Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 13 of 13 for “"heterodyne detection"”.
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Comparison of Direct and Heterodyne Detection Optical Intersatellite Communication Links
The performance of direct and heterodyne detection optical intersatellite communication links are evaluated and compared. It is shown that the performance of optical links is very sensitive to the pointing and tracking errors at the transmitter and receiver. In the presence of random pointing and …
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Distributed fibre sensing using microwave heterodyne detection of spontaneous Brillouin backscatter
… documented, with all recent cases using direct detection of the backscattered power. As the input pulse power is increased, nonlinear processes ensue, compromising the accuracy of the sensor. These processes were investigated both experimentally and theoretically for a range of input pulse …
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Characterization of coherence in forward-scattered photons in tubid medium using heterodyne detection
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.
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Interferometric, acousto-optic modulated diffuse correlation spectroscopy @ 1064 nm (AOM-iDCS) toward higher sensitivity, non-invasive measurement of cerebral blood flow
… (1064 nm), acousto-optic modulation, and heterodyne detection to enhance CBF sensitivity and reduce extracerebral contamination. In each domain of improvement, we develop theory to describe the detected optical signals, advance hardware to enable measurements, and characterize the …
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Phase-locking terahertz quantum cascade lasers for high dynamic range heterodyne imaging
… This can be achieved using a combination of heterodyne detection and a phase-locked loop to selectively lower the system noise floor while preserving signal power. In this thesis, an optical phase-locked loop using a Schottky diode mixer and 3rd order DFB QCLs is implemented to achieve a …
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Minimally invasive diagnostic imaging using high resolution Optical Coherence Tomography
… In addition, through the use of coherent heterodyne detection techniques, the capability to visualize pathological tissue architecture in vivo for both animal and human experimental trials has been demonstrated. Because OCT can perform such "optical biopsy" with resolutions approaching …
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Spontaneous brillouin scattering quench diagnostics for large superconducting magnets
… Brillouin scattered light was measured using heterodyne detection. A pulsed laser was used to probe the fiber using Optical Time Domain Reflectometry (OTDR) to define the spatial resolution. The spontaneous Brillouin frequency shift and linewidth as a function of temperature agree well with …
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Generation and application of squeezed light
… a better signal to noise ratio in the subsequent heterodyne detection of the Sagnac phase shift. The major part of this thesis is dedicated to the analysis of the “squeezed reservoir laser”, which is of a more theoretical nature. The laser is treated as an open quantum system which is coupled to a …
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Nanoscale infrared absorption imaging and tomography
… we show the AFM-IR signal (recorded using heterodyne detection) can be described as the product of the local photo-induced, sample expansion and the cantilever resonance response (responsivity). We use the insight obtained to develop a new approach for removing cantilever responsivity …
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Optical characterization of complex mechanical and thermal transport properties
… and phase grating signal contributions using heterodyne detection. This allowed the measurement of thermal transport in lead telluride and gallium arsenide-aluminum arsenide superlattices, and also provided the first direct observation of the initial crossover from diffusive to ballistic …
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Ultra-Narrow Laser Linewidth Measurement
… the loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI) for ultra-narrow linewidth measurement, including the theoretical analysis, experimental implementation, further modification on the system and more applications. Recently, less than 1kHz linewidth fiber lasers …
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On the Dynamics of Single-Electron Tunneling in Semiconductor Quantum Dots under Microwave Radiation
… in quantum dots. Both techniques are called heterodyne detection of photon-induced tunnel current (photocurrent). In one method, two coherent continuous microwave sources with a slight frequency offset are combined to generate a flux of microwave photons. The photon intensity varies in time …