Explore the magic of light

As one of the most notable innovations in the 21st century, lasers have played an indispensable role in  numerous studies and applications. What are the differences between lasers, i.e., the acronym of "light amplification by stimulated emission of radiation" and other kinds of light, such as sunlight and those from light bulbs? It takes a magic process, called stimulated emission, which was discovered and studied last century by scientists including Albert Einstein who developed the theory to explain this fascinating process leading to one of the most important inventions in the field of photonics. Different from many lights we have seen in our daily lives, a laser beam includes coherent photons that behave coherently. In other words, all the light photons within a laser beam have the same frequency, phase and direction. The highly directional and focused laser beams have been exploited for processing materials, trapping of atoms and ions, precision measurement, high-precision medical surgery, just to name a few. Lasers have also significantly influenced our daily lives, giving rise to novel devices for light sources, printing, data storage, medical treatment, etc. In this lecture, I will guide you to an excursion to experience the microscale world where the first laser was born, and the macroscale world where lasers create miracles.