Abstract
A reflective outcoupler is demonstrated which can allow for stable surface emission from a quantum cascade laser and has potential for cost-effective wafer-scale manufacturing. This outcoupler is integrated with an amplified, electrically tunable laser architecture to demonstrate high power surface emission at a wavelength near 4.9 μm. Single mode peak power up to 6.7 W is demonstrated with >6 W available over a 90 cm−1 (215 nm) spectral range. A high quality output beam is realized with a simple, single-layer, anti-reflective coating. The beam shape and profile are shown to be independent of wavelength.
Highlights
Monolithic edge-emitting quantum cascade laser (QCL) technology, which relies on cleaved facets for laser operation, has demonstrated wide tuning and high output power from a single aperture[6,7]
An alternative strategy is to utilize a reflective outcoupler, which takes in-plane light and redirects it either out of the top surface or through the laser substrate. This approach has been used for near-infrared lasers in the past, including the in-plane surface emitting laser (IPSEL), folded cavity surface emitting laser (FCSEL), and horizontal cavity surface emitting laser (HCSEL)[14,15,16]
The Sampled grating distributed feedback (SGDFB) section and absorbing termination design and fabrication are identical to that used in ref.[13], with the exception that the grating period used for this device was 775 nm
Summary
Monolithic edge-emitting quantum cascade laser (QCL) technology, which relies on cleaved facets for laser operation, has demonstrated wide tuning and high output power from a single aperture[6,7]. A commercially successful demonstration of this method in the near-infrared is the vertical cavity surface emitting laser (VCSEL), which can be produced in large quantities and 2-D arrays for high power illuminators[10]. The device performance is very sensitive to the operating wavelength This architecture allows for the incorporation of laser and detector on the same chip and in the same beam path, which makes for a compact, easy-to-align, chemical sensor[12]. This is highlighted in a recent publication, where a tunable laser and grating outcoupler were integrated to realize surface emission with monolithic beam steering[13]. Correspondence and requests for materials should be addressed to M.R. (email: razeghi@ eecs.northwestern.edu) www.nature.com/scientificreports/
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