M. Bellini

Tunable far infrared spectroscopy of 16O3 ozone

In this note we report the observation of 63 pure rotational lines in the spectral region 1.5-4.1 THz with Doppler-limited resolution and very high accuracy

Precise measurement of molecular dipole moments with a tunable far-infrared Stark spectrometer: application to HOCl

Stark measurement of the electric dipole moment components of H16O35Cl is performed with a tunable far-infrared spectrometer at the European Laboratory for Nonlinear Spectroscopy, Firenze, Italy. Two pure rotational transitions are analyzed, namely, the 11,1–00,0 at approximately 628 GHz and the asymmetry doublet 43,2–32,1, 43,1–32,2 at approximately 3.1 THz. The values obtained for μa and μb represent the first reported measurement of dipole moments from far-infrared transitions with an accuracy up to several parts in 104.

High sensitivity and precision spectroscopy in the far infrared

Absolute frequency determination with an accuracy of 10−9 and relative absorption sensitivity of 10−4 is obtained by the difference generation from stabilized CO2 lasers in a MIM diode (TuFIR). Applications to the detection of magnetic dipole transitions in atomic oxygen, to the LiH and LiD far infrared spectrum and to transient species like HO2 are reported. Precise measurements constitute tests for models of atoms and very light molecules and are extended to the analysis of collisional lineshapes.

Domain-Engineered Ferroelectric Crystals for Nonlinear and Quantum Optics

Nonlinear optics studies the class of phenomena occurring when an intense light field, typically from a laser source, modifies the optical properties of a transparent material in a nonlinear way. The polarization (vec{P}(vec{x},t)) of the material can be written as a power series in the field strength (vec {E}(vec{x},t)) : n n

Laboratory measurements of rotational transitions of lithium hydride in the far-infrared

vec{P}=chi^{(1)}vec{E}+chi^{(2)}vec{E}^{2}+chi^{(3)}vec{E}^{3}+cdots

Stark and Frequency Measurements in the FIR Spectrum of H2O2

n nwhere χ (i) is the i-order optical susceptibility of the material. Nonlinear phenomena arise from the nonzero value of the χ (2) susceptibility in noncentrosymmetric crystals. A large class of nonlinear materials (among them LN, KTP, BBO, and LBO) has been studied and used since 1960’s for up/down-conversion of the existing laser sources to wavelength regions which are not directly accessible otherwise. Some of these materials also belong to ferroelectrics, and this feature can be exploited to engineer the orientation of their nonlinear susceptibility. One of the earliest and most commonly used material is LiNbO3 (LN), because of its high nonlinear coefficient (d 33≈27 pm/V) and its wide transparency range from the UV to the mid IR (0.3÷5 μm). A technique giving access to d 33 in LN for optimizing nonlinear conversion processes, named quasi-phase-matching (QPM), was thought even before the first fabrication of this material. About 20 years later, the first experimental demonstration of this idea was obtained, and nowadays periodic poling of ferroelectrics crystals is a widely spread technology making these devices world-wide used and commercially available.