Measurement of the binding energy of ultracold 87Rb133Cs molecules using an offset-free optical frequency comb

We report the binding energy of Rb87Cs133 molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of ∼5 kHz over an energy-level difference of more than 114THz; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of h×114268135.24(4)(3)MHz. To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule

Three-dimensional terahertz imaging using swept-frequency feedback interferometry with a quantum cascade laser

We demonstrate coherent three-dimensional terahertz imaging by frequency modulation of a quantum cascade laser in a compact and experimentally simple self-mixing scheme. Through this approach we can realize significantly faster acquisition rates compared to previous schemes employing longitudinal mechanical scanning of a sample. We achieve a depth resolution of better than 0.1 μm with a power noise spectral density below −50 dB/Hz, for a sampling time of 10 ms/pixel

Spectral broadening caused by dynamic speckle in self-mixing velocimetry sensors

Self-mixing laser sensors require few components and can be used to measure velocity. The self-mixing laser sensor consists of a laser emitting a beam focused onto a rough target that scatters the beam with some of the emission re-entering the laser cavity. This ‘self-mixing’ causes measurable interferometric modulation of the laser output power that leads to a periodic Doppler signal spectrum with a peak at a frequency proportional to the velocity of the target. Scattering of the laser emission from a rough surface also leads to a speckle effect that modulates the Doppler signal causing broadening of the signal spectrum adding uncertainty to the velocity measurement. This article analyzes the speckle effect to provide an analytic equation to predict the spectral broadening of an acquired self-mixing signal and compares the predicted broadening to experimental results. To the best of our knowledge, the model proposed in this article is the first model that has successfully predicted speckle broadening in a self-mixing velocimetry sensor in a quantitative manner. It was found that the beam spot size on the target and the target speed affect the resulting spectral broadening caused by speckle. It was also found that the broadening is only weakly dependent on target angle. The experimental broadening was consistently greater than the theoretical speckle broadening due to other effects that also contribute to the total broadening

RoSco Schematics

<p>This zip file contains the complete schematics for RoSco. RoSco - Rodent Scope - A user-configurable digital wireless telemetry system for freely behaving animals.</p

Feedback interferometry and diffuse reflectance imaging with terahertz quantum cascade lasers

We demonstrate security-relevant imaging and sensing techniques that exploit the intense coherent THz emission from quantum-cascade lasers (QCLs). Imaging and spectral discrimination (in the 3–3.4 THz range) between visibly-concealed powdered compounds is achieved through diffuse-reflectance imaging using a frequency-switchable THz QCL. Feedback-interferometry techniques are used to perform imaging and surface-profiling at 2.6 THz with no need for any external radiation detector. This coherent (homodyne) detection scheme allows THz imaging at round-trip distances of > 20 m through air, or with resolutions of ~200 μm