Patrick Baird

Abstract:

We report the design and characterization of an optical shutter based on a piezoelectric cantilever. Compared to conventional electro-magnetic shutters, the device has intrinsically low power and is acoustically quiet. The cantilever position is controlled by a high-voltage op-amp circuit for easy tuning of the range of travel, and mechanical slew rate, which enables a factor of 30 reduction in mechanical noise compared to a rapidly switched device. We achieve shuttering rise and fall times of 11 μs, corresponding to mechanical slew rates of 1.3 ms^-1, with a timing jitter of less than 1 μs. When used to create optical pulses, we achieve minimum pulse durations of 250 μs. The reliability of the shutter was investigated by operating continuously for one week at 10 Hz switching rate. After this period, neither the shutter delay or actuation speed had changed by a measurable amount.

Abstract:

An absolute frequency measurement has been made of the 2S 1/2- 2F 7/2 electric octupole transition in a single ion of 171Yb +. The implementation of a diode-based probe laser stabilized to this highly forbidden transition has resulted in an improvement of more than one order of magnitude upon the lowest published uncertainty. After correcting for systematic shifts, the frequency was determined to be 642 121 496 772 646.22(67) Hz. This corresponds to a fractional uncertainty of 1.0 × 10 -15. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Abstract:

The 2S1/2-8D5/2 transition in atomic hydrogen has been observed as part of the preparation for a Rydberg constant determination at the National Physical Laboratory, UK. We describe this observation and the ongoing improvements to the experimental apparatus. ©2008 Crown.