307 research outputs found
Fibre interferometry for differential measurements
This thesis investigates the use of interferometry as an interrogation technology for the measurement of differential length at two widely separate locations. Differential length measurements are essential and can have many applications in industrial processes, therefore accurate measurements can be a critical. Such differential length measurements can be applied to aspects of differential pressure. Using an all optical fibre approach, the research utilises the effects of light interference for both low coherent and high coherent light sources for the determination of a differential length between individual sensing cavities separated by up to 10’s of meters. The construction of the differential length interrogation system makes use of two Fabry-Perot cavities arranged in a tandem configuration, as a means of determining the differential length between them. Such an arrangement provides a common path through which an optical broadband light source at a central wavelength of 1550 nm can propagate. As a consequence of this configuration, differential lengths are made simply using one single measurement, removing the need to determine each individual length. An additional benefit of this common optical path prevents environmental factors such as temperature and air pressures from affecting the measurement length in question. Using a scanning reference Michelson interferometer to induce an optical path change, low coherence interference effects are present when the optical path length of the differential Fabry-Perot cavities is equal to the optical path length difference in the Michelson interferometer. Using a separate DFB laser light source to illuminate the reference interferometer high coherence interference fringes, present when the optical path length of one interferometer arm is changing due to a piezo fibre stretcher, can be analysed to provide an accurate length determination. Taking into consideration the noise within the system the interrogation technique has a length measurement resolution of 27.43 nm. Demonstrations show that a differential length of 82.539 μm could be measured with an uncertainty of 41.00 nm. Through the characterisation of a deformable silicon diaphragm, it would be possible to construct a sensing system capable of measuring a differential pressure of 1 Pa in 100 kPa. This however would require a 9.13 mm thick diaphragm, with a radius of 0.35 m. Such a diaphragm would be out of the question and so further investigation into reducing the length measurement resolution would need to be carried out
Technical Design Report EuroGammaS proposal for the ELI-NP Gamma beam System
The machine described in this document is an advanced Source of up to 20 MeV
Gamma Rays based on Compton back-scattering, i.e. collision of an intense high
power laser beam and a high brightness electron beam with maximum kinetic
energy of about 720 MeV. Fully equipped with collimation and characterization
systems, in order to generate, form and fully measure the physical
characteristics of the produced Gamma Ray beam. The quality, i.e. phase space
density, of the two colliding beams will be such that the emitted Gamma ray
beam is characterized by energy tunability, spectral density, bandwidth,
polarization, divergence and brilliance compatible with the requested
performances of the ELI-NP user facility, to be built in Romania as the Nuclear
Physics oriented Pillar of the European Extreme Light Infrastructure. This
document illustrates the Technical Design finally produced by the EuroGammaS
Collaboration, after a thorough investigation of the machine expected
performances within the constraints imposed by the ELI-NP tender for the Gamma
Beam System (ELI-NP-GBS), in terms of available budget, deadlines for machine
completion and performance achievement, compatibility with lay-out and
characteristics of the planned civil engineering
Dispersive Fourier Transformation for Versatile Microwave Photonics Applications
Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well
Synchronous Meteorological Satellite Phase B Study Report
Design of base line system for synchronous meteorological satellit
Focal position-controlled processing head for a laser pattern generator (LPG) for flexible micro-structuring
In micro-structuring processes a direct structuring of the substrate is, in most cases, not
possible and therefore the profile is first obtained in photo resist and then, in a second step,
transferred into the substrate. The resist structuring can be performed using the flexible
characteristics of a laser pattern generator (LPG). In these processes, there is a beneficial
relationship between the apparatus/equipment expense and the obtainable processing results.
For a reproduceable processing result in all micro structuring tasks, good reproducibility of all
process relevant parameters is required. In the application of a laser pattern generator, precise
control of the focal position of the strongly focussed laser beam relative to the processing
surface must be maintained. [Continues.
Laser Wire Scanner Compton Scattering Techniques for the Measurement of the Transverse Beam Size of Particle Beams at Future Linear Colliders
This archive summarizes a working paper and conference proceedings related to
laser wire scanner development for the Future Linear Collider (FLC) in the
years 2001 to 2006. In particular the design, setup and data taking for the
laser wire experiments at PETRA II and CT2 are described. The material is
focused on the activities undertaken by Royal Holloway University of London
(RHUL).Comment: 61 page
High Frequency DC/DC Boost Converter
The goal of this work was to design and test a functional proof of concept of a high frequency DC to DC boost converter. The scope of this work included the design, simulation, part selection, PCB layout, fabrication, and testing of the three major design blocks. The design uses a closed loop error amplifier circuit, a power stage, and a ramp waveform generator circuit. The switching frequency will be adjustable, with a maximum goal of 20MHz
Mid-infrared dual comb spectroscopy with asynchronous optical parametric oscillators
Dual-comb spectroscopy (DCS) is a novel approach that uses asynchronous broadband coherent sources to achieve Fourier-transform-like spectroscopy but with no moving parts and at kHz acquisition rates. To date, fully resolved and accurate dual-comb spectrometers have been demonstrated in the near-infrared and applied to broadband spectroscopy for precise measurement of molecular centerlines, spectral lidar, and greenhouse gases from the near- to mid-IR.
This thesis describes DCS with asynchronous optical parametric oscillators and explores their applications in rapid, high-resolution broadband spectroscopy in the mid-infared. Initially a dual-comb spectrometer was designed with two identical optical parametric oscillators (OPOs) pumped by two identical Yb:fibre lasers and its stability performance was characterized measuring relative intensity noise. First experiments were accomplished by using free-running independent MgO:PPLN based OPOs with a repetition-rate difference of 500 Hz, achieving resolutions of 0.2 cm-1 across a wavelength range 3.1 to 3.5 μm; an absolute wavelength calibration technique was employed to allow registration and averaging of consecutively acquired dual-comb spectra. Then experiments were repeated with a dual-comb source for the spectral fingerprint region based on a pair of entirely free-running OPOs, each pumped by a 1-µm femtosecond laser and utilizing the new gain medium orientation-patterned gallium phosphide (OPGaP) to produce broadband idler pulses tunable from 6–8 µm. Methane absorption spectroscopy in the deep infrared region was demonstrated with the same wavelength calibration approach for both dual-comb spectrometers, leading to a high quality and low-noise absorbance measurement with spectral coverage simultaneously spanning the methane P, Q and R branches in good agreement with the Hitran database
- …