Enhanced Delivery and Detection of Terahertz Frequency Radiation from a Quantum Cascade Laser Within Dilution Refrigerator
jats:titleAbstract</jats:title>jats:pWe report on significant enhancements to the integration of terahertz (THz) quantum cascade lasers (QCL) and THz detection with a two-dimensional electron gas (2DEG) within a dilution refrigerator obtained by the inclusion of a multi-mesh 6 THz low-pass filter to block IR radiation, a Winston cone to focus light output, and gating the 2DEG for optimised sensitivity. We show that these improvements allow us to obtain a > 2.5 times reduced sample electron temperature (160 mK compared with 430 mK previously), during cyclotron resonance (CR) measurements of a 2DEG under QCL illumination. This opens up a route to performing sub-100 mK experiments using excitation by THz QCLs.</jats:p>
Acknowledgements: The authors acknowledge EPSRC funding (Grants EP/P021859/1, EP/W028921/1, and EP/V004743/1). W.M. thanks Trinity College Cambridge for a Junior Research Fellowship. Thanks also goes to Yuqing Wu for helping with device fabrication.
Engineering and Physical Sciences Research Council (EP/W028921/1)