Novel designs and waveguides in terahertz quantum cascade lasers

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• Mr. Yash Shah, SP Group, Cavendish Laboratory, Cambridge
• Monday 17 November 2014, 14:15-15:15
• Mott Seminar Room, Cavendish Laboratory, Department of Physics.

If you have a question about this talk, please contact Teri Bartlett.

20 years since the invention of the quantum cascade laser(QCL) and more than a decade since the first terahertz(THz) QCl was realised, certain issues still remain on the improvement of performance of these lasers. QCL , being a unipolar device, finds it’s analogy with a four level semiconductor system, there is an injector and collector on either side of the radiative states (upper and lower lasing states) which form reservoirs. The electrons enter the upper lasing level through the injector and are recycled by the collector. This forms one period in the QCL . A cascade of these periods causes one electron to emit n(theoretically) photons where n is the number of periods at the designed electric field.The Fabry Perot cavity is formed by a waveguide ridge with the and the superlattice structure forming the gain medium. The facets are atomically cleaved planes and serve as the mirrors for the resonant cavity.

In this talk, I will provide an overview of novel active region designs and waveguides researched and the continuing effort to provide a better the performance of THz QCL . These QCLs were designed to provide a broadband spectrum, ~ .65 THz with a temperature performance of 105 K. Will dwell further into potential designs that could be optimised to provide a better spectrum at a higher temperature. Will end the talk with ideas on improving the beam pattern with an integrated waveguide as will as working intrinsically on the mode confined in the active region.

This talk is part of the Semiconductor Physics Group Seminars series.

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