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The discovery of Photonic spin Hall effect (PSHE) on surface plasmon polaritons (SPPs) is an important progress in photonics. In this paper, a method of realizing multi-channel PSHE in two-dimensional metal-air-metal waveguide is proposed. By modulating the phase difference $$\phi$$ ϕ and polar angle $$\theta$$ θ of the dipole source, the SPP can propagate along a specific channel. We further prove that PSHE results from the component wave interference theory. We believe that our findings will rich the application of SPPs in optical devices.

The finding of Photon Hall effect (PHE) on metal surface is an important progress in photonics, but it will be more practical if PHE can be realized in line-type waveguide. In this paper, we suggested a way to realize PHE in two-dimensional photonic crystal (PC) waveguide. Numerical simulation results show that the propagating direction and strength of light in the PC waveguide can be controlled by the polarization state of incident light. Different from the PHE on metal surface, the PHE in PC waveguide can be driven not only by circularly polarized light, but also by linearly polarized light. The PHE in PC waveguide can be attributed to the interference of the two component waves excited by the incident light.

A general method is proposed to describe the energy levels of the interface states in one-dimensional photonic crystal (PC) heterojunction [Formula: see text] containing dispersive or non-dispersion materials. We found that the finite energy levels of the interface states for the finite configuration can be described totally by the dispersion relation of the PC with a periodic unit [Formula: see text]. It is further found that this method is also applicable for the case of defect modes. We believe our method can be used to guide the practical application.

The zero-refraction property of a metal film can be used to image so that the metal film behaves as a superlens. Experimentally, the metal superlens is sandwiched between the photosensitivity resist (PR) and the dielectric spacer in the photolithograph device to produce images. In this paper, the imaging conditions of the metal superlens, or the parameters of the device containing the superlens are investigated in detail. It is found that the energy zero-refraction effect is the intrinsic property of the metal superlens. The permittivities of the dielectrics at the two sides of the superlens will influence the imaging quality. The rule is drawn for obtaining best images: the two dielectrics should have the same permittivities, so-called symmetry case, and the real part of the permittivity of the metal superlens plus the dielectric permittivity is just equal to 1, i.e. ϵ ( dielectric ) + ϵ r ( superlens ) = 1 .

In this paper, Dirac point method is used to study the interface state of one-dimensional photonic crystal heterojunction [Formula: see text] containing dispersive materials GaAs. We found that the energy levels of the interface states satisfy a simple sinusoidal function. We investigate the variation of the energy levels of the interface states with the incident angle, it is found that these interface states move toward high-frequency with the increase of the incident angle. At the same time, it is found that there is an extra localized band and it is further proved that the extra band corresponds to the defect band, and the energy levels of the defect band possess the same behavior with those of interface states.

A very facile way to obtain multiple interface modes in a one-dimensional photonic crystal heterostructure is proposed in this Letter. We found that the interface modes can be generated by introducing the interfaces, and the number of interface modes equals the number of introduced interfaces. All these interface modes originating from a different geometric Zak phase can create two band branches governed by the two different interfaces. We further find that the two band branches can be renormalized into one band branch with discrete energy levels in the form of sinusoidal function. We believe that these findings can be used to provide direct guidance for practical application and can also make the estimation of practical samples more convenient.

This paper studies optical transmission through an interface between two slits with different widths in a sheet composed of an ideal conductor. Such a structure is of potential use in fabricating optical diode and may be the simplest one compared to other designs. Our calculations show that there is a critical wavelength. When the light wavelength is below the critical wavelength, the transmissivity is unidirectional. The expression of the stable transmissivity as a function of the ratio of the widths of the two slits was obtained analytically. Particularly, at the critical wavelength, the transmissivities are zero. This phenomenon has great potential for application in the manufacture of wavelength blockers.

We report an intense (∼10mW) and ultra-broadband (∼150 THz) THz to infrared (IR) source with a Gaussian wavefront, emitted from nano-pore-structured metallic thin films with femtosecond laser pulse excitation. The underlying mechanism has been proposed as thermal radiation. In addition, an intense coherent THz signal was generated through the optical rectification process simultaneously with the strong thermal signal. This unique feature opens up new avenues in biomedical research.

One kind of optical unidirectional transmission structures is proposed which is composed of a metal subwavelength slit dressed by one or two gratings. Simulation results show that the gratings with different geometry parameters can play different roles. One role is the convergence effect and the other is shield effect. Each effect can independently cause the unidirectional transmission with special properties. These two effects are explained in view of optical reciprocal theorem. Combination of the two effects results in excellent unidirectional transmission properties.

Terahertz (THz) spectroscopic sensing and imaging has identified its potentials in a number of areas such as standoff security screening at portals, explosive detection at battle fields, bio-medical research and so on. With these needs, the development of an intense and broadband THz source has been a focus of THz research. In this work, we report an intense (~10 mW) and ultra-broadband (~150 THz) THz to infrared (IR) source with a Gaussian wavefront, emitted from nano-pore-structured metallic thin films with femtosecond laser pulse excitation. The underlying mechanism has been proposed as thermal radiation. In addition, an intense coherent THz signal was generated through the optical rectification process simultaneously with the strong thermal signal. This unique feature opens up new avenues in biomedical research.

We calculate the omnidirectional dispersion spectrum for one-dimensional (1D) photonic crystals (PCs) inserting multiple photonic quantum-wells (PQWs) with the use of the plane-wave expansion method in combination with a supercell technique. We find that the localized defect modes significantly depend on the number of the PQWs and the configuration. This may provide a new way to engineer the dispersions of the composite PCs to meet the requirements of optical or microwave devices.

The parametric amplification (PA) and second harmonic generation (SHG) from quasi-one-dimensional aperiodic optical superlattices (AOSs) are investigated in the cases of large, intermediate, and small signals of the pumping light wave. The optimal design of the AOSs is carried out with the use of the simulated annealing (SA) method. The numerical simulations show that the constructed AOSs can achieve multiple wavelength PA (or SHG) with identical amplification (or identical conversion efficiency) at the pre-assigned wavelengths. The variations of the normalized intensities of the PA signal (or the pumping fundamental wave (PFW)) for the PA process with the distance of propagation of the light wave from the interface of the AOSs at the pre-assigned wavelengths exhibit monotonically increasing (or decreasing) behavior. So do the variations of the normalized intensities of the second harmonic wave (SHW) (or the fundamental wave (FW)) for the SHG. This strongly supports the fact that the contribution of each individual unit domain in the constructed samples to the PA (or SHG) is constructive accumulation, favorable for the PA (or SHG) process. The saturation phenomenon of the PA (or SHG) signal is observed.

We investigate the evolution of the band gap in one-dimensional (1D) photonic crystals (PC) with the gradual modifications of structural configurations from photonic quantum wells to PC heterostructures. The transmissive spectra are calculated with the use of scattering matrix method. We find that the transmissive spectra and confined states strongly depend on the structural configurations of samples.

Ultra-thin optical coating comprising nanometer-thick silicon absorbing films on iron substrates can display strong optical interference effects. A resonance peak of longitudinal Kerr rotation with the silicon thickness of was found at the wavelength of 660 nm. The optical properties of silicon thin films were well controlled by the sputtering power. Non-iridescence color exhibition and Kerr rotation enhancement can be manipulated and encoded individually.

By the multiple reflections and transmissions in a dielectric on a ferromagnetic metal, color and Kerr rotation correlate with each other. It is revealed that the real refractive index of dielectric plays a major role on the variations of color and Kerr signal, while the absorbing term adjusts the intensive color exhibition and Kerr enhancement at much thinner dielectric thickness. The intensive Kerr signal variation is always accompanied by the color transition with the dielectric thickness changing. Experimental results observed in silicon(or silica)/iron samples are well consistent with calculations. Nanometer dielectric optical coating can not only enhance Kerr effect but also endow magnetic surface with chromatics, which has promising potential applications in anti-fake brands, colorful decorations, camouflages, and even bionics.

The one-way devices in optical circuits are the key components just as the diodes in electric circuits, which allow the light going in only one direction. A novel one-way transmission structure is proposed which is a curved waveguide containing a confined photonic crystal. When the waveguide is made of perfect electric conductor, the exact calculation results demonstrate that the device shows excellent one-way properties. The forward transmissivity approaches 100% and the largest transmission ratio exceeds 100.92N, where N is the cell number of the photonic crystal in the structure. When the waveguide is made of real metal, the device also presents excellent one-way transmission properties, which can be confirmed by an approximate calculation as well as by the simulation. In working region, the lowest forward tranmissivity is about 30% and the largest one exceeds 70%. The highest transmission ratio exceeds 104.

A simple optical structure, termed a pillar-slit structure, is proposed to enhance the contrast ratio of the weak optical signal. The structure consists of a metal slit surrounded by two metal pillars and can be directly incorporated onto optical sensors. The waves excited on the incident surface are modulated by the pillars and then scattered by the slit entrance so as to generate the in-slit surface plasmon polaritons passing through the slit. The transmission power is modified by the surface wave intensity. This structure is capable of suppressing background and enhancing signal light simultaneously. A calculated illustration by the numerical simulation method shows that an increase of the contrast ratio can be exceeded 900 times.

We investigate the extraordinary optical transmission of a subwavelength elliptic hole array in a metal by a proposed simple method. The transmission strength depends on the polarization direction of the incident light. The polarization excitation ratio of the surface plasmon polariton (SPP) governs the transmissivity. There is an interplay between the adjacent holes which is caused by the transverse magnetic filed of SPP on the surfaces of the metal.

In the past few years, new applications of terahertz wave have given rise to the development of intense terahertz wave source and modulation of terahertz wave [1–4]. However, rigorous experimental conditions or few theoretical explanations were in these works. In this paper, a method to enhance and control the THz pulse generation in air plasma by external electric field is proposed. Two theoretical models, the optics Four-Wave-Mix-Frequency and the electrodynamics electromagnetic radiation are given to explain the results of the proposed method respectively.

We have studied multiple wavelength second harmonic generation (SHG) in one-dimensional multiple photonic quantum-wells (PQWs) structure made of linear and nonlinear material. The numerical simulations show that the devised sample can achieve simultaneously multiple wavelength SHG with nearly identical conversion efficiency by the modulation of both the linear and nonlinear optical coefficient. The fundamental wave frequencies are aimed at the defect states by modulating the linear optical coefficient. The optimal arrangement of the polarization directions of the ferroelectric domains in multiple PQWs are determined by simulated annealing method. By tuning the polarization directions of the domains, the conversion efficiencies of "forward" and "backward" for multiple wavelength SHG can be flexibly modulated.

One of the keys to understanding the extraordinary optical transmission in a subwavelength metal slit is in what field mode is excited. We find that, compared to the usual surface plasmon polariton (SPP), the wavelength of the excited mode is squeezed and will become smaller as the slit width does. This mode is called an in-slit SPP. We show how the wavelength of this mode can be solved by a formula and clearly analyze the physical reason for the wavelength squeeze. Furthermore, the similarities and differences of the wavelength squeeze between normal incidence and oblique incidence are pointed out.

We use the transfer-matrix method to research the band structures in one-dimensional photonic crystals composed of anomalous dispersion material (saturated atomic cesium vapor). Our calculations show that that type of photonic crystal possesses an ultra-narrow photonic band gap and this band gap is tunable when altering the electron population in the atomic ground state of the anomalous dispersion material by the optical pumping method.