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2D Phase masks

Phase masks are the production tool used to write gratings in fibers and waveguides. Ibsen Phase masks incorporate unbeatable, interferometric (holographic) patterning technology into a production friendly Phase mask.

– enabling single-step patterning of 2D gratings on planar wafers

Ibsen introduces 2D Phase masks for one-step generation of 2D square lattice grating patterns on planar wafers.

2D gratings can now be manufactured by the established Phase mask principles by simply exposing the wafer through an Ibsen 2D Phase mask at Bragg angle incidence, similar to the well known NFH Phase mask mode of operation (i.e. Bragg angle illumination).

By single exposure through an Ibsen Phase mask, and subsequent development of the photo-resist, and etching into the wafer, 2D square lattice grating structures as shown below can be written over large areas on a wafer.

Important features of our line of 2D Phase masks are:

  • Single exposure process for 2D square lattice grating structures
  • Square lattice periodicity possible down to 260 nm
  • Period accuracy and uniformity of +/- 0.01 nm
  • Hole diameter is controlled by exposure time
  • High contrast in interference pattern
  • Inherently free of stitching errors.
  • Optimized to illumination wavelength from 193-800 nm
  • Can be optimized to any polarization – including unpolarized
  • Phase mask parameters are individually specified – including unique part number – on each Phase mask

Principle

The 2D square lattice Phase mask is illuminated at the Bragg angle, similar to the well known 0/-1 order Phase mask principle. The 2D Phase mask diffracts this illumination into multiple orders – the coherent interference pattern between these accurately reproduces the 2D Phase mask periodicity. Our innovative production techniques allow us to manufacture Phase masks with periods down to 200 nm, while the 2D Phase mask principle of operation limits the upper lattice periodicity to 687 nm (with 435 nm illumination).

The Bragg angle is given by the following equation:

2D Bragg angle equation

For a given illumination wavelength, the fundamentally possible periodicities are given by the following Criteria of Suitability:

2D Phase mask Criteria of Suitability equation

, where Λ is the 2D grating periodicity and λ is the illumination wavelength

 

Parameter Specification
Grating periods 260 nm – 687 nm
Illumination wavelengths 193 nm – 435 nm
Material UV grade fused silica
Period accuracy +/- 0.01 nm
Period uniformity +/- 0.01 nm
Standard grating sizes 10 mm x 10 mm
Ø1″
Ø2″