Chapter 1. Hot atomic vapour for photonic crystal based optical components -- Chapter 2. Highly efficient graphene-based optical components for networking applications -- Chapter 3. A Nonlinear Optical Benzil Single Crystal for Photonic applications -- Chapter 4. Highly efficient materials for photonic crystal-based optical components -- Chapter 5. Fabrication of Unidirectional Grown 1, 3, 5-Triphenylbenzene Single Crystal for Nonlinear Optical and Fast Neutron Detector Applications -- Chapter 6. Two-dimensional Photonic Crystal-based Filters Review -- Chapter 7. Photonic crystal based 2D demultiplexer for DWDM systems -- Chapter 8. Investigation of Ultra-Small Efficient Encoders and Decoders for High-Speed Optical Communication Systems -- Chapter 9. Photonic Crystal Fibers for Sensing Applications -- Chapter 10. Photonic Crystal biosensors for health care and pathologic diagnostic application -- Chapter 11. High frequency Photonic Crystal based Terahertz Antenna for Medical Applications -- Chapter 12. Role of photonics in energy crisis.