Abstract
We demonstrate a surface grating coupled substrate emitting quantum cascade ring laser with high power room temperature continuous wave operation at 4.64 μm. A second order surface metal/semiconductor distributed-feedback grating is used for in-plane feedback and vertical out-coupling. A device with 400 μm radius ring cavity exhibits an output power of 202 mW in room temperature continuous wave operation. Single mode operation with a side mode suppression ratio of 25 dB is obtained along with a good linear tuning with temperature. The far field measurement exhibits a low divergent concentric ring beam pattern with a lobe separation of ∼0.34°, which indicates that the device operates in fundamental mode (n = 1).
Highlights
quantum cascade lasers (QCLs) are transverse magnetic (TM) polarized, which means that the electric field is in the growth direction
Surface emitting QCLs cannot be realized in a structure similar to vertical cavity surface emitting lasers (VCSELs), in which light propagates in the growth direction
Photonic crystal distributed-feedback (PCDFB) QCLs have been proposed to improve the far-field in two directions.[14]
Summary
Due to its rapid development in the past two decades, quantum cascade lasers (QCLs) have become a reliable option for coherent light source emitting in the mid-infrared spectral region.[1,2,3] High power, continuous wave (CW) single mode operation and low divergent surface emission are highly desirable qualities in many applications such as chemical sensing, spectral imaging, and freespace communications.[4,5,6,7] As an intersubband device, QCLs are transverse magnetic (TM) polarized, which means that the electric field is in the growth direction. Low divergent, substrate emitting quantum cascade ring laser in continuous wave operation
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