2.09†µm high-gain, high-energy sub-nanosecond laser amplification system and its application to a millijoule-level mid-infrared ZnGeP2 optical parametric generator.

In this Letter, we report for the first time to our knowledge a 2 mJ-level 2.09 µm Ho:YAG regenerative amplifier (RA) seeded by the first-stage Ho-doped fiber (HDF) preamplifier of a gain-switched laser diode (GSLD). After the single-pass power amplifier (SPPA), the output of a 2.09 µm pulse laser with 1 kHz, 570 ps, and >10 mJ was achieved. The overall gain of the whole amplifier system was greater than 90 dB, providing a novel, stable, and reliable sub-nanosecond (sub-ns) pump source operating at a pulse repetition frequency (PRF) of 1 kHz for an optical parametric generator (OPG) based on ZnGeP2 (ZGP). Specifically, for the ZGP OPG structure, a maximum pulse energy of 1.82 mJ at 3-5 µm had been achieved with an injected pump pulse energy of 5.47 mJ, corresponding to a slope efficiency of 39.5% and an optical-to-optical conversion efficiency (OOCE) of 33.27%.

Narrowband mid-infrared optical parametric generator based on a type-II BaGa4Se7 crystal.

In this Letter, we first reported on a mid-infrared double-pass optical parametric generator (OPG) based on a single type-II phase-matching BaGa4Se7 (BGSe) crystal, pumped at 2.1 µm. The OPG achieved a maximum pulse energy of 55 µJ for generating narrowband mid-infrared laser pulses. The signal and idler lights exhibited center wavelengths of 4.04 and 4.33 µm, respectively, with bandwidths of 18.6 nm (11.4 cm-1) and 20.4 nm (10.9 cm-1). To improve the output performance, we utilized a cascaded scheme of type-I ZnGeP2 (ZGP) and type-II BGSe crystals. The spectral bandwidths of the signal and idler lights, nearing 4 µm, were narrower than 170 nm (90 cm-1), representing a significant improvement over the ZGP OPG. The cascaded OPG achieved a remarkable total optical-to-optical conversion efficiency (OOCE) of 14.9% and a maximum pulse energy of 0.329 mJ.

Influence of ambient temperature on an Yb:YAG disk laser with anti-Stokes fluorescence cooling.

In general, the operating characteristics of solid-state lasers are significantly impacted by the ambient temperature, especially for Yb:YAG crystal with an anti-Stokes fluorescence cooling effect. In this Letter, the influence of the ambient temperature on the operating characteristics at the zero thermal load (ZTL) state is studied for an Yb:YAG disk crystal with a 1030 nm intra-cavity-pumped scheme. Theoretical analysis indicates that the output power of the laser at the ZTL state is significantly enhanced as the ambient temperature increases. Experimental results show that when the ambient temperature increases to 40°C, the output power of the laser at the ZTL state can reach 1.11 W, which is more than twice than that achieved at an ambient temperature of 25.5°C. This Letter provides a technical pathway for achieving a higher-power radiation-balanced laser (RBL).

Parallel beam splitting and controlling system based on cascaded acousto-optic modulators.

In recent years, ultrashort pulse lasers (lasers) have been already widely used for providing excellent laser machining quality for the electronics industry, replication tools, and other applications. However, the major drawback of this processing is low efficiency, especially for a large number of laser ablation demands. In this paper, a beam-splitting approach based on cascaded acousto-optic modulators (AOMs) is proposed and analyzed in detail. The cascaded AOMs can split a laser beam into several beamlets with the same propagation direction. These beamlets can be switched on and off individually, and the beam pitch can be changed independently. At the same time, the experimental setup of three cascaded AOM beam splittings is built up to verify the capability of the high-speed control (switching rate:1 MHz), high-energy utilization rate (>96% at three AOMs), and high-energy splitting uniformity (nonuniformity: 3.3%). This scalable approach enables the processing of arbitrary surface structures with high quality and efficiency.

Diaminocyclobutenediones as potent and orally bioavailable CXCR2 receptor antagonists: SAR in the phenolic amide region.

A series of potent and orally bioavailable 3,4-diaminocyclobutenediones with various amide modifications and substitution on the left side phenyl ring were prepared and found to show significant inhibitory activities towards both CXCR2 and CXCR1 receptors.

Synthesis and structure-activity relationships of heteroaryl substituted-3,4-diamino-3-cyclobut-3-ene-1,2-dione CXCR2/CXCR1 receptor antagonists.

Comprehensive SAR studies were undertaken in the 3,4-diaminocyclobut-3-ene-1,2-dione class of CXCR2/CXCR1 receptor antagonists to explore the role of the heterocycle on chemokine receptor binding affinities, functional activity, as well as oral exposure in rat. The nature of the heterocycle as well as the requisite substitution pattern around the heterocycle was shown to have a dramatic effect on the overall biological profile of this class of compounds. The furyl class, particularly the 4-halo adducts, was found to possess superior binding affinities for both the CXCR2 and CXCR1 receptors, functional activity, as well as oral exposure in rat versus other heterocyclic derivatives.

Stereoselective synthesis of L-oliose trisaccharide via iterative alkynol cycloisomerization and acid-catalyzed glycosylation.

[formula: see text] The synthesis of an all-alpha L-oliose diastereomer of digitoxin provides valuable insights into the generality and protective-group dependence of acid-catalyzed glycosylations of glycals to 2-deoxycarbohydrates.