Binming Liang

Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution.

Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals.

Influence of surface termination on inverse Goos–Hänchen shift of negatively refractive photonic crystals

The effect of surface termination on the inverse Goos Hanchen (GH) shift of two dimensional (2D) negatively refractive photonic crystal (NRPhC) containing air holes arranged in hexagonal lattice in a dielectric background is investigated for TM polarization. Results show that the magnitude of the inverse GH shift of 2DNRPhC strongly depends on surface termination even for an incident beam with a fixed frequency and incidence angle. Further study by calculating the dispersion of surface mode of 2D-NRPhC as a function of surface termination reveals that 2DNRPhC presents large inverse Goos Hanchen shift at those terminations where surface mode is excited, that is, large inverse Goos-Hanchen shift originates from backward surface mode of 2DNRPhC. In addition, the coupling coefficient of incident field into the field of surface mode as a function of surface termination is studied and demonstrates above results. This paper provides technical information regarding the combination of various functional photonic elements in the design of integrated optical circuits.

Negative refraction and birefringence in a two-dimensional flat perfect photonic crystal

A new kind of birefringence is found in a two-dimensional (2D) flat perfect photonic crystal (PhC). It is different from the one in the normal biaxial crystal, but qualitative, and comes from the positive and negative refraction in the 2D flat perfect PhC. The quantitative relationship between the refractive index and the incident angle are plotted, by the analysis of the equal-frequent surface (EFS) of the perfect PhC. The plot is consisted of three branches---the main across 0° to 45.53° of the incident angle, the upper across 33.3° to 38.53° and the lower across 38.53° to 45.53°. The upper reveals the positive refraction; the lower and the main reveal the negative ones. The finite-difference time-domain (FDTD) simulations are performed, and the relevantly quantitative measurement validates the quantitative relationship by the analysis of the EFS, but a 2.67° shift to the bigger incident angle. A novel beam guiding is observed, which is resulted not from the guiding in a defect photonic crystal (PhC) but from the negative refraction in a two-dimensional (2D) flat perfect PhC slab.

Direct measurement of the negative Goos–Hänchen shift of single reflection in a two-dimensional photonic crystal with negative refractive index

The negative Goos-Hänchen shift (GHS) on a two-dimensional photonic crystal with an effective negative refractive index is investigated by simulation and experiment. The measured refractive index of the fabricated photonic crystal is nearly -0.44. The difference between the Goos-Hänchen shift of the transverse electric wave GTE and that of the transverse magnetic wave GTM (DGHS) in the height direction of a silicon rod is measured at three incident angles. The result shows that DGHS is always smaller than -GTM, thus GTE<0; therefore, the negative GHS does occur on the surface of the photonic crystal with a negative refractive index.

Subwavelength imaging of a point source based on two-dimensional photonic crystals.

A new two-dimensional (2D) photonic crystal (PC) structure with effective refractive index approaching -1, consisting of periodic array air holes in silicon, is proposed. The light radiated from a point source can form an image through a single wedge PC. Numerical results show that the half-width of the image reaches 0.44λ, which is lower than half of the incident wavelength. In addition, the light through the combination of two of the same PCs can also form subwavelength imaging of which the half-width reaches 0.67λ, and the image almost flipped 180° compared with a point source.

Influence of Temperature on Reflectivity of Symmetrical Metal-Cladding Optical Waveguide

The influence of temperature on the reflectivity of symmetrical metal-cladding optical waveguide (SMCOW) is studied theoretically by means of single-factor investigation under spectral and angular interrogation mode of operation. The theoretical model for temperature dependence of reflectivity includes the temperature dependence of refractive index and thickness of guiding layer, the temperature dependence of the metal film thickness and metal-dielectric function. It is found that the effect of temperature on the reflectivity of SMCOW is mainly attributed to the temperature dependence of refractive index and thickness of guiding layer; on the contrary, the temperature properties of metal film hardly contribute to the influence of temperature on the reflectivity. Based on the analysis, the sensitivities of SMCOW with guiding layer made up of different optical glasses are computed under both spectral and angular interrogation. This letter is supposed to provide direction in designing SMCOW sensors against the temperature variation.

Double Doppler effect in two-dimensional photonic crystal with negative effective index

The inverse Doppler effect in photonic crystal with negative refractive index had been proofed experimentally in our previous research. In this paper, we studied the spatial harmonics of Bloch wave propagating in such PhCs by FFT method. The lagging and front phase evolutions reveal that both backward wave and forward wave exist in these harmonics. Subsequently, we studied the double Doppler effect phenomenon that both the normal and inverse Doppler exist in one photonic crystal simultaneously by using the improved dynamic FDTD method which we made it suitable for dealing with moving objects. The simulative Doppler frequency shifts were consistent with the theoretical values. Our study provides a potential technology in measurement area.

Analysis on the temperature property of sensors based on symmetrical metal-cladding optical waveguide

The analysis of the temperature property of sensors based on symmetrical metal-cladding optical waveguide (SMCOW) is focused on analyzing the temperature property of reflectivity of SMCOW sensors, which is theoretically studied with single-factor investigation under spectral and angular interrogation scheme. There are mainly four factors influencing the temperature dependence of reflectivity, it is the temperature dependence of refractive index and thickness of guiding layer, along with the temperature dependence of the metal film thickness and metal-dielectric function. The simulation result shows that the effect of temperature on the reflectivity of SMCOW is mainly attributed to the temperature dependence of refractive index and thickness of guiding layeron the contrary, the temperature properties of metal film hardly contributes to the influence of temperature on the reflectivity. Based on the analysis, the sensitivities of SMCOW with guiding layer of different optical glasses are computed under both spectral and angular interrogation. This paper is supposed to provide direction in designing temperature-sensitive SMCOW structure sensors.

High-sensitivity low-cost temperature sensor based on symmetrical metal-cladding optical waveguide

The temperature-dependent reflection spectrums of ultrahigh order guided modes of symmetrical metal-cladding waveguide (SMCW) are measured in angular interrogation. The results show that the reflection spectrum is characterized by extremely narrow resonance dip, which agrees well with numerical calculation. Based on the falling or rising edge of resonance dip of ultrahigh order guided modes of SMCW, a temperature sensor with characteristic of high sensitivity is proposed. Meanwhile, by experimentally determine the linear character between the shift of resonance angle and the variation of temperature, a method of angle compensation is put forward to extend the sensing range. Owing to its characteristics of high sensitivity, low cost and easy fabrication, the temperature sensor based on SMCW will be a promising sensor in many fields.

The organic plastic photonic crystal for terahertz filter

The paper is mainly concerned with the study of the PBG (Photonic Band Gap) in 2D photonic crystal which consists of a hexagonal lattice of circular dielectric rods with Polyethylene. The result indicates that its PBG is very narrow. According that, a narrow band filter has been obtained by choosing certain parameters of the photonic crystal.