This project was focused on the creation of a gold-coated grating structure capable of inducing a surface plasmon polariton within the mid-infrared region, enhancing emissions at specific wavelengths based on the grating periodicity. The grating structure was formed on a silicone elastomer, polydimethylsiloxane (PDMS), in order to give the structure, the ability to have the periodicity dimensions of the grating altered by applying a stress, thereby changing the location of the emission enhancement, giving the device the potential to be used as an infrared strain sensor. Creation of the structure employed a top-down, micro-scale fabrication technique referred to as Direct Laser Writing (DLW). Using a light-sensitive, negative-tone photoresist material, a grating was patterned onto a glass substrate via photopolymerization, in which areas exposed to an ultraviolet (UV) laser were rendered insoluble by forming cross-links on the portions of the resist which interacted with the UV source. This grating was then placed under a custom-designed mold which was then filled with liquid PDMS and cured for 3 hours at 60°C to cure (harden or cross-link) and leaving an inverse elastomer pattern behind once the cured PDMS was peeled off the substrate. Upon coating the structure with a ~80 nm thick layer of gold, a Fourier Transform infrared (FTIR) spectrometer was used to measure the thermal emissions spectrum of the sample grating at a high temperature (~200°C) and under different strains. These spectra were then analyzed to look for selective emission enhancements caused by the grating structure due to the inducing of a surface plasmon polariton (SPP), as well as changes in the location and nature of these enhancements based on applied strains. Final results showed two sets of enhancement behaviors with the application of uniaxial strain: a shifting of the region of peak emission enhancement to higher wavelengths, and a broadening of the region of enhancement. However, more testing is needed in order to determine the precise causes of the behavior and to quantify it in such a way that it could be turned into a functioning sensor device.

The manipulation of photons, especially the control of spontaneous emission, has become a core area of photonics research in the 21st century. One of the key challenges is the control of the broadband emission profile of thermal emitters. Recently, attention has focused on resonant nanophotonic structures to control the thermal emission with most of the work concentrating on the mid-infrared wavelength range and/or based on metallic nanostructures. However, the realisation of a high temperature, single wavelength, narrowband and efficient thermal source, remains a challenge. In this project, four individual nanophotonic resonant structures are presented for the control of thermal emission, all operating in the near-infrared (≈ 1.5 μm) wavelength range. The work is split over two different emission materials; gold and doped silicon. While I present two successful designs of narrowband thermal emitters from gold, the main backbone of the research is concentrated on doped silicon as the emission material. By combining the weak broadband absorption of doped silicon with a photonic crystal resonator, resonantly enhanced narrowband absorption is achieved. Using Kirchhoff's law of thermal radiation which equates the absorptivity and emissivity, narrowband absorption leads to narrowband emission, which is the underlying principle used throughout the work presented in this thesis to achieve narrowband thermal emission. One common oversight in many of the presented thermal emitter designs is the angular emission dependence, i.e. how the emission wavelength behaves away from surface normal. Typically, since the majority of the devices are based on periodic structures, the resonant emission wavelength changes with emission angle, which is not ideal. Here, the angular sensitivity is considered and addressed, by constructing a device that is based on localised confined resonances and not on propagating resonances, it is possible to achieve a truly monochromatic source i.e. one with the same emission wavelength in all directions, all the way up to an angle of 90°. Finally, the devices presented here demonstrate that weak absorption together with photonic resonances can be used as a wavelength-selection mechanism for thermal emitters, both for the enhancement and the suppression of emission away from the resonant wavelength.