Integrated Infrared Spectrometers for Consumer Applications

Near-infrared (NIR) spectroscopy is a non-destructive analytical technique used to identify and quantify components in a sample by measuring the absorption of near-infrared light (700 – 2500 nm spectral range). This technique is employed across diverse industries including pharmaceuticals, agriculture, and food processing for tasks such as determining the nutrient content of soil, analyzing the composition of drugs, and assessing the quality of food products. There is strong motivation to integrate miniaturized NIR spectroscopic sensors into consumer products such as wearables and smartphones, which would provide consumers with valuable information without the need for complex instrumentation and trained personnel. For example, on-skin measurements with such sensors could provide more information about our health compared to today’s wearable devices, which typically measure heart rate and oxygen saturation. Additionally, we could gain direct insights into the nutritional information of the food on our plates. However, bringing this technology to consumer products requires affordable and miniaturized devices, which poses challenges, particularly at wavelengths beyond 1000 nm where cheap and ubiquitous silicon-based photodetectors become ineffective due to silicon’s transparency. Thin-film photodiodes based on colloidal quantum dots (CQDs) have emerged as a promising approach to enable affordable sensors at longer wavelengths. CQDs are chemically synthesized nanocrystals with remarkable emissive and absorption properties, and they can be deposited in form of thin films over large areas. Our group has been developing this technology for over seven years, leveraging expertise from various domains including material science, semiconductors, micro/nanofabrication, and photonics. More recently, we patented and demonstrated a new approach for spectral sensing by combining our CQD photodiodes with another emerging technology – optical metasurfaces, which will be the foundation and a starting point for this topic.  

The goal of this PhD is to advance spectral sensing based on thin-film photodiodes, targeting high sensitivity, high spectral resolution and fabrication scalability which is necessary for consumer applications.   

This PhD therefore has two important pillars: