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

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

Analysis of nanometer displacement measurement using the self-mixing technique based on VCSEL

We report that gold-coating has a significant effect on the plasmon properties of both triangular and rhombic Au-Ag nanostructure arrays. Both finite-difference time-domain and discrete dipole approximation methods are used to calculate the optical properties of the nanostructure array. We changed the thickness of the gold-coating and the refractive index of the medium surrounding the nanostructure array and obtained the maximum refractive index sensitivity. The electric field distribution of the triangular nanostructure array is also explored by a FDTD method. The calculated results show that gold-coating has a significant effect on the plasmon properties of the triangular and rhombic Au-Ag nanostructure array and the rhombic nanostructure array has a higher refractive index sensitivity than the triangular nanostructure array

Plan-view Si(111) samples for surface science and TEM studies

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