Mid-infrared (mid-IR) spectroscopy is a nearly universal way to identify chemical and biological substances, as most of the molecules have their vibrational and rotational resonances in the mid-IR wavelength range. Commercially available mid-IR systems are based on bulky and expensive equipment, while lots of efforts are now devoted to the reduction of their size down to chip-scale dimensions. The use of silicon photonics for the demonstration of mid-IR photonic circuits will benefit from reliable and high-volume fabrication to offer high performance, low cost, compact, lightweight and power consumption photonic circuits, which is particularly interesting for mid-IR spectroscopic sensing systems that need to be portable and low cost. Among the different materials available in silicon photonics, Germanium (Ge) and Silicon-Germanium (SiGe) alloys with a high Ge concentration are particularly interesting because of the wide transparency window of Ge up to 15 μm. In this context, the objective of this thesis is to investigate a new Ge-rich graded SiGe platform for mid-IR photonic circuits. Such new plateform was expected to benefit from a wide transparency wavelength range and a high versatility in terms of optical engineering (effective index, dispersion, ...). During this thesis, different waveguides platforms based on different graded profiles have been investigated. First it has been shown that waveguides with low optical losses of less than 3 dB/cm can be obtained in a wide wavelength range, from 5.5 to 8.5 μm. A proof of concept of sensing based on the absorption of the evanescent component of the optical mode has then been demonstrated. Finally, elementary building blocs have been investigated. The first Bragg mirror-based Fabry Perot cavities and racetrack resonators have been demonstrated around 8 μm wavelength. A broadband dual-polarization MIR integrated spatial heterodyne Fourier-Transform spectrometer has also been obtained. All these results rely on material and device design, clean-room fabrication and experimental characterization. This work was done in the Framework of EU project INsPIRE in collaboration with Pr. Giovanni Isella from Politecnico Di Milano.

The mid-infrared (Mid-IR) wavelength range is important for applications including medical and security imaging, environmental trace gas sensing and free space communications. However, photonic integrated circuits (PICs) in the mid-IR range are under-developed which significantly slows the possible reduction of mid-IR system size, weight, and coupling losses and limits the development of highly functional mid-IR photonic modules with lower cost. In this dissertation, a solution to mid-IR photonic integration was demonstrated using a compact, widely tunable mid-IR transmitter and a mid-IR amplifying photo-detector, both which can be integrated with the mid-IR source.

This Spotlight provides a comprehensive introduction to the research history and leading-edge studies of mid-infrared germanium photonics. Topics include waveguides, grating couplers, microresonators, photonic crystal waveguides and cavities, photonic integrated circuits, and applications in information science, nonlinear optics, and biochemical sensing. The text is intended as a useful reference for beginners and experts in the integrated optics community.

Mid-infrared Optoelectronics: Materials, Devices, and Applications addresses the new materials, devices and applications that have emerged over the last decade, along with exciting areas of research. Sections cover fundamentals, light sources, photodetectors, new approaches, and the application of mid-IR devices, with sections discussing LEDs, laser diodes, and quantum cascade lasers, mid-infrared optoelectronics, emerging research areas, dilute bismide and nitride alloys, Group-IV materials, gallium nitride heterostructures, and new nonlinear materials. Finally, the most relevant applications of mid-infrared devices are reviewed in industry, gas sensing, spectroscopy, and imaging. This book presents a key reference for materials scientists, engineers and professionals working in R&D in the area of semiconductors and optoelectronics. Provides a comprehensive overview of mid-infrared photodetectors and light sources and the latest materials and devices Reviews emerging areas of research in the field of mid-infrared optoelectronics, including new materials, such as wide bandgap materials, chalcogenides and new approaches, like heterogeneous integration Includes information on the most relevant applications in industry, like gas sensing, spectroscopy and imaging

This graduate-level textbook presents the principles, design methods, simulation, and materials of photonic circuits. It provides state-of-the-art examples of silicon, indium phosphide, and other materials frequently used in these circuits, and includes a thorough discussion of all major types of devices. In addition, the book discusses the integrated photonic circuits (chips) that are currently increasingly employed on the international technology market in connection with short-range and long-range data communication. Featuring references from the latest research in the field, as well as chapter-end summaries and problem sets, Principles of Photonic Integrated Circuits is ideal for any graduate-level course on integrated photonics, or optical technology and communication.

Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared telecom wavelengths. Besides these, it has very high refractive index, and also a broad optical transparency window over the entire mid-IR till about 8[Mu]m. Photonic crystal is well known that it can slow down the speed of light. It also can provide a universal platform for microcavity optical resonators with high quality factor Q and small modal volumes. The slow light effect, high Q and small modal volumes enhance light-matter interaction, together with high refractive index of silicon can be utilized to build a highly sensitive, high throughput sensor with small footprint. In this research, we have demonstrated highly compact and sensitive silicon based photonic crystal biosensor by engineering the photonic crystal microcavity in both cavity size and cavity-waveguide coupling condition. We have developed solutions to increase biosensor throughput by integrating multimode interference device and improving the coupling efficiency to a slow light photonic crystal waveguides. We have also performed detailed investigations on silicon based photonic devices at mid-infrared region to develop an ideal platform for highly sensitive optical absorption spectroscopy on chip. The studies have led to the demonstration of the first slot waveguide, the first photonic crystal waveguide, and the first holey photonic crystal waveguide and first slotted photonic crystal waveguide in silicon-on-sapphire at mid-infrared. The solutions and devices we developed in our research could be very useful for people to realize an integrated photonic circuit for biological and chemical sensing in the future.

The development of integrated silicon photonic circuits has recently been driven by the Internet and the push for high bandwidth as well as the need to reduce power dissipation induced by high data-rate signal transmission. To reach these goals, efficient passive and active silicon photonic devices, including waveguide, modulators, photodetectors,