Photonic crystals are artificially engineered periodic dielectric structures that manipulate the propagation of electromagnetic waves through photonic band gap formation and wave interference effects. Light localisation phenomena in such structures, including defect-mode confinement and disorder-induced localisation, have attracted strong research attention due to their applications in optical communication, sensing, and integrated photonics. Indian research groups have contributed significantly to theoretical modelling, numerical simulation, fabrication, and device-level applications of photonic crystals across microwave, terahertz, and optical regimes. This paper presents a comprehensive study of photonic crystals and light localisation phenomena with emphasis on Indian contributions, combining theoretical foundations with an applied experimental research methodology. Using a simulation-supported experimental design, the study evaluates band gap behaviour, defect-induced localisation, and transmission control. The results indicate strong field confinement and tunable localisation in defect-engineered photonic crystal structures. The discussion highlights implications for optical devices and future Indian research directions in nanophotonics.
Kumar et al. (Sun,) studied this question.