Optical Waveguides with Compound Multiperiodic Grating Nanostructures for Refractive Index Sensing

Table 1

Investigated nanostructures. For all structures substrate refractive index and waveguide refractive index . is the periodicity and the duty cycle (ratio of high-index material to substrate material in one period). For the aperiodic sequences is the bit length.

	Type	Description
M	Monoperiodic	= 400 nm; = 0.5
C2	Compound multiperiodic nanostructure with two periods	= 350 nm; = 450 nm; = 3150 nm; Duty cycle combinations: = 0.1 = 0.5; = 0.2 = 0.5; = 0. = 0.5; = 0.5 = 0.5; = 0.1 = 0.22; = 0.2 = 0.22; = 0.4 = 0.22; = 0.5 = 0.22
C3a	Compound multiperiodic nanostructure with three periods	= 350 nm; = 400 nm; = 450 nm: = 25200 nm; Duty cycle combinations: = 0.1 = 0.2 = 0.33; = 0.2 = 0.2 = 0.33; = 0.4 = 0.2 = 0.33; = 0.5 = 0.2 = 0.33; = 0.1 = 0.2 = 0.22: = 0.2 = 0.2 = 0.22; = 0.4 = 0.2 = 0.22; = 0.5 = 0.2 = 0.22
C3b	Compound multiperiodic nanostructure with three periods	= 300 nm; = 400 nm; = 500 nm: = 6000 nm; Duty cycle combinations: = 0.1 = 0.2 = 0.3; = 0.3 = 0.2 = 0.3; = 0. = 0.2 = 0.3; = 0.6 = 0.2 = 0.3; = 0.1 = 0.2 = 0.2: = 0.3 = 0.2 = 0.2; = 0. = 0.2 = 0.2; = 0.6 = 0.2 = 0.2
C4	Compound multiperiodic nanostructure with four periods	= 250 nm; = 350 nm; = 400 nm; = 450 nm: = 126000 nm; = 0.2
RS	Rudin-Shapiro	Substitution AA → AAAB, AB → AABA, BA → BBAB, BB → BBBA; = 25 nm; = 128 series components; = 6375 nm supercell periodicity
ThM	Thue-Morse	Substitution A → AB, B → BA; = 50 nm; = 128 series components; = 12750 nm supercell periodicity
F	Fibonacci	Substitution A → AB, B →A; = 50 nm; = 144 series components; = 14350 nm supercell periodicity