Figure 2 illustrates a series of monan operations applied to the amplitude envelopes of the harmonics of a sung vocal 'ah' sound.
The necessary time averages in equation (6) are easily computed making use of the orthogonality of the spherical harmonics.
On the other hand, harmonics generated in a laser-plasma interaction may offer an alternative efficient method.
However, for attosecond pulses, generation high order harmonics is implied.
A shor t analysis of the different physical mechanisms giving rise to harmonics generation is presented.
In the three figures the circular and triangular data points are relative to the 13 th and to the 5 th harmonics, respectively.
There is another possibility that may help in harmonics generation with pulses longer than 100 fs.
Even when the fundamental frequency is masked, it may be recovered from the pulse period and the surviving harmonics.
