Dual-Wavelength Bad Cavity Laser as Potential Active Optical Frequency Standard

We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118℃ and 144℃, both the 1359nm and 147Ohm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127℃ Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359nm and 1470nm lasers. The 147Ohm laser linewidth is measured to be 407.3Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.

Experimental Scheme of 633 nm and 1359 nm Good-Bad Cavity Dual-Wavelength Active Optical Frequency Standard

The experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical frequency stan- dard is proposed, where He-Ne 633nm and Cs 1359nm stimulated emissions are working at good-cavity and bad-cavity regimes, respectively. The cavity length is stabilized by locking the 633nm output frequency to a super-cavity with the Pound Drever-Hall （PDH） technique. The frequency stability of 1359 nm bad-cavity stim- ulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633nm PDH system due to the suppressed cavity pulling effect of active optical clock, and the quantum limited linewidth of 1359nm output is estimated to be 72.5 mHz.

Realization of population inversion between 7S_(1/2) and 6P_(3/2) levels of cesium for four-level active optical clock

We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.

Baker's Yeast Mediated Reduction of Optically Active Diketone

Baker's Yeast mediated reduction of optically active diketone has been described.

Synthesis of optically active lactide catalyzed by nanocrystals of La-Ti composite oxides

With sol-gel method,nanometer La-Ti composite oxides were prepared.By means of atomic force microscope,the surface pattern,particle size distribution and specific surface area were studied.The newly prepared nanocrystals of La-Ti composite oxides were used as the catalysts to catalyze the dehydration of external compensated lactic acid to lactide.The lactide product was measured by polarimeter and micropolariscope.The results demonstrate that the ratio between D-lactide and L-lactide will not be equal to 1-1 if nanocrystals of La-Ti composite oxides are used as the catalysts,which implies,that nanocrystals of La-Ti composite oxides may be potential catalysts with a good selectivity.

NEW OPTICALLY ACTIVE AROMATIC POLYIMIDES Ⅱ: SYNTHESIS AND PROPERTIES OF OPTICALLY ACTIVE AROMATIC POLYIMIDE BASED ON (R)-(+)-2, 2′-BIS (2-TRIFLUORO-4-AMINOPHENOXY)-1, 1′-BINAPHTHYL

Optically active (R)-(+)-2, 2' -bis(2 -trifluoro-4 -aminophenoxy)- 1, 1' -binaphthyl was prepared from1, 1'-bi-2-naphthol. The optically active aromatic polyimide was also successfully synthesized. This newpolymer has good solubility, thermal stability etc. Its specific rotation was found to be +174°, and itschiroptical property was also studied.

SYNTHESIS OF OPTICALLY ACTIVE POLY (N-VINYLCARBAZOLE)S

The organic salts as initiators [A*B-+(-):Ph*3C+ClO4-, Ph(3)*C+SbCl6-, (-)Sp*(ClO4-)-Cl-+ and (-)(Sp)(2)*(+3)(ClO4-)(3)] and catalysts [A(+)B*(-):(+)CSA*, A*B-+*(-):Ph(3)*C+(+)CSA*(-) and (-)Sp*(+)(+)CSA*] are prepared and characterized by specific rotation. The asymmetrically stereoselective induction of the initiators and catalysts in thc polymerization of N-vinylcarbazole is in an order of A*B-+*(-) > A(+)B*(-) > A*B-+(-). The specific rotations of obtained poly(N-vinylcarbazole) (PVCZ) generally are in accordance with mentioned order.

Convenient synthesis of some optically active 1,4-benzodiazepin-2,5-diones

Isatoic anhydride was reacted with several L-amino acids to give the corresponding （2S）-N-（o-aminobenzoyl）-2-alkylaminoacetic acids. The latter compounds were treated with phosphoryl chloride under reflux temperature to afford the cyclized products, （3S）-3-alkyl-3,4-dihydro- 1 H- 1,4-benzodiazepin-2,5-diones. 2007 M. Bakavoli. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Attempt to Resolute Chiral Clusters by Optically Active Hydrazide

A new kind of hydrazone (I) diastereoisomers was prepared with enantiomeric hydazide (II) and chiral cluster (III), which was characterized by HMBC. Unfortunately, the mixture could not be separated into pure diastereoisomer. This could be a direction to separate the racemic chiral clusters.

STUDY ON METHANOLYSIS STABILITY OF OPTICALLY ACTIVE COPOLYMERS OF TRIPHENYLMETHYL METHACRYLATE AND METHYL METHACRYLATE

The methanolysis of poly(triphenylmethyl methacrylate) (PTrMA) and its copolymers P(TrMA-co-MMA), P(TrMA-b-MMA) has been studied in the presence of anhydrous methanol at 40 degrees C by electroconductometric method. It has been found that the methanolysis stability can be obviously improved for the copolymer, especially, the radom copolymer, P(TrMA-co-MMA).

Optically Active Alcohols: Resolution and Synthesis from Asymmetric Reduction of Prochiral Ketones

The recent methods of resolution, enantiomeric excess determination and synthesis of optically active alcohols from asymmetric reduction of prochiral ketones are reviewed in the article with references. Important functions and applications of optically active alcohols in biological and chemical research area are described in an introduction part. The following part deals with resolution and enantiomeric excess determination of racemic alcohols. The next part discusses asymmetric reduction of prochiral ketone and related compounds, which including: (a) Reduction by chirally modified aluminum and boron hydrides; (b) Catalytic reduction with chiral transition metal complexes; (c) Enantioselective reduction by hydride transfer from carbon; (d) Biocatalytic reduction; (e) Asymmetric synthesis of chiral nonracemic alcohols with help of physical methods. A conclusion about optically active alcohols from asymmetric reduction of ketones followes in the final part of article.

Synthesis of Methylated β-Cyclodextrins Derived Optically Active Poly(N-diphenylmethyl maleimide)

The methylated β-cyclodextrins derived optically active polymers are firs synthesized through asymmetric polymerization of N-diphenylmethyl maleimide with lithium salt of heptakis(2,6-O-dimethyl) β-cyclodextrin (DM-β-CD) as an initiator. The resulting polymers show negative specific rotation which is opposite in sign to that of DM-β-CD. The asymmetric induction is further confirmed by circular dichroism. The structure is characterized by IR and NMR spectroscopies

OPTICALLY ACTIVE COPOLYESTERS BASED ON AXIALLY DISSYMMETRIC 1,1’-BINAPHTHALENE-2,2’-DIYL UNITS

Optically active copolyesters based on axially dissymmetric 1,1'-binaphthalene-2,2'-diyl units have been preparedand characterized by specific rotation, ^(13)C-NMR and CD spectra. The results show that the rotation signs of tribasiccopolyesters or the mixture of corresponding homopolyesters obey a three dimensional quadrant pattern. The composition ofthe copolyesters was determined from ^(13)C-NMR spectra to be triad sequence distributions and corresponding with the ratioby feed.

Resolution of 3,3'-Dioxo-1,1'(3H,3(H)spirobi[isobenzofuran] -5,6,5'6'-tetracarboxylic acid and Optically active Polyimides thereof

3,3`-Dioxo-1,1'(3H,3'H)spirobi[isobenzofuran]-5,6,5',6'-tetracarboxylic acid 1 was resolved successfully and the corresponding optically active polyimides PI were synthesized. The properties of the optically active PI and the racemic one were investigated. The results showed that the specific rotation of (-)-PI was about two times to that of the (+)-PI, and the regularity of the optically active PI was higher than that of the racemic one.

RAPID SYNTHESIS OF NOVEL OPTICALLY ACTIVE POLY(AMIDE-IMIDE)S DERIVED FROM N,N'-(PYROMELLITOYL)-BIS-L-ALANINE DIACID CHLORIDE AND HYDANTOIN DERIVATIVES UNDER MICROWAVE IRRADIATION

Eight novel poly(amide-imide)s were synthesized under microwave irradiation by using a domestic microwaveoven from the polycondensation reactions of N.N'-(pyromellitoyl)-bis-L-alanine diacid chloride(1)with eight differentderivatives of hydantoin compounds(2a-h)in the presence of a small amount of a polar organic medium such as o-cresol.The polycondensation proceeded rapidly,compared with the conventional solution polycondensation and was completedwithin 8-10 min,producing a series of new poly(amide-imide)s(3a-h)with inherent viscosities about 0.35-0.68 dL/g inhigh yields.The obtained PAIs(3a-h)were fully characterized by means of FT-IR spectroscopy,elemental analyses,inherentviscosity(ηinh),solubility and specific rotation measurements.All of the resulting polymers show optical rotation and areoptically active.Thermal properties of the poly(amide-imide)s were investigated by using thermal gravimetric analysis(TGA).

A SIMPLE AND CONVENIENT ROUTE FOR PREPARATION OF OPTICALLY ACTIVE BICYCLOLACTONES

Optically active bicyclolactones 4 were prepared via a new simple route.

Synthesis of optically active polymers bearing amino acid moieties by atom transfer radical polymerization

We report here an approach toward the synthesis of optically active polyacrylamide bearing amino acid moieties, poly[Nmethacryloyl L-leucine methyl ester] （PMALM）, with controlled average number molecular weight （Mn） and relatively narrow polydispersity index （PDI, Mw/Mn 〈 1.3） by atom transfer radical polymerization （ATRP） using initiating system methyl 2-bromopropionate/CuBr/tris（2-dimethylaminoethyl） amine. The optical properties of the resulting polymers were evaluated from specific optical rotation value and CD spectra.