Optical modulational instability (MI)1 is characterized by the instability of continuous waves to amplitude perturbations at certain frequencies, which grow exponentially from noise. This effect was first observed in the nonlinear propagation of infrared light in optical fibers,2 and was characterized by THz intensity modulation. It was recently proposed and observed that MI occurs in the normal CVD region for nonlinearly coupled, orthogonally polarized waves copropagating in a birefringent fiber.3 Since MI generally builds up from noise, the MI oscillations will have random fluctuating phase (and timing) with respect to the pump from laser pulse to pulse, and therefore the use of MI as a source of THz pulse trains is difficult. In this paper visible MI oscillations, which are stable from laser pulse and adjustable from ~1-3 THz are generated in a birefringent fiber.
© 1991 Optical Society of AmericaPDF Article