PREFACE This book deals with the optics of picosecond and femtosecond light pulses,primarily at wavelengths in the visible range and longer.Research in ultrafast optics started roughly forty years ago,and although this field is now tremendously active,in many aspects it has also reached a level of maturity.However,relatively few broad treatments of ultrafast optics are available.It is hoped that this book,which is both detailed and comprehensive,will be a valuable resource not only for graduate students and researchers seeking to enter ultrafast optics but also for colleagues already engaged in this fascinating field. I would like to mention a few pertinent points about my perspective in this book.First, in keeping with my training as an electrical engineer,the signals aspect of ultrafast optics is emphasized.That is,I often attempt to capture the detailed form of ultrashort pulses as they are transformed in various optical systems or evolve inside mode-locked lasers.Similarly, the detailed form of measurement data,as in ultrashort pulse characterization and ultrafast spectroscopy,is analyzed when possible. Second,although adetailed theoretical treatment is often presented,I strive to balance this with an experimental perspective.Accordingly,many examples of data from the literature are included,especially in the later chapters.These examples are selected to provide concrete illustration of material that otherwise might remain abstract,to provide evidence of certain important phenomena,and sometimes to illustrate applications. Third,although the suite of applications of ultrafast optics is now very rich,this book is concerned primarily with fundamental principles.No attempt is made to cover the applications space comprehensively.Two applications are covered in some depth:ultrafast spectroscopy and ultrafast electromagnetic pulse generation and measurement.Both of these are subjects of individual chapters.Certain other applications,such as the application of optical frequency combs for precision frequency metrology,are discussed briefly within appropriate sections of related text. Fourth,the book is focused on ultrafast optics in visible and lower-frequency spectral bands,on time scales down to femtoseconds,and at intensities for which perturbative non- linear optics applies.Under these conditions the motions of bound electrons that mediate xiiiPREFACE This book deals with the optics of picosecond and femtosecond light pulses, primarily at wavelengths in the visible range and longer. Research in ultrafast optics started roughly forty years ago, and although this field is now tremendously active, in many aspects it has also reached a level of maturity. However, relatively few broad treatments of ultrafast optics are available. It is hoped that this book, which is both detailed and comprehensive, will be a valuable resource not only for graduate students and researchers seeking to enter ultrafast optics but also for colleagues already engaged in this fascinating field. I would like to mention a few pertinent points about my perspective in this book. First, in keeping with my training as an electrical engineer, the signals aspect of ultrafast optics is emphasized. That is, I often attempt to capture the detailed form of ultrashort pulses as they are transformed in various optical systems or evolve inside mode-locked lasers. Similarly, the detailed form of measurement data, as in ultrashort pulse characterization and ultrafast spectroscopy, is analyzed when possible. Second, although a detailed theoretical treatment is often presented, I strive to balance this with an experimental perspective. Accordingly, many examples of data from the literature are included, especially in the later chapters. These examples are selected to provide concrete illustration of material that otherwise might remain abstract, to provide evidence of certain important phenomena, and sometimes to illustrate applications. Third, although the suite of applications of ultrafast optics is now very rich, this book is concerned primarily with fundamental principles. No attempt is made to cover the applications space comprehensively. Two applications are covered in some depth: ultrafast spectroscopy and ultrafast electromagnetic pulse generation and measurement. Both of these are subjects of individual chapters. Certain other applications, such as the application of optical frequency combs for precision frequency metrology, are discussed briefly within appropriate sections of related text. Fourth, the book is focused on ultrafast optics in visible and lower-frequency spectral bands, on time scales down to femtoseconds, and at intensities for which perturbative non￾linear optics applies. Under these conditions the motions of bound electrons that mediate xiii