Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer

This is the final version. Available on open access from AIP Publishing via the DOI in this recordWe systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic Fe layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially at for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of of up to two in field.The authors like to acknowledge support via the EPSRC Centre for Doctoral Training in Metamaterials (Grant No. EP/L015331/1). EH acknowledges support from EPSRC fellowship (EP/K041215/1). TK, TSS, MK and GJ acknowledge the German Research Foundation for funding through the collaborative research centers SFB TRR 227 Ultrafast spin dynamics (project B02) and SFB TRR 173 Spin+X as well as the Graduate School of Excellence Materials Science in Mainz (MAINZ, GSC 266). TK also acknowledges funding through the ERC H2020 CoG project TERAMAG/Grant No. 681917

Optical transmission matrix as a probe of the photonic interaction strength

We demonstrate that optical transmission matrices (TM) of disordered complex media provide a powerful tool to extract the photonic interaction strength, independent of surface effects. We measure TM of strongly scattering GaP nanowires and plot the singular value density of the measured matrices and a random matrix model. By varying the free parameters of the model, the transport mean free path and effective refractive index, we retrieve the photonic interaction strength. From numerical simulations we conclude that TM statistics is hardly sensitive to surface effects, in contrast to enhanced backscattering or total transmission based methods

Optical transmission matrix as a probe of the photonic strength

We demonstrate that optical transmission matrices (TM) of disordered complex media provide a powerful tool to extract the photonic interaction strength, independent of surface effects. We measure TM of strongly scattering GaP nanowires and plot the singular value density of the measured matrices and a random matrix model. By varying the free parameters of the model, the transport mean free path and effective refractive index, we retrieve the photonic interaction strength. From numerical simulations we conclude that TM statistics is hardly sensitive to surface effects, in contrast to enhanced backscattering or total transmission based methods.We acknowledge support from ERC grant 27948, NWOVici, STW, the Royal Society, and EPSRC through fellowship EP/J016918/1

The Laser

The laser is an oscillator of light using an amplification process based on stimulated emission from atoms in an optical resonator. Laser light has a narrow spectral width and a high degree of spatial coherence. Laser beams are highly directional and can be focused into a tiny spot. Pulsed lasers produce ultrashort light pulses with ultrahigh peak power. Since its invention in 1960, the laser has enabled many scientific discoveries and has been at the core of a plethora of light-based technologies. It is truly a light fantastic

Ricci Collineations for type B warped space-times

We present the general structure of proper Ricci Collineations (RC) for type B warped space-times. Within this framework, we give a detailed description of the most general proper RC for spherically symmetric metrics. As examples, static spherically symmetric and Friedmann-Robertson-Walker space-times are considered.Comment: 18 pages, Latex, To appear in GR