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Conference on Lasers and Electro-Optics

Realization of negative dispersion without absorption

Andreas Wicht, A. Rocco, M. Muller, R.-H. Rinkleff, K. Danzmann

Published Nov 27, 2002• 0 citations
Publisher

Abstract

Summary form only given. We report on the experimental realization of negative-dispersion in nevertheless nonabsorbing media. Such media are relevant for various reasons. They may be used, for example, inside a cavity to increase its bandwidth without sacrificing its buildup (white light cavity). This could be a promising application for gravitational wave detectors. Furthermore, white-light cavities are real distance measurement devices, because residual frequency noise of the laser used to measure the cavity length does not effect the measurement.

DOI
10.1109/iqec.1998.680398

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Negative dispersion without absorption in atomic ensembles

Rocco, Alessandra

Dott. Alessandra Rocco Negative dispersion without absorption in atomic ensembles In this work the optical properties of a calcium atomic beam, strongly driven on the transition, are investigated, in order to obtain a coherently prepared medium with the right amount of negative dispersion at a point of zero absorption. From the theory it is well known that a strongly driven Two-Level system exhibits such properties. Such a medium could in particular be used to fill an optical resonator in order to obtain a broadband high finesse cavity (White Light Cavity). For the investigations a spectroscopic method had been used, consisting of a Mach-Zehnder interferometer with a phase modulated arm. In this way it is possible to perform a high sensitive simultaneous measurement of both phase shift and absorption profiles in a calcium atomic beam, for an increasing driving field, which frequency is stabilized on the transition 4s2 S0 4s4p P1 at 423nm. For the first time both absorption and phase shift were systematic investigated as function of the driving field intensity, while it was developed a new geometrical configuration for the atomic oven which permitted to reach a higher particle density in the interaction zone. It was then possible to calculate the values of derivative of phase shift and absorption at the transition frequency, where the dispersion results anomalous, having fitted the measured curves to the phase shift and absorption profiles for a strongly driven Two-Level Atom. An analysis of the evolution of the both the quantities as driving field function could be then performed. The theoretical analysis of the strongly driven two level system could then be experimentally verified, especially that the absorption decreases stronger than dispersion with an increasing driving field. It was in fact measured a decreasing of a factor 53 in the dispersion, between the not driven and driven atomic system while the corresponding absorption decreased of a factor 330, for a value of the driving field of D 2π54.4MHz. The possibility of inserting the medium inside an optical resonator to obtain a broadband high finesse cavity has also been discussed. The data analysis showed that even if the λ compensation was reachable in the achieved condition, the residual absorption was still too high to realize a White Light Cavity. The configuration for further development of the system which should allow this realization was also analyzed, together with a comparison with the performances of different atomic systems.

•Jan 1, 2001•1 citation

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We discuss bandwidth enhancement of a cavity without reducing its maximum intensity buildup in a regime where the light propagation dynamics is crucial. The enhancement relies on a frequency-dependent phase compensation via negative dispersion provided by a coherently prepared atomic medium in the cavity. We analyze the spatiotemporal dynamics in such a white-light cavity with a full simulation of the field propagation. We find that the probe field dispersion is in addition changed by a coherent field which is generated within the medium via four-wave mixing. Counterintuitively, this in-medium dynamics leads to a further enhancement of the cavity bandwidth.

arXiv:0806.2450•Physical Review A•Nov 17, 2008•23 citations
Summary form only given. We report on the experimental realization of negative-dispersion in nevertheless nonabsorbing media. Such media are relevant for various reasons. They may be used, for example, inside a cavity to increase its bandwidth without sacrificing its buildup (white light cavity). This could be a promising application for gravitational wave detectors. Furthermore, white-light cavities are real distance measurement devices, because residual frequency noise of the laser used to measure the cavity length does not effect the measurement.
Recently, the design of a white-light cavity has been proposed using negative dispersion in an intracavity medium to make the cavity resonate over a large range of frequencies and still maintain a high cavity buildup. This Letter presents the first demonstration of this effect in a free-space cavity. The negative dispersion of the intracavity medium is caused by bifrequency Raman gain in an atomic vapor cell. A significantly broad cavity response over a bandwidth greater than 20 MHz has been observed. A key application of this device would be in enhancing the sensitivity-bandwidth product of the next generation gravitational wave detectors that make use of the so-called signal-recycling mirror.
Summary form only given. We study the optical properties of negative dispersive but nevertheless transparent media. Such medium can be generated using atomic phase coherence. Theoretical studies have shown that strongly driven two level systems may exhibit the desired optical properties, that is negative dispersion of a well defined amount at a point of vanishing absorption. When this medium is placed inside an optical resonator the linewidth is increased without sacrificing its build up. We present the experimental setup which is used to realize a negative dispersive non-absorbing medium. To obtain a strongly driven two level system a calcium atomic beam is pumped at the transition 4s/sup 21/S/sub 0//spl rarr/4s4p/sup 1/P/sub 1/. The optical properties of the beam are studied.
We experimentally demonstrate that broad, tunable bandwidth of an optical ring cavity can be achieved by making use of the negative dispersion of the Kerr nonlinear refractive index in the three-level electromagnetically-induced transparency medium. For a given cavity field intensity, the white-light cavity condition can always be satisfied by choosing the appropriate coupling beam parameters. This white-light cavity scheme can be used effectively to achieve large buildup intensity in the signal-recycling cavity with a broad bandwidth in future advanced gravitational wave detectors.
Over the past 15 years, several groups have engineered media that are both strongly dispersive and roughly transparent for some finite bandwidth. Relationships and intuitive models that are satisfactory when it is reasonable to neglect dispersion may then fail. We analyze three such cases of failure. First, a simple generalization of the Abraham and Minkowski momenta to dispersive media entails multiplying each per-photon momentum by n/ngn/n_gn/ng​, where nnn is the refractive index and ngn_gng​ is the group index. The resulting forms are experimentally relevant for the case of the Abraham momentum, but not for the Minkowski momentum. We show how dispersion modulates the displacement of a sphere embedded in a dispersive medium by a pulse. Second, pulse transformation in a nonstationary medium is modulated by the presence of dispersion. Using an explicit description of the kinetics of dispersive nonstationary inhomogeneous media, we show how the group velocity can modulate pulse response to a change in the refractive index and how Doppler shifts may become large in a dispersive medium as the velocity of the Doppler shifting surface approaches the group velocity. We explain a simple way to use existing technology to either compress or decompress a given pulse, changing its bandwidth and spatial extent by several orders of magnitude while otherwise preserving its envelope shape. Finally, we note that the nature of a single optical cavity quasimode depends on intracavity dispersion. We show that the quantum field noise associated with a single cavity mode may be modulated by dispersion. For a well-chosen mode in a high-Q cavity, this can amount to either an increase or a decrease in total vacuum field energy by several orders of magnitude. We focus on the "white light cavity," showing that the quantum noise of an ideal white light cavity diverges as the cavity finesse improves.
Dott. Alessandra Rocco Negative dispersion without absorption in atomic ensembles In this work the optical properties of a calcium atomic beam, strongly driven on the transition, are investigated, in order to obtain a coherently prepared medium with the right amount of negative dispersion at a point of zero absorption. From the theory it is well known that a strongly driven Two-Level system exhibits such properties. Such a medium could in particular be used to fill an optical resonator in order to obtain a broadband high finesse cavity (White Light Cavity). For the investigations a spectroscopic method had been used, consisting of a Mach-Zehnder interferometer with a phase modulated arm. In this way it is possible to perform a high sensitive simultaneous measurement of both phase shift and absorption profiles in a calcium atomic beam, for an increasing driving field, which frequency is stabilized on the transition 4s2 S0 4s4p P1 at 423nm. For the first time both absorption and phase shift were systematic investigated as function of the driving field intensity, while it was developed a new geometrical configuration for the atomic oven which permitted to reach a higher particle density in the interaction zone. It was then possible to calculate the values of derivative of phase shift and absorption at the transition frequency, where the dispersion results anomalous, having fitted the measured curves to the phase shift and absorption profiles for a strongly driven Two-Level Atom. An analysis of the evolution of the both the quantities as driving field function could be then performed. The theoretical analysis of the strongly driven two level system could then be experimentally verified, especially that the absorption decreases stronger than dispersion with an increasing driving field. It was in fact measured a decreasing of a factor 53 in the dispersion, between the not driven and driven atomic system while the corresponding absorption decreased of a factor 330, for a value of the driving field of D 2π54.4MHz. The possibility of inserting the medium inside an optical resonator to obtain a broadband high finesse cavity has also been discussed. The data analysis showed that even if the λ compensation was reachable in the achieved condition, the residual absorption was still too high to realize a White Light Cavity. The configuration for further development of the system which should allow this realization was also analyzed, together with a comparison with the performances of different atomic systems.
We discuss bandwidth enhancement of a cavity without reducing its maximum intensity buildup in a regime where the light propagation dynamics is crucial. The enhancement relies on a frequency-dependent phase compensation via negative dispersion provided by a coherently prepared atomic medium in the cavity. We analyze the spatiotemporal dynamics in such a white-light cavity with a full simulation of the field propagation. We find that the probe field dispersion is in addition changed by a coherent field which is generated within the medium via four-wave mixing. Counterintuitively, this in-medium dynamics leads to a further enhancement of the cavity bandwidth.