Room-temperature polariton parametric scattering driven by a one-dimensional polariton condensate

We demonstrate a novel way to realize room-temperature polariton parametric scattering in a one-dimensional ZnO microcavity. The polariton parametric scattering is driven by a polariton condensate, with a balanced polariton pair generated at the adjacent polariton mode. This parametric scattering is experimentally investigated by the angle-resolved photoluminescence spectroscopy technique under different pump powers and it is well described by the rate equation of interacting bosons. The direct relation between the intensity of the scattered polariton signal and that of the polariton reservoir is acquired under nonresonant excitation, exhibiting the explicit nonlinear characteristic of this room-temperature polariton parametric process.     

Gap polariton solitons

We report the existence, and study mobility and interactions of gap polariton solitons in a microcavity with a periodic potential, where the light field is strongly coupled to excitons. Gap solitons are formed due to the interplay between the repulsive exciton-exciton interaction and cavity dispersion. The analysis is carried out in an analytical form, using the coupled-mode (CM) approximation, and also by means of numerical methods.     

Phonon-induced polariton superlattices

We show that the coherent interaction between microcavity polaritons and externally stimulated acoustic phonons forms a tunable polariton superlattice with a folded energy dispersion determined by the phonon population and wavelength. Under high phonon concentration, the strong confinement of the optical and excitonic polariton components in the phonon potential creates weakly coupled polariton wires with a virtually flat energy dispersion.     

Terahertz phonon polariton imaging

In this article, we primarily review the time-resolved imaging of THz phonon polariton, which is generated by femtosecond laser in ferroelectric crystal. We pay more attention to the imaging in thin crystal, which can be used as an integration platform for terahertz-optics or terahertz-electrics. The imaging techniques, which can get quantitatively in-focus time-resolved images, are introduced in more detail. They have made enormous progress in recent years, and are powerful tools for the research of phonon polariton, optics, and THz wave. We also briefly introduce the generation principle and general propagation properties of THz phonon polariton.     

Angle-resonant stimulated polariton amplifier

We experimentally demonstrate resonant coupling between photons and excitons in microcavities which can efficiently generate enormous single-pass optical gains approaching 100. This new parametric phenomenon appears as a sharp angular resonance of the incoming pump beam, at which the moving excitonic polaritons undergo very large changes in momentum. Ultrafast stimulated scattering is clearly identified from the exponential dependence on pump intensity. This device utilizes boson amplification induced by stimulated energy relaxation.     

Evanescent Waves and Energy Conservation

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Evanescent field fibre-optic chlorine sensor

An evanescent field fibre-optic sensor for detecting chlorine in water is proposed and studied experimentally. The technique is based upon evanescent field absorption through the colour development of reacting diethyl phenylene diamine with chlorine, which forms an azo compound. Sensor systems with single and multi-fibre sensing elements were designed, constructed and evaluated for linearity of response, sensitivity, and reproducibility of results. The experimental results establish the feasibility of detecting low concentration chlorine in water using the proposed method. The results for an improved design are indicative of reasonably good reproducibility and linearity of the sensor response.     

Statistical properties of polariton states

Summary The unitary transformation that relates free polarization and photon states to polariton states is constructed. The time evolution of an arbitrary initial state in terms of the polariton Hamiltonian is presented. The many-photon components of polariton states as well as the transition probabilities to polariton states and the intrinsec and time-dependent polariton squeezing are discussed.     

Large-area surface-plasmon polariton interference lithography

Large-area surface-plasmon polariton (SPP) interference lithography is presented, which uses an attenuated total reflection-coupling mode to excite the interference of the SPPs. The interference of the SPPs causes a highly directional intensity range in a finite depth of the electric field, which is good for noncontact. Finite-difference time-domain simulations of the interference on a thin resist layer show that broad-beam illumination with a p-polarized light at a wavelength of 441 nm can produce features as small as 60 nm with high contrast, smaller than lambda/7. Our results illustrate the potential for patterning periodic structures over large areas at low cost.     

Dynamical theory of polariton amplifiers

We present the theory of the dynamics of the polariton amplifier in the region of small polariton densities. We give an analytical solution for the polariton condensate density matrix and show that the formation of a coherent quantum state is possible. Once the condensate is formed, the coherence becomes macroscopically long living. Polariton amplifier represents, therefore, an optical memory element, where the input weak coherent signal can be amplified and kept.     

Tunable surface plasmon polariton microcavity

The tunability of a one-dimensional surface plasmon polariton microcavity is studied theoretically, which is formed by seven silver ridges. The magnitude of the electric-field intensity of the microcavity mode is enhanced by two orders compared with that of the perfect silver ridge array. The localization properties of the surface plasmon polariton microcavity can be tailored by adjusting the structure parameters or by changing the refractive index of the covering material. The potential applications in photonics devices are also discussed.     

Coupled surface polariton with guided wave polariton modes in asymmetric metal clad dielectric waveguides

It is emphasized that in metal-dielectric layered systems with a thin metallic layer, surface plasmon-polaritons (SP) can couple with guided wave polaritons (GWP) and form new hybrid modes with properties of both SP and GWP. This is illustrated by analyzing the properties of electromagnetic modes in an asymmetric metal-clad-dielectric-slab waveguide and their dependence on the thickness of metal cladding.     

Amplitude-mode dynamics of polariton condensates

We study the stability of collective amplitude excitations in nonequilibrium polariton condensates. These excitations correspond to renormalized upper polaritons and to the collective amplitude modes of atomic gases and superconductors. They would be present following a quantum quench or could be created directly by resonant excitation. We show that uniform amplitude excitations are unstable to the production of excitations at finite wave vectors, leading to the formation of density-modulated phases. The physical processes causing the instabilities can be understood by analogy to optical parametric oscillators and the atomic Bose supernova.     

Theory of ferromagnetic polariton linewidths

The interaction between magnons and photons which is responsible for magnetic polariton formation is expressed in terms of second quantized operators, and it is confirmed that the polariton dispersion curve obtained by diagonalizing the Hamiltonian is the same as that found classically. A term describing relaxation of the polariton by the two magnon mechanism which is often dominant in ferromagnetic resonance is then introduced. The lineshape function for inelastic light scattering is calculated by a Greens function technique. On the assumption that the lineshape can be approximated as a Lorentzian an expression for the linewidth is derived. The linewidth is zero when the polariton frequency Ω lies outside the magnon manifold, and increases discontinuously from zero at w = ¦γ¦H₀, where H₀ is the (internal) static field.     

Interactions in confined polariton condensates

We investigate the effect of interactions in zero-dimensional polariton condensates. The shape of the condensate wave function is shown to be modified by repulsive interactions with the reservoir of uncondensed excitons. In large micropillar cavities, when uncondensed excitons are located at the center, the condensate is ejected toward the pillar edges. The same effect results in the generation of optical traps in wire cavities. Once polariton condensates are spatially separated from the excitonic reservoir, spectral signatures of polariton-polariton interactions within the condensate are evidenced.