ИСТИНА

In our work we fabricate and characterize the integrated optical scheme implementing the 4x4 Hadamard operation. We use the femtosecond laser writing technique to fabricate the optical scheme in fused silica. The optical circuit realizing 4x4 Hadamard transformation is described by unitary matrix and includes 4 balanced beam splitters and 1 permutation. First, we experimentally characterized both types of beam splitters in order to establish optimal circuit geometry and fabrication regime. We fabricated the series of identical elements and analyzed their reproducibility and errors. Further we compared the results obtained with numerical model of transformation stability and established that precise operation performance is achievable. Finally, the Hadamard transformation was realized.