Method of producing thick nonlinear optical gratings

A method of producing a thick nonlinear optical grating (2) with a thickness of several hundred microns from an initial thick nonlinear optical grating (1), the thickness (E2) of the nonlinear optical grating (2) being greater than the thickness (E0) of the initial nonlinear optical grating (1), said initial grating comprising at least one plurality of mutually parallel plane layers (20), said layers having at least two nonlinear coefficients having algebraically different values, said initial grating having a first face (11) and a second face (12) that are approximately parallel to each other and approximately perpendicular to the mean plane of the layers, and said second face (12) being free, characterized in that it comprises the following production steps:

• a first step of determining the thickness (E01, E02) of that upper part of the initial grating (1) which lies beneath the second face (12), which upper part has structural imperfections;
• a second step of polishing the second face (12) of said initial grating (1), making it possible to remove the upper part having said imperfections and to obtain a polished and plane third face (13), said face approximately perpendicular to the mean plane of the layers (20);
• a third step of cleaning and checking said third face (13);
• and
• at least a fourth step of epitaxially depositing at least one layer (1a, 1b) of material deposited on said third face (13), the epitaxial growth reproducing, in said deposited layer, a structure similar to that of the initial grating, the combination of the initial grating (1) and said deposited layer (1a, 1b) constituting the nonlinear optical grating (2).