput and effects the overall process quality. The Chirped Pulsed Oscillator (CPO) is a new approach that resolves this problem. By adding a multipass cell into a standard oscillator, the cavity is extended. The low repetition rate results in pulse energies an order of magnitude higher. In contrast to a standard femtosecond oscillator, the CPO works in the positive dispersion regime whereby multiple pulsing is avoided. In this talk we will review the basic idea behind the CPO and will give an overview about the work we do at Macquarie University in the field of microfabrication of photonic structures and devices, aiming towards the development of the Photonic Chip. Amongst others, we will include our abilities in point-by-point inscription of fibre-Bragg gratings and the fabrication of waveguide structures in various materials, including laser-active crystals and chalcogenide glasses.