Realising photonic circuitry for future optical networks

The current challenge facing the optical communications community is to develop robust, flexible, upgradeable and integrated devices which provide high bandwidth at a low-cost, low power consumption, and low footprint for Metropolitan Area Networks. One solution to this problem is the all-optical integrated circuit, the photonic equivalent of the analogue electronic integrated circuit. Significant attention has recently been directed to the use of femtosecond laser pulses for inscribing optical components inside transparent materials in order to help realise this goal. Indeed, tightly focused infrared femtosecond laser pulses can induce refractive index changes inside glass samples with similar contrasts to the core/cladding of conventional optical fibre. We have demonstrated that optical waveguides can be written in a range of glass materials such as fused silica and (doped and un-doped) phosphate glasses. Waveguides written in active glasses can be used as single pass amplifiers or as compact laser sources following the addition of cavity reflectors. In our most recent experiments we fabricated low-loss (0.39 dB/cm) optical waveguides in non-doped phosphate glass; these results represent the lowest reported losses in this material and will enable the manufacture of high gain amplifiers and lasers in erbium doped or erbium/ytterbium co-doped phosphate glasses. In fact, we have also recently shown that our waveguides fabricated in co-doped phosphate glass exhibit an internal gain of 4.33 dB over a length of 5 cm when pumped with 980 nm light. A review of these milestones plus our current research on 2-D and 3-D optical splitters and wavelength specific devices in a range of glass materials will be presented.