LNOI-based spot-size converter directly coupled with single-mode fiber

Abstract

The invention discloses an LNOI-based spot size converter directly coupled with a single-mode optical fiber and a method, relates to the field of integrated optics, and aims to solve the problem of efficient coupling between an optical fiber and an LNOI chip. The structure is composed of a substrate, a buffer layer and a waveguide layer from bottom to top, the waveguide layer can be divided into two parts in the light field transmission direction, the first part is a double-layer forward conical area made of low-refractive-index waveguides and used for mode field conversion between an input light field and a reverse conical area, and the second part is a reverse conical region formed by etching the top layer lithium niobate and is used for final mode field transformation with the LNOI chip waveguide. Through the design of the double-layer forward conical area, the transition effect between the reverse conical region and an external input light field is achieved, the coupling between the reverse conical region and a larger input mode field can be achieved, the conversion efficiency is further improved, the whole structure is more compact and efficient, and large-scale light path integration is better achieved.

Description

Technical field: [0001] The invention belongs to the field of integrated optics, in particular to an LNOI fundamental mode speckle converter directly coupled with a single-mode optical fiber and a method thereof, which can be used for efficient coupling between an optical fiber and an LNOI chip. Background technique [0002] As a new type of material, lithium niobate (LN) has many excellent optical properties, including large electro-optic coefficient, nonlinear optical effect, wide optical transparent window, good temperature stability, low thermo-optic coefficient, etc. Therefore, in the past In the past ten years, lithium niobate has developed rapidly in the field of integrated optics. In order to further meet the development requirements of the miniaturization of integrated photonic devices, lithium niobate on insulator (lithium niobate on insulator, LNOI) was manufactured based on ion implantation and wafer bonding technology by thinning lithium niobate to hundreds of n...

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Problems solved by technology

Out-of-plane coupling can also be called vertical coupling, among which the grating coupler is the most representative. The grating coupler has many advantages such as large alignment tolerance, flexible coupling position, compact structure, etc., so it is generally suitable for the test of optical chips, but limited Due to the principle of diffraction, grating coupling is sensitive to wavelength and polarization, it is difficult to achieve high coupling bandwidth and polarization independence, and grating coupling lacks a reasonable packaging solution in practical applications; in-plane coupling can also be called end-face coupling, traditional end-face Coupling is to directly connect the end face of the fiber pigtail with the end face of the chip waveguide. This coupling method requires strict alignment between the fiber and the waveguide, the alignment tolerance is very limited, and there is a problem of mode field mismatch between the fiber and the waveguide, which leads to Coupling inefficiency

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