Antoine F. J. Runge

Material properties of tapered crystalline silicon core fibers

Crystalline silicon optical fibers are emerging as a promising platform for a wide range of optoelectronic applications. Here we report a crystallographic study of the material properties within silicon fibers that have been post-processed via a tapering procedure to obtain small, few micron-sized core diameters. Our results reveal that the tapering process can improve the polysilicon quality of the core through the formation of large, centimeter long crystal grains, thus significantly reducing the optical losses.

Wavelength Conversion and Supercontinuum Generation in Silicon Optical Fibers

This paper describes the state of the art in wavelength conversion and supercontinuum generation using glass-clad silicon core optical fibers. Such semiconductor fibers have enjoyed considerable attention due to their intrinsically high third-order nonlinearities, which are markedly higher than in conventional infrared glasses. Results to date from small core silicon fibers fabricated using both the high-pressure chemical vapor deposition technique and the molten core drawing method are presented. Also discussed are directions for continued study and development, including engineering the dispersion and nonlinear properties as well as improved interconnection.

Silicon fibre nano-spike for robust coupling to silica fibres

Making use of the attractive properties of silicon (Si), a wide array of highly functional photonic devices have been demonstrated over the past few decades [1]. Although planar platforms are still the most prominent choice for integrated systems, more recently silicon fibres have gained increased attention due to their simple fabrication methods and flexible device designs [2]. However, despite their physical similarity to traditional single-mode fibres (SMFs), coupling light efficiently into and out of these devices remains a difficult task due to the high refractive index of the Si core, which results in significant reflection losses and a large mode mismatch. A few solutions have been proposed to overcome this integration challenge, including the use of microstructured fibre designs to better match the mode area [2] and chemical etchants to reduce the reflection at the interface [3], though so far no method has addressed both issues simultaneously. Thus a promising alternative solution would be to adapt the well-established inverse taper approach widely employed by the planar community [4], which is also gaining attention within the novel material fibre community [5]. The key idea behind this approach is that by decreasing the Si core to nanoscale dimensions at the facet, the guided mode spreads out to better match both the area and the effective index of the SMF mode. In this paper, we demonstrate the fabrication and optical characterization of the first Si fibre nano-spike which has been directly spliced to SMF.

Laser annealing of low temperature deposited silicon waveguides

We report the fabrication of low temperature deposited polysilicon waveguides using a laser annealing process. Micro-Raman and XRD measurements reveal the quasi-single crystal-like quality of the material, which exhibits low optical losses of 5.13 dB/cm.

Tapered silicon core fibers with nano-spikes for optical coupling via spliced silica fibers

Reported here is the fabrication of tapered silicon core fibers possessing a nano-spike input that facilitates their seamless splicing to conventional single mode fibers. A proof-of-concept 30 µm cladding diameter fiber-based device is demonstrated with nano-spike coupling and propagation losses below 4 dB and 2 dB/cm, respectively. Finite-element-method-based simulations show that the nano-spike coupling losses could be reduced to below 1 dB by decreasing the cladding diameters down to 10 µm. Such efficient and robust integration of the silicon core fibers with standard fiber devices will help to overcome significant barriers for all-fiber nonlinear photonics and optoelectronics.

Advancing silicon photonics by germanium ion implantation into silicon

We review our recent developments of the trimming techniques for correcting the operating point of ring resonator and Mach-Zehnder Interferometers (MZIs). This technology has been employed to fine-tune the effective index of waveguides, and therefore the operating point of photonic devices, enabling permanent correction of optical phase error induced by fabrication variations. Large resonance wavelength shift of ring resonators was demonstrated, and the shift can be tuned via changing the laser power used for annealing. A higher accuracy trimming technique with a scanning laser was also demonstrated to fine-tune the operating point of integrated MZIs. The effective index change of the optical mode is up to 0.19 in our measurements, which is approximately an order of magnitude improvement compared to previous work, whilst retaining similar excess optical loss.

Optical-resonance-enhanced nonlinearities in a MoS 2 -coated single-mode fiber

Few-layer molybdenum disulfide (MoS2) has an electronic band structure that is dependent on the number of layers and, therefore, is a very promising material for an array of optoelectronic, photonic, and lasing applications. In this Letter, we make use of a side-polished optical fiber platform to gain access to the nonlinear optical properties of the MoS2 material. We show that the nonlinear response can be significantly enhanced via resonant coupling to the thin film material, allowing for the observation of optical modulation and spectral broadening in the telecom band. This route to access the nonlinear properties of two-dimensional materials promises to yield new insights into their photonic properties.

Dataset for: Ion implantation in silicon for trimming the operating wavelength of ring resonators

In recent years, we have presented results on the development of erasable gratings in silicon to facilitate wafer scale testing of photonics circuits via ion implantation of germanium. Similar technology can be employed to control the operating wavelength of ring resonators, which is very sensitive to fabrication imperfections. Ion implantation into silicon causes radiation damage resulting in a refractive index increase, and can therefore, form the basis of multiple optical devices. In this paper, we discuss design, modeling, and fabrication of ring resonators and their subsequent trimming using ion implantation of germanium into silicon, followed by either rapid thermal annealing or localized laser annealing. The results confirm the ability to permanently tune the position of the resonant wavelength to any point inside the free spectral range of the ring resonator, thus, greatly reducing the amount of power required for active tuning of these devices.

Dataset for Wavelength conversion and supercontinuum generation in silicon optical fibers

Dataset supports:nPeacock, A. et al (2017). Wavelength conversion and supercontinuum generation in silicon optical fibers. IEEE Journal of Selected Topics in Quantum Electronics.

Germanium implanted photonic devices for post-fabrication trimming and programmable circuits

We reviewed our recent developments on the post-fabrication trimming techniques and programmable photonic circuits based on germanium ion implanted silicon waveguides. Annealing of ion implanted silicon can efficiently change the refractive index. This technology has been employed to fine-tune the optical phase, and therefore the operating point of photonic devices, enabling permanent correction of optical phase error induced by fabrication variations. High accuracy phase trimming was achieved with laser annealing and a real-time feedback control system. Erasable waveguides and directional couplers were also demonstrated, which can be used to implement programmable photonic circuits with low power consumption.