Ultrafast laser processing:: new options for three-dimensional photonic structures

Using tightly focused ultrashort laser pulses allows the direct writing of three-dimensional photonic structures in different glasses and also crystalline media. One of the main drawbacks of this technology is, however, the limited writing speed achieved so far. In this paper we shall review our recent advances in the direct writing of three-dimensional integrated-optical devices and discuss a new approach using a fibre-based femtosecond laser system producing 300 fs pulses with pulse energies of 0.6 muJ at 2 MHz repetition rate. Using this laser system we fabricated low-loss waveguides (less than 0.5 dB cm(-1)) at writing speeds of 100 mm s(-1) for the first time. The influence of the writing speed on the produced structures as well as their optical properties will be discussed in detail.