A Design Method for Diffractive Optical Elements Suitable for Multiple Wavelengths

Abstract

The invention discloses a design method applicable to multi-wavelength diffractive optical elements. The design method includes: 1), determining wavelengths of lasers for diffractive optical element design and optical field distribution corresponding to each wavelength; 2), determining a target image and an imaging distance corresponding to each wavelength; 3), determining the overall size and the phase order of a diffractive optical element; 4), designing a single-wavelength diffractive element applicable to each wavelength according to the target image corresponding to each wavelength by a GS algorithm; 5), taking a diffractive element height corresponding to the longest wavelength acquired in the step 4) as an initial height, and adding a center height to each pixel point of the diffractive element; 6), subtracting an equivalent phase corresponding to each pixel point structure height, adjusted in the step 5), of each wavelength from an equivalent phase of the single-wavelength diffractive element, corresponding to each wavelength, at the pixel point; 7), repeating the step 5) and the step 6), and completing iteration when the quadratic sum of differences of the wavelengths is minimum; 8), quantizing designed phases.

Description

technical field [0001] The invention belongs to the field of applied optics, in particular to a design method for a diffractive optical element flexibly used for multiple wavelengths. Background technique [0002] Diffractive optical elements (Diffractive optical elements, DOE) is a device developed based on light wave diffraction theory. It has been widely used in the fields of laser spot shaping, spot correction, beam quality improvement and laser processing efficiency improvement. [0003] The traditional DOE has a single working wavelength, which greatly limits its application range. In 1978, Dammann proposed the concept of phase plate for color light separation for the first time, using only one phase plate to successfully separate different lights into different diffraction orders, but only simply separated the light and did not study the imaging . Subsequently, domestic and foreign scientific research workers carried out related research on multi-wavelength diffrac...

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Problems solved by technology

Subsequently, domestic and foreign scientific research workers carried out related research on multi-wavelength diffraction elements. Doskolovich, L.L. determined the depth of each step of the diffraction element structure through the wavelength ratio, and then iterated through the errors of each surface shape, and achieved a simple light field However, due to the non-linearity of the step depth, it is not conducive to processing and production; Bengtsson proposed an algorithm to discretize the input surface and the output surface, and realized the two wavelengths at a certain distance on the premise of ensuring the linearity of the step depth. Then Yusuke Ogura optimized the weights in the algorithm on the basis of it, and realized the design of diffraction elements for multi-wavelength separation imaging. This method is good for processing, but the number of image points obtained is limited, and its output light The distance of the field is relatively short; Xuegong Deng and Ray T.Chen used two diffraction elements cascaded on the basis of the single-wavelength GS algorithm to balance the weight of imaging of different wavelengths, and realized the separation and focusing of multiple wavelengths. Due to the limitation of alignment error, this method cannot be practical in practice.

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