Recently, there have been significant advances in measuring and controlling the phase of ultrashort optical pulses. These developments have begun to blur the distinction between optics and electronics. In the latter it is possible to completely characterize both the amplitude and phase of the electric field by simply displaying the electrical waveform on an oscilloscope. The phase, of curse, is relative to an external clock, for example, the oscilloscope trigger signal. With increasing frequency, such complete characterization becomes increasingly difficult until one reaches optical frequencies (300-600 Thz) where fundamental physics become a roadblock to determining the phase. Detection of optical electromagnetic waves is accomplished via a square-law detector, meaning that only the intensity of the light can be observed on the resulting electrical signal. Thus any phase information of the optical wave is lost. It is, of course, possible to measure the relative phase between two different optical with the same or similar frequencies, for example the arms of an interferometer or frequency components of a chirped pulse. But this measurement does not provide any information about the absolute phase of the optical field itself. Accordingly, the phase remains an unknown quantity. For sufficiently short optical pulses, the peak of the pulse envelope itself provides a phase reference, which in turn can easily be referenced to a radio frequency clock signal. Recent progress in ultrafast optics has made it possible to control the evolution of this carrier-envelope phase and promises to yield measurement of the phase directly, thereby enabling the synthesis of electronic waveforms at optical frequencies.
Toward Optical Frequency Electronics
ultrafast, waveform synthesis
and Cundiff, S.
Toward Optical Frequency Electronics, Toward Optical Frequency Electronics
(Accessed September 30, 2023)