Mid-infrared trace gas detection using continuous-wave difference frequency generation in periodically poled RbTiOAsO4

Non-centrosymmetric sulfides A2Ba6MnSn4S16 (A = Li, Ag): syntheses, structures and properties

Li₂Ba₆MnSn₄S₁₆ and Ag₂Ba₆MnSn₄S₁₆ are synthesized for the first time. By modulating disordered sites with Mn²⁺, they not only show strong SHG responses and wide band gaps (5.1, 2.7 × AgGaS₂; 2.88, 2.76 eV), but also possess paramagnetism.

Bond-Selective Imaging of Cells by Mid-Infrared Photothermal Microscopy in High Wavenumber Region

Using a visible beam to probe the thermal effect induced by infrared absorption, mid-infrared photothermal (MIP) microscopy allows bond-selective chemical imaging at submicron spatial resolution. Current MIP microscopes cannot reach the high wavenumber region due to the limited tunability of the existing quantum cascade laser source. We extend the spectral range of MIP microscopy by difference frequency generation (DFG) from two chirped femtosecond pulses. Flexible wavelength tuning in both C-D and C-H regions was achieved with mid-infrared power up to 22.1 mW and spectral width of 29.3 cm^-1. Distribution of fatty acid in live human lung cancer cells was revealed by MIP imaging of the C-D bond at 2192 cm^-1.

[A3X][Ga3PS8] (A = K, Rb; X = Cl, Br): promising IR non-linear optical materials exhibiting concurrently strong second-harmonic generation and high laser induced damage thresholds

We have developed a new series of salt-inclusion chalcogenides, which are promising IR-NLO materials exhibiting large second-harmonic generation and high laser-induced damage thresholds.

Mid-far infrared (IR) non-linear optical (NLO) materials are of great importance in military and civil fields. However, commercial IR-NLO crystals (such as AgGaS₂, AgGaSe₂ and ZnGeP₂) do not currently satisfy the requirements of large second-harmonic generation (SHG) and high laser induced damage thresholds (LIDTs), which seriously limits their practical applications. Herein, we have developed a new series of salt-inclusion chalcogenides, [A₃X][Ga₃PS₈] (A = K, Rb; X = Cl, Br), which are constructed from alternate stacking of adamantane-like [Ga₃PS₁₀]^6– cluster layers and cationic [A₃X]²⁺ salt layers. Importantly, they display both large SHG responses of several-fold and high LIDTs for dozens of times that of commercial AgGaS₂, which exhibit the highest LIDTs among the reported IR-NLO materials with a larger SHG conversion efficiency than that of AgGaS₂. These properties together with wide transparent region, type I phase-matching features and congruent-melting behaviors indicate they are promising IR-NLO materials.

K2Sn2ZnSe6, Na2Ge2ZnSe6, and Na2In2GeSe6: a new series of quaternary selenides with intriguing structural diversity and nonlinear optical properties

New selenides K₂Sn₂ZnSe₆, Na₂Ge₂ZnSe₆, and Na₂In₂GeSe₆ exhibit diverse structures and Na₂In₂GeSe₆ possesses a moderate second harmonic generation response.

A difference frequency generation spectrometer and its detection of atmospheric N2O

The paper reports the realization and characterization of a difference frequency generation spectrometer using periodically poled lithium niobate (PPLN) crystal. The pump and signal laser we used is a Ti:sapphire ring laser and a diode pumped monolithic Nd:YAG laser, respectively. The continuous wave (cw) infrared radiation from 2.8 to 4.8 microm has been generated. The idler radiation can be used to study fundamental absorption bands of molecules and trace gas detection. In this work, we report the detection of nitrous oxide (N(2)O) in atmosphere, the minimum detectable concentration of 10.9 ppbV was achieved using a Herriott cell with the optical path length of 100 m.

Widely tunable continuous-wave mid-infrared radiation (5.5-11 microm) by difference-frequency generation in LiInS2 crystal

The first demonstration, to the best of our knowledge, of continuous-wave (cw) difference-frequency generation (DFG) in LiInS2 crystal is reported. Wide spectral coverage (5.5-11.3 microm) has been obtained with angle and wavelength tuning for type II (eoe) critically phase-matched parametric interaction. The phase-matching conditions in cw DFG have been investigated, which allowed us to improve the Sellmeier parameters by use of a two-pole dispersion equation. An effective nonlinear coefficient deff = 6.9 +/- 0.8 pm/V has been determined at approximately 7 microm relative to the well-known nonlinear coefficient d36 of AgGaS2, which yields a power-conversion efficiency of approximately 12.4 microW/(W2 cm). We evaluated the high-resolution spectral characteristics of the DFG source by recording C2H2 and SO2 spectra.