Quantum-limited noise performance of a mode-locked laser diode

Low-noise operation of a 9-GHz hybridly mode-locked laser diode is demonstrated. The integrated timing jitter was 47 fs (10 Hz to 10 MHz) and 86 fs (10 Hz to 4.5 GHz), with a pulse width of 6.7 ps. The noise performance as a function of filter bandwidth and oscillator noise is also addressed.     

T-ray computed tomography

We demonstrate a tomographic imaging modality that uses pulsed terahertz (THz) radiation to probe the optical properties of three-dimensional (3D) structures in the far-infrared. This THz-wave computed tomography (T-ray CT) system provides sectional images of objects in a manner analogous to conventional CT techniques such as x-ray CT. The transmitted amplitude and phase of broadband pulses of THz radiation are measured at multiple projection angles. The filtered backprojection algorithm is then used to reconstruct the target object, including both its 3D structure and its frequency-dependent far-infrared optical properties.     

Suppression of classic and quantum radiation pressure noise by electro-optic feedback

We present theoretical results that demonstrate a new technique that can be used to improve the sensitivity of thermal noise measurements: intracavity intensity stabilization. It is demonstrated that electro-optic feedback can be used to reduce intracavity intensity fluctuations, and the consequent radiation pressure fluctuations, by a factor of 2 below the quantum-noise limit. We show that this reduction is achievable in the presence of large classic intensity fluctuations in the incident laser beam. The benefits of this scheme are a consequence of the sub-Poissonian intensity statistics of the field inside a feedback loop and the quantum nondemolition nature of radiation pressure noise as a readout system for the intracavity intensity fluctuations.     

Frequency locking a laser to an optical cavity by use of spatial mode interference

We present a novel technique to frequency lock a laser to an optical cavity. This technique, tilt locking, utilizes a misalignment of the laser with respect to the cavity to produce a nonresonant spatial mode. By observing the interference between the carrier and the spatial mode one can obtain a quantum-noise-limited frequency discriminator. Tilt locking offers a number of potential benefits over existing locking schemes, including low cost, high sensitivity, and simple implementation.     

Reactions involving fluoride ion. Part 40. Amines as initiators of fluoride ion catalysed reactions

Tetrakis(dimethylamino)ethene (TDAE) and trimethylamine react with anhydrous unsaturated fluorocarbons to produce, ‘in situ’, powerful fluoride- ion sources. These are used to initiate carbon- carbon bond forming reactions eg. oligomerisation and polyfluoroalkylation, and many of these reactions occur efficiently in the absence of a solvent.     

On the stereochemistry of photoaddition between α,β-unsaturated ketones and olefins. III.

The α,β-unsaturated ketone $\text{1}$ yields with allene the photocycloadduct $\text{3}$ predicted by our empirical photoaddition rule and the byproduct 7. The formation of this material may be rationalized by the sequence $\text{1}$ → $\text{4}$ → $\text{5}$ → $\text{6}$ → $\text{7}$. The isomeric ketone $\text{2}$ is unreactive under the same conditions, since α addition is prohibited by the rule and β addition is severely blocked.     

Electron transmission through ultra-thin insulating barriers

We propose a model to explain the exponential dependence of the electron transmission coefficient through ultra-thin (4–12 Å average thickness) evaporated films of Al₂O₃. The mechanism involves molecular pinholes in the Al₂O₃ rather than tunneling.