University of Birmingham > Talks@bham > Metamaterials and Nanophotonics Group Seminars > Metamaterial/graphene amplitude and frequency modulators for the active control of terahertz quantum cascade lasers

Metamaterial/graphene amplitude and frequency modulators for the active control of terahertz quantum cascade lasers

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If you have a question about this talk, please contact Dr Miguel Navarro-Cia.

Fast, integrated optoelectronic devices, such as amplitude and frequency modulators, are in high demand in THz science and technology as they bridge the gap between sources and detectors thus enabling a myriad of applications in spectroscopy, imaging and communications. In combination with terahertz quantum cascade lasers (QCLs) they provide a powerful tool for external, all-electronic, full control of the laser emission in external cavity configurations. Amplitude and frequency modulators are based on the interplay between metallic metamaterial resonant units, typically arranged in mm-size arrays, and chemical vapor deposition (CVD) grown graphene, providing the active component. An amplitude modulator, based on split ring resonator (SRR) arrays, is used as an external optoelectronic mirror in an external cavity QCL configuration, demonstrating full switching of the THz QCL emission, realizing an electrical chopper operating at MHz reconfiguration speeds and efficiently reinforcing single mode emission, a mandatory prerequisite in several spectroscopic applications. The realization of active frequency modulators, capable of achieving an all-electronic tuneable dispersion, has been obtained by adopting a more complex metamaterial design based on coupled resonant units, reminiscent of the electromagnetic induced transparency, interacting with patterned CVD graphene. Unique QCL emission features emerged when using the frequency modulator as a dispersive optoelectronic mirror in an external cavity configuration. These include the achievement of optical bistability, an all-electronic switch between two different frequencies emitted in single-mode.

This talk is part of the Metamaterials and Nanophotonics Group Seminars series.

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