Quasi-phase matching is a technique for phase matching nonlinear optical interactions in which the relative phase is corrected at regular intervals using a structural periodicity built into the nonlinear medium. The theory of quasiphase-matched second harmonic generation is presented in both the space domain and the wave vector mismatch domain. Departures from ideal quasi-phase matching in periodicity, wavelength, angle of propagation, and temperature are examined to determine the tuning properties and acceptance bandwidths for second harmonic generation in periodic structures. Numerical examples are tabulated for periodically poled lithium niobate. Various types of errors in the periodicity of these structures are then analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve. This analysis is useful for establishing fabrication tolerances for practical quasi-phasematched devices. A method of designing structures having desired phase-matching tuning curve shapes is also described which makes use of varying domain lengths to establish a varying effective nonlinear coefficient along the interaction length.

Quasi-phase matching is a technique for phase matching nonlinear optical interactions in which the relative phase is corrected at regular intervals using a structural periodicity built into the nonlinear medium. The theory of quasiphase-matched second harmonic generation is presented in both the space domain and the wave vector mismatch domain. Departures from ideal quasi-phase matching in periodicity, wavelength, angle of propagation, and temperature are examined to determine the tuning properties and acceptance bandwidths for second harmonic generation in periodic structures. Numerical examples are tabulated for periodically poled lithium niobate. Various types of errors in the periodicity of these structures are then analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve. This analysis is useful for establishing fabrication tolerances for practical quasi-phasematched devices. A method of designing structures having desired phase-matching tuning curve shapes is also described which makes use of varying domain lengths to establish a varying effective nonlinear coefficient along the interaction length.

We have designed and built a single-crystal fiber growth apparatus. The apparatus employs novel optical, mechanical, and electronic control systems that enable the growth of high optical quality single-crystal fibers. We have grown oriented single-crystal fibers of four refractory oxide materials, Al2O3, Cr:Al2O3, Nd:YAG, and LiNbO3. These materials exhibit similar growth characteristics and yield fibers of comparable quality. Fibers as small as 20 μm in diameter and as long as 20 cm have been grown. Measured optical losses at 1.06 μm for a 10-cm-long, 170-μm-diam Cr:Al2O3 fiber were 0.074 dB/cm.

We introduce a laser assisted electron beam induced deposition (LAEBID) process which is a nanoscale direct write synthesis method that integrates an electron beam induced deposition process with a synchronized pulsed laser step to induce thermal desorption of reaction by-products. Localized, spatially overlapping electron and photon pulses enable the thermal desorption of the reaction by-product while mitigating issues associated with bulk substrate heating, which can shorten the precursor residence time and distort pattern fidelity due to thermal drift. Current results demonstrate purification of platinum deposits (reduced carbon content by ~50%) with the addition of synchronized laser pulses as well as a significant reduction in deposit resistivity. Measured resistivities from platinum LAEBID structures (4 × 10(3)μΩ cm) are nearly 4 orders of magnitude lower than standard EBID platinum structures (2.2 × 10(7)μΩ cm) from the same precursor and are lower than the lowest reported EBID platinum resistivity with post-deposition annealing (1.4 × 10(4)μΩ cm). Finally the LAEBID process demonstrates improved deposit resolution by ~25% compared to EBID structures under the conditions investigated in this work.

The unique optical properties of surface plasmon resonances in nanostructured materials have attracted considerable attention, broadly impacting both fundamental research and applied technologies ranging from sensing and optoelectronics to quantum computing. Electron energy-loss spectroscopy (EELS) in the transmission electron microscope has revealed valuable information about the full plasmonic spectrum of these materials with nanoscale spatial resolution. Here we report a novel approach for experimentally accessing the photon-stimulated electron energy-gain and stimulated electron energy-loss responses of individual plasmonic nanoparticles via the simultaneous irradiation of a continuous wave laser and continuous current, monochromated electron probe. Stimulated gain and loss probabilities are equivalent and increase linearly in the low-irradiance range of 0.5 × 108 to 4 × 108 W/m2, above which excessive heating reduces the observed probabilities; importantly in our low-irradiance regime, the photon energy must be tuned in resonance with the plasmon energy for the stimulated gain and loss peaks to emerge. Theoretical modeling based on Fermi’s golden rule elucidates how the plasmon resonantly and coherently shuttles energy quanta between the electron probe and the radiation field and vice versa in stimulated electron energy-loss and -gain events. This study opens a fundamentally new approach to explore the quantum physics of excited-state plasmon resonances that does not rely on high-intensity laser pulses or any modification to the EELS detector.

A new optical delivery system has been developed for the (scanning) transmission electron microscope. Here we describe the in situ and “rapid ex situ” photothermal heating modality of the system, which delivers >200 mW of optical power from a fiber-coupled laser diode to a 3.7 μm radius spot on the sample. Selected thermal pathways can be accessed via judicious choices of the laser power, pulse width, number of pulses, and radial position. The long optical working distance mitigates any charging artifacts and tremendous thermal stability is observed in both pulsed and continuous wave conditions, notably, no drift correction is applied in any experiment. To demonstrate the optical delivery system’s capability, we explore the recrystallization, grain growth, phase separation, and solid state dewetting of a Ag0.5Ni0.5 film. Finally, we demonstrate that the structural and chemical aspects of the resulting dewetted films was assessed.

Focused helium ion (He) milling has been demonstrated as a high-resolution nanopatterning technique; however, it can be limited by its low sputter yield as well as the introduction of undesired subsurface damage. Here, we introduce pulsed laser- and gas-assisted processes to enhance the material removal rate and patterning fidelity. A pulsed laser-assisted He milling process is shown to enable high-resolution milling of titanium while reducing subsurface damage in situ. Gas-assisted focused ion beam induced etching (FIBIE) of Ti is also demonstrated in which the XeF precursor provides a chemical assist for enhanced material removal rate. Finally, a pulsed laser-assisted and gas-assisted FIBIE process is shown to increase the etch yield by ∼9× relative to the pure He sputtering process. These He induced nanopatterning techniques improve material removal rate, in comparison to standard He sputtering, while simultaneously decreasing subsurface damage, thus extending the applicability of the He probe as a nanopattering tool.

Quasi-phase-matched room-temperature frequency doubling to generate blue, green, and red light was demonstrated using periodically poled LiNbO3 crystals. A 1.24-mm-long sample in an external resonant cavity generated 1.7 W of green power from an input of 4.2 W at the 1.064 μm Nd:YAG laser line when heated to 140 °C to compensate for a slight error in periodicity.