Abstract:We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our measurements we are able to reconstruct the magnetic field and, finally, the position and time-dependent Poynting vector which shows the flow of energy behind the sample. Our results show that it is possible to study the flow of light near sub-wavelength plasmonic structures such as slit-arrays and, by implication, other metamaterial samples.

We report on the observation of terahertz transparency in random arrays of the single rectangular holes and slits with the areal coverage of only 12%. The terahertz transparency occurs at the fundamental shape resonance of the rectangular holes and confirms the theoretical predictions of earlier works of García-Vidal et al. [Phys. Rev. Lett. 95, 103901 (2005)] on single rectangular holes and of Ruan and Qiu [Phys. Rev. Lett. 96, 233901 (2006)] on random arrays of holes.

Terahertz transmission filters have been manufactured by perforating metal films with various geometric shapes using femtosecond laser machining. Two dimensional arrays of square, circular, rectangular, cshaped, and epsilon-shaped holes all support over 99% transmission at specific frequencies determined by geometric shape, symmetry, polarization, and lattice constant. Our results show that plasmonic structures with different geometric shaped holes are extremely versatile, dependable, easy to control and easy to make terahertz filters. J. B. Pendry, "Negative refraction makes a perfect lens," Phys. Rev. Lett. 85, 3966 (2000). 7.J. T. Shen, R. B. Catrysse, and S. Fan, "Mechanism for designing metallic metamaterials with a high index of refraction," Phys. Rev. Lett. 94, 197401 (2005). 8.M. J. Lockyear, A. P. Hibbins, J. R. Sambles, and C. R. Lawrence, "Microwave transmission through a single subwavelength annular aperture in a metal plate," Phys. Rev. Lett. 94, 193902 (2005). 9.

Background: Although recent studies suggest high accuracy of breast magnetic resonance imaging (MRI) in predicting residual tumor extent after neo-adjuvant systemic treatment (NST), its use is still controversial. In this study, we aimed to identify predictive factors of MRI accuracy after NST to determine a subgroup of patients in whom the use of MRI provides best additional benefit. Materials and methods:Clinicopathologic and molecular profiles of breast cancer patients were investigated and their relationships with MRI accuracy were analyzed. predicted residual tumor extent with higher accuracy than ultrasonography. Triple-negative (TN) tumors showed highest correlation between MRI-measured and pathologic tumor size (r = 0.781) when compared with other subtypes. Multivariate analysis showed age and HER2 expression status as independent factors predicting MRI accuracy. When patients were classified based on their age and HER2 status, relatively older patients (>45) with HER2-negative tumors showed highest MRI accuracy. This finding was further validated using an independent cohort of 63 consecutive patients.Conclusion: Age and HER2 status independently affected MRI accuracy after NST. This observation may guide more tailored approach in using MRI in breast cancer patients undergoing NST.