Practical and High-Energy Near- to Mid-Infrared Femtosecond Oscillators for Directly Writing Silicon Waveguides in Three Dimensions

Direct-writing of optical waveguides using femtosecond lasers has been the subject of much research since the first demonstration 10 years ago. Despite the great potential of optically-written semiconductor waveguides, there remains an almost universal absence of research in this area. The most likely explanation for this is a practical one; only Ti:sapphire amplifiers can typically provide sufficient pulse energy for waveguide creation but their 800nm wavelength is not transmitted by semiconductors such as silicon, so the creation of sub-surface waveguides is impossible. We propose to address this problem by developing a new energy-scaling approach to femtosecond optical parametric oscillators based on combining cavity-dumping with extended-cavity operation. In this way we expect to produce near- and mid-infrared pulses with energies around 1uJ which should be sufficient to write waveguides in various materials, and we intend to verify this by concentrating on waveguide creation in silicon wafers. The project combines broad expertise in the Ultrafast Optics Group in femtosecond laser machining , sub-surface silicon microscopy and femtosecond parametric source development .