Quantification of losses in bent waveguide distributed Bragg reflector diode lasers at 785 nm

An experimental study of 785 nm straight and bent waveguide distributed Bragg reflector (DBR) diode lasers is presented. For comparison, DBR lasers with S-bend-shaped waveguides and different lateral S-bend offsets were manufactured. Straight waveguide Fabry-Pérot and DBR diode lasers are characterized as reference. All devices show narrowband emission and optical output powers of about 200 mW. For straight waveguide DBR lasers with measured DBR reflectivities of 45%, a grating loss of αDBR = 9.0 cm-1 is obtained. The additional losses for bent waveguides (αBend) with lateral offsets of 40 µm, 60 µm and 70 µm are 0.6 cm-1, 1.6 cm-1 and 3.2 cm-1, respectively. This confirms the non-linear dependence obtained in simulations of S-bend losses as a function of the lateral S-bend offset. The results enable an increased understanding of bent waveguide devices and help to improve the lateral-longitudinal layouts, e.g., of Y-branch multi-wavelength diode lasers.