Carrier-envelope phase detection by Quantum Interference Control of Injected Currents
Original Publication Date: 2001-Oct-10
Included in the Prior Art Database: 2005-Jun-09
National Institute of Standards and Technology
Recently there has been a dramatic breakthrough in the field of optical frequency metrology and optical clocks [1-3]. This has been based on the utilization of modelocked lasers, which produce ultrashort (- 10 fs) pulses, to produce a regularly spaced "comb" of optical frequencies. If this comb is sufficiently broad, so that is spans a factor of two in optical frequencies (an octave), it is possible to directly determine the optical frequencies of all of the comb lines by measuring two radio frequencies. These two frequencies are the repetition rate of the modelocked laser (f p) and the carrier-envelope frequency (8). Since these frequencies can be readily compared to a Cs clock, this enables determination of the absolute optical frequencies. This only requires a single modelocked laser, as opposed to the complex chain that was needed prior to this development. We call this a "self-referencing" technique. In apparently unrelated work, a group at the University of Toronto (led by professors John Sipe and Henry van Driel) have develop a method of "Quantum interference control of injected currents" (QIC) [4-6]. In this work, they have been able to demonstrate that they can induce an electrical current in a semiconductor that flows in a direction determined by the relative phases between two optical beams. One of the optical beams has a frequency that is exactly twice that of the other (i.e. they are separated by an octave). This occurs due to quantum interference between the charge carriers produced by the two individual optical beams.