K. Kuan

Fifty percent internal slope efficiency femtosecond direct-written Tm³⁺:ZBLAN waveguide laser.

We report a 790 nm pumped, Tm³⁺ doped ZBLAN glass buried waveguide laser that produces 47 mW at 1880 nm, with a 50% internal slope efficiency and an M² of 1.7. The waveguide cladding is defined by two overlapping rings created by femtosecond direct-writing of the glass, which results in the formation of a tubular depressed-index-cladding structure, and the laser resonator is defined by external dielectric mirrors. This is, to the best of our knowledge, the most efficient laser created in a glass host via femtosecond waveguide writing.

Extruded tellurite glass and fibers with low OH content for mid-infrared applications

Reducing the hydroxyl group content in tellurite glass fibers is essential to exploit the intrinsic mid-infrared transparency of tellurite glass for optical fiber devices. We report the first extruded tellurite glass fibers with low hydroxyl (OH) group content using dry atmosphere for glass melting. For small melt volumes, optimized melting conditions have been identified that enable the absorption at the OH peak at 3.3 µm to be reduced by more than an order of magnitude compared with glasses melted in open air. Annealing and dehydration of tellurite glass in open air was found not to change the OH content. The loss of optical fibers drawn from extruded rods was reduced from ~20 dB/m at 2.0 µm for glass melted in open air to 0.8 dB/m for glass melted in dry atmosphere.

Diamond in tellurite glass: a new medium for quantum information.

M. R. Henderson, B. C. Gibson, H. Ebendorff-Heidepriem, K. Kuan , S. Afshar V., J. O. Orwa, I. Aharonovich ,S. Tomljenovic-Hanic, A. D. Greentree, S. Prawer, and T. M. Monro

5-benzylidenerhodanine and 5-benzylidene-2-4-thiazolidinedione based antibacterials.

Herein we outline the antibacterial activity of amino acid containing thiazolidinediones and rhodanines against Gram-positive bacteria Staphylococcus aureus ATCC 31890, Staphylococcus epidermidis and Bacillus subtilis ATCC 6633. The rhodanine derivatives were generally more active than the analogous thiazolidinediones. Compounds of series 5 showed some selectivity for Bacillus subtilis ATCC 6633, the extent of which is enhanced by the inclusion of a non-polar amino acid at the 5-position of the core thiazolidinediones and rhodanines scaffolds. SAR data of series 8 demonstrated improved activity against the clinically more significant Staphylococci with selectivity over Bacillus subtilis ATCC 6633 induced by introduction of a bulky aryl substituent at the 5-position of the core scaffolds.

Total Synthesis and Structure Revision of (−)-Siphonodictyal B and Its Biomimetic Conversion into (+)-Liphagal

The structure of siphonodictyal B has been reassigned on the basis of the total synthesis of both possible C-8 epimers. The revised structure of siphonodictyal B was converted into liphagal by acid catalyzed rearrangement of a proposed epoxide intermediate. This biomimetic cascade features a succession of four distinct reactions (epoxidation, o-quinone methide formation, ring expansion, and benzofuran formation) that occur in a one-pot operation under mild conditions. During these studies we also isolated a surprisingly stable o-quinone methide that supports our mechanistic proposal for liphagal biosynthesis.

Synthesis of a Liphagal–Frondosin C Hybrid and Speculation on the Biosynthesis of the Frondosins

A hypothesis for the biosynthesis of the frondosins A-E is presented. Synthesis of a liphagal-frondosin C hybrid molecule has been achieved, with the frondosin C 6-7-5-6 ring system being constructed by a photochemical process that follows an intramolecular Paternò-Büchi reaction/fragmentation pathway.

A Biomimetic Synthetic Approach to the Frondosins

The frondosins are a family of five marine sponge-derived meroterpenoids. We propose that the 6–7 ring system common to each of the frondosins is biosynthesized via ring expansion of a 6–6 ring system. Compelling evidence in favour of this proposal was obtained in the form of a biomimetic synthesis of the frondosin 6–7 ring system, which features a highly stereo- and regio-selective ring expansion cascade reaction as the key step.

Diamond in glass, a new platform for quantum photonics

Diamond color centers represent one of the most important frontiers for room-temperature solid-state quantum devices. Here we show the incorporation of fluorescent diamond nanoparticles into tellurite glass optical fibers. This system offers a new platform for quantum sensing and robust single photon collection and distribution.

Towards hybrid diamond optical devices

Diamond is emerging as an optical supermaterial, due to its wide transparency bandwidth, excellent thermooptic properties and most notably its stable, large dipole moment, room temperature, single photon emitting colour centres. In this paper we present recent progress in the characterization of non radiative and radiative decay in single impurities and the fabrication of hybrid diamond-tellurite optical structures‥ First, we present direct imaging of the emission pattern of individual ion implanted chromium-based single photon emitters in diamond and measure their quantum efficiency. By comparing the decay rates from the single chromium emitters at different depths in the diamond crystal, we measured an average quantum efficiency of 28%. Second, a hybrid approach involving a soft glass tellurite host material has been introduced, allowing nitrogen-vacancy (NV-) diamond emitters to be built into an optical fibre. The potential of integrating Cr-related centres in hybrid optical structures is also discussed.

A 40% slope efficiency 790nm pumped 1.9µm Tm 3+ : ZBLAN directly-written waveguide laser

The short to mid-infrared spectral regions are key to many applications that require low-cost and spectrally selective sources of coherent radiation. To name a few applications, they range from trace gas spectroscopy to process control, environmental safety monitoring, and testing of infrared countermeasure systems.