Compact mid-infrared vertical-cavity lasers

Coherent emitters for the mid-infrared spectral range (3-30 microns) are of considerable importance due to the many gas absorptions lines in this region permitting sensitive high-resolution gas analysis. Therefore, mid-infrared lasers are important tools for many applications such as ambient pollution monitoring or analyzing exhaled air for medical diagnostics. For these applications, usually edge-emitting semiconductor diode lasers made from lead salt (IV-VI) compounds are used because they benefit from their favorable electronic band structure with nearly mirror-like valence and conduction bands and the low non-radiative Auger recombination rates. However, the conventional edge-emitting lasers exhibit significant disadvantages for gas sensing applications like an asymmetric beam profile and a strongly divergent beam. Therefore, in this project compact IV-VI vertical-emitting lasers for the mid-infrared will be developed. These novel vertical-cavity surface-emitting lasers (VCSELs) offer not only very small beam divergence but also single mode operation and simplified monolithic integration, both favorable for device applications. The IV-VI VCSEL multi-layer structures will be grown by molecular beam epitaxy and consist of high-reflectivity Bragg interference mirrors, for which only a few layer pairs are required for the desired reflectivities above 99 %. We will develop different active laser structures to optimize the device performance. Optically pumped lasers operating in continuous-wave-mode at room temperature will be demonstrated using cheap readily available continuous-wave GaAs-based near-infrared laser diodes, which will be integrated together with the IV-VI laser to form small, compact devices. Subsequently, these novel lasers will be fully characterized and optimized with regard to linewidth, output power, laser threshold, divergence angle and tunability, which are the crucial properties for applications of mid-infrared lasers. Alternative to this optical pumping scheme, our lasers will also be operated by electrical pumping for which appropriate doping and device processing will be developed. The such developed IV-VI lasers will mark a big advance for scientific research and meet the industrial needs for cheap and compact mid-infrared laser sources strongly facilitating their integration in a wide range of applications

Coherent emitters for the mid-infrared spectral range (3-30 microns) are of considerable importance due to the many gas absorptions lines in this region permitting sensitive high-resolution gas analysis. Therefore, mid-infrared lasers are important tools for many applications such as ambient pollution monitoring or analyzing exhaled air for medical diagnostics. For these applications, usually edge-emitting semiconductor diode lasers made from lead salt (IV-VI) compounds are used because they benefit from their favorable electronic band structure with nearly mirror-like valence and conduction bands and the low non-radiative Auger recombination rates. However, the conventional edge-emitting lasers exhibit significant disadvantages for gas sensing applications like an asymmetric beam profile and a strongly divergent beam. Therefore, in this project compact IV-VI vertical-emitting lasers for the mid-infrared will be developed. These novel vertical-cavity surface-emitting lasers (VCSELs) offer not only very small beam divergence but also single mode operation and simplified monolithic integration, both favorable for device applications. The IV-VI VCSEL multi-layer structures will be grown by molecular beam epitaxy and consist of high-reflectivity Bragg interference mirrors, for which only a few layer pairs are required for the desired reflectivities above 99 %. We will develop different active laser structures to optimize the device performance. Optically pumped lasers operating in continuous-wave-mode at room temperature will be demonstrated using cheap readily available continuous-wave GaAs-based near-infrared laser diodes, which will be integrated together with the IV-VI laser to form small, compact devices. Subsequently, these novel lasers will be fully characterized and optimized with regard to linewidth, output power, laser threshold, divergence angle and tunability, which are the crucial properties for applications of mid-infrared lasers. Alternative to this optical pumping scheme, our lasers will also be operated by electrical pumping for which appropriate doping and device processing will be developed. The such developed IV-VI lasers will mark a big advance for scientific research and meet the industrial needs for cheap and compact mid-infrared laser sources strongly facilitating their integration in a wide range of applications.