The University of Southampton

Photonic Sytems, Circuits and Sensors PhD Projects

Silicon Photonics based optical modulators

Supervisor: Graham Reed
Co-Supervisor: Shin Saito (ECS)

The supervisors have recently been awarded a new EPSRC grant (EP/M009416/1) entitled “Si Fin Modulator for Low Power Interconnection”.

The student will work alongside the RA on the project to develop a silicon photonics technology based upon etching completely vertical faces of the (111) plane to the substrate by anisotropic Tetra-Methyl-Ammonium-Hydroxide (TMAH) wet etching. This will minimise scattering loss and therefore will facilitate development of a more efficient photonics platform. Within this structure we will also develop a new type of modulator based upon carrier accumulation, enhancing the capacitance of the device appropriately.

The resources of the project will be leveraged to maximise the impact of the student’s work, and to enhance progress, maximising the effectiveness of both the studentship and the additional EPSRC grant funding.

Silicon and germanium chemical photonics sensors

Supervisor: Prof Goran Mashanovich (ORC)
Co-supervisor: Prof Andrea Russell (Chemistry)

A number of molecules show strong absorption bands in the mid-infrared wavelength region (3μm<λ<15μm). As silicon and germanium are transparent in the mid-IR, they are main candidates for compact photonic circuits and systems for bio/chemical sensing. In this project material platforms will be first developed, functionalization of the surface performed and finally different sensing schemes investigated (e.g. absorption and Raman spectroscopy). In this multidisciplinary project, the student will work with researchers from photonics, chemistry and electronics and computer science. The state of the art facilities at the Southampton Nanofabrication Centre, Chemistry department and Optoelectronics Research Centre will be available for the design, fabrication and characterisation of mid-infrared sensors.

Wideband mid-infrared photonic circuits

Supervisor: Prof Goran Mashanovich
Co-supervisor: Prof G T Reed

To fully utilize the potential of the mid-IR wavelength range (2-15 μm), particularly for sensing applications, photonic material platforms should be transparent in a wide wavelength range and also individual photonic devices, as well as integrated circuits, should operate over that range, which is very challenging to achieve. The project will comprise of the design of silicon and germanium based wideband waveguides, passive devices such as splitters and couplers, and also active devices (detectors and sources) using novel approaches. Particular attention will be paid to the choice of the material platform, which should be low loss and also enable realisation of efficient photonic devices at longer wavelengths. These devices will be fabricated, characterised, and eventually integrated in the state-of-the-art Zepler Institute facilities. There will be an intensive collaboration with universities of Sheffield (UK) and Malaga (Spain), and with the National Research Council in Canada.

High speed mid-infrared photodetectors

Supervisor: Prof Goran Mashanovich
Co-supervisor: 
Dr Radan Slavik

Recently there has been tremendous interest in extending photonics beyond its traditional spectral regions, which is visible light (e.g., for imaging) and near-infrared “light” (e.g., for telecommunications). The mid-infrared region with wavelengths beyond 3 µm has a great potential important application areas such as environmental sensing, homeland security, and medicine. It will also give additional spectrum bandwidth for free-space communications for 6G networks and beyond. However, today performance of photonics components (e.g., light sources, modulators, waveguides, and detectors) operating in the mid-infrared region needs significant improvement to be of practical interest in the above-mentioned applications.

The project will investigate new integrated (small size, efficient, integrable with other components on the same photonics chip) detectors for the mid-infrared region that will be significantly faster than those available today. It will also deal with the integration of these detectors with optical waveguides, allowing for signal detection using techniques known from today’s telecommunications (e.g., heterodyne detection) that can detect weak signals with significantly better signal-to-noise ratio than simple direct detection. This is expected to revolutionize all the potential applications in the mid-infrared, as background noise at room temperature is very strong in this spectral region, requiring advanced detection techniques to mitigate it.

The project will suit a person interested in a broad range of photonics, as it will involve a range of activities required in photonics, e.g., design and fabrication of integrated optics, characterisation of the fabricated devices, and building/testing of photonics systems.

Optical Device Trimming

Supervisor: Prof Graham Reed 
Co-supervisor: Prof Goran Mashanovich

A recent graduate from the Silicon Photonics group has developed erasable grating couplers for wafer scale testing. The technique used is to cause radiation damage via ion implantation which causes a substantial change in refractive index. This damage can be locally annealed via a focussed laser to remove the refractive index change thus “erasing” the damage.

We wish to apply this technology to trimming of devices in silicon photonics that are highly sensitive to fabrication variations, even in advanced lithography fabrication plants. A typical example is a ring resonator which may exhibit a resonant wavelength error of 1nm for a 1nm fabrication error. This effectively prevents reliable fabrication. By applying damage to the ring, we expect to be able to partially anneal the damage to select a suitable wavelength of operation, thus trimming the device. Whilst there is huge demand for trimming, there is currently no viable technique.

A patent application is being prepared. The thesis of the recently graduated student has been restricted for 1 year to complete filing.

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