METHOD FOR ANTIREFLECTION OF ENDS OF ACTIVE Cr:ZnS WAVEGUIDES BASED ON SURFACE MICROSTRUCTURING Russian patent published in 2023 - IPC G02B6/10 

FIELD: optical materials.

SUBSTANCE: obtaining antireflection microstructures on optical surfaces. Methods for obtaining antireflection microstructures on optical surfaces of active Cr:ZnS waveguides in the mid-infrared (from 2 to 10 mcm) range. Claimed method of antireflection of the ends of active Cr:ZnS waveguides based on surface microstructuring is designed to suppress the reflection and scattering of electromagnetic waves from 2 to 10 mcm, falling on the surface of the substrate at angles in the range from 0 to 40 degrees, from the surface of the end of the active Cr:ZnS waveguide and thus increasing the transmission of electromagnetic waves through the active Cr:ZnS waveguide, by modifying the flat surface of the end face of the active Cr:ZnS waveguide using direct laser ablation with single ultrashort laser radiation pulses, which uses a laser producing ultrashort laser radiation pulses, a lens for focusing ultrashort pulses laser radiation relative to the upper boundary of the substrate, a positioner that moves the substrate in three coordinates relative to the focusing point of ultrashort laser radiation pulses. The method includes placing an active Cr:ZnS waveguide relative to the focusing point of ultrashort laser radiation pulses, where the end face of the active Cr:ZnS waveguide is directly exposed to ultrashort laser radiation pulses, and ultrashort laser radiation pulses physically affect the surface of the active Cr:ZnS waveguide end face to remove material from the end surface of the active Cr:ZnS waveguide by ablation, forming a hole or a depression. The positioner continuously moves the end of the active Cr:ZnS waveguide, synchronized with the repetition rate of ultrashort laser pulses, to form holes on the flat top surface of the substrate. At the same time, the created surface microstructure has distances between holes less than the shortest wavelength of electromagnetic waves, and the depth of the holes is greater than the shortest wavelength of electromagnetic waves. Moreover, the effective refractive index of the surface microstructure monotonically increases from the environment to the material substrate.

EFFECT: reduction of losses during transmission of electromagnetic waves due to reflection from the microstructure of the surface topography at the ends of active Cr:ZnS waveguides by 15%.

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