Optical singularity dynamics and spin-orbit interaction due to a normal-incident optical beam reflected at a plane dielectric interface

Debnath, Anirban; Kumar, Nitish; Baishya, Upasana; Viswanathan, Nirmal K.

doi:10.1103/physreva.107.013522

Cited by 6 publications

(2 citation statements)

References 64 publications

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“…For the purpose of experimental observations, we build an optical system based on a normal incidence and reflection scheme [4,8,10,22,24,26,27], as shown in figure 12. A Gaussian He-Ne laser beam (λ = 632.8 nm) from the source L S is passed through a collimating lens pair L P .…”

Section: Methodsmentioning

confidence: 99%

Complex far fields and optical singularities due to propagation beyond tight focusing: combined effects of wavefront curvature and aperture diffraction

Kumar,

Debnath,

Viswanathan

2024

J. Opt.

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All optical systems, which involve the collimation of a reﬂected, transmitted or scattered wave subsequent to tight focusing, are subject to two kinds of deviations. One is the wavefront curvature due to inaccurate focal placement of the interface or scatterer particle under consideration, and the other is the diﬀraction caused by the ﬁnite lens aperture. In the present paper we explore these phenomena in detail by considering a rigorous simulated model and an appropriate experimental setup. We hence demonstrate the complicated intensity proﬁles and optical singularity characteristics of the observed far ﬁeld. Then we describe ways to minimize these deviations in a general experiment. But more importantly, our analysis proves that these deviations by themselves are signiﬁcant optical phenomena of fundamental interest. The observed complex ﬁeld proﬁles have similarities to standard diﬀraction-limited tight focal ﬁelds, though our ﬁeld detection is diﬀerent from the standard schemes. This indicates the relevance of these complex ﬁelds to a larger class of systems involving wavefront curvature and aperture diﬀraction. The detailed analysis and results of the present paper already serve as core explorations of these optical phenomena; and we also suggest future research directions where these system aspects can be purposefully created and explored further.

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Section: Methodsmentioning

confidence: 99%

Complex far fields and optical singularities due to propagation beyond tight focusing: combined effects of wavefront curvature and aperture diffraction

Kumar,

Debnath,

Viswanathan

2024

J. Opt.

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“…the spin-dependent transverse displacement of the centroid of the beam) without a hole represents another type of topological state [4,6,15,16]. Therefore, changing the relative weights of these two OAM contributions makes a transition between these two types of SOIs, which can be regarded as a topological phase transition (TPT) [17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Chirality-enabled topological phase transitions in parity-time symmetric systems

Cao,

Sheng,

Zhou

et al. 2024

New J. Phys.

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Photonic spin Hall effect (PSHE) in chiral PT-symmetric systems exhibits many exotic features, but the underlying physical mechanism has not been well elucidated. Here, through rigorous calculations based on full-wave theory, we reveal the physical mechanism of the exotic PSHE and identify a chirality-enabled topological phase transition. When circularly polarized light is incident on a chiral PT-symmetric system, the transmitted beam contains two components: a spin-flipped abnormal mode that acquires a geometric phase (exhibiting a vortex or a spin-Hall shift), and a spin-maintained normal mode that does not exhibit such a phase. If the phase difference between the cross-polarized Fresnel coefficients cannot be ignored, it results in a chirality-enabled phase and intensity distribution in the abnormal mode, which induces an exotic PSHE. Consequently, as the incident angle increases, a chirality-induced topological phase transition occurs, namely the transition from the vortex generation to the exotic PSHE. Finally, we confirm that the asymmetric and periodic PSHE in the chiral slab is also related to the phase difference between the cross-polarized Fresnel coefficients. These concepts and findings also provide an opportunity for unifying the phenomena of topological phase transitions in various spin-orbit photonic systems.

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Measurement of surface chirality at near-normal incidence

Baishya

Viswanathan

2023

Applied Physics Letters

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The chirality of a medium is typically measured either by transmitting a beam of light through it or by single or multiple interface reflection at large and/or special angles of incidence. We propose and demonstrate here the experimental measurement of surface chirality of z-cut quartz crystal by reflecting a focused beam of light at a near-normal angle of incidence. A small difference in the reflection coefficients between orthogonal elliptically polarized incident beam of 10−4 is measured in the dark-field region of the reflected light via the weak measurement method, taking advantage of the significant transverse spin-shift (TSS) that arises due to the interaction. The TSS behavior is simulated for different chiral parameters (±γ) of the material. The experimental results match well with the theoretically simulated behavior to quantify γ of quartz crystal used as an example interface. The significance of our method can be of interest for a wide variety of fundamental and applied investigations.

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Optical singularity dynamics and spin-orbit interaction due to a normal-incident optical beam reflected at a plane dielectric interface

Cited by 6 publications

References 64 publications

Complex far fields and optical singularities due to propagation beyond tight focusing: combined effects of wavefront curvature and aperture diffraction

Complex far fields and optical singularities due to propagation beyond tight focusing: combined effects of wavefront curvature and aperture diffraction

Chirality-enabled topological phase transitions in parity-time symmetric systems

Measurement of surface chirality at near-normal incidence

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