The phenomenon of trapping a broad spectrum of light is known as “rainbow trapping” and is achieved by using all-dielectric, hybrid metallo-dielectric, or all-metallic configurations. The latter architectures allow strong confinement but exhibit very high ohmic losses. This results in practical lifetimes of trapped modes to less than 1 ps. Therefore, novel strategies are required to be devised for trapping and, subsequently, releasing broadband electromagnetic field with lifetime > 1 p s . We present a rainbow trapping configuration using the excitation of multiple optical Tamm (OT) modes in an one-dimensional chirped photonic crystal (CPC) designed for adiabatically coupling counterpropagating modes. In the geometry, the backscattered phase undergoes multiple discontinuities ( = π ), which enables excitation of many OT modes in the presence of a thin plasmon-active metal, which is placed adjacent to the terminating layer of CPC. All the OT modes are spatially separated in the CPC, and the strong modal confinement manifests into group velocities as low as 0.17 c . The time-domain simulations depict mode-localization in the dielectric sections of CPC, which manifest into lifetimes ∼ 3 p s .

Adiabatic following has been an widely-employed technique for achieving near-complete population transfer in a ‘two-level’ quantum mechanical system. The theoretical basis, however, could be generalized to a broad class of systems exhibiting SU(2) symmetry. In the present work, we present an analogy of population transfer dynamics of a two-level atomic system with that of light propagation in a classical ‘one-dimensional’ photonic crystal, commonly known as distributed-Bragg-reflector (DBR). This formalism facilitates in adapting the idea of adiabatic following, more precisely the rapid adiabatic passage (RAP) which is usually encountered in a broad class of quantum-mechanical systems. We present a chirped DBR configuration in which the adiabatic constraints are satisfied by virtue of optimally chirping the DBR. The reflection spectrum of the configuration exhibit broadening of photonic bandgap (PBG) in addition to a varying degree of suppression of sharp reflection peaks in the transmission band. The intermodal coupling between counter-propagating modes as well as their phase-mismatch, for the DBR configuration, exhibits a longitudinal variation which is usually observed in ‘Allen-Eberly’ scheme of adiabatic population transfer in two-level atomic systems.

The transmission of light through a periodically stratified medium such as a photonic crystal (PC) results in acquiring a “quantized” geometric phase, which is also known as a “topological phase.” This gives rise to the possibility of structuring optical beams through an appropriate experimental design. In addition, the broad transmission spectral bands of a PC provides a versatile platform for structuring optical beams over broad spectral bandwidth. Here, we present a simple and flexible route to generate first-order Hermite–Gaussian, i.e.,  H G 01 or H G 10 , beams utilizing the light transmitted from conventional one-dimensional PCs and provide a theoretical insight using finite-difference time-domain (FDTD)-based simulations. We also show that the technique could be employed for achieving beam structuring in reflected light beams, and consequently, it provides a plausible route for wavefront shaping involving high optical power.

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Quantum mechanical Stern–Gerlach (SG)-like effects are unusual to explore in the domain of optics due to the absence of any interaction of photons or optical waves with the conventional magnetic field. A few recent investigations point toward the possibility of observing an SG-like effect in nonlinear optics via wedge-shaped poling in a long lithium niobate (LN) crystal to generate a spatially varying analogous magnetic field ( B → A ). This leads to two different propagation directions for the mutually orthogonal states formed by superposition of signal and idler modes (states) with opposite phases. In this work, we present theoretical formalism to show an equivalent SG-like splitting in a frequency downconversion process and experimentally validate the assertion by producing a suitable transverse gradient in B → A through an in-homogeneous pump wavefront. The experimental results show SG-like splitting in an optical parametric generation (OPG) process using a widely used periodically poled LN (PPLN) crystal and a pump laser exhibiting a suitable spatial beam profile. The experimentally measured deviation angle for the mutual beam closely matches with the prediction from theoretical formalism using a Gaussian pump wavefront.