Metrology of Complex Refractive Index for Solids in the Terahertz Regime Using Frequency Domain Spectroscopy

Frequency domain spectroscopy allows an experimenter to establish optical properties of solids in a wide frequency band including the technically challenging 10 THz region, and in other bands enables metrological comparison between competing techniques. We advance a method for extracting the optical properties of high-index solids using only transmission-mode frequency domain spectroscopy of plane-parallel Fabry-Perot optical flats. We show that different data processing techniques yield different kinds of systematic error, and that some commonly used techniques have inherent systematic errors which are underappreciated. We use model datasets to cross-compare algorithms in isolation from experimental errors, and propose a new algorithm which has qualitatively different systematic errors to its competitors. We show that our proposal is more robust to experimental non-idealities such as noise or apodization, and extract the complex refractive index spectrum of crystalline silicon as a practical example. Finally, we advance the idea that algorithms are complementary rather than competitive, and should be used together as part of a toolbox for better metrology.Comment: 21 pages, 11 figures, 4 appendice

Road Transport Infrastructure and Economic Growth in Kenya

The empirical debate on the role of road transport infrastructure on domestic economic growth is inconclusive and is characterized by two main opposing views: the road-led economic growth hypothesis and the distorting effect of infrastructure growth hypothesis. The objective of this paper is to examine the effect of road transportation infrastructure on economic growth in Kenya using time series data over the period 1990-2020. Empirically, the study develops a transport-growth model that is an extension of Solow (1956) neoclassical growth function and estimates the model with time series data of Kenya. The study adopted Autoregressive Distributed Lag (ARDL) model and Granger causality approach as the technique for testing the study relationship. The key finding of this study demonstrated that the growth in road length as proxied by road sector expenditure contributed positively to economic growth in both short-run and long run. Applying error correction model, it was observed that there is causality between road infrastructure development and economic growth. This study, therefore, interrogates and accepts the infrastructure–growth hypothesis that increased road transport infrastructure stimulates long-run economy expansion in the Kenyan context. The study suggests that expansion of road transport infrastructure will lead to substantial growth of the Kenya economy though gross capital formation. Therefore, within its stated scope, this finding informs the formulation of relevant and vibrant study transport policy to boost road infrastructure growth and hence sustainable economic growth in Kenya. JEL Classification: H54, E23, C23 Keywords: Transport infrastructure, economic growth, road, public–partnership, error correction model, and road financing, HDM-4. DOI: 10.7176/JAAS/80-01 Publication date:September 30th 202

Repulsive Casimir forces between solid materials with high refractive index intervening liquids

In order to explore repulsive Casimir/van der Waals forces between solid materials with liquid as the intervening medium, we analyze dielectric data for a wide range of materials as for example PTFE, polystyrene, silica and more than twenty liquids. Although significant variation in the dielectric data from different sources exist, we provide a scheme based on measured static dielectric constants, refractive indices, and applying Kramers Kronig (KK) consistency to dielectric data to create accurate dielectric functions at imaginary frequencies. The latter is necessary for more accurate force calculations via the Lifshitz theory allowing reliable predictions of repulsive Casimir forces.Comment: 20 pages, 7 figures, 1 tabl

Mode locking in the ring laser gyroscope: Reduced threshold for two cavity modes

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A ring laser gyroscope is a device which employs a ring laser to measure rotation. A ring laser supports two beams propagating in opposite directions around the ring resonator. When the gyroscope is rotated, the frequencies of the two beams split by an amount proportional to the rate of rotation: the device works by measuring this frequency splitting. The main problem of ring laser gyroscope design is the frequency synchronisation - lock-in - of the two beams at low rates of rotation. Lock-in arises from weak mutual coupling caused by backscattering at the mirrors and results in a dead band around zero. One of the possible solutions to this problem is a two-mode ring laser in which two modes oscillate simultaneously and interact to reduce the dead band. The present work reviews the theory of lock-in and offers a theoretical basis for this approach, as well as providing experimental evidence to support it

Fiscal Decentralization and Energy Consumption: A Race to Decentralization

This study examines the effect of fiscal decentralization, in the form of shifting responsibilities of tax revenues, expenditure and planning from the central government to lower local governments, as well as rapidly rising income, on energy consumption for 47 Kenyan counties over the period 2013 to 2017. This study employs panel methodology and the ordinary least squares regression model to investigate this effect in Kenya. The index of fiscal decentralization is measured by the ratio of sub-national revenue to total public revenue. This analysis has policy implications for economic growth, poverty level, race to energy decentralization and energy demand. The study findings demonstrate that higher fiscal decentralization is associated with higher energy consumption in Kenya; the internally generated revenue enhances electricity demand through improved energy infrastructure, energy innovations and connectivity. This can also be attributed to economic resources, administration, service delivery, and infrastructure planning being decentralized to the sub-national level. This underscores the need to provide policies and strategies that will guide the integration of the energy sector into development programmes, plans and processes at the sub-national level to advance energy system decentralization, connectivity and cumulative energy consumption. Keywords: Energy consumption, Decentralization, Energy efficiency, Sub-national, Taxation DOI: 10.7176/EJBM/14-22-07 Publication date: November 30th 202

Electrical and radiation characteristics of semilarge photoconductive terahertz emitters

We present experimental characterization of semilarge photoconductive emitters, including their electrical/photoconductive parameters and terahertz spectra. A range of emitters were studied and fabricated on both LT-GaAs and SI-GaAs, having a variety of electrode geometries. The spatial cone of terahertz radiation was defined. The dependencies of the photocurrent and the terahertz power on the bias voltage and the laser power were determined. A Fourier-transform interferometer is used to determine the terahertz spectra and to clarify the effects of the substrate and electrode geometry