An infrared (IR) absorber based on the metamaterial structure is proposed theoretically and numerically. The near-unity absorption can be achieved at a certain wavelength by optimizing geometrical parameters of the structure. Moreover, we can switch a single-band absorber to dual-band absorber by decreasing the thickness of top metallic layer which is perforated by an air-filled ribbon. At the same time, we confirm that the mechanism of this two absorption bands is completely different. The simultaneous effects of the magnetic resonance and the cavity resonance occur at our proposed structure. Besides according to the control of polarization direction, the absorption peaks occur at the two constant wavelengths, and the superposed value of this two absorption peaks is always close to a constant. Based on this phenomenon, a simple dual-band absorber is designed when the thickness of top shaped metallic film is relatively large. The cavity response is not the existence in this condition. These results that we obtain may provide some promising applications such as sensors, thermal imagers, and IR detectors.
Metamaterials have attracted a lot of attention in the past decade, because of its remarkable properties in electronics and photonics. Recently, a new kind of two-dimensional metamaterial named metasurface have led the research front. Metasurfaces show up excellent optical properties by patterning planar nanostructures. Novel optical phenomena based on graphene include ultra-thin focusing, anomalous reflection or refraction strong spin-orbit and so on. In this work, we have designed a novel infrared light polarized beam splitter by combining the 2D array of graphene with a subwavelength-thickness optical cavity, which demonstrated great splitting effect in infrared wavelength. Our demonstration pave a novel way for the infrared light polarized beam splitting.
We describe a novel beam splitter with advantages of a single-layer, compact and vertical coupling structure, which is based on Bragg diffraction conditions and phase match equation. FDTD method is used to optimize the design of beam splitter. The result of simulation shows that both polarizations incident light are separated into two beams of nearly equal power (near 43% split and 45% split, respectively), which are coupled into opposite directions in the waveguide. For TE mode, the coupling efficiency of the right direction and the left direction are 42.54% and 43.68, respectively. That of TM mode is 46.03% and 44.07%, respectively. The power difference for two polarizations of two output port is less than 1% and 2%, in addition, 40nm and 65nm bandwidth is achieved.
Because of the diffraction limit of light, the scale of optical element stays in the order of wavelength, which makes the interface optics and nano-electronic components cannot be directly matched, thus the development of photonics technology encounters a bottleneck. In order to solve the problem that coupling of light into the subwavelength waveguide, this paper proposes a model of coupler based on metal materials. By using Surface Plasmon Polaritons (SPPs) wave, incident light can be efficiently coupled into waveguide of diameter less than 100 nm. This paper mainly aims at near infrared wave band, and tests a variety of the combination of metal materials, and by changing the structural parameters to get the maximum coupling efficiency. This structure splits the plane incident light with wavelength of 864 nm, the width of 600 nm into two uniform beams, and separately coupled into the waveguide layer whose width is only about 80 nm, and the highest coupling efficiency can reach above 95%. Using SPPs structure will be an effective method to break through the diffraction limit and implement photonics device high-performance miniaturization. We can further compress the light into small scale fiber or waveguide by using the metal coupler, and to save the space to hold more fiber or waveguide layer, so that we can greatly improve the capacity of optical communication. In addition, high-performance miniaturization of the optical transmission medium can improve the integration of optical devices, also provide a feasible solution for the photon computer research and development in the future.
A new 4×4 point to point router is investigated with the transfer matrix method. Its routing paths and low loss of power are successfully demonstrated. The proposed design is easily integrated to a larger scale with less microring resonators, and the power loss from the input port to the output port is demonstrated to be lower than 10%. All of the microrings designed here have the identical radii of 6.98 μm, and they are all in resonance at a wavelength of 1550 nm. Both the gap between the microring and the bus waveguide and the gap between two neighbouring rings are 100 nm. The width of bus waveguide as well as the microrings is designed to be 200 nm. Free spectral range (FSR) is supposed to be around 17 nm based on the parameters above. A large extinction ratio (ER) is also achieved, which shows the high coupling efficiency to a certain extent. Thermal tuning is employed to make the microrings be in resonance or not, not including the two microring resonators in the middle. In other words, the two microrings are always in resonance and transport signals when the input signals pass by them. Hence, only two microrings are needed to deal with if one wants to route a signal. Although this architecture is blocking and not available for multicasting and multiplexing, it is a valuable effort that could be available for some optical experiments on-chip, such as optical interconnection, optical router.
Based on the theory of information optics and the needs of perfect shuffle (PS) transform, a new method of achieving a PS transform is reported by using a subwavelength binary blazed grating (SBBG) array. Comparison the multilevel gratings, SBBG array can be fabricated only one step by photolithography and reactive ion etching (RIE). The SBBG array was designed to six channels PS transform, and transformation of two-neighboring channels was simulated by finite difference time domain (FDTD). The first order diffraction efficiency of SBBG designed here is larger than 80%, and has wide spectra and large incident angular tolerance by rigorous coupled-wave analysis (RCWA). The cross talk of neighboring channels was smaller than 3.24%. The theoretical analysis and computation show that PS transform using SBBG array has advantages of small size, compact structure, low loss and crosstalk, and easy to integrate with other photoelectric device. Consequently, it can be used in optical communication and optical information processing.
How to improve the sensitivity of new pattern of gyroscope which is based on micro ring resonator is widely researched. And periodically modulating coupling coefficient and area are the two most common schemes. Moreover, when the area of the square difference is large enough, the precision of gyroscope of the latter is higher than that of the former by 1 to 2 orders of magnitude. But increasing modulation area will narrow the transmission band, it will impact on our measurement of the inertial rotation. What’s more, this modulation method is very sensitive to the coupling coefficient between the micro rings. Simultaneously, the slope of the center resonance peak will be quickly decayed with the increase of the coupling coefficient. Generally, there's no sense to our modulation when the coupled coefficient is over 0.1. In this paper, we use the way of combining the two schemes to study the performance of the gyroscope which includes it's precision and how to reduce interference when it applied to devices. We found that the accuracy of rotation produced by our scheme is higher than that of simply modulating coupling coefficient or coupling area. And the sensitivity of gyroscope achieved by the new method is times higher than that of the general of coupled resonator optical waveguide, and there is almost no limit to the coupled coefficient based on our coupling scheme. What’s more, the steepest transmission resonance of the transmission band appears at Ω = 0 and other resonance peaks around the center resonance are completely suppressed because of the effective superlattice structure, which will effectively reduce the interference during our measurement.