There has been a longstanding doubt that the conversion efficiency of high harmonics in solids is much lower than expected at such a high level of electron density. To address this issue, we revisit the dynamical process of high harmonic generation (HHG) in solids in terms of wavelet interference. We find that the constructive interference among the wavelets has intrinsic consistency with the phase matching of coupled waves in nonlinear optics, which we call Bloch-wave phase matching. Our analysis indicates that most of the wavelets are out of phase and coherently canceled out during the solid HHG process, leading to only a small fraction of excited electrons effectively contributing to HHG. Consequently, the conversion from the excited electron to HHG is fairly low. Moreover, a Bloch-wave phase-matching scheme is proposed and a nearly 3 orders of magnitude enhancement of solid HHG can be achieved by engineering the crystal structures. Our Letter addresses a longstanding doubt and provides a novel idea and theoretical guidance for realizing efficient all-solid-state tabletop ultraviolet light sources.
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http://dx.doi.org/10.1103/PhysRevLett.133.116902 | DOI Listing |
Wave mixing (WM) techniques are crucial for applications such as supercontinuum generation, frequency conversion, and high-dimensional quantum encoding. However, their efficiency is often limited by complex phase-matching requirements, and current insights into phase-matching mechanisms for high-order WM remain limited. To address this, compact optical path configurations with high-peak-power, synchronous, multicolor ultrafast laser sources are needed to enhance high-order wave-mixing efficiency.
View Article and Find Full Text PDFThe PT-symmetric waveguides have been frequently discussed in the photonics community due to their extraordinary properties. Especially, the study of power transmission is significant for switching applications. The aim of this study is to extract the mode power transmission parameters based on the coupled mode equations and analyze the power properties of the PT-symmetric system.
View Article and Find Full Text PDFAdaptive mode-selective multiplexers offer the potential to control the modal content within multimode fibers for space division multiplexing (SDM). To such an end, spatial light modulators allow programmable control over the phase, amplitude, and polarization of optical wavefronts. One of the major challenges is to precisely match the manipulated beam to the waveguide modes in the multimode fiber.
View Article and Find Full Text PDFIn this paper, a high-power UV-pumped BBO optical parametric oscillator (OPO) is presented by increasing the working temperature of the nonlinear crystal to fasten the color center recovery speed and further decrease the color center density. When the working temperature of the BBO crystal was experimentally increased from 135 °C to 185 °C, the output power was scaled up from 1.20 W to 2.
View Article and Find Full Text PDFCongruent lithium niobate is a type of lithium niobate crystal with a mature growth process and is widely used in nonlinear optics research. Its refractive index accuracy will play a crucial role in the research and application of nonlinear optics. In this paper, we theoretically analyze the accuracy and reliability of nonlinear methods and experimentally measure the refractive index of ordinary light at different wavelengths and temperatures in a non-critical phase matching LN crystal by the sum-frequency generation and spontaneous parametric down-conversion processes, with the help of the existing accurate Sellmeier equation for the refractive index of extraordinary light.
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