Acylation of Meldrum’s acid with arylacetic acid imidazolides as a convenient method for the synthesis of 4-aryl-3-oxobutanoates

C-Acylation of Meldrum’s acid by (het)arylacetic acids in ethanol in the presence of 1,1′-carbonyldiimidazole leads to ethyl 4-(het)aryl-3-oxobutanoates in high yields.     

Fluorescence modulation of eosin Y in a PMMA film by diarylethene switching

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Measurement of Dispersion Characteristics of Integrated Optical Microresonators and Generation of Coherent Optical Frequency Combs

Journal of Experimental and Theoretical Physics - Optical frequency combs are a unique tool for fundamental metrology, spectroscopy, and a broad spectrum of applications. High-Q microresonators...     

Fabrication of quasi-optical selective elements for the terahertz range in the form of pseudometallic structures via deep X-ray lithography

A technique for fabricating self-bearing pseudometallic structures, which hold promise for utilization as quasi-optical frequency-selective elements in the terahertz range of the electromagnetic spectrum, is discussed. The technique is based on microstructuring a continuous dielectric layer via stencilled X-ray lithography involving synchrotron radiation with subsequent metallization of the entire structure surface. The main manufacturing schemes are described, including fabrication of the initial substrates and X-ray masks. Examples of samples of the produced selective elements, such as frequency filters and flat lenses, as well as their operating characteristics, are presented.     

Generation of Optical Frequency Combs in an Optical Microresonator Pumped by a 780-nm Laser Diode in Self-Injection Locking Regime

Journal of Experimental and Theoretical Physics - Experimental data for the generation of optical frequency combs in magnesium fluoride microcavities with whispering gallery modes at 780 nm are...     

Pinacol rearrangement of cyclopent-3-en-1,2-diols: Cyclopentenone formation and interrupting reaction

Cyclopentenyl carbocations formed as a result of the protonation of 3,4-substituted cyclopent-3-en-1,2-diols can give either cyclopent-2-en-1-one derivatives via pinacol rearrangement or interrupted reaction products similar to the Nazarov intermediate.     

New thermally stable photochromic di(het)arylethenes of the cyclopentenone series

Oxidation of 2,3-diarylcyclopent-2-en-1-ones with m-chloroperoxybenzoic acid gave new thermally stable sulfone derivatives of photochromic diarylethenes. The spectral properties of the compounds obtained (the wavelengths of the maxima of the absorption bands of their initial and cyclic forms, the quantum yields of photocyclization and photobleaching reactions) as well as their thermal stability and fatigue resistance were examined. The relationship between the structures of the synthesized compounds and their photochromic properties was determined. The energy differences between the ground-state molecules of the starting and photoinduced isomers of 2,3-diarylcyclopent-2-en-1-ones were calculated by the DFT/B3LYP1 method with the 6-31G(d) basis set. The calculated energy differences can be used to predict and explain such spectral characteristics of photochromic diarylethenes as the thermal stability of photoinduced isomers and the quantum yields of cycloreversion reactions.     

Recent advances in laser self-injection locking to high-Q microresonators

The stabilization and manipulation of laser frequency by means of an external cavity are nearly ubiquitously used in fundamental research and laser applications. While most of the laser light transmits through the cavity, in the presence of some back-scattered light from the cavity to the laser, the self-injection locking effect can take place, which locks the laser emission frequency to the cavity mode of similar frequency. The self-injection locking leads to dramatic reduction of laser linewidth and noise. Using this approach, a common semiconductor laser locked to an ultrahigh-Q microresonator can obtain sub-Hertz linewidth, on par with state-of-the-art fiber lasers. Therefore it paves the way to manufacture high-performance semiconductor lasers with reduced footprint and cost. Moreover, with high laser power, the optical nonlinearity of the microresonator drastically changes the laser dynamics, offering routes for simultaneous pulse and frequency comb generation in the same microresonator. Particularly, integrated photonics technology, enabling components fabricated via semiconductor CMOS process, has brought increasing and extending interest to laser manufacturing using this method. In this article, we present a comprehensive tutorial on analytical and numerical methods of laser self-injection locking, as well a review of most recent theoretical and experimental achievements.