Pulse Measurement Techniques for Fiber Optics

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Title: Two New Laser Pulse-Measurement Techniques for Fiber Optics: Measuring Ultraweak Ultrashort Pulses and Spatio-Temporally Complex Multi-Spatial-Mode Pulses Non-Technical Description: This project will involve developing two laser pulse-measurement techniques to solve two important unsolved problems in fiber optics and fiber lasers. The first will solve the long-standing problem of the development of an ultrasensitive pulse-measurement technique for very low-energy and relatively long laser pulses-pulses with very low intensities. Such pulses occur in essentially all telecommunications environments, but also in many other fields. The second measurement technique is for the fiber-mode-dispersion problem: different spatial modes propagate at different velocities in a fiber and so require a complete spatiotemporal light-measurement technique. The proposed technique simultaneously generates many different-color holograms on a single camera frame and will also be simple, fast, and convenient. Technical Description: Current pulse-measurement techniques must use a thin nonlinear-optical crystal, whose output scales as the square of the intensity and crystal thickness and so yields a weak output beam. The first proposed technique will instead use a very thick nonlinear-optical crystal, much longer than is possible in other techniques, in a novel manner to yield much higher efficiency. This crystal also simultaneously spectrally resolves the generated pulse. Collinear, orthogonally polarized beams and a Type II crystal will also be required. The second proposed technique generates multiple holograms simultaneously, one for each wavelength in the pulse. Because a hologram using single-wavelength light can yield the complete spatial electric field of a beam, generating many holograms, one for each wavelength, coupled with a complete measurement of the reference pulse, yields the complete spatio-spectral and spatio-temporal electric field of even complex multi-mode light. Even better, it can do so using only a single camera frame. Additional frames using additional delays between the unknown and reference pulses can extend the range to arbitrarily large delays and numbers of modes. Both techniques will be very inexpensive, compact, experimentally simple to build and use, and easily constructed from off-the-shelf components.