|MEMON FAISAL AHMED||Cycle: XXX |
Tutor: Major Research topic
:High Index Optical Waveguides and Devices in Silicon Oxycarbide
Advisor: MELLONI ANDREA IVANOAbstract:
Silicon oxycarbide (SiOC) is a versatile material that has been used in technologically important applications such as, anode material in lithium ion batteries, interlayer dielectric, rare-earth doped optical amplifiers, photoluminescence and electroluminescence by several researchers. However, to-date silicon oxycarbide has not been used in photonics applications. In my PhD, silicon oxycarbide thin films have been deposited with reactive rf magnetron sputtering technique. The optical properties of the synthesized SiOC films are studied comprehensively studied applying different characterization techniques. The structural and chemical properties are characterized with XRD and XPS which confirm amorphous phase and continuous change in composition of the deposited films under the control of deposition conditions. The optical properties, refractive index and extinction coefficient which are two important parameters to realize optical waveguides ad devices are reported and acquired with ellipsometry over a broad wavelength spectrum extending from 300 nm to 1600 nm. It is experimentally observed that refractive index of the SiOC can be tuned over a large range from 1.45 to 2.8 at the wavelength 1550 nm and the extinction coefficient is below 10-4 for all the compositions of the deposited films. The study of optical properties indicates potential of the SiOC for integrated photonics applications. To this aim optical waveguides in silicon oxycarbide films with different refractive index (i.e. composition) have been realized using photolithography and reactive ion etching techniques. The optical waveguides are characterized on a controlled optical setup with small core fibres (i.e mode field diameter = 3.6 μm) and the losses are measured. The optical waveguides with refractive index n=1.7 exhibit low losses at standard telecommunication wavelength λ=1550 nm. The loss at λ=1550 nm is measured to be 4 dB/cm that is a good number at high refractive index. Such high refractive index value is not achievable with the state-of-the-art silicon oxynitride (SiON) technology. Currently, in addition to optical waveguides with different refractive index, complex optical devices such as optical couplers and ring resonators are under development and characterization stage. In the future, thermos-optic effect, higher order non-linearity, electrochromism and intercalation mechanism in SiOC waveguides will be explored.