Monolithic silicon photonic crystals on various platforms [electronic resource] : from sensors to mirrors
Keywords: Electrical Engineering.

Scaling and integration have been keywords for the semiconductor and electronics industries since the second half of the twentieth century to achieve fast and low power-consuming devices with multiple functionalities. In the optics world, the integration of different optical elements also leads to the creation of novel devices with new and synergetic functionalities. This dissertation presents the monolithic silicon photonic crystal (PC) slab, a versatile nanophotonic device, integrated on different optical platforms -- optical fibers and MEMS scanners -- performing as sensors and mirrors that overcome existing problems and allow for expanded scope of applications. PCs enable sensitive and robust sensors for a large number of measurands, including temperature, refractive index, displacement, pressure, and acceleration. The small volume of two-dimensional PC sensors also makes them ideal for integration onto the facet of optical fibers. PC fiber tip sensors are highly sensitive to changes in the refractive index and temperature while remaining compact and robust. In comparison to conventional fiber sensors such as fiber Bragg gratings (FBG) or long period fiber gratings (LPFG), they are attractive in several aspects. PC fiber tip sensors have better sensitivity to refractive index and temperature than FBG sensors and have much smaller sensing volumes than FBGs and LPFGs. Their small size allows them to combine high sensitivity with structural robustness. The most attractive feature may be that PC fiber tip sensors also return a spectrally rich signal with independently shifting resonances that can be used to extract multiple physical properties of the measurand and distinguish between them. Moreover the chemically and mechanically robust composition of the sensors is suitable for harsh environment applications, especially for high temperature sensing. PCs can be also designed as broadband high reflectivity mirrors, making them an ideal candidate for reflectors in optical micro-electro-mechanical systems (MEMS). Conventional metal mirrors suffer from fragility and limited power and temperature tolerance, and distributed Bragg reflectors are often incompatible with optical MEMS devices due to their mechanical rigidity and stress. On the other hand, PC mirrors are compact, highly reflective, and robust without excessive rigidity and stress. Therefore, we integrate monolithic silicon PC mirrors on a two-axis electrostatic MEMS scanner, extending the scanner operation into new fields such as high power laser steering. The reflective surfaces of the MEMS scanner are transfer-printed PC mirrors with low polarization dependence, low angular dependence, and high reflectivity above 90% over the wavelength band of 1550~1570nm. The transfer-printing technique increases design flexibility by allowing optical components with different characteristics to be integrated on a common MEMS platform. In the case of the PC mirror, it does not result in changes to the original mechanical characteristics of the scanner due to its small form factor.