Single mode 660 nm DBR tapered laser with 1 W optical output power

For several non-destructive spectroscopy methods based on quantum mechanical effects (e.g. MID-IR quantum-OCT) the size of currently used solid state lasers prevents effective miniaturization. Red-emitting diode lasers with single longitudinal and single lateral mode emission are therefore required for successful out-of-the lab usage. To address this challenge, the FBH developed specialized tapered lasers (TPL) emitting near 660 nm with an integrated tenth order distributed Bragg reflector (DBR) surface grating, requiring only a single epitaxy step. The facets were passivated and coated to obtain reflectivities of 5% for the front and 30% for the rear facet. The DBR-TPL chips were mounted p-side down on CVD-diamonds with structured contacts to allow separate contacting of the ridge waveguide (RW) and tapered (TP) sections. The DBR-TPLs feature a nearly diffraction limited output beam with a spectral width below 0.5 pm, corresponding to a coherence length of almost 1 m. An optical output power of more than 1 W could be demonstrated at currents of 50 mA and 2.5 A for the RW and TP sections, respectively. The beam quality at 1 W was M²_1/e² = 1.1 (M²_4σ = 2.1). The DBR-TPLs are a first important component in the concept for a miniaturized portable quantum-OCT scanner. Here, the sample will be illuminated with MID-IR photons while the entangled NIR photons will be measured with a cost-effective, Si-based spectrometer.