1. INTRODUCTIONWith the normal evolution of the properties of light, an optimal amount of guided light energy occurs in the form of evanescent waves which are very sensitive to changes occurring in the external environment, form a photonic band gap multilayer structure by propagating electromagnetic waves of certain wavelengths. . Electromagnetic (EM) waves with frequencies within the photonic band gaps (PBG) [1, 2] cannot propagate through the structure. Localized states can be created in PBGs by introducing defects into periodic structures. Due to their ability to control the propagation of light and the possibility of many new optical devices, PCs have recently been the subject of extensive study. If the PBG can reflect incident EM waves at any angle with any polarization, then an omnidirectional band gap (OBG) can be achieved with negligible loss in a specific frequency range [3-6]. He found that one-dimensional PCs (1DPCs) can have OBGs, and the general conditions for obtaining OBGs in 1DPCs are presented in the DIGITAL METHOD and have potential applications [7, 8], such as omnidirectional terahertz mirrors [ 9], controllable switching [10], tunable polarizer [11], narrow-band filters [12] and refractometric optical detection [13], etc. One-dimensional ternary photonic crystals (1DTPC) are also proposed to obtain the extended OBGs [11, 14-19]. 1DTPCs are made of three layers of material in one period of the network. The wavelength range of OBGs can be improved by 108 nm when the structure was modified by sandwiching a thin layer of ZrO2 between two layers demonstrated by Awasthi et al [16]. When the sandwiched layer was CeF3, the enhancement in the range was 120 nm. OBGs can be meaningful measures middle of paper. The use of a one-dimensional ternary PBG structure is not limited to improved refractive index detection, but it can be extended to improved temperature detection. by filtering the third layer of material with liquid crystals, in which changes in refractive index can be thermally induced.5. FUTURE SUGGESTIONS: The refractometric optical sensor can be used as an index sensor to detect adulteration of different materials as well as liquids or gases. It has been observed that a slight change in refractive index in the layers of material causes the detection of change in refractive index of the medium due to which it can easily differentiate the layers which are changed due to their different peaks transmission or their transmittivity. The sensitivity and manufacturing of different compounds can be improved and monitored by the application of this detection method.