Researchers are increasingly leveraging ultrashort light pulses in areas as diverse as high smallscale lithography and high-speed switching and communications. In fact, a simple system for attosecond pulse generation using optic devices known as multistage microring resonators has been proposed by P.P. Yupapin and S. Chaiyasoonthorn from King Mongkut's Institute of Technology (Ladkrabang, Bangkok) and N. Pornsuwancharoen from both King Mongkut's and Rajamangala University of Technology Isan (Sakonnakon, Thailand).

Essentially, a soliton light pulse with a 1550-nm wavelength feeds multistage microring resonators. There, the ring radii of the recently integrated devices ranges from 5 to 10 m. When input peak power of 12 W is applied to the system, a pulse with of 50 attoseconds is achieved.

The researchers make use of the nonlinear behavior of light traveling in a microring resonator, when a soliton pulse is entered into the nonlinear Kerr effects medium. The ring radii for the multistage microring resonators are 10, 5, and 10 m. The soliton pulse is coupled into the system with K = 0.25 0.5. The selected input pulse widths are 50 ns, 50 ps, and 50 fs with a wavelength of 1550 nm. After passing the first microring resonator, some of the optical power is coupled into the second and third ring resonators with small waveguide loss of 0.5 dB/mm reported.

The researchers demonstrated that it is feasible to generate ultrashort pulses in the range of 50 attoseconds and beyond. Because of optical-material bandwidth limitations, however, detecting such a pulse poses a problem. The critical element is thus the detection technique rather than device materials or pulse-generation approaches. See "Attosecond Pulse Generation Using The Multistage Nonlinear Mirroring Resonators," Microwave And Optical Technology Letters, December 2008, p. 3108.