Active and passive mid-infrared photonic devices in ZnSe based materials

The work described in this thesis details the development of mid-infrared waveguide laser sources created through the fabrication of waveguide structures in Cr2+: ZnSe using ultrafast laser inscription (ULI). Current quantum cascade laser (QCL) technology in the 2 – 5 μm region offer compact and robust sources suited to use outside the laboratory but the technology does not offer the high average powers, >100 mW, and wide tuneability, 2 – 3.3 μm of Cr2+: ZnSe laser sources. The development of a Cr2+: ZnSe waveguide laser source provides an environmentally robust product with access to powers and tuneable ranges greater than that provided by QCL systems. The first phase of the investigation produced the first successful refractive index modification of ZnSe using ULI. Both positive and negative refractive index changes were achieved and utilised to fabricate a range of waveguides in ZnSe and Cr2+: ZnSe. Low loss near-infrared waveguides were demonstrated through exploitation of the positive refractive index change. Low loss mid-infrared depressed cladding waveguides were subsequently demonstrated utilising the negative refractive index change. These waveguides were characterised at wavelengths of 1928, 2300 and 3390 nm as representative of pump and signal wavelengths in Cr2+: ZnSe laser systems. Finally, the newly fabricated Cr2+: ZnSe waveguides were constructed into waveguide laser cavities and pumped with a thulium fibre laser source operating at 1928 nm. Laser operation is demonstrated in both waveguides devices at wavelengths of 2573 and 2486 nm with a maximum achieved output power of 285 mW and a slope efficiency of 45%. Furthermore, a tuneable laser source is constructed in the Littman-Metcalf configuration exhibiting a maximum tuning range of 510 nm, 2330-2840 nm, with output powers exceeding 25 mW across the full range. These waveguide laser devices offer an environmentally robust and compact source in the 2 – 3 μm region with improvements upon maximum power and tuneability ranges in current quantum cascade laser sources. The waveguide laser sources reported open the door to products offering the robust nature of QCL sources with the higher powers and 2 – 3 μm tuneability associated with current bulk Cr2+: ZnSe laser systems.Engineering and Physical Sciences Research Council (EPSRC

Preparing an Election Petition in Missouri

Initiative and referendum petitions provide citizens with the power to make and overturn existing laws. Through the initiative petition, the people can compel an election on the question of enacting an amendment to the Missouri Constitution or enacting a proposed law. Through the referendum petition, the people can compel an election to decide whether an existing law should be retained. The procedure to be followed in drafting these petitions is specified in the Constitution and Statutes of Missouri.Reviewed October 1993

Diazepam enhances the action but not the binding of the GABA analog, THIP

GABA (4-aminobutyric acid) and its bicyclic analog THIP (4,5,6,7-tetrahydroisoxazolo-[4,5-c]-pyridin-3-ol) produced membrane hyperpolarization and increased chloride ion conductance of mouse spinal cord neurons in cell culture. Above 1 nM diazepam enhanced the actions of both GABA and THIP with similar potency and efficacy. Diazepam has been shown to enhance the binding of [3H]GABA to rat brain membranes over similar concentration ranges, with the EC50 values for enhancement of [3H]GABA binding and increase in membrane conductance being similar. In contrast, binding of [3H]THIP has been shown to be unaltered by diazepam under a variety of conditions. The possible reasons for such a discrepancy between these electrophysiological and neurochemical results with THIP are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24844/1/0000270.pd

Benzodiazepine Ro 15-1788: Electrophysiological evidence for partial agonist activity

The effects of diazepam and Ro 15-1788 were assessed upon responses of mouse spinal cord (SC) neurons in cell culture to the amino acid neurotransmitters 4-aminobutyric acid (GABA) and S-glutamic acid. Diazepam (100 nM) enhanced GABA responses by 65 +/- 3% (113 cells), while Ro 15-1788 (100 nM) failed to alter GABA responses but reduced their enhancement by diazepam. Higher Ro 15-1788 concentrations (1 [mu]M or 10 [mu]M) enhanced GABA responses to a moderate extent, while blocking further enhancement of GABA by diazepam. Neither diazepam nor Ro 15-1788 affected glutamate responses or resting membrane potential or conductance of spinal cord neurons. These results provide electrophysiological support for partial agonist, rather than pure antagonist, activity of Ro 15-1788.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25039/1/0000466.pd