Albert Einstein's significant contributions to optics and photonics extend beyond the photoelectric effect, including his formulation of the A and B coefficients, which are fundamental to laser theory. He introduced the concept of quantized energy in the electromagnetic radiation field, building on Max Planck's work, and provided a framework for understanding spontaneous and stimulated emission. The constancy of the speed of light, while initially an educated guess rather than a well-established fact, became a cornerstone of his theory of relativity. Einstein's insights into the nature of light and its interaction with matter were pivotal in advancing quantum mechanics. Overall, his work laid essential groundwork for modern photonics.
