Graphene thermal infrared emitters integrated into silicon photonic waveguides

Cost-efficient and easily integrable broadband mid-infrared (mid-IR) sources would significantly enhance the application space of photonic integrated circuits (PICs). Thermal incandescent sources are superior to other common mid-IR emitters based on semiconductor materials in terms of PIC compatibility, manufacturing costs, and bandwidth. Ideal thermal emitters would radiate directly into the desired modes of the PIC waveguides via near-field coupling and would be stable at very high temperatures. Graphene is a semi-metallic two-dimensional material with comparable emissivity to thin metallic thermal emitters. It allows maximum coupling into waveguides by placing it directly into their evanescent fields. Here, we demonstrate graphene mid-IR emitters integrated with photonic waveguides that couple directly into the fundamental mode of silicon waveguides designed for a wavelength of 4,2 {\mu}m relevant for CO${_2}$ sensing. High broadband emission intensity is observed at the waveguide-integrated graphene emitter. The emission at the output grating couplers confirms successful coupling into the waveguide mode. Thermal simulations predict emitter temperatures up to 1000{\deg}C, where the blackbody radiation covers the mid-IR region. A coupling efficiency {\eta}, defined as the light emitted into the waveguide divided by the total emission, of up to 68% is estimated, superior to data published for other waveguide-integrated emitters.Comment: 24 page

Mid-infrared photonic devices for on-chip optical gas sensing

Gas detection is crucial in a wide range of fields and applications, such as safety and process control in the industry, atmospheric sciences, and breath diagnostics. Optical gas sensing offers some key advantages, compared to other sensing methods such as electrochemical and semiconductor sensing: high specificity, fast response, and minimal drift. Wavelengths between 3 and 10 μm are of particular interest for gas sensing. This spectral range, called the mid-infrared (mid-IR), is also known as the fingerprint region, because several gas species can be identified by their sharp absorption lines in this region. The most relevant mid-IR-active gases are the trace gases carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), ammonia (NH3), and nitrous oxide (N2O). They are greenhouse gases, contributing to global warming. They are waste products of human activities and widely used in agriculture and industry. Therefore, it is crucial to accurately and extensively monitor them. However, traditional optical gas sensors with a free-space optical path configuration, are too bulky, power-hungry, and expensive to be widely adopted. This thesis presents mid-IR integrated photonic devices that enable the on-chip integration of optical gas sensors, with a focus on CO2 sensing. The reported technologies address the fundamental sensor functionalities: light-gas interaction, infrared light generation, and infrared light detection. The thesis introduces a novel mid-IR silicon photonic waveguide that allows a light path as long as tens of centimeters to fit in a volume smaller than a few cubic millimeters. Mid-IR CO2 spectroscopy demonstrates the high sensing performance of the waveguide. The thesis also explores the refractive index sensing of CO2 with a mid-IR silicon photonic micro-ring resonator. Furthermore, the thesis proposes platinum nanowires as low-cost infrared light sources and detectors that can be easily integrated on photonic waveguides. Finally, the thesis presents a large-area infrared emitter fabricated by highs-peed wire bonding and integrated in a non-dispersive infrared sensor for the detection of alcohol in breath. The technologies presented in this thesis are suited for cost-effective mass production and large-scale adoption. Miniaturized integrated optical gas sensors have the potential to become the main choice for an increasingly broad range of existing and new applications, such as portable, distributed, and networked environmental monitoring, and high-volume medical and consumer applications

Mid-infrared photonic devices for on-chip optical gas sensing

Gas detection is crucial in a wide range of fields and applications, such as safety and process control in the industry, atmospheric sciences, and breath diagnostics. Optical gas sensing offers some key advantages, compared to other sensing methods such as electrochemical and semiconductor sensing: high specificity, fast response, and minimal drift. Wavelengths between 3 and 10 μm are of particular interest for gas sensing. This spectral range, called the mid-infrared (mid-IR), is also known as the fingerprint region, because several gas species can be identified by their sharp absorption lines in this region. The most relevant mid-IR-active gases are the trace gases carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), ammonia (NH3), and nitrous oxide (N2O). They are greenhouse gases, contributing to global warming. They are waste products of human activities and widely used in agriculture and industry. Therefore, it is crucial to accurately and extensively monitor them. However, traditional optical gas sensors with a free-space optical path configuration, are too bulky, power-hungry, and expensive to be widely adopted. This thesis presents mid-IR integrated photonic devices that enable the on-chip integration of optical gas sensors, with a focus on CO2 sensing. The reported technologies address the fundamental sensor functionalities: light-gas interaction, infrared light generation, and infrared light detection. The thesis introduces a novel mid-IR silicon photonic waveguide that allows a light path as long as tens of centimeters to fit in a volume smaller than a few cubic millimeters. Mid-IR CO2 spectroscopy demonstrates the high sensing performance of the waveguide. The thesis also explores the refractive index sensing of CO2 with a mid-IR silicon photonic micro-ring resonator. Furthermore, the thesis proposes platinum nanowires as low-cost infrared light sources and detectors that can be easily integrated on photonic waveguides. Finally, the thesis presents a large-area infrared emitter fabricated by highs-peed wire bonding and integrated in a non-dispersive infrared sensor for the detection of alcohol in breath. The technologies presented in this thesis are suited for cost-effective mass production and large-scale adoption. Miniaturized integrated optical gas sensors have the potential to become the main choice for an increasingly broad range of existing and new applications, such as portable, distributed, and networked environmental monitoring, and high-volume medical and consumer applications

Mid-infrared photonic devices for on-chip optical gas sensing

Gas detection is crucial in a wide range of fields and applications, such as safety and process control in the industry, atmospheric sciences, and breath diagnostics. Optical gas sensing offers some key advantages, compared to other sensing methods such as electrochemical and semiconductor sensing: high specificity, fast response, and minimal drift. Wavelengths between 3 and 10 μm are of particular interest for gas sensing. This spectral range, called the mid-infrared (mid-IR), is also known as the fingerprint region, because several gas species can be identified by their sharp absorption lines in this region. The most relevant mid-IR-active gases are the trace gases carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), ammonia (NH3), and nitrous oxide (N2O). They are greenhouse gases, contributing to global warming. They are waste products of human activities and widely used in agriculture and industry. Therefore, it is crucial to accurately and extensively monitor them. However, traditional optical gas sensors with a free-space optical path configuration, are too bulky, power-hungry, and expensive to be widely adopted. This thesis presents mid-IR integrated photonic devices that enable the on-chip integration of optical gas sensors, with a focus on CO2 sensing. The reported technologies address the fundamental sensor functionalities: light-gas interaction, infrared light generation, and infrared light detection. The thesis introduces a novel mid-IR silicon photonic waveguide that allows a light path as long as tens of centimeters to fit in a volume smaller than a few cubic millimeters. Mid-IR CO2 spectroscopy demonstrates the high sensing performance of the waveguide. The thesis also explores the refractive index sensing of CO2 with a mid-IR silicon photonic micro-ring resonator. Furthermore, the thesis proposes platinum nanowires as low-cost infrared light sources and detectors that can be easily integrated on photonic waveguides. Finally, the thesis presents a large-area infrared emitter fabricated by highs-peed wire bonding and integrated in a non-dispersive infrared sensor for the detection of alcohol in breath. The technologies presented in this thesis are suited for cost-effective mass production and large-scale adoption. Miniaturized integrated optical gas sensors have the potential to become the main choice for an increasingly broad range of existing and new applications, such as portable, distributed, and networked environmental monitoring, and high-volume medical and consumer applications

On-chip dispersion spectroscopy of CO2 using a mid-infrared microring resonator

We demonstrate on-chip molecular fingerprinting by measuring the refractive index dispersion of gas in the mid-IR using a thermally tuned suspended silicon microring resonator. We show CO2 sensing down to 1000 ppm at 4.23 µm wavelength.QC 20210916</p

On-chip dispersion spectroscopy of CO2 using a mid-infrared microring resonator

We demonstrate on-chip molecular fingerprinting by measuring the refractive index dispersion of gas in the mid-IR using a thermally tuned suspended silicon microring resonator. We show CO2 sensing down to 1000 ppm at 4.23 µm wavelength

A fast uncooled infrared nanobolometer featuring a hybrid-plasmonic cavity for enhanced optical responsivity

We demonstrate the first uncooled single-nanowire-based infrared bolometer to detect sub-mW optical signals up to MHz frequencies. The bolometer consists of a Pt nanowire on a suspended silicon hybrid-plasmonic cavity, and exhibits enhanced optical responsivity compared to nanowires on unstructured and non-suspended substrates. Low-cost monolithically integrated infrared detectors are needed for the rapidly growing field of silicon photonic sensors. The high speed of our nanobolometer enables advanced modulation schemes for noise reduction and avoidance of low-frequency thermal cross-talk, as well as power saving by pulsed operation. Furthermore, its simple integration and small footprint make it a cost effective detector for sensing applications.QC 20170124</p

Carbon dioxide absorption spectroscopy with a mid-infrared silicon photonic waveguide

Carbon dioxide (CO2) is a gas vital for life on Earth. It is also a waste product of human activities and is widely used in agriculture and industry. Its accurate sensing is therefore of great interest. Optical sensors exploiting the mid-infrared light absorption of CO2 provide high selectivity, but their large size and high cost limit their use. In this Letter, we demonstrate CO2 gas sensing at 4.2 µm wavelength using an integrated silicon waveguide, featuring a sensitivity to CO2 of 44% that of free-space sensing. The suspended waveguide is fabricated on a silicon-on-insulator substrate by a single-lithography-step process, and we route it into a mid-infrared photonic circuit for on-chip-referenced gas measurements. Its demonstrated performance and its simple and scalable fabrication make our waveguide ideal for integration in miniaturized CO2 sensors for distributed environmental monitoring, personal safety, and medical and high-volume consumer applications