Enhancement Of Interferometric Precision Using Fast Light

Abstract

We show that anomalous dispersion characteristic of fast-light can be used to enhance the sensitivity of optical interferometry under certain conditions. In particular, we show that a dual-chamber Fabry-Perot interferometer with a shared mirror-pair can be used in a way so that its sensitivity is increased by operating near the critically anomalous dispersion condition where the group index is much less than unity. The enhancement factor can be as high as 10 8 for realistic conditions. The process of bi-frequency pumped Raman gain in a Λ-type atomic medium can be used to achieve this effect. PACS Codes: 0.37.-a, 0.07.-a, 45.40.Cc Metrological applications deal with ultra-precision standards that require measurements using optical interferometers with extremely high sensitivity [1-4]. Recent experiments have shown that 'slow' or 'fast' group velocities in different kinds of material medium can drastically enhance the dispersion property under resonance condition [5-9]. It has been predicted that nonlinear Kerr index change of an active material in a photonic crystal based waveguide Mach-Zehnder interferometer (MZI) system can be dramatically enhanced using slow group velocity of light [10].

Demonstration of interferometer sensitivity varying as the inverse of the group index

“…2a, the EIT-affected cavity linewidth (~ 1.5 MHz) is narrower by a factor of nearly five than the cavity linewidth without dispersion. Note that this is also narrower than the empty cavity linewidth (3 MHz), as expected from the theoretical model [5].…”

“…In a recent study, we discussed a cavity-based optical gyroscope consisting of a dispersive medium, where the shift in the cavity resonance frequency due to a rotation varies inversely as the group index associated with the medium dispersion. In particular, it was shown that the sensitivity of the gyroscope is enhanced by many orders of magnitude using an intra-cavity negative dispersion with the group index approaching a null value, a condition known as the critically anomalous dispersion (CAD) [5]. We have already realized experimentally a cavity with an intra-cavity medium near the CAD condition [6].…”

Tailorable dispersion in a four-wave mixing laser

“…(1) seems to indicate that the resonance frequency has an infinite response to a cavity path-length change; however, an infinite number of round trips are required to achieve the steady state [8]. Nevertheless, a quite significant enhancement of the cavity response can theoretically be achieved, as suggested for cases of passive cavities filled with dispersive media [9,10] and cavities with actively controlled atomic dispersion [6,11]. For the passive-cavity case, there has been experimental demonstration of increasing cavity response by a factor of 5 [9].…”

Experimental constraints of using slow-light in sodium vapor for light-drag enhanced relative rotation sensing

“…Such an interferometer may use slow light induced dispersive drag for enhanced sensitivity in relative rotation sensing. In this case, the rotational fringe shift is augmented by the group index or the dispersion in the medium, which, for realistic conditions, can yield many orders of magnitude improvement in the sensitivity of the gyroscope [11].An experimental implementation of the interferometric gyroscope relies on using an EIT medium, so that the counter-rotating optical fields experience resonant dispersion along the entire optical path. A relative motion between the medium and interferometer is also needed [11].…”

“…In this case, the rotational fringe shift is augmented by the group index or the dispersion in the medium, which, for realistic conditions, can yield many orders of magnitude improvement in the sensitivity of the gyroscope [11].…”