This presentation provides an overview of photonic measurement techniques and their use in isolating faults and locating defects in ICs. It covers transmission, reflectance, and absorption methods, describing key interactions and important parameters and equations. Reflectance methods discussed include electro-optical probing (EOP), electro-optical frequency modulation (EOFM), and laser-voltage imaging (LVI). Absorption methods covered include those based on the absorption of light in semiconductors, as in optical beam induced current (OBIC), light-induced voltage alteration (LIVA), and laser-assisted device alteration (LADA), and those based on absorption in metals, as in thermally induced voltage alteration (TIVA), optical beam induced resistance change (OBIRCH), and thermoelectric voltage generation or Seebeck effect imaging (SEI). The presentation also covers thermoluminescence (lock-in thermography) and electroluminescence (photon emission) measurement methods and assesses hardware security risks posed by current and emerging photonic localization techniques.