High-Resolution Plasmonic Filter and Refractive Index Sensor Based on Perturbed Square Cavity with Slits and Orthogonal Feeding Scheme

Abstract

We present a plasmonic bandpass filter and refractive index sensor based on perturbed square cavity resonator with slits, which is fed by orthogonally oriented feeding waveguides. The slits provide size reduction in comparison to conventional square cavities and better coupling to the waveguides, while the perturbation and orthogonal feeding scheme provide a pair of transmission zeros in the response of the structure. In that manner, a bandpass filter with high transmission, narrow bandwidth, and excellent selectivity can be readily designed. Moreover, with a slight modification of the structure, a very sharp Fano-like response can be obtained and employed for refractive index sensing with high sensitivity and figure of merit.

A Plasmonic Structure of Fano Resonance in the MIM Waveguide with r-Shaped Resonator for Refractive Index Sensor

“…, where 𝜀 ∞ =3.7 is the dielectric constant at infinite frequency, ω is the angular frequency of incident light in vacuum, 𝜔 𝑝 =1.38×10 16 Hz is the bulk plasma frequency of free conduction electrons, and γ=2.73×10 13 Hz is the electron collision frequency According to the standing wave theoretic, constructive interference should become when the resonance condition is satisfied: 4𝜋𝑅𝑒(𝑛 𝑒𝑓𝑓 )𝑙 1 /𝜆 + 𝜙 = 2𝑚𝜋, 𝑚 = 1, 2, 3, . .…”

“…Surface plasmon polaritons (SPPs), which originate from the interaction of incident photons and free electrons on the metal surface, propagate along with the metal-dielectric interface and have the potential to overcome the light diffraction limit, localization of light in subwavelength, and high level of integration capability [1][2][3]. SPPs have applications in optical devices such as switches [4,5], sensors [6][7][8][9], integrated photonic devices [10], demultiplexers [11], and filters [12,13]. One of the greatly pledging waveguide structures is the metal-insulator-metal (MIM) waveguide, which has excesses such as low bending loss, simple structure, long propagation distance, deep sub-wavelength confinements, and easy integration [14][15][16][17][18].…”

Plasmonics for Telecommunications Applications

“…In addition to plasmonic waveguides, nanoantennas, and modulators, previously discussed, plasmonic filters are deserving attention for telecommunications applications, by virtue of their ability for frequency-selective absorption/transmission of optical signals, through proper design of metallic nanostructures [164][165][166]. Importantly, plasmonic notch filters inspired in tooth-based waveguides [167][168][169] have recently been developed at THz frequency range [170,171].…”

Multiple-Mode Bowtie Cavities for Refractive Index and Glucose Sensors Working in Visible and Near-infrared Wavelength Ranges

“…with different structural configurations undergo a potential role in generating a better light-matter interaction in the MIM-cavity waveguide system [38][39][40]. Recently, several MIM waveguide with different shape of cavities has been proposed and investigated for the plasmonic sensor, such as rectangular/circular ring cavity [41], tooth-shaped cavity [42], trapezoid cavity [43], ring cavity with metal baffles [44], asymmetric double elliptic cylinders [45], Bragg grating cavity [46], fillet cavity [47], metallic nanorods in hexagonal configuration [48], stub coupled with a square cavity [49] and so forth.…”