0/-1 order phase masks (NFH)

Cost-effective fabrication of low period gratings, typically in high refractive index materials

Low-cost production of gratings on planar wafers can be accomplished by use of the Nearfield Holography (NFH) technique, which employs a special type of phase mask. The phase mask is made for easy use in a specially modified mask aligner (commercially available from Süss MicroTec) with a conventional UV source as illumination. This technology has distinct production advantages over grating fabrication by direct holography or direct e-beam technology. In addition of fabrication of gratings on semiconductor DFB lasers, the technique is also advantageous in a number of other fine-pitch applications within the telecommunications and sensor industries.

Sample applications include:

  • DFB lasers

  • DBR lasers

  • Integrated planar optics

  • Sensors

  • Biochips


It is imperative that the Phase mask is accurate, uniform and defect-free. Through scientific principles and constants of nature, our fabrication process ensures absolute pitch accuracy.

All our production processes take place in a cleanroom environment, giving you high yield through nearly defect-free Phase masks. Phase masks and the NFH technology are thus suitable for mass production of distributed feedback (DFB) lasers.

Other important features of our line of 0/-1 order Phase masks are:

  • Phase mask pitches down to 260 nm

  • Period accuracy and uniformity better than 0.01 nm

  • Inherently free of stitching errors

  • Optimized for the required illumination wavelength

  • Phase mask parameters are individually specified – including unique serial number – on each phase mask

0/-1 order Phase mask

Fused silica transmission gratings

Learn how our transmission gratings work in this white paper about fused silica transmission gratings. This technology is the one used when producing Ibsen’s grating products.

See white paper


The 0/-1 order principle is advantageous for fine-pitch applications that require complete elimination of unwanted orders. In this geometry, light incident at the Bragg angle is diffracted partially into the minus first order. Self-interference between the minus first order and the undiffracted zero order creates an interference pattern with a pitch equal to the phase mask pitch. Thus, 0/-1 order phase masks have half the pitch of the equivalent +1/-1 order phase masks. Our innovative production techniques allow us to manufacture 0/-1 order phase masks with periods down to 260 nm.


0/-1 order Phase mask principle sketch

Product range and specifications

Grating periods260 nm - 600 nm
Illumination wavelengths193 nm - 800 nm
MaterialUV grade fused silica
Period accuracy+/- 0.01 nm
Period uniformity+/- 0.01 nm
Standard grating sizesØ1"
Fringe visibility>98%

Which phase mask to use?

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