Coherence effects in quantum optics yesterday, today and tomorrow

Summary form only given. Historically, coherence effects such as the Hanle effect, quantum beats, and coherent population trapping served to define the physics of the field. More recently, applications of phase coherent media have yielded electromagnetically induced transparency (EIT), lasers operating without population inversion (LWI), quantum noise suppression via the correlated emission laser, and ultraslow light having a group velocity of a few meters per second. In the near future, we will most likely have new physics and devices such as: ultra high precision magnetometers and gyros using phase coherent media; new kinds of spectroscopy; short wavelength lasers without inversion; new sources of IR radiation as well as new IR detectors.