Silicon photonics has been a very buoyant research field in the last several years mainly because of its potential for telecom and datacom applications. However, prospects of using silicon photonics for sensing in the mid-IR have also attracted interest lately. In this paper, we present our recent results on waveguide based devices for near-and mid-infrared applications. The silicon-on-insulator platform can be used for wavelengths up to 4μm, therefore different solutions are needed for longer wavelengths. We show results on passive Si devices such as couplers, filters and multiplexers, particularly for extended wavelength regions, and finally present integration of photonics and electronics integrated circuits for high speed applications.

Grating couplers are used to efficiently couple light from an optical fibre to a silicon waveguide as they allow light to be coupled into or out from any location on the device without the need for cleaving. However, using the typical surface relief grating fabrication method reduces surface planarity and hence makes further processing more difficult. The ability to manufacture high quality material layers on top of a grating coupler allows multiple active optical layers to be realized for multi-layer integrated optical circuits, and may enable monolithic integration of optical and electronic circuits on separate layers. Furthermore, the nature of the refractive index change may enable removal via rapid thermal annealing for wafer scale testing applications. We demonstrate for the first time a coupling device utilising a refractive index change introduced by lattice disorder. Simulations show 44% of the power can be extracted from the waveguide by using uniform implanted gratings, which is not dissimilar to the performance of typical uniform surface relief gratings currently used. Losses determined empirically, of 5.5dB per coupler have been demonstrated. 5958-5964 (1997). 32. G. F. Cembali, P. G. Merli, and F. Zignani, "Self-annealing of ion-implanted silicon: First experimental results," Appl. Phys. Lett. 38(10), 808-810 (1981 75-77 (2008).

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-We present Bragg gratings with an effective index change introduced by implanting germanium at only 15KeV. An extinction ratio of 35dB at 1350nm is demonstrated for device lengths of 600μm, furthermore laser annealing is demonstrated. IntroductionIn the information age current technologies struggle to deliver the data rates required by modern communications and computer bus systems. Silicon photonics has the potential of overcoming some of these obstacles by relying on a well understood material system and technology [1]. However the full adoption of silicon based photonics would require complex integrated optoelectronic systems to be manufactured in high volumes at low costs. These requirements cannot be met without enabling a wafer scale testing [2] strategy in a similar fashion to what has been happening for many decades in the integrated electronics industry. The current challenge for silicon photonics in this area is represented by the inability of the light signal to access a processed wafer without substantially modifying the wafer surface. Most of the solutions presented for light coupling into test samples rely on substantially modifying the structure of the material to enable end fire coupling, prism coupling [3], inverted tapers [4], and cantilever structures [5]. Introducing these kinds of test points, or even wavelength selective test points such as etched or metal gratings on a processed wafer can potentially introduce undesired alterations of the light propagation, such as scattering and losses, as well as interfering with successive processing steps. In order for optical wafer scale testing to become a viable technology, optical wafer scale testing should be implemented as a minimally intrusive technology. The use of ion implanted optical structures is particularly suited for these applications, as the refractive index change can be introduced on the wafer surface without altering the general topography of the wafer. Furthermore, since the planarity of the wafer is retained, it could be possible to employ these structures for applications that require extensive surface interaction such as bonding or flip chip interactions, and sensing. The use of a low energy/low dose implant conditions (10 15 ion/cm 2 , as opposed to general doping densities which can reach 10 19 ion/cm 2 ) potentially allows minimal optical losses to be introduced by the implantation process.

Test points are essential in allowing optical circuits on a wafer to be autonomously tested after selected manufacturing steps, hence allowing poor performance or device failures to be detected early and to be either repaired using direct write methods, or a cessation of further processing to reduce fabrication costs.Grating couplers are a commonly used method for efficiently coupling light from an optical fibre to a silicon waveguide. They are relatively easy to fabricate and they allow light to be coupled into/out from any location on the device without the need for polishing, making them good candidates for an optical test point.A fixed test point can be added for this purpose, although traditionally these grating devices are fabricated by etching the silicon waveguide, and hence this permanently adds loss and leads to a poor performing device when placed into use after testing. We demonstrate a similar device utilising a refractive index change induced by lattice disorder. Raman data collected suggests this lattice damage is reversible, allowing a laser to subsequently erase the grating coupler.