Upconversion raster scanning microscope for long-wavelength infrared imaging of breast cancer microcalcifications

This is the final version. Available from Optical Society of America via the DOI in this record. Long-wavelength identification of microcalcifications in breast cancer tissue is demonstrated using a novel upconversion raster scanning microscope. The system consists of quantum cascade lasers (QCL) for illumination and an upconversion system for efficient, high-speed detection using a silicon detector. Absorbance spectra and images of regions of ductal carcinoma in situ (DCIS) from the breast have been acquired using both upconversion and Fourier-transform infrared (FTIR) systems. The spectral images are compared and good agreement is found between the upconversion and the FTIR systems.European Unio

Carrier lifetime of GeSn measured by spectrally resolved picosecond photoluminescence spectroscopy

We present an experimental setup capable of time-resolved photoluminescence spectroscopy for photon energies in the range of 0.51 eV to 0.56 eV with an instrument time response of 75 ps. The detection system is based on optical parametric three-wave mixing, operates at room temperature, has spectral resolving power, and is shown to be well-suited for investigating dynamical processes in germanium-tin alloys. In particular, the carrier lifetime of a direct-bandgap Ge1−xSnx film with concentration x = 12.5 % and biaxial strain −0.55 % is determined to be 217 ± 15 ps at a temperature of 20 K. A room-temperature investigation indicates that the variation in this lifetime with temperature is very modest. The characteristics of the photoluminescence as a function of pump fluence are discussed

Media 1: The still unknown azobenzene - Wavelength dependent photoanisotropy in amorphous azobenzene polymers

Originally published in Optics Express on 28 January 2013 (oe-21-2-1812

A silicon source of heralded single photons at 2 μm

Mid infrared integrated quantum photonics is a promising platform for applications in sensing and metrology. However, there are only few examples of on-chip single photon sources at these wavelengths. These have limited performances with respect to their C-band counterparts. In this work, we demonstrate a new approach to generate heralded single photons in the mid infrared on a silicon chip. By using a standard C-band pump, the inter-modal spontaneous four wave mixing enables the generation of the herald idler at 1259.7 nm and the heralded signal at 2015 nm. The idler photon is easily detected with a common infrared single photon detector while the signal photon is upconverted to the visible before its detection. In this way, we are able to operate a mid infrared source without the need of mid infrared detectors and laser sources. By measuring a heralded $g^{(2)}$ of $0.23 \, \pm \, 0.08$ we demonstrate the single photon behaviour of the source as well as the feasibility of multi-photon coincidence measurements beyond 2 $\mu$m with our setup. The source exhibits a high intrinsic heralding efficiency of $(59 \, \pm \,5)\%$, a maximum coincidence to accidental ratio of $40.4 \, \pm \, 0.9$ and a generation probability of $\left( 0.72 \, \pm \, 0.10 \right)$ W$^{-2}$