Arbitrarily rotated optical axis waveguide induced by a trimming line.

Rotated optical axis waveguides can facilitate on-chip arbitrary wave-plate operations, which are crucial tools for developing integrated universal quantum computing algorithms. In this paper, we propose a unique technique based on femtosecond laser direct writing technology to fabricate arbitrarily rotated optical axis waveguides. First, a circular isotropic main waveguide with a non-optical axis was fabricated using a beam shaping method. Thereafter, a trimming line was used to create an artificial stress field near the main waveguide to induce a rotated optical axis. Using this technique, we fabricated high-performance half- and quarter-wave plates. Subsequently, high-fidelity (97.1%) Pauli-X gate operation was demonstrated via quantum process tomography, which constitutes the basis for the full manipulation of on-chip polarization-encoded qubits. In the future, this work is expected to lead to new prospects for polarization-encoded information in photonic integrated circuits.

Femtosecond laser self-assembly for silver vanadium oxide flower structures.

Flower-like silver vanadium oxide (SVO) micropatterns were realized by femtosecond laser in situ writing from its precursor. Self-assembled petals irradiated by a femtosecond laser were observed standing on the substrate along the scanned routine assisted by the formation of silver seeds and plasmonic-mediated effects. By controlling the concentration of ammonium monovanadate and the laser exposure time, a different thickness of petals was manipulated from ∼100 nm to micrometers. The SVO products were confirmed Ag4V2O7, AgVO3, and part of Ag3VO4 by x-ray diffraction (XRD) measurement. Photon-driven self-assembly for in situ fabrication of microstructures looks to be an effective and facile technique for SVO and other functional compounds.

Plasmonic nano-imprinting by photo-doping.

A method to directly explore the effect of electron density on the surface plasmon wave and the corresponding laser-induced structures is demonstrated by controllable doping of silver nitrate (AgNO3) into a water-soluble polymer polyvinyl alcohol (PVA). It is shown that periodic nanostructures on PVA appeared only when the electron density was more than 6×1020 cm-3 and became uniform when doping density corresponded to 1.2×1021 cm-3. Photo-excitation of electrons in the Ag-doped PVA defined by laser fluence determined the conditions of surface plasmon wave and formation of nanostructures on the surface. The Drude-Lorentz model was used to describe the formation conditions of surface wave and to estimate the period of the structures. The demonstrated photo-electron doping brings required means to control the formation of laser-induced patterns with an optical sub-wavelength resolution.

Mirror-rotation-symmetrical single-focus spiral zone plates.

In this Letter, we report mirror-rotation-symmetrical single-focus spiral zone plates (MS-SZPs) fabricated by femtosecond laser direct writing. The novel optical element can generate a single-focus vortex beam, owing to the element's complicated continuous surface. The MS-SZP surface possesses reverse mirror-rotation symmetry, which ensures that the transfer element has the same surface morphology as the original element. Both the transfer element and original element have good optical properties. The single-focus behavior was investigated by a microscopic imaging system and found to be in good agreement with theoretical simulation results. The innovative optical component is expected to be widely used in optical communication, quantum computation, optical manipulation, and other fields.