In this paper, we discuss the fabrication of a dielectric photonic crystal (PhC)-based Fano-filter device, as well as a numerical investigation of its spectral characteristics. The process parameters affecting the structural and physical properties of the fabricated device are discussed in detail, along with their influence on the spectral properties of the filter. The considered experimental problem is a three-layered PhC structure, fabricated using focused ion-beam (FIB) technology, designed to operate in the near-infrared (NIR) range. The studied parameters include the shape of PhC elements, depth of the structures, cladding layer thicknesses, and the refractive index of the material. Numerical design and simulations are performed using an open-source python-based Finite-difference time-domain (FDTD) simulation tool. The proposed optical filter device operates based on the principle of guided-mode resonance, and achieved a maximum quality factor value in the range of 800.
In this work, a novel idea of optical switch design based on guided mode resonance in the photonic crystal structure is numerically investigated. The designed switching device work on the principle of optical amplification and wavelength shift of data signal with the help of a control signal. The data signal can be coupled into the waveguide using guided-mode resonance, whereas, a control signal is index-coupled into the waveguide to influence the data signal. The optical switching action is optimized by introducing a photonic crystal cavity and varying the number of photonic crystal elements, where the resonant wavelength, reflection peaks, linewidth, and quality factor of the data signal can be adjusted. The device is based on low refractive index contrast dielectric materials compatible with fiber optic communication and can operate in a near-infrared range of around 1.55 μm. The numerical simulations are carried out in an open source finite-difference time-domain-based software. An optical switching action is achieved with 7% amplification in the data signal at a central wavelength of 1.55 µm with a maximum shift of the wavelength of 0.001 µm. The proposed device can be easily implemented in cascade designs of programmable photonic and optical switching circuits.
In this work, fabrication of a dielectric photonic crystal device and numerical study of its spectral characteristics as a refractive index sensor are presented for near infrared range. The proposed nanosensor device is composed of low-cost dielectric materials, i.e., silicon dioxide and niobium pentoxide, and is fabricated using focused ion-beam milling lithography. In the first part, the fabrication process of the device is discussed, along with the process parameters and their effects on the structural properties of the resulting photonic crystal elements. In the second part, the device is numerically tested as a sensor for the biological refractive index range of 1.33 to 1.4. The performance considerations of the biosensor device are studied for 12 different structural profiles based on the fabrication results. It is shown that the angular-wall-profile of the fabricated structures downgrades the performance of the sensor, and the optimum value of hole depth should be in the range of 930–1500 nm to get the best performance. A sensitivity of 185.117 nm/RIU and a figure of merit of 9.7 were recorded for the optimum design of the device; however, a maximum sensitivity of 296.183 nm/RIU and a figure-of-merit of 13.184 RIU−1 were achieved. The device is recommended for a variety of biosensing applications due to its inert material properties, stable design and easy integration with fiber-optic setups.
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