Miniaturized red-emitting hybrid semiconductor MOPA modules with small-sized Faraday isolators

Summary form only given. Gas lasers such as the HeNe-laser at 633 nm or the Kr-laser at 647 nm are still widespread in use for applications that require visible, highly coherent radiation. Replacing the gas lasers with semiconductor lasers that provide a beam with similar output power, wavelength and coherence would significantly improve the degree of miniaturization and lead to an abundance of new fields of applications.Earlier works already demonstrated the successful manufacturing of single-mode, high-power semiconductor lasers at wavelengths beyond 650 nm [1, 2]. To extend this work below 650 nm and to improve the optical output power and coherence properties we developed distributed-Bragg-reflector ridge-waveguide lasers (DBRRWL) at 633 nm and 647 nm with linewidths close to 1 MHz [3, 4]. The wavelength of the DBR-RWL can be tuned by changing the current and the temperature. This in turn changes the output power, which is undesirable for most applications. Also due to the lower mirror reflectivities in comparison to gas lasers, the DBR-RWLs are more susceptible to external feedback from back reflections of optical elements.