Mohammad Kamandi

Enantiospecific Detection of Chiral Nanosamples Using Photoinduced Force

Author(s): Kamandi, M; Albooyeh, M; Guclu, C; Veysi, M; Zeng, J; Wickramasinghe, K; Capolino, F | Abstract:

Giant field enhancement in longitudinal epsilon-near-zero films

Author(s): Kamandi, M; Guclu, C; Luk, TS; Wang, GT; Capolino, F | Abstract:

Photo-induced force vs power in chiral scatterrers

We study isotropic chiral polarizable particles in the interaction with circularly polarized travelling electromagnetic waves. We derive the expressions for the scattered and extinct power of such particles in terms of their polarizabilities for incident waves with opposite handedness i.e., right or left handed circular polarization. Moreover, we extract similar expressions for the exerted force on such particles induced by the proposed incidences. Based on our theoretical results, we present the link between the calculated power and force and demonstrate how these two different physical observables give rise to equivalent understanding of properties of chiral inclusions. This paves the way to formulate two alternatives to perform either the photo-induced force microscopy or power spectroscopy based on the merits of each. We also provide an original method to measure the magnetoelectric polarizability of isotropic chiral particles.

Giant field enhancement in anisotropic epsilon-near-zero films(Conference Presentation)

We investigated anisotropic epsilon-near-zero (AENZ) films under TM-polarized plane wave incidence and found they possess peculiar properties. In particular we studied uniaxially anisotropic films where either the permittivity along the surface normal or along the transverse plane tends to zero while the other one does not. Previously, numerous applications of isotropic epsilon-near-zero (ENZ) films including radiation pattern tailoring, enhanced harmonic generation, optical bistability and energy squeezing have been studied. A notable property of these materials is the capability of enhancing electric field. In this paper the capability of AENZ films in local electric field enhancement has been quantified and several AENZ conditions are reported with superior performance in comparison to (isotropic) ENZ films. Specifically, sensitivity to film thickness and losses, and the range of angles of incidence have been elaborated with the aim of achieving large electric field enhancement in the film. It has been proved that in comparison to the (isotropic) ENZ case the AENZ film’s field enhancement is not only much larger but it also occurs for a wider range of angles of incidence. Furthermore the field enhancement in AENZ does not exhibit significant dependence on the film thickness unlike the isotropic case. The effect of loss on the value of the field enhancement is also investigated emphasizing the advantages of AENZ versus ENZ. Realization of AENZ materials can be done by a multilayered media made of a stack of conductive and insulator layers or by stacking semiconductor layers. This giant field enhancement is an important target in nonlinear optics for applications like second harmonic generation and other applications like light generation

Unscrambling Structured Chirality with Structured Light at the Nanoscale Using Photoinduced Force

We show that the gradient force generated by the near field of a chiral nanoparticle carries information about its chirality. On the basis of this physical phenomenon we propose a new microscopy technique that enables the prediction of spatial features of chirality of nanoscale samples by exploiting the photoinduced optical force exerted on an achiral tip in the vicinity of the test specimen. The tip–sample interactive system is illuminated by structured light to probe both the transverse and longitudinal (with respect to the beam propagation direction) components of the sample’s magnetoelectric polarizability as the manifestation of its sense of handedness, i.e., chirality. We specifically prove that although circularly polarized waves are adequate to detect the transverse polarizability components of the sample, they are unable to probe the longitudinal component. To overcome this inadequacy and probe the longitudinal chirality, we propose a judiciously engineered combination of radially and azimuthally...

Structured light to reveal nanoscale magnetism and chirality

We explore possibilities to enhance magnetic-magnetic and magnetic-electric interactions between light and matter at nanoscale. We conceive magnetic nanoantennas to enhance magnetic local fields and hence enable the possibility to directly interact with magnetic dipolar transitions in matter. We also take advantage of certain structured beams because of their strong longitudinal magnetic field at their beam axes. This leads to the conception of a new microscopy technique based on photo-induced force related to magnetism and also to chirality of particles at nanoscale. Photo-induced magnetism and chirality at nanoscale are phenomena that are notoriously hard if not impossible to detect at nanoscale without the advent of nanoantennas and metamaterials.