Ultrasensitive spectroscopy, the ultrastable lasers, the ultrafast lasers, and the seriously nonlinear fiber: a new alliance for physics and metrology

We now appreciate the fruit of decades of development in the independent fields of ultrasensitive spectroscopy, ultrastable lasers, ultrafast lasers, and nonlinear optics. But a new feature of the past two or three years is the explosion of interconnectedness between these fields, opening remarkable and unexpected progress in each, due to advances in the other fields. For brevity, we here focus mainly on the new possibilities in the field of optical frequency measurement.