The increased demand for modern optical components necessitates an interferometric system that can rapidly and accurately measure wavefront phase errors during the complete fabrication process, from generation to polishing. The suitability of infrared wavelengths for several optical testing applications is well known, as are the greatly increased speed and accuracy of phase-shifting interferometric techniques. Therefore, this dissertation discusses extensively three topics: (1) the demonstration theoretically and experimentally of the feasibility of using a pyroelectric vidicon for infrared phase-shifting interferometry, (2) the design and fabrication of a prototype next-generation optical shop infrared phase-shifting interferometric system, and (3) the definition and quantification of the fundamental system performance parameters and limitations. Additionally, some application examples of infrared phase-shifting interferometry are presented, and specific recommendations for future work are included with the conclusions.

Pyroelectric energy scavenging is the process of converting wasted energy from a system to power another one, based on the pyroelectric effect of piezoelectric materials. Pyroelectrically generated power is a function of the surface of material, the pyroelectric coefficient, and the temporal temperature gradient. In the current project, a simple model is developed to predict the power generation based on the temporal change in temperature of material. In addition, a model is validated with experimental measurements from several piezoelectric materials. It is shown that energy generation can be enhanced by using piezoelectric materials with significantly higher pyroelectric coefficients such as pre-stressed piezoelectric materials or thin films. Meanwhile, a method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. Besides, simple analytic expressions are developed for ideal voltage, power and power densities as a function of pyroelectric constant, permittivity, surface area, thickness, temperature variation.

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Dielectrics are materials that can be polarized by an applied electric field. As the essential property for dielectrics, the relationship between electric field and dielectric polarization, has been widely studied and used in the area of electrical engineering. Representative applications are insulators and electrical energy storage capacitors. For some types of dielectrics, the dielectric polarization is not only decided by the applied electric field, but also is affected by mechanical and thermal properties. This work studies the electro-mechanical and electro-thermal energy inter-conversions and proposes the design of power converters for these materials. Piezoelectric effect is a cross-coupling between mechanical property and electrical property of dielectrics. It is a reversible process where external electric potential can generate internal mechanical force while external mechanical force can also generate internal electric potential. This effect is utilized to build a piezoelectric transformer (PT) by combining two sets of piezoelectric material together. One set is used as the input, to cause a geometric strain by applied electric field, while the other set is used as the output, to generate an electric charge by the coupled mechanical stress. Compared to traditional magnetic transformers, PTs store energy in mechanical inertia and compliance and therefore they do not generate electromagnetic noise. They are suitable for batch mass manufacturing since there is no winding requirement. Among many types of PTs, radial PT and Rosen-type PT are most widely used. To provide a guide for the design of PT-based converters, the electrical characteristics of PTs are first analyzed. The accuracy and applicability of different levels of models of PTs are compared and discussed. The detailed universal attributes of PTs, which include the gain characteristic, the input impedance characteristic and the efficiency characteristic, are also derived. In addition, with the assistance of additional compensation component(s), PTs can provide better performance. The impacts of the input and output inductors and capacitors on gain and efficiency characteristics of a PT are analyzed. Tunable PT is a recently developed raidal PT with three ports: input, output, and control ports. When connected with different impedance at the control port, tunable PT has different voltage gain characteristics. It is proposed to use this property for output voltage regulation while keeping constant switching frequency to ensure high efficiency operation of the PT in PT-based power converters. A closed-loop control scheme is proposed, where the regulation is done by a duty cycle controlled switched capacitor at the tunable PT control port. Two types of output filter are also analyzed and compared. Dc-dc converters with power rating ranging from 30 W to 100 W are built to verify the proposed design. Rosen-type PT features natural mechanisms for high transform ratio in a compact planar form, which provide an alternative solution for dc bus-fed high step-down voltage-ratio auxiliary power supplies in medium-/high-voltage systems without using bulky magnetic transformer with high turns numbers. The design procedure of the Rosen-type PT-based high step-down voltage-ratio dc-dc converter is presented. The proposed design is validated by a prototype with height of 1 cm, whose nominal output power is 5 W, input voltage ranges from 200 V to 1.5 kV, regulated output voltage is 5 V. Pyroelectric effect is a cross-coupling between thermal property and electrical property in some dielectrics. It is also reversible. The pyroelectric effect refers to the polarization change caused by temperature change, while the reversed pyroelectric effect refers to a temperature change generated by a electric field change. The reversed pyroelectric effect can be used for building a environmentally friendly thermodynamic system. Electrical characterization of the pyroelectric material is executed to facilitate the design of the power converter needed in the corresponding thermodynamic system. Specifically, this work proposes an energy recovery circuit to increase the coefficient of performance of the system since during the thermodynamic cycle, part of the electrical driving work does not pump heat and may therefore be recovered. / Doctor of Philosophy / When a dielectric material is placed in an electric field, electric charges slightly shift from their average equilibrium positions, causing dielectric polarization. In the area of electromagnetism, dielectric material is widely used as an electrical insulator and to build capacitors. For some types of dielectrics, dielectric polarization is not only affected by electric field. Strong couplings between electrical and mechanical characteristics, and between electrical and thermal characteristic also exist and can be utilized in practical applications. Piezoelectric effect is a coupling between electrical and mechanical characteristics. It is a reversible process where external electric potential can generate internal mechanical force and vice versa. It can be utilized to build transformers, which do not require coil winding nor generate electromagnetic interference compared to their magnetic counterparts. This work analyzed the electrical characteristics of piezoelectric transformers and proposed the design of dc-dc converters based on different types of piezoelectric transformers for different applications, which include tunable radial piezoelectric transformer-based power converters and Rosen-type piezoelectric transformer-based step-down converter with high voltage conversion ratio. (Reversed) pyroelectric effect is a coupling between electrical and thermal characteristics in some dielectrics. An adiabatically applied or removal electric field results in an increase or decrease in the temperature of the corresponding material. This effect can be used to build a environmentally friendly thermodynamic system instead of the most prevalent vapor compression method which involves the use of hydro-fluorocarbon gases leading to global warming and ozone depletion. Electrical characterization is executed first to facilitate the design of the power converter needed by the thermodynamic system. In addition, during the thermal cycle, part of the work done to drive representative cycles does not pump heat and may therefore be recovered. This work proposed circuit featuring energy recovery to provide the desired electric field for driving the thermodynamic system and charge recycling to improve the system efficiency.

The Mg-modified lead titanate [(Pb1-xMgx)TiO3,abbreviated to PMT] thin films were deposited on Pt/SiO2/Si substrates by spin coating with sol-gel processing in this thesis. 1,3 propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of thin film. By changing the Mg content (0~10 mol%) and the heating temperature (500~800¢J), the effects of various processing parameters on the thin films growth are studied. The effects of various Mg contents on the response of pyroelectric IR detector devices are studied also. Experimental results reveal that the Mg contents will influence strongly on grain size, dielectricity, ferroelectricity and pyroelectricity of PMT thin films. With the increase of Mg content, the grain size of PMT thin film decrease slightly, and the lattice structure of PMT thin film will change from tetragonal to cubic when the Mg content over 8 mole%. The relative dielectric constant of PMT thin film increases from 25 up to 91. The tan

The lithium tantalite [LiTaO3,abbreviated to LT] thin films were deposited on Pt/SiO2/Si substrates by spin coating with sol-gel processing and rapid thermal processing in this thesis. 1,3 propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of thin film. By changing the heating rate (600~3000¢J/min) and the heating temperature (500~800¢J), the effects of various processing parameters on the thin films growth are studied. The effects of various heating rate on the response of pyroelectric IR detector devices are studied also. Experimental results reveal that the heating rate will influence strongly on grain size, dielectricity, ferroelectricity and pyroelectricity of LT thin films. With the increase of heating rate, the grain size of LT thin film decreases slightly, and the C-axis orientation is enhanced. The relative dielectric constant of LT thin film increases from 28 up to 45.6, the tand increases from 0.033 to 0.134, Ec increases from 122 KV/cm to 183 KV/cm, Pr increases from 7.45 mC/cm2 to 12.12 mC/cm2, and g increases from 9.33´10-9 C/cm2K up to 2.66´10-8 C/cm2K, respectively, as the heating rate increases form 600 up to 3000¢J/min. In addition, the results also show that the LT thin film possesses the largest figures of merit Fv (2.19¡Ñ10-10 Ccm/J) and Fm (4.01¡Ñ10-9 Ccm/J) at the heating temperature of 700¢J and heating rate of 1800¢J/min. The voltage responsivities (Rv) measured at 80 Hz increase from 5496 to 8455 V/W and the specific detecivities (D*) measured at 300 Hz increase from 1.94¡Ñ108 to 2.38¡Ñ108 cmHz1/2/W with an increase of heating rate from 600 to 1800¢J/min. However, the voltage responsivity and the specific detecivity decrease with heating rate in excess of 1800¢J/min. The results show that LT1800 pyroelectric thin film detector exists both the maximums of voltage responsivity and specific detecivity. Therefore, LT1800 thin film exhibits the best IR characteristics for detector material.

Pyroelectric Detector (PED) models are developed considering the classical heat balance equation to simulate the detector’s response under specified radiation conditions. Studies on the behaviour of a PED are presented under the conditions of step function and a pulsed load. Finite Element Methods (FEMs) have been used to obtain 3D models of the resulting temperature field in a Lithium Tantalate (LiTaO3) pyroelectric crystal, incorporated in a complete commercial detector, taking into account details of its geometry and thermal connectivity. The novelty is the achieved facility to predict the response to pulsed radiation, which is valuable for the engineering of pulsed-source sensor systems requiring detection at room temperature. In this thesis, we present a signal processing (SP) algorithm, which combines the principle of Quadrature Synchronous Demodulation (QSD) and Gated Integration (GI), to achieve an improved signal-to-noise ratio (SNR) in pulsed signal measurements. As a first step, the pulse is bracketed by a gating window and the samples outside the window are discarded. The gate duration is calculated to ensure that the periodic signal at the output has an 'apparent' duty factor close to 0.5. This signal is then fed continuously for QSD to extract the magnitude and phase of its fundamental component, referenced to a sinusoidal signal with period defined by the gate length. An improved SNR performance results not only from the increase of the average signal energy, but also from the noise suppression inherent to the QSD principle. We introduce this method as Gated Quadrature Synchronous Demodulation (GQSD), emphasizing the synergy between GΙ and QSD.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

The pyroelectric ceramic thin films and detectors based on PbTiO3 that exhibits a low dielectric constant and a high pyroelectric coefficient were fabricated by a sol-gel method in this thesis. The lanthanum (La) and calcium (Ca) were adopted as dopants. The PLT and PCT thin films were deposited on Pt/SiO2/Si substrates by spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of thin film. By changing the dopant content and the heating temperature, the effects of various processing parameters on the thin films growth are studied. The effects of various dopant contents on the response of pyroelectric detectors are also discussed. Experimental results reveal that the dopant contents will influence strongly on the characteristics of thin films such as microstructure, dielectricity, ferroelectricity and pyroelectricity. With the increase of dopant content, the grain size, the coercive field (Ec) and the remanent polarization (Pr) of thin films decrease. The relative dielectric constant (£`r) and the pyroelectric coefficient (g) of thin films increase with increasing the dopant content. In addition, the results also show that the PLT(10) and the PCT(25) thin films exhibit large figures of merit Fv for voltage responsivity (Rv) and Fm for specific detectivity (D*) at the heating temperature of 700¢J. In the pyroelectric properties of thin film detectors, Rv and D* increased with an increase of dopant content. However, Rv and D* decreased when La and Ca content exceeded 10 mol% and 25 mol%, respectively. The PLT(10) and the PCT(25) pyroelectric thin film detectors exist both the maximums of Rv and D*. The results are consistent with the evaluations of Fv and Fm of thin films.

The pyroelectric ceramic thin films and detectors based on PbTiO3[abbreviated to PT] that exhibit a low dielectric constant and a high pyroelectric coefficient, which were fabricated by a sol-gel method in this thesis. The (PVDF/PT) pyroelectric bilayer thin films with low leakage current were deposited on PbTiO3/Pt/SiO2/Si substrates by the spin coating. 1,3 propanediol was used as solvent to minimize the number of cycles of the spin coating and drying processes to obtain the desired thickness of PbTiO3 thin film. By changing the concentrations of PVDF solutions (0.6M~1.0M) and thickness of PVDF thin films (50nm~580nm), the effects of various processing parameters on the bilayer thin films growth and the response of pyroelectric infrared detector device are studied. Experimental results reveal that the thickness of PVDF thin films will influence strongly on dielectricity, ferroelectricity, leakage current and pyroelectricity of (PVDF/PT) bilayer thin films. With the increase of the thickness of PVDF thin films, the relative dielectric constant of (PVDF/PT) bilayer thin films decrease from 63 to 20. The tan£_ increases from 0.00152 to 0.0024, leakage current decreases from 1.54x10-6 A/cm2 to 3.86x10-7 A/cm2, Ec decreases from 70.7 KV/cm to 35 KV/cm, Pr decreases from 6.29 £gC/cm2 to 1.14 £gC/cm2, and £^ decreases from 22.5x10-9 C/cm2K to 6.8 x10-9 C/cm2K with an increase of the thickness of PVDF thin film. In addition, the results also show that the largest figure of merit Fv is 1.31x10-10 Ccm/J as the thickness of PVDF thin film is 80nm. With the increase of the thickness of PVDF thin film, the figure of merit Fm decreases from 2.26x10-8 Ccm/J to 1.07x10-8 Ccm/J. The voltage responsivities (Rv) measured at 20 Hz decrease from 1383 V/W to 804 V/W and the specific detectivities (D*) measured at 100Hz decrease from 2.72x107 cmHz1/2/W to 1.71x107 cmHz1/2/W. From the result of D*/J, the result shows the device possesses the best property as the thickness of the PVDF thin film is 165nm. Therefore, the (PVDF/PT) bilayer thin film with the thickness 165nm of PVDF thin film is the most suitable for the applications of pyroelectric thin film IR detectors.