Generation Of Ultra-Stable Signal Twins And Idler Twins By Coupled Optical Parametric Oscillators: Applications In Remote Sensing

We will summarize the progress made on investigation of coupled optical parametric oscillators using a single pair of nonlinear-optical crystals forming the twins. A single signal is split into signal twins whereas a single idler is split into two idler twins. Such twins are ultra-stable since their frequency difference is insensitive to the change of the pump wavelength and temperature fluctuation. It exhibits the inverse proportionality of the frequency separation on the length of each of the crystals and difference of the group indices of the signal and idler waves. What is unique about such coupled optical parametric oscillators lies in the fact that the frequency separation can be scaled to a few 100 GHz from a few THz by using just a single pair of the twins. Such a significant reduction opens up novel applications of such coupled optical parametric oscillators in remote sensing by heterodyning the output beams generated by the ultrastable twins in a photodiode.