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We present a comprehensive study of dual optical parametric oscillation (OPO) within one cavity, which is commonly used as the pump source of terahertz (THz) wave difference frequency generation (DFG). The growth of two output wavelengths with the OPO input energy is not synchronized, due to the competition. This phenomenon is analyzed experimentally and theoretically, to our knowledge, for the first time. A two-stage growth of the product of dual-wavelengths’ energies (also the output of THz-DFG) is predicted: first as a line and later as a parabola. With a homemade organic crystal, monochromatic THz-DFG is achieved under the pump of this dual-OPO. A tuning range up to 30 THz and a highest signal-to-noise ratio of 600:1 (27.8 dB) are obtained at room temperature.

Ring‐opening copolymerization (ROCP) of L‐lactide (L‐LA) and (3S)‐benzyloxymethyl‐(6S)‐methyl‐morpholine‐2,5‐dione [(3S, 6S)‐BMMD] initiated by creatinine acetate, a biogenic organic compound, was performed in the bulk at 130 °C. The copolymerization was well controlled as evidenced by that both the measured values of number‐average molecular weight (Mn,NMR(OH) and Mn,NMR(COOH)) and serine molar fraction (FBz.ser) of synthesized copolymers were close to the corresponding theoretical values; and that the higher isotacticity of synthesized copolymers (85–86%) and lower racemization degree of the ROCP. After removing O‐benzyls of the copolymers with Et3SiH/Et3N/CH2Cl2 under catalysis of PdCl2, functional biodegradable copolymers of L‐lactic acid (L‐Lac) and L‐Ser with designed molar fraction of serine (Fser 1.35%, 3.57%, 5.41%), narrow molecular weight distribution (polydispersity index 1.10–1.36), and improved hydrophilicity (θstat 82.3–89.6°) were finally obtained. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A novel microgel-supported acylating reagent (MGAR) was prepared by combining ring-opening metathesis polymerization (ROMP) and Activators Re-Generated by Electron Transfer for Atom Transfer Radical Polymerization (ARGET ATRP): (1) synthesis of an ATRP macroinitiator 3 by living ROMP of oxanorbornene-based activated ester 1, derived from N-hydroxysuccinimide, using the Grubbs initiator RuCl(2)(PCy(3))(2)(=CHPh) and (Z)-but-2-ene-1,4-diyl bis(2-bromopropanoate) (BDBP) as a terminating agent; (2) synthesis of MGAR 4 by ARGET ATRP of styrene (S) and divinylbenzene (DVB) using the prepared macroinitiator 3, a CuCl(2)/Me(6)TREN (tris[2-(dimethylamino)ethyl]amine) catalyst system, a Sn(Oct)(2) [tin(II)2-ethylhexanoate] reducing agent. The synthesized microgels 4 exhibit excellent acyl (acetyl, benzoyl, phenylsulfonyl) transfer properties for primary and secondary amines (n-BuNH(2), Et(2)NH, morpholine, etc.) under mild conditions (25 degrees C, 13.5-14 h) affording N-acylamines with high yield (95.6-100%) and purity (94.1-96.0%).

The optical-induced dielectric tunability properties of DAST crystal in THz range were experimentally demonstrated. The DAST crystal was grown by the spontaneous nucleation method (SNM) and characterized by infrared spectrum. With the optimum wavelength of the exciting optical field, the transmission spectra of the DAST crystal excited by 532 nm laser under different power were measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. The transmitted THz intensity reduction of 26 % was obtained at 0.68 THz when the optical field was up to 80 mW. Meanwhile, the variation of refractive index showed an approximate quadratic behavior with the exciting optical field, which was related to the internal space charge field of photorefractive phenomenon in the DAST crystal caused by the photogenerated carrier. A significant enhancement of 13.7 % for THz absorption coefficient occurred at 0.68 THz due to the photogenerated carrier absorption effect in the DAST crystal.