Compact 589 nm yellow source was reported and generated from intracavity frequency-doubling of c-cut YVO 4 / Nd:YVO 4 /YVO 4 Raman laser. A Cr 4+ :YAG/YAG composite was adopted for compact passively Q-switching operation. Double-end composited Nd:YVO 4 crystal was designed to reduce the thermal effect and increase Raman crystal length. Both noncritical phase-matching (NCPM) LBO crystal and critical phase-matching (CPM) BBO crystal were used as frequency doubling crystal for comparison. 780 mW output power of 589 nm yellow emission was achieved with an incident pump power of 16 W. The pulse repetition frequency and pulse width were 41 kHz and 3.6 ns at the maximum output power, respectively. The results show passively Q-switched operation provides a compact method to obtain 589 nm yellow emission.
We demonstrate second harmonic generation by using an amorphous silicon metamaterial fabricated on the tip of an optical fiber that collects the generated light. The metamaterial is a double-chevron array that supports a closed-mode resonance for the fundamental wavelength at 1510 nm with a quality factor of 30. The normalized resonant second harmonic conversion efficiency calculated per intensity and square of interaction length is ∼10−11 W−1, which exceeds the previously achieved value for a silicon metamaterial by two orders of magnitude.
Despite recent tremendous progress in optical imaging and metrology1–6, there remains a substantial resolution gap between atomic-scale transmission electron microscopy and optical techniques. Is optical imaging and metrology of nanostructures exhibiting Brownian motion possible with such resolution, beyond thermal fluctuations? Here we report on an experiment in which the average position of a nanowire with a thermal oscillation amplitude of ∼150 pm is resolved in single-shot measurements with subatomic precision of 92 pm, using light at a wavelength of λ = 488 nm, providing an example of such sub-Brownian metrology with ∼λ/5,300 precision. To localize the nanowire, we employ a deep-learning analysis of the scattering of topologically structured light, which is highly sensitive to the nanowire’s position. This non-invasive metrology with absolute errors down to a fraction of the typical size of an atom, opens a range of opportunities to study picometre-scale phenomena with light.
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