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Method for making a waveguide in a substrate using a femtosecond laser

Delay foilsIntegrated photonicsPolarization of lightQuantum technologiesWave guides

Introduction

Method for manufacturing with femtosecond laser technology, optical waveguides with an inclined birefringence axis, usable in all respects as integrated birefringent waveplates. The simplicity of the proposed method makes it particularly interesting, especially when compared with the complexity required to manufacture equivalent devices with lithographic techniques.

Technical features

The method includes preparing a substrate including a free surface, focusing a femtosecond laser beam into the substrate, in order to induce a change in the refractive index of a volume of that substrate around the focal region and a change in a direction of propagation of the femtosecond laser beam to achieve a propagation direction, which describes a predetermined angle with respect to the normal to the free surface of the substrate, and the translation of the focal region with respect to the substrate, to generate the waveguide segment. The possibility of having arbitrary transformations of the polarization state is a crucial requirement in numerous applications (from optical detection to optical communications and both in classical and quantum regime) and whenever interference phenomena must be exploited and often require severe stability requirements of phase and benefit greatly from a monolithic integrated optics approach. The simplicity of the present invention overcomes the complexity necessary to manufacture equivalent devices with traditional lithographic techniques, forming part of the known art.

Possible Applications

  • Classic optics;
  • Quantum technologies;
  • Context of quantum sensing;
  • Quantum encryption.

Advantages

  • No use of conventional lithographic techniques;
  • Control and manipulation of the polarization state of a laser beam;
  • Precise control of the angle of inclination;
  • Waveguide segments that act as integrated wave sheets;
  • Simple and inexpensive approach.