Distortion free, high delay-bandwidth product data buffer using fast-light based white light cavities

Yanyan Ma, Rong Wu, Longfei Li

H. Yum, M. Salit, M. S. Shahriar

We propose a distortion-free data buffering system using a fast-light based white light cavity. This system offers a breakthrough in overcoming the delay-bandwidth product constraint in dispersion-based buffers, and can be realized using optical fibers.

H. Yum, May E. Kim, Y. J. Jang +1 more

Recently, a tunable bandwidth white light cavity (WLC) was demonstrated by using an anomalously dispersive intra-cavity medium to adjust a cavity linewidth without reducing the cavity buildup factor [G.S. Pati et al., Phys. Rev. Lett. 99, 133601 (2007)]. In this paper, we show theoretically how such a WLC can be used to realize a distortion-free delay system for a data pulse. The system consists of two WLCs placed in series. Once the pulse has passed through them, the fast-light media in both WLCs are deactivated, so that each of these now acts as a very high reflectivity mirror. The data pulse bounces around between these mirrors, undergoing negligible attenuation per pass. The trapped pulse can be released by activating the fast-light medium in either WLC. Numerical simulations show that such a system can far exceed the delay-bandwidth constraint encountered in a typical data buffer employing slow light. We also show that the pulse remains virtually undistorted during the process.

H. J. Schulte, Alexander Rack

W. J. Firth

H. Yum

Techniques to control dispersion in a medium have attracted much attention due\nto potential applications to devices such as ring laser gyroscopes, interferometric\ngravitational wave detectors, data buffers, phased array radars and quantum information\nprocessors. Of particular interest is an optical resonator containing a medium with an\nanomalous dispersion corresponding to fast-light, which behaves as a White Light\nCavity (WLC). A WLC can be tailored to improve the sensitivity of sensing devices as\nwell as to realize an optical data buffering system that overcomes the delay-bandwidth\nproduct of a conventional cavity.\nThis dissertation describes techniques to tailor the dispersion for fast-light in\nintracavity media. We present first a demonstration of fast-light in a photorefractive\ncrystal. When placed inside a cavity, such a medium could be used to enhance the\nbandwidth of a gravitational wave detector. We then describe how a superluminal laser\ncan be realized by adding anomalously dispersive medium inside a ring laser. We\nidentify theoretical conditions under which the sensitivity of the resonance frequency to a change in the cavity length is enhanced by as much as seven orders of magnitude. This\npaves the way for realizing a fast-light enhanced ring laser gyroscope, for example. This\nis followed by the development of a novel data buffering system which employs two\nWLC systems in series. In this system, a data pulse can be delayed an arbitrary amount\nof time, without significant distortion. The delay time is independent of the data\nbandwidth, and is limited only by the attenuation experienced by the data pulse as it\nbounces between two high-reflectivity mirrors. Such a device would represent a\nsignificant breakthrough in overcoming the delay-time bandwidth product limitation\ninherent in conventional data buffers.\nWe then describe our experimental effort to create a fiber-based WLC by using\nstimulated Brillouin scattering (SBS). Experimental results, in agreement with our\ntheoretical model presented here, show that the WLC effect is small under the conditions\nsupported by current fiber optic technology. We conclude that future efforts to induce a\nlarge WLC effect would require fibers with high Brillouin coefficient and low\ntransmission loss, as well as optical elements with very low insertion loss and high\npower damage thresholds.