There is a growing interest in achieving new chemical sensing devices able to provide enough roughness, in-situ detection and selectivity. These new tools should be easily integrated in other systems; to analyse the quality and composition of the products at the petrochemical and pharmaceutical industry, to evaluate harmful emissions in automotive and environmental monitoring, and to provide with non-invasive devices the medical diagnostics field. One could even dream about sensors integrated in our fridges scanning for bacteria that would notify about which foods are in bad conditions.
Mirphab – Mid-Infrared Photonics Devices Fabrication for Chemical Sensing and Spectroscopic Applications – is an EC funded project granted with € 13 m in a public-private partnership with Photonics21, with the goal of creating a commercially viable pilot line for the fabrication of mid-infrared sensors that is ready for business by 2020. Mirphab has launched its first open call.
Recently, mid-infrared (MIR) spectroscopy has attracted the interest of the sensing industry due to the possibility of developing low-cost and miniaturized devices able to be integrated in existing equipment for on-line and in-situ monitoring of chemical species. These devices will allow real-time and selective detection of the chemical compound of interest. Since MIR light is interacting with the molecular vibrations, each molecule presents a unique absorption spectrum providing a simple solution for sensing. Chemicals exhibit in this wavelength band, the “fingerprint region”, intense adsorption feature that allows superior detection capabilities and unambiguous identification.
The Mirphab pilot line
The Mid-Infrared Photonics Devices Fabrication for Chemical Sensing and Spectroscopic Applications initiative was launched in January 2016 to be in the service of the European photonic industry by providing high quality MIR photonic components, by reducing the investment cost to access to innovative MIR solutions, and by aiming companies to integrate µ-sensors into their products. Mirphab will be an open technology platform with special focus on SMEs, providing services for device design and fabrication from chip processing on wafer level to packaging and testing as well as training services to pilot line customers.
For that, the Mirphab consortium consists of a core technology group capable of handling both Si and III-V processing, and able to exploit the capability of a mixed Si/III-V technology bringing unexplored capabilities to sensors, enabling many applications not addressable with the technologies and components available today. This core technology group is composed of both, established industrial players and major research institutes, covering the whole value chain from epitaxial layer and device design up to packaging and module integration. Based on a massive use of IC / MEMS technologies, the pilot line will enable a variety of new key functionalities for next generation chemical sensing and spectroscopy, allowing cost, power consumption and size reduction.
Assembly of building blocks
The aim of the Mirphab project is to provide each customer with a unique chemical detector / spectrometric system by combining sources, photonic circuits and detectors in a standard packaging. The spectrometer system offered by Mirphab will consist of: MIR sources, optics, MIR detectors and packaging (Fig. 1). Interband cascade lasers (ICLs), quantum cascade lasers (QCLs) are the MIR emitters available working by Fabry-Perot, distributed feedback Bragg (DFB) or external cavity (EC) technology. Regarding passive components, three integrated photonic platforms will be available: a silicon-on-insulator (SOI) waveguide platform, a SiGe/Si platform and a Ge/SiGe platform. MIR detectors available are type-II InAs/GaSb superlattice (T2SL), InAsSb and quantum cascade detectors (QCD). Finally, according to the specifications provided accompanied by the users, these components will be chained together either by hybrid or monolithic assembly to realize systems in package (SIP) or systems on chip (SOC) devices.
The ICL-based sources use injected electrons to emit multiple photons by interband transitions and to produce coherent radiation in the wavelength range 3 – 6 µm. ICL are fabricated by stacking layers of InAs, GaSb, AlSb and related alloys growth by molecular beam epitaxy (MBE).
The QCL-based sources are unipolar devices in which the laser emission is achieved through the use of intersubband transitions in a repeated stack of semiconductor multiple quantum well layers achieving coherent radiation in the wavelength range 4 – 12 µm. QCL stacks are fabricated by molecular beam epitaxy (MBE) growth of III-V layers (mainly InGaAs/InAlAs).
For cooled operation at 80 K in the 3 – 5 µm regime, the T2SL detector technology is well established and has very high performance. The challenge here is to develop uncooled and / or TE-cooled single element operation at extended wavelengths in 5 – 12 µm range. For that, optically immersed T2SL detectors on GaAs substrates will be developed. Standardization of growth, processing, assembly and characterization procedures will be a priority.
The InAsSb detector are based on nearly lattice matched on GaSb substrate and are able to detect at a wavelength below 4.6 µm. The sensor is based on a double barrier hetero-structure optimized for operation between 250 K and room temperature.
In integrated photonics, a waveguide is the equivalent of an optical fiber: light beams can be routed, combined, split or make interfering anywhere on a planar substrate using simple optical functions fabricated on the waveguides. In the last few years, IMEC and CEA-Leti have designed, fabricated, and characterized MIR waveguides for a variety of commercial, scientific and military applications (Fig. 2). Three technologies are available via Mirphab: Si on insulator (SOI) waveguides for applications requiring wavelengths between 2 and 4 µm, SiGe/Si based graded index stack to cover the full (3 – 8 μm) band and Ge/SiGe technology in order to address spectral range above 8 µm. The wavelength at which the molecule of interest is absorbing will define the MIR source, the photonic integrated circuit (PIC) and the detector that will be integrated in your sensing system.
The µ-assembly of optical components as well as the packaging of laser and detector chips will be carried out to facilitate the integration in the customer equipment. On the other hand, the standardization of tests for industrial manufacturing and long term operation including accelerated aging will be performed. With respect to µ-assembly, fabricated QCL and ICL arrays will be used together with the optical silicon combiner to deliver a fully monolithic tunable source. Packaging and assembly related challenges of MIR laser components for subsequent integration towards µEC modules will be investigated. In this context, various packaging options (EPI up chip mounting, flip chip mounting, chip on submount configurations etc.) with the corresponding requirements are investigated and the related soldering processes and interfaces with respect to soldering materials and temperatures, and contact layer thickness will be defined.
How to get a chemical sensor customized for your application
Mirphab has launched its first open call. If your company is interested in moving towards the future of the real-time chemical sensing, submit your application via the Mirphab website.
First step to apply is the registration of your interest in which you provide basic company information and give a short description of the project to be realized. By registering your company, you will be informed as potential user that new calls are launched and ready to accept applications. A technological expert can provide support for completing the following steps of the application. The submitted proposals will be evaluated by the steering committee.
Successful applications will be granted up to the 70% of the total cost of the project or up to € 230 k. Mirphab will award a total of ten demonstration proposals in five different calls. End users granted by Mirphab will be requested to cover up to 30 % of the developments costs according to the funding rules in use for the participation to EC funded projects. The services provided are the design, the fabrication and assembly of the components and test prototypes of the devices realized according the specifications. Mirphab also provides its customers with training for platform users bringing the developed processes and tools to a wider audience including in depth training for experienced engineers.
The Mirphab pilot line is a unique chance to expand your business in the field of real-time chemical sensors at a minimum capital investment. Do you want to play a significant role in the photonic industrial transformation of Europe?