Showing papers by "Michael Bass published in 2012"

AMG 386 in combination with sorafenib in patients with metastatic clear cell carcinoma of the kidney: a randomized, double-blind, placebo-controlled, phase 2 study.

Abstract: Upregulation of proangiogenic factors in response to inactivation of the von Hippel-Lindau (VHL) gene is a critical component in the development and progression of clear cell renal cell carcinoma (RCC).1 Several inhibitors of the vascular endothelial growth factor (VEGF) signaling pathway have been shown to improve outcomes in patients with metastatic RCC (mRCC).1 However, because almost all patients ultimately develop resistance to therapy, combination treatment strategies that may result in more complete angiogenesis inhibition are of interest.2 The angiopoietin-1/angiopoietin-2 and Tie2 (tyrosine kinase with immunoglobulin-like and EGF-like domains 2) receptor axis may be a legitimate target for inhibiting angiogenesis in mRCC. Preclinical studies have demonstrated that its components are regulated by VHL and are dysregulated in RCC cell lines.3 Plasma angiopoietin-2 concentrations are significantly elevated in patients with mRCC (compared with localized disease or healthy controls), and increase at the time of disease progression.4 Concurrent blockade of the angiopoietin and VEGF pathways augments inhibition of angiogenesis and tumor growth in tumor xenograft models.5 Hence, combinations of angiopoietin/Tie2 inhibitors and VEGF inhibitors might induce clinically meaningful activity. AMG 386 is an investigational recombinant peptide-Fc fusion protein that neutralizes the receptor-ligand interaction between Tie2 and angiopoietin-1/2.5 In Colo205 xenograft models, simultaneous antagonism of angiopoietin-1/2 with AMG 386 suppressed tumor growth more effectively than did selective inhibition of angiopoietin-1 or angiopoietin-2 alone.5 Interim results of a phase 1b study suggested that treatment of patients who have mRCC with sorafenib or sunitinib plus AMG 386 had an acceptable toxicity profile, distinct from that of VEGF inhibitors, and may have antitumor activity.6 We evaluated in a phase 2 study the tolerability and anti-tumor activity of AMG 386 plus sorafenib in previously untreated patients who have clear cell mRCC.

Spectral engineering of optical fiber preforms through active nanoparticle doping

Abstract: Europium doped alkaline earth fluoride [Eu:AEF2 (AE = Ca, Sr, Ba)] nanoparticles were synthesized and systematically incorporated into the core of modified chemical vapor deposition (MCVD)-derived silica-based preforms by solution doping. The resulting preforms were examined to determine the impact of the nanoparticles chemistry on the spectroscopic behavior of the glass. The dominant existence of Eu3+ was demonstrated in all preforms, which is in contrast to conventional solution doped preforms employing dissolved europium salts where Eu2+ is primarily observed. Raman spectroscopy and fluorescence lifetime measurements indicated that the nanoparticles composition is effective in controlling, at a local chemical and structural level, the spectroscopic properties of active dopants in optical fiber glasses. Further, there is a systematic and marked increase in radiative lifetime, τ, of the Eu3+ emission that follows the cationic mass; τCa < τSr < τBa with the BaF2-derived sample yielding a 37% lengthening of the lifetime over the CaF2-derived one. Such nanoscale control of what otherwise is silica glass could be useful for realizing property-enhanced and tailored spectroscopic performance from otherwise “standard” materials, e.g., vapor-derived silica, in next generation optical fibers.

Transverse mode competition in gain-guided index antiguided fiber lasers

Abstract: Single-mode laser action has been reported previously in a gain-guided, index antiguided fiber using a scalable side pumping scheme. In this paper we demonstrate the role of transverse mode competition on laser oscillation in such a fiber laser. It enables single, lowest-order mode lasing with a beam quality of M2<2 when using a combination of large fiber core radius and low output coupler reflectivity previously considered to rule out gain-guided index antiguided lasing with such beam quality. In addition, the larger core radii fibers and low output coupler reflectivity enables improved slope efficiency. Both theoretical analysis and experimental results are presented demonstrating mode competition governed lasing in a gain-guided, index antiguided fiber.

Think Outside the Fiber: Imaging Amplifier for Space-Multiplexed Optical Transmission

Abstract: This paper proposes a simple and practical method to amplify signals for space-multiplexed optical transmission. In this amplification technique, the output facet of the multicore or multimode fiber is mapped back to the same type of fiber after passing through an imaging and bulk amplifying region. Simulations are carried out for a seven-core multicore fiber with the signal lasers amplified by a bulk erbium-ytterbium-doped phosphate glass amplifier. Amplifier gain of ~20 dB is achieved at an input power of 6 mW for each individual core with an optical power conversion efficiency of 32.5%. The proposed amplifier technique does not have a core or mode count limit for multicore and multimode fibers.

Systems and methods for amplifying space-multiplexed optical signals

Abstract: In one embodiment, an optical system for amplifying space-multiplexed optical signals includes an input fiber that propagates multiple spatially-separated optical signals and a bulk amplifier formed of a doped material that receives the multiple spatially-separated optical signals and simultaneously amplifies those signals to generate multiple amplified signals.

High power fiber lasers

Abstract: This review concentrates on the progress and developments that have led to explosive growth in high power continuous wave (CW) fiber lasers over the last decade. Here we arbitrarily defined high power fiber operation as being close to a single mode in beam output with powers in the kilowatt range. This growth has largely been led by Yb fiber lasers up to now. However, in this review, we also highlight the potential for high power, high brightness operation of two alternative approaches, thulium fiber lasers that operate at 2 mm wavelength, and CW Raman fiber lasers (RFLs), which have yet to reach kW power levels.

Single mode operation of elliptical gain guided and index antiguided fibers

Abstract: Elliptical gain guiding fibers in which gain guiding effects are dominant compared to conventional index guiding fiber is analyzed by solving Mathieu equations with complex-valued fiber parameters. The properties of mode propagation and single mode operation are evaluated in this elliptical gain guiding fiber with the assumption of a uniform gain distribution in the active core medium. Threshold for lossless mode propagation increases exponentially with the eccentricity of the elliptical cross section. Further, the difference in threshold between the lowest two order modes is constant for arbitrary eccentricity.

Sub-5-pm linewidth, 130-nm-tuning of a coupled-cavity Ti:sapphire oscillator via volume Bragg grating-based feedback

Abstract: A novel coupled-cavity Ti:sapphire oscillator architecture featuring a volume Bragg grating as a feedback element is presented. The oscillator provides continuous wave lasing within a spectral linewidth as narrow as 5 pm. The output can be wavelength-tuned over an ultrabroad spectral range of 130 nm, extending from 714 to 842 nm. This unique combination of narrow spectral linewidth and wide tuning range makes the laser suitable for applications such as sensing and Raman and absorption spectroscopy. The laser also displays ideal TEM00 mode operation throughout its tuning range with output powers beyond 300 mW. Detailed studies of the cw lasing dynamics across the wide tuning range are described. The general architecture of this design can be implemented for high resolution tuning across the broad spectral emission bands of other solid state lasers with single mode operation.