RESUMEN
We demonstrate the operation of a closed-loop fast-light cavity that allows rapid (~10 ms) measurements of the cavity mode frequency and its uncertainty. We vary the scale factor by temperature tuning the atomic density of an intracavity vapor cell. The cavity remains locked even as the system passes through the critical anomalous dispersion where a pole is observed in the scale factor. Positive and negative scale-factor enhancements as large as |S| ≈70 were obtained. To our knowledge, these are the first experiments that demonstrate a scale-factor enhancement in a closed-loop fast-light device by changing the optical path length, laying the groundwork for the improvement of cavity-based metrology instruments such as optical gyroscopes.
RESUMEN
We show that the optical output of a temperature and current-tuned Fabry-Perót diode laser system, with no external optical feedback and in which the frequency is locked to Doppler-free hyperfine resonances of the 87Rb D2 line, can achieve high frequency stability and accuracy. Experimental results are presented for the spectral linewidth, frequency stability, and frequency accuracy of the source. Although our optical source is limited by a short-term spectral linewidth greater than 2 MHz, beat signal measurements from two such sources demonstrate a frequency stability of 1.1 kHz, or minimum Allan deviation of 4×10-12, at an integration time τ=15 s and with a frequency accuracy of 60 kHz at τ=300 s. We demonstrate the use of the optical source for the precision measurement of hyperfine level frequency spacings in the 5P3∕2 excited state of 87Rb and provide an accurate frequency scale for optical spectroscopy.
RESUMEN
We demonstrate for a passive optical cavity containing a dispersive atomic medium, the increase in scale factor near the critical anomalous dispersion is not cancelled by mode broadening or attenuation, resulting in an overall increase in the predicted quantum-noise-limited sensitivity. Enhancements of over two orders of magnitude are measured in the scale factor, which translates to greater than an order-of-magnitude enhancement in the predicted quantum-noise-limited measurement precision, by temperature tuning a low-pressure vapor of non-interacting atoms in a low-finesse cavity close to the critical anomalous dispersion condition. The predicted enhancement in sensitivity is confirmed through Monte-Carlo numerical simulations.
RESUMEN
We present measurements of the signal and group velocities for chirped optical pulses propagating through a GaAs cavity. The signal velocity is based on a specified signal-to-noise ratio at the detector. Under our experimental conditions, the chirp substantially modifies the group velocity of the pulse, but leaves the signal velocity unaltered. At unity transmittance, the velocities are equal. In general, when the transmittance is less than unity, the group velocity is faster than the signal velocity. While the group velocity can be negative, the signal velocity is always less than c/n, where c is the speed of light in vacuum and n is the refractive index of GaAs. To our knowledge, this is the first measurement of both the group velocity and the signal velocity in any system.
RESUMEN
We use symbolic dynamics to examine the flow of information in unidirectionally coupled chaotic oscillators exhibiting synchronization. The theory of symbolic dynamics reduces chaos to a shift map that acts on a discrete set of symbols, each of which contains information about the system state. Using this transformation we explore so-called achronal synchronization, in which the response lags or leads the drive by a fixed amount of time. We find fundamental tradeoffs between the precision to which the drive state is detected, the quality of synchronization attained, and the delay or anticipation exhibited by the response system. To illustrate these tradeoffs, we provide a physical example using electronic circuits.
RESUMEN
In this paper we report an extension to the concept of generalized synchronization for coupling different types of chaotic systems, including maps and flows. This broader viewpoint takes disparate systems to be synchronized if their information content is equivalent. We use symbolic dynamics to quantize the information produced by each system and compare the symbol sequences to establish synchronization. A general architecture is presented for drive-response coupling that detects symbols produced by a chaotic drive oscillator and encodes them in a response system using the methods of chaos control. We include experimental results demonstrating synchronization of information content in an electronic oscillator circuit driven by a logistic map.
RESUMEN
We present experimental and theoretical results on the transit time of optical pulses propagating through bulk media of finite length, specifically GaAs and silica. The transit time of the peak of the pulse varies with the central wavelength due to the étalon effects caused by the reflectivity at the air/medium boundaries. For transform limited optical pulses, the transit time as a function of wavelength follows the transmittance spectrum, that is, the longest transit time occurs at the transmittance maxima where the cavity dwell time is the longest and the shortest transit time occurs at the transmittance minima. The results are dramatically different for chirped pulses obtained by modulating the injection current of a diode laser. The range in the transit times for chirped pulses is a factor of four times larger compared with transform limited pulses. In addition, the transit time for chirped pulses propagating through the GaAs sample is negative at certain wavelengths. Also, the transmitted pulse is not distorted. Although modulating the injection current of a diode laser is the most common method for generating optical pulses, to our knowledge this is the first reported observation of the transit time of these chirped optical pulses propagating through a simple étalon structure.
