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.
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.
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.
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.
A compact polarization beam splitter (PBS) based on a microring resonator is proposed and demonstrated numerically by utilizing the full vectorial mode-matching (FVMM) theory and the coupled mode theory (CMT), which are introduced in the aspects of the width of waveguide, the height of waveguide, the radius of microring, and coupling coefficient, etc. Simultaneously, the finite difference time-domain (FDTD) method, a powerful and accurate method for finite size structure, is chosen to simulate and design this PBS. When TE and TM polarized light at 1.55μm are launched into the input port simultaneously, the resonator will drop TM polarized light to the drop port and transmit TE polarized light to the through port. In this way, two orthogonal polarization states are split and transferred to different output ports. The extinction ratio in the order of 10dB is achieved initially based on our recent work. The initial experimental results are also given, which includes three microring resonator with the radius of 15μm, 10μm, and 5μm, respectively. The proposed PBS structure could be utilized to develop ultracompact optical polarization modulating device for large-scale photonic integration and optical information processing.