Low-power programmable integrated photonic circuits fabricated by femtosecond laser micromachining

Photonic integrated circuits (PICs) are steadily becoming an established technology with a wide range of applications in communications, sensing and analog signal processing. PICs manipulate light signals using waveguides, directional couplers and phase shifters as building blocks. Recently, there has been growing interest in fully reconfigurable PICs, which can be programmed to perform any linear transformation on the input signal. Femtosecond Laser Micromachining (FLM) is a versatile fabrication technology that allows rapid and cost-effective fabrication of PICs. Reconfigurability in FLM PICs is implemented by means of thermal phase shifters, which provide optical signal modulation without added signal loss. Until recently only few thermal shifters could be fabricated on the same chip due to their high power dissipation and thermal crosstalk. This limitation can be overcome with the introduction of isolation structures fabricated via FLM, which provide a more than ten-fold reduction in dissipated power and crosstalk, allowing us to fabricate fully programmable PICs with tens of thermal shifters integrated into the same device.