Laguerre-Gauss beam generation in IR and UV by subwavelength surface-relief gratings

The angular momentum of light can be described by the states of spin angular momentum, associated with polarization, and orbital angular momentum, related to the helical structure of the wave front. Laguerre-Gaussian beams carry orbital angular momentum and their generation can be done by using an optical device known as q-plate. However, due to the usage of liquid crystals, these components may be restricted to operate in specific wavelengths and low power sources. Here we present the fabrication and characterization of q-plates made without liquid crystals, using processes of e-beam lithography, atomic layer depositions and dry etch techniques. We exploit the phenomenon of form birefringence to give rise to the spin-to-orbital angular momentum conversion. We demonstrate that these plates can generate beams with high quality for the UV and IR range, allowing them to interact with high power laser sources or inside laser cavities.Comment: 10 pages, 11 figure

Wave Propagation Retrieval Method For Metamaterials: Unambiguous Restoration Of Effective Parameters

In this article we propose a new direct method of effective parameters restoration that is based on the wave propagation phenomenon. It retrieves the effective properties unambiguously, is applicable to thick metamaterial (MTM) slabs and is easy in implementation. It is validated on the case studies of fishnet, split cube in carcass, Jerusalem cross and ultrahigh refractive index MTMs. The constraints of the method are designated.Comment: 14 pages, 10 figures, submitted to Physical Review

Homogenization of resonant chiral metamaterials

Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as e.g. propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size a critical density exists above which increasing coupling between neighboring meta-atoms prevails a reasonable homogenization. On the contrary, a dilution in excess will induce features reminiscent to photonic crystals likewise prevailing a homogenization. Based on Bloch mode dispersion we introduce an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all.Comment: 8 pages, 7 figure

TEACHERS’ INFLUENCE ON STUDENTS IN THEIR LIFELONG DEVELOPMENT

The impact teachers have on their students is imprinted to a much extent in each person’s life. Every child, teenager or adult speaks of present or previous experiences related to teachers who left their marks on their development in life. Teachers are important people in children’s life providing them with education, discipline, motivation and role-models. The guiding role of teachers is not limited to school classroom and school disciplines, but it surpasses didactic activities and extends into personal life. Truth is that children feel differently the influence exerted by teachers due to their sensitivity, personalities, life experiences. The identification of the aspects that influence students to a greater or less extent is important as it helps to shape a profile of an authentic teacher as s/he is perceived by students. Such a perspective may help teachers become aware of their role in students’ lives and as a consequence they should make adjustments in order to become better partners for their students.The present paper intends to study teachers’ impact on students in their life lifelong development. The aspects taken into consideration, according to specific literature and experiences in classrooms, were: school performances, behavioural patterns, adjustment to school requirements, motivation for learning, professional choices for future careers, outlooks on life. The research methods were the investigation based on questionnaire, the conversation and the systematic observation. The participants in the research were 200 students from two school levels: high school (students 15-19 years old) and faculty (students 19-30 years old). The data collected were processed using the SPSS analysis. The results of the research could be used to increase teachers’ awareness on their impact on students in their lifelong development.