Quantum Dot Emitter Arrays: Tunable Light Sources for Near-Infrared Spectroscopy

H. Schlicke, L. Niemann, Ö. Tokmak, H. Weller, J.-S. Niehaus
Fraunhofer CAN,

Keywords: near infrared, spectroscopy, quantum dots, color conversion, short wave infrared


Semiconductor nanoparticles, so-called quantum dots (QDs), are versatile materials for applications requiring light of specific and precisely tuned wavelengths. Due to the nanoscale dimensions of these particles the quantum size effect comes into play. Here, as a consequence of the small size, excited charge carriers are confined, causing their energy levels to shift. This effect leads to a virtually continuous tunability of the particle materials' band gap - and hence their optical absorption and emission characteristics - by adjustment of the particle size. Due to their high color purity, today's most prominent application of QDs is in display technology, as color converters converting the light of blue LEDs into green and red light, then serving in combination as backlight in high-quality TVs. Based on the principle of color-conversion QDs having a tunable band gap in the near-infrared (NIR) wavelength range can serve as tunable light sources for NIR spectroscopy. These particles are capable of absorbing visible or short-wavelength NIR light and converting it into an NIR emission, which is defined by their material and size. Within the framework of the project TUNARR we aim at the development of arrays containing QD pixels with adjustable emission characteristics. These pixels are excited using visible light of conventional LEDs and convert it into the NIR range. In this contribution we demonstrate the fabrication of arrays with well defined pixels containing NIR-QD emitters and their first application as light sources in a prototypical spectrometer. Due to their high degree of tunability and miniaturizability, NIR-QD based emitter arrays are highly interesting for future portable NIR spectrometers.