Active polarisation control of a quantum cascade laser using tuneable birefringence in waveguides.

We discuss the design, modelling, fabrication and characterisation of an integrated tuneable birefringent waveguide for quantum cascade lasers. We have fabricated quantum cascade lasers operating at wavelengths around 4450 nm that include polarisation mode converters and a differential phase shift section. We employed below laser threshold electroluminescence to investigate the single pass operation of the integrated device. We use a theory based on the electro-optic properties of birefringence in quantum cascade laser waveguides combined with a Jones matrix based description to gain an understanding of the electroluminescence results. With the quantum cascade lasers operating above threshold we demonstrated polarisation control of the output.

A surface-patterned chip as a strong source of ultracold atoms for quantum technologies.

Laser-cooled atoms are central to modern precision measurements. They are also increasingly important as an enabling technology for experimental cavity quantum electrodynamics, quantum information processing and matter-wave interferometry. Although significant progress has been made in miniaturizing atomic metrological devices, these are limited in accuracy by their use of hot atomic ensembles and buffer gases. Advances have also been made in producing portable apparatus that benefits from the advantages of atoms in the microkelvin regime. However, simplifying atomic cooling and loading using microfabrication technology has proved difficult. In this Letter we address this problem, realizing an atom chip that enables the integration of laser cooling and trapping into a compact apparatus. Our source delivers ten thousand times more atoms than previous magneto-optical traps with microfabricated optics and, for the first time, can reach sub-Doppler temperatures. Moreover, the same chip design offers a simple way to form stable optical lattices. These features, combined with simplicity of fabrication and ease of operation, make these new traps a key advance in the development of cold-atom technology for high-accuracy, portable measurement devices.

Quantum cascade lasers with an integrated polarization mode converter.

We discuss the design, fabrication and characterization of waveguide polarization mode converters for quantum cascade lasers operating at 4.6 µm. We have fabricated a quantum cascade laser with integrated polarization mode converter that emits light of 69% Transverse Electrical (TE) polarization from one facet and 100% Transverse Magnetic (TM) polarization from the other facet.

In vivo selection of autologous MGMT gene-modified cells following reduced-intensity conditioning with BCNU and temozolomide in the dog model.

Chemotherapy with 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) and temozolomide (TMZ) is commonly used for the treatment of glioblastoma multiforme (GBM) and other cancers. In preparation for a clinical gene therapy study in patients with glioblastoma, we wished to study whether these reagents could be used as a reduced-intensity conditioning regimen for autologous transplantation of gene-modified cells. We used an MGMT(P140K)-expressing lentivirus vector to modify dog CD34(+) cells and tested in four dogs whether these autologous cells engraft and provide chemoprotection after transplantation. Treatment with O(6)-benzylguanine (O6BG)/TMZ after transplantation resulted in gene marking levels up to 75%, without significant hematopoietic cytopenia, which is consistent with hematopoietic chemoprotection. Retrovirus integration analysis showed that multiple clones contribute to hematopoiesis. These studies demonstrate the ability to achieve stable engraftment of MGMT(P140K)-modified autologous hematopoietic stem cells (HSCs) after a novel reduced-intensity conditioning protocol using a combination of BCNU and TMZ. Furthermore, we show that MGMT(P140K)-HSC engraftment provides chemoprotection during TMZ dose escalation. Clinically, chemoconditioning with BCNU and TMZ should facilitate engraftment of MGMT(P140K)-modified cells while providing antitumor activity for patients with poor prognosis glioblastoma or alkylating agent-sensitive tumors, thereby supporting dose-intensified chemotherapy regimens.

Modulation of plasma antidiuretic hormone levels does not change the magnitude of the LPS-induced febrile response in Pekin ducks.

The objective of this study was to determine the effect of modulating the plasma concentrations of the avian antidiuretic hormone, arginine vasotocin (AVT), upon the febrile response to lipopolysaccharide (LPS) in Pekin ducks. LPS, intravenously administered into conscious control birds at a dose of 1 microg x kg(-1), caused a monophasic increase in body temperature of 0.85 +/- 0.12 degrees C associated with a Thermal Response Index of 2.5 +/- 0.6 C degrees h. Plasma AVT concentrations in the control birds also increased with the progression of the fever response, more than doubling from their basal values. Ducks in which the circulating level of AVT had either been elevated by the intravenous infusion of the peptide or dehydration, or reduced by the administration of a specific AVT antibody prior to LPS administration, produced body temperature profiles and Thermal Response Index values that did not differ significantly from those of the control birds. The lack of any direct effect of variations in plasma AVT concentrations upon the magnitude of the fever response indicates that the LPS-induced elevation in plasma AVT is not associated with modulating the rise in body temperature obtained in avian fever.

All-optical switching based on nondegenerate phase shifts from a cascaded second-order nonlinearity.

All-optical switching by using a nondegenerate cascaded second-order nonlinearity is described wherein a phase shift is induced at one frequency owing to the presence of intense light at a different frequency. A Mach-Zehnder waveguide device is proposed to take advantage of this process and has applications for all-optical switching and demultiplexing, potentially at power levels near 10 W by using quasi-phase matching in semiconductor waveguides.

Picosecond pump-probe interferometric measurement of optical nonlinearity in semiconductor-doped fibers.

Refractive and absorptive optical nonlinearity can be distinguished using a pump-probe interferometric technique with picosecond time resolution. The method is applied to both resonant and nonresonant nonlinearities in optical fibers and reveals marked differences between the relaxation behavior of the refractive and absorptive nonlinearity in certain cases. A monomode fiber doped with CdS(x)Se(1-x) semiconductor nanocrystals exhibits a large optically induced phase shift with ~10-psec relaxation time, which is many orders faster than the relaxation of the absorptive nonlinearity under identical conditions.

Picosecond pump-probe interferometric measurement of optical nonlinearities in channel waveguides.

An interferometric technique for measuring with picosecond resolution the time evolution of the real and imaginary components of optical nonlinearities in channel waveguides is described. Characteristics of the technique are illustrated with measurements of band-filling optical nonlinearities in CdS(x)Se(1-x)-doped glass channel waveguides.