Figure 1
Basic concept of the proposed time magnifier in the frequency (top) and time domain (bottom). The multiplication between the optical input signal spectrum (a) with a frequency comb realized by the transfer function of a ring resonator with an infinitely high finesse (b) results in a convolution between the input signal and a Dirac delta comb in the time domain, or an infinite number of time copies of the input signal (d). In the next step, a set of two cascaded modulators (e) enables the convolution in the frequency domain between the discrete signal spectrum (c), produced by the ring resonator and a rectangular frequency comb. In the corresponding time domain, this is the multiplication of the signal copies with a sinc pulse sequence (g). Since the free spectral range of the ring is slightly different from the repetition rate of the sequence, the signal copies are sampled at different positions. The sampling points are the integral of the sequence over the repetition rate (blue dots) and the envelope of the sampling points gives the stretched input pulse (blue dashed line).
