Promoting spintronic terahertz radiation via Tamm plasmon coupling

Spectral fingerprint and terahertz(THz)field-induced carrier dynamics demands the exploration of broadband and intense THz signal sources.Spintronic THz emitters(STEs),with high stability,a low cost,and an ultrabroad bandwidth,have been a hot topic in the field of THz sources.One of the main barriers to their practical application is lack of an STE with strong radiation intensity.Here,through the combination of optical physics and ultrafast photonics,the Tamm plasmon coupling(TPC)facilitating THz radiation is realized between spin THz thin films and photonic crystal structures.Simulation results show that the spectral absorptance can be increased from 36.8%to 94.3%for spin THz thin films with TPC.This coupling with narrowband resonance not only improves the optical-to-spin conversion efficiency,but also guarantees THz transmission with a negligible loss(~4%)for the photonic crystal structure.According to the simulation,we prepared this structure successfully and experimentally realized a 264%THz radiation enhancement.Furthermore,the spin THz thin films with TPC exhibited invariant absorptivity under different polarization modes of the pump beam and weakening confinement on an obliquely incident pump laser.This approach is easy to implement and offers possibilities to overcome compatibility issues between the optical structure design and low energy consumption for ultrafast THz optospintronics and other similar devices.

Spintronic terahertz emitter with integrated electromagnetic control

Spintronic thin films are considered as one of the promising terahertz(THz)source candidates,owing to their high performance and low cost.Much effort has been made to achieve spintronic THz sources with broadband and high conversion efficiency.However,the development of spintronic THz emitters with good compatibility,low cost,and miniaturized technology still faces many challenges.Therefore,it is urgent to extend commercial and portable spintronic THz emitters to satisfy many practical applications.Herein,we design a new generation of spintronic THz emitters composed of an alter-nating electromagnet and a miniaturized electronic controller.Not only can this new type of spintronic THz emitter largely simplify the ancillary equipment for spintronic sources,it also has a twice larger THz signal compared to the traditional THz time-domain spectroscopy systems with a mechanical chopper.Experimental results and theoretical calculations for electromagnetic coils show that our design can stably generate THz signals that are independent of the frequency and magnetic field of alternating signals.As the spin thin film is optimized,a magnetic field as low as 75 G satisfies the require-ment for high performance THz emission.Hence,not only is the efficiency of the pump power enhanced,but also the driving current in the electromagnet is decreased.We believe that it has a wide range of applications and profound implications in THz technology based on spintronic emitters in the future.