You have stated that the choice of the 10 nanometers central air-hole defect is smaller than the guided wavelength. Is this 10 an arbitrary number or a result of considering the diminishing return effects?
Thank you for your insightful question. The choice of a 110 nm (not 10 nm) central air-hole defect is not arbitrary, but rather the result of a careful optimization process that takes into account both physical principles and practical fabrication constraints.
First, the dimension is deliberately chosen to be subwavelength (i.e., smaller than the operating wavelength) to enable the slot-waveguide effect, which relies on the discontinuity of the electric displacement field at high-index-contrast interfaces. This effect becomes significant only when the low-index region is sufficiently narrow—typically on the order of tens to hundreds of nanometers—to concentrate and enhance the optical field.
Second, we considered diminishing returns in terms of optical confinement and modal loss. As the core size decreases below a certain threshold, the increase in field enhancement becomes marginal, while fabrication complexity and scattering losses rise significantly. Through systematic simulations, we found that 110 nm offers an optimal trade-off between strong field confinement and practical realizability, balancing performance with feasibility.
Thus, the selected value is both physically motivated and numerically validated, ensuring that the fiber operates effectively within the subwavelength regime while remaining manufacturable with current technology.
