Structural, Spectroscopic, Linear, and Nonlinear Optical Analyses of Oxalic Acid Ammonium Dichromate Single Crystal for Photonic Applications

ABSTRACT The slow evaporation solution growth method was employed to successfully grow single crystals of oxalic acid ammonium dichromate (OAAD). x‐Ray diffraction (XRD) examination was utilized to verify the grown samples' structural integrity and crystallinity. Thorough spectroscopic analyses, such as FTIR spectroscopy and UV–vis–NIR absorption, demonstrated the presence of functional groups related to nonlinear optical (NLO) activity as well as an optical transparency window. To evaluate the material's suitability for photonic applications, linear optical metrics, including the absorption coefficient, refractive index, and optical band gap, were computed. The Kurtz–Perry powder approach was implemented to assess nonlinear optical behavior, and the results validated the efficiency of second harmonic generation (SHG), indicating a high NLO response. The effective relative second harmonic generation efficiency of OAAD is 0.93 times greater than that of the reference material KDP. The broad band gap, demonstrable SHG efficiency, and good optical transparency of OAAD crystals highlight their potential as prospective candidates for advanced photonic and optoelectronic devices.