9 results about "Reciprocal lattice" patented technology

Systems, methods, and media for calibrating a scanning electron microscope (SEM). The system includes a processor and a memory. The memory stores instructions that, when executed by the processor, configure the system to perform operations. An electron microscope image of a periodic structure is generated by the SEM. A Fourier transform of the electron microscope image is computed to generate a spectrum. Reciprocal lattice vectors are computed based on a known periodicity of the periodic structure. A pixel mask is generated based on the reciprocal lattice vectors and applied to filter the spectrum. A quality metric is generated based on an aggregate magnitude of the filtered spectrum and a magnitude of a zero-frequency component of the filtered spectrum. A pixel scaling parameter, focus parameter, and / or stigmation parameter of the SEM are determined based on the quality metric.

A reciprocal lattice image, which represents a lattice point group of a reciprocal lattice, is generated by performing a two-dimensional Fourier transform on a target image. In addition, a target lattice, in which an arrangement of the lattice point group approximates an arrangement of a target focal spot group, is estimated with reference to a lattice vector of the reciprocal lattice. Then, lattice coordinates of a lattice point, which is closest to a target focal spot, of the target lattice are assigned to each corresponding target focal spot, thereby pairing the target focal spot with a reference focal spot.

Systems, methods, and media for calibrating a scanning electron microscope (SEM). The system includes a processor and a memory. The memory stores instructions that, when executed by the processor, configure the system to perform operations. An electron microscope image of a periodic structure is generated by the SEM. A Fourier transform of the electron microscope image is computed to generate a spectrum. Reciprocal lattice vectors are computed based on a known periodicity of the periodic structure. A pixel mask is generated based on the reciprocal lattice vectors and applied to filter the spectrum. A quality metric is generated based on an aggregate magnitude of the filtered spectrum and a magnitude of a zero-frequency component of the filtered spectrum. A pixel scaling parameter, focus parameter, and / or stigmation parameter of the SEM are determined based on the quality metric.

The invention discloses a photon chip with an electrically-controlled angle and a light modulation method, which utilize a method that a main shaft rotates after an electric field is applied to an electro-optical crystal, rotate the polarization state of light, generate an additional reciprocal lattice vector and compensate phase mismatch in second-order nonlinear optical frequency conversion. Voltage control over the laser emission angle is achieved, and no mechanical motion is included. According to the implementation scheme, large-range wavelength tuning is adopted, and meanwhile, dispersion structures such as gratings are matched to realize angle tuning. The large-range wavelength tuning realizes second-order nonlinear optical frequency conversion through a phase matching method of rotating a polarization state.

This invention provides a multi-channel three-dimensional quasi-phase matching method and apparatus. The method includes: focusing fundamental frequency light through a microscope objective to obtain fundamental frequency light with a modified focusing state; incident the modified fundamental frequency light onto a nonlinear photonic crystal via normal incidence, and obtaining an outgoing second harmonic through the nonlinear photonic crystal; and finally, outputting multi-channel frequency-doubled light waves based on the outgoing second harmonic. This invention focuses fundamental frequency light onto a nonlinear photonic crystal via a microscope objective, changing the direction range of the incident fundamental frequency wave vector simply by altering the numerical aperture of the focusing objective. Combined with the spatial reciprocal lattice vector combination of the three-dimensional nonlinear photonic crystal, the quasi-phase matching condition is satisfied, achieving variable multi-channel frequency doubling. This invention achieves controllable multi-channel second harmonic generation without structural changes.

The present invention discloses a phase matching method and device for optical nonlinear frequency conversion. The method comprises the following steps: multiple light fields are incident along the X-axis onto a periodically poled lithium niobate crystal whose optical axis and positive and negative domain polarization directions are both along the Z-axis; an electric field is applied to the front and rear sides of the periodically poled lithium niobate crystal in the Y-axis direction to rotate the polarization of the light field, so that the light field forms a sine or cosine oscillation form in the X-Z plane projection to provide a reciprocal lattice vector, which is used to compensate for momentum mismatch in the process of second-order nonlinear optical effects to achieve phase matching; the device does not need to rotate multiple layers of two-dimensional optical materials one by one, and can adjust the compensated reciprocal lattice vector to achieve rapid tuning.

This invention relates to the field of metasurface technology, specifically disclosing a nonlinear beam shaping method based on stacked moiré metasurfaces. The method includes: obtaining the frequency harmonic wavelength of the fundamental light and the target emission angle of the nonlinear beam; calculating the quasi-period of the moiré lattice of the stacked moiré metasurface; calculating the correspondence between the lattice period and the twist angle of the stacked moiré metasurface; obtaining a stacked moiré metasurface with the stated correspondence; and forming a nonlinear beam by irradiating the fundamental light onto the stacked moiré metasurface, wherein the emission angle of the nonlinear beam is the target emission angle. This invention calculates the correspondence between the lattice period and the twist angle of the stacked moiré metasurface based on the target emission angle of the nonlinear beam, fabricates stacked moiré metasurfaces with different lattice periods and twist angles, and forms rich momentum components through the combination of reciprocal lattice vectors of multiple basic metasurfaces, thereby precisely modulating the nonlinear beam.

A method of operating a spectrometer includes positioning a crystal analyzer such that a first reciprocal lattice vector corresponding to a first crystal surface of the crystal analyzer is coplanar with a source axis and a detector axis; and performing a first scan by changing a first angle between the source axis and the first crystal plane and changing a second angle between the detector axis and the first crystal plane such that the first angle is substantially equal to the second angle; rotating the crystal analyzer such that a second reciprocal lattice vector corresponding to a second crystal surface of the crystal analyzer is coplanar with the source axis and the detector axis; and performing a second scan by changing the first angle and changing the second angle such that the first angle is substantially equal to the second angle.

The light emitting device of the present disclosure is an S-iPM laser with M-point oscillation of a phase modulation layer. In-plane wave number vectors of 4 directions each including a wave number spread corresponding to an angle spread of emergent light from the light emitting device are formed on a reciprocal lattice space of the phase modulation layer. A magnitude of at least one of the in-plane wave number vectors is less than 2π / λ. A prescribed phase distribution included in the phase modulation layer includes an element for condensing the emergent light.