Interferometric measurement of the resonant absorption and refractive index in rubidium gas

We present a laboratory demonstration of the Kramers-Kronig relation between the resonant absorption and refractive index in rubidium gas. Our experiment uses a rubidium vapor cell in one arm of a simple Mach-Zehnder interferometer. As the laser frequency is scanned over an atomic resonance, the interferometer output is affected by variations of both the absorption and refractive index of the gas with frequency, all of which can be calculated in a straightforward manner. Changing the vapor density and interferometer phase produces a family of different output signals. The experiment was performed using a commercially available tunable diode laser system that was designed specifically for the undergraduate physics laboratory. As a teaching tool this experiment is reliable, fun, and instructive, while it also introduces the student to some sophisticated and fundamental physical concepts

Response to "Comment on 'A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy"' [Rev. Sci. Instrum. 80, 126107 (2009)]

The preceding comment by Sloman points out that the absolute accuracy of a temperature controller may be compromised by thermistor self-heating. We measured the self-heating of the thermistor used in our temperature controller, verifying a systematic error of nearly 200 mK. However, this error is reduced by over an order of magnitude with a slight change in our original circuit design. With this change, our controller does achieve an absolute temperature accuracy of 100 mK, limited mainly by the stated absolute accuracy of the thermistor used in the circuit

A versatile thermoelectric temperature controller with 10 mK reproducibility and 100 mK absolute accuracy

We describe a general-purpose thermoelectric temperature controller with 1 mK stability, 10 mK reproducibility, and 100 mK absolute accuracy near room temperature. The controller design is relatively simple and could be readily modified for use in different experimental circumstances. We also describe a time-domain numerical model that allows one to characterize the stability and transient behavior of the system being controlled, even in the presence of elements with highly nonlinear responses

A Dual Diffusion Chamber for Observing Ice Crystal Growth on c-Axis Ice Needles

We describe a dual diffusion chamber for observing ice crystal growth from water vapor in air as a function of temperature and supersaturation. In the first diffusion chamber, thin c-axis ice needles with tip radii ~100 nm are grown to lengths of ~2 mm. The needle crystals are then transported to a second diffusion chamber where the temperature and supersaturation can be independently controlled. By creating a linear temperature gradient in the second chamber, convection currents are suppressed and the supersaturation can be modeled with high accuracy. The c-axis needle crystals provide a unique starting geometry compared with other experiments, and the dual diffusion chamber allows rapid quantitative observations of ice growth behavior over a wide range of environmental conditions

Practical considerations for the generation of large-order spherical harmonics

Techniques for generating large-order Y^m_l(θ, ϕ) are discussed