High spectral radiance distributed Bragg reflector tapered diode lasers at 1060 nm with novel internal output DBR-grating

摘要

Distributed Bragg reflector tapered diode lasers (DBR-TPL) emitting at 1064 nm are highly efficient and narrowbandlight sources which e.g. can be used for the treatment of eye diseases including the two main causes of blindnessworldwide (i.e diabetic retinopathy and age-related macular degeneration) by laser coagulation via second harmonicgeneration (SHG) to the green spectral region.In this work, we present DBR-TPL with an additional internal DBR-grating at the output side of the tapered amplifiersectionin comparison with DBR-TPL with standard facet coating of different reflectivities.Our DBR-TPLs are based on an epitaxial structure with a large and asymmetric waveguide to realize a small vertical farfield for optimal coupling into SHG-crystals. All DBR-TPL consist of a 2 mm long ridge waveguide section, whichcontains a 1 mm long passive DBR-grating section at the end for longitudinal mode filtering. The amplifier-section is4 mm long and forms a taper with a full angle of 6°.The influence of the front mirror reflectivity on laser performance including reliability is investigated. The DBR-TPLemit up to 9 W of optical output power in continuous wave operation at 25°C in a longitudinal single mode at 1064 nmand yet the spectral width remains below 20 pm. In favor of a high radiance the power content in the central lobe at atotal optical output power of 8 W is greater than 75% for almost all devices. Aging tests revealed significant differencesin the lifetime of the devices depending on their front facet reflectivity or length of the front DBR-grating, respectively.