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An integrated analysis of laser induced breakdown (LIB) and the associated micro-cavitation in a water-like bio-tissue is developed in this study. With this integrated analysis using minimum experimentally fitted parameters, threshold energies of LIB in bio-tissue under different numerical apertures of the focusing lenses can be determined, which provides similar values as the corresponding experimental measurements. The integrated analysis can also determine the electron temperature and number density when LIB is triggered, which also fall in the same order as the corresponding experimental measurements. In addition, the rapid size increment of plasma plume through laser supported detonation wave during a LIB can be observed with the integrated analysis. The developed integrated analysis becomes unstable when strong pressure wave presents due to strong heating and the following rapid expansion of the bio-tissue under higher input laser energy (compared with the threshold energy of LIB). Therefore, for simulating high energy LIB and the following micro-cavitation in a bio-tissue, a more advanced numerical scheme that can better capture the propagation of pressure wave will be required in the future.

An integrated analysis considering radiative energy transport among each component and carrier generation in the photovoltaic (PV) material is established for solar thermophotovoltaic (STPV) devices. STPV has been estimated with previous thermodynamics analysis to provide up to ∼85% solar energy conversion efficiency (ECE) because of its capability to convert broadband solar radiation to narrowband thermal radiation that can be fully used with PV materials. However, in previous demonstrations, the ECE of STPVs is less than 10%, even with ∼200 solar radiation concentrations. Based on our analysis, the maximum ECE of STPV without any radiation heat loss control is nearly zero when the solar concentration ratio is 1 and is ∼18.78% when the solar concentration ratio is 1000. Maximum ECE of STPV with spectral selected absorber optimized for 1000 K level temperature, which has been proposed in recent STPV studies, can be ∼9.56% when the solar concentration is 1 and can be ∼31.72% when the solar concentration ratio is 1000. Maximum ECE of STPV with our proposed multi-layered radiation shield to prevent radiative heat loss from the STPV to the ambient can provide ECE up to ∼9.53% and ∼57.02%, when the solar concentration ratio is 1 and 1000, respectively. When we combine both the spectral selected absorber and our designed radiation shield, the ECE value of STPV can be up to ∼20.65% and ∼59.23% when the solar concentration ratio is 1 and 1000, respectively. It is also observed that a ∼1 µm level bandwidth of photonic crystal (PhC), a device that can control the emission bandwidth, is required for STPV to achieve high ECE under each solar concentration ratio with difference radiative heat loss control.

A Tayler series expansion based high accuracy meshfree method (TS-HAMM) is developed to calculate first and second derivatives of property values stored in dispersed particle clouds. Compared with other meshfree methods such as smoothed particle hydrodynamics (SPH), TS-HAMM can (a) systematically increase accuracies in gradient, derivative and Laplacian calculations with similar computational cost; (b) provide boundary conditions directly from conservation equations at the fluid/solid interfaces with guaranteed order of accuracy; (c) simulate fluid dynamics and heat transfer of low viscous weakly compressible fluid (e.g. water) directly without making incompressible assumptions. Through numerical verifications with water-like low viscous low compressible fluid in Couette flow, lid-driven flow inside a cavity, and natural convection inside an enclosure, we justify the validity of TS-HAMM in simulating fluid dynamics and heat transfer of water-like low viscous weakly compressible fluid, which are challenging with other meshfree methods such as smoothed particle hydrodynamics (SPH).

A methodology of 3D photolithography through light field projections with a microlens array (MLA) is proposed and demonstrated. With the MLA, light from a spatial light modulator (SLM) can be delivered to arbitrary positions, i.e., voxels, in a 3D space with a focusing scheme we developed. A mapping function between the voxel locations and the SLM pixel locations can be one-to-one determined by ray tracing. Based on a correct mapping function, computer-designed 3D virtual objects can be reconstructed in a 3D space through a SLM and a MLA. The projected 3D virtual object can then be optically compressed and delivered to a photoresist layer for 3D photolithography. With appropriate near-UV light, 3D microstructures can be constructed at different depths inside the photoresist layer. This 3D photolithography method can be useful in high-speed 3D patterning at arbitrary positions. We expect high-precision 3D patterning can also be achieved when a femtosecond light source and the associated multi-photon curing process is adopted in the proposed light field 3D projection/photolithography scheme. Multi-photon polymerization can prevent the unwilling patterning of regions along the optical path before arriving to the designed focal voxels as observed in our single photon demonstrations.

A numerical analysis capable of describing the early stage of a thermal microcavitation process in a water-rich biotissue without avalanche breakdown was developed. The analysis successfully reproduced the laser-induced heating, vapor bubble formation, bubble expansion, and shockwave propagation inside a water-rich biotissue during a thermal microcavitation process. Based on the analysis, it was determined that the evolution of the temperature, pressure, and laser-induced shockwave is dependent on the incident laser energy and laser pulse width. On the other hand, the early stage dynamics of the microcavitation process showed little dependence on the elastic modulus of the biotissue for the laser and tissue conditions studied.

To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.

The flow passing a single sphere moving in a micro–tube is investigated theoretically. Two cases are studied. Case I is for a single sphere moving along the centreline, while case II is for a single sphere moving parallel to the centreline of a micro–tube. The range of Knudsen numbers to be studied lies between 0.01 and 0.1 so that the Navier–Stokes equations with slip boundary conditions are the appropriate system to be analysed. The stream–function method is used to obtain analytic solutions for case I, while the reflection method is used for case II. The effects due to the slip boundary conditions on the flow field, resultant force on the sphere, pressure drop over the sphere, terminal velocity of the sphere, etc., are calculated and discussed.

Pulsed laser ablation (266 nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm−2. Characterization of particles and correlation with inductively coupled plasma mass spectrometer (ICP–MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP–MS, the Zn and Al signals intensities were greater by factors of ∼50 and ∼12 for fs versus ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the 66Zn transient signal by a factor of 10 compared to nanosecond laser pulses.

A study was made of the cooling of the laser induced vapor plume in background air. The temperature and size variations of the vapor plume were determined from spectroscopic measurements during the first few tens of microseconds after the laser pulse. Experiments were carried out over a range of laser spot sizes and energies. The energy transport by thermal radiation from the vapor plume to the background air and to the test sample was formulated. Spectral line by line calculations were made by (a) calculating the detailed line emission profiles (valid for all optical depths), as well as by (b) dividing the lines into being either optically thin or optically thick. The calculations agreed with one another and with the experimental results for the decreasing vapor plume temperature. It was also shown that for optically thin conditions, which are often valid for small vapor plumes, the variation of the surface reflectivity of the test sample had very little effect on the cooling process. For optically thin conditions, the temperature decrease of the vapor plume was independent of the plume size, shape, and position. For larger optical thicknesses of the vapor plume, the calculations showed that the reflectivity of the sample surface and the size of the vapor plume would dramatically affect cooling of the vapor plume.

Laser ablation has proven to be an effective method for generating nanoparticles; particles are produced in the laser induced vapor plume during the cooling stage. To understand the in situ condensation process, a series of time resolved light scattering images was recorded and analyzed. Significant changes in the condensation rate and the shape of the condensed aerosol plume were observed in two background gases, helium and argon. The primary particle shape and size distributions were measured using a transmission electron microscope, a scanning electron microscope, and a differential mobility analyzer. The gas dynamics simulation included nucleation and coagulation within the vapor plume, heat and mass transfer from the vapor plume to the background gas, and heat transfer to the sample. The experimental data and the calculated evolution of the shape of the vapor plume showed the same trend for the spatial distribution of the condensed particles in both background gases. The simulated particle size distr...