Abstract-Additive manufacture of photonic components for the terahertz band

Journal of Applied Physics

Enrique Castro-Camus,  Martin Koch, Arturo I. Hernandez-Serrano,

A 3D terahertz gradient-refractive index lens designed by transformation optics is achieved by fabricating “woodpile” structures with varying dimensions of subwavelength dielectric unit cells using the projection microstereolithography technique. Both simulation and experimental investigations confirm that the lens delivers an imaging resolution very close to the diffraction limit over a frequency range from 0.4 to 0.6 THz.31 Reproduced with permission from Zhou et al., Adv. Opt. Mater. 4, 1034 (2016). Copyright 2016 Wiley-VCH Verlag GmbH & Co. KGaA.

https://aip.scitation.org/doi/10.1063/1.5140270

In this Perspective contribution, we present a brief review of the literature available on optical devices for terahertz frequencies, followed by an analysis of the challenges faced by this technology and its future potential to generate complex photonic systems, and in principle the possibilities of this technique for the production of components for the infrared and visible band.

Abstract-Modelling the carrier dynamics of semiconductors to understand their terahertz emission (Conference Presentation)

Enrique Castro-Camus, Mariana Alfaro-Gomez, Sofia C. Corzo-Garcia, Arturo I. Hernandez-Serrano,  Oleg Mitrofanov,

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10756/107560B/Modelling-the-carrier-dynamics-of-semiconductors-to-understand-their-terahertz/10.1117/12.2321155.short

We use a Monte-Carlo model to simulate semi-classical photo-carrier dynamics on bulk InAs, InGaAs and GaAs that leads to terahertz emission after ultrafast photoexcitation. This detailed model has allowed us to understand various aspects of the THz emission process, including the near-field distribution which has been experimentally observed, the role of the excess excitation photon energy, and the relative importance of the surface field driven, diffusive (photo-Dember) and ballistic currents. In order to understand the near-field emission we coupled a finite-difference time-domain routine to the carrier dynamics simulation, by doing this, we were able to analyse the near terahertz field emission caused by the motion of such carriers even when the excitation is performed at normal incidence. We found that both the current parallel, which has traditionally been assumed not to take part in the emission, and normal to the interface take a relevant role in the terahertz generation. We performed another set of simulations for different bandgaps and excitation-photon energies in order to compare the emission power of all three semiconductors as function of excitation photon energy finding that the carrier excess excitation energy is more relevant to explain their performance difference than their motilities. We conclude that ballistic transport after photoexcitation is the dominant mechanism for terahertz emission instead of diffusion driven or surface field driven charge separation, which were traditionally considered the most relevant mechanisms.