+1/-1 order phase masks (FBG)
Easy and cost-effective fabrication of Bragg gratings
Ibsen’s +1/-1 order principle phase masks ensure quality and facilitate production in the telecommunications, sensor, and laser industries. In the production of fiber and waveguide Bragg gratings, the phase mask is illuminated by a high-power UV laser, typically an excimer laser or frequency-doubled gas laser. Self-interference between the diffracted orders produces the required pitch in the fiber or waveguide.
Features
Any deviation from the desired grating structure in the Phase mask is transferred directly to the fiber or waveguide. It is therefore imperative that the Phase mask pitch is accurate, uniform, and defect-free. Through scientific principles and constants of nature, our fabrication process ensures absolute pitch accuracy. In addition, geometric principles in our production equipment ensure strict uniformity, eliminating e-beam drawbacks such as stitching errors and field distortion.
Other important features of our line of +1/-1 order Phase masks are:
Phase mask pitches for all fiber/waveguide applications, down to 260 nm period and through the 1310 and 1550 nm wavelength ranges
Period accuracy and uniformity better than 0.01 nm
Highly suppressed residual zero order (typical: 0-2%)
Optimized for illumination from 193 nm to 800 nm
Inherently free of stitching errors
Continuous linear chirp available
Multiple period phase masks are possible
Tilted gratings are possible
Phase shifts are possible
Optimized for any illumination wavelength
Phase mask parameters are individually specified – including unique part number – on each phase mask
Principle
Using the +1/-1 order principle, the phase mask is optimized to diffract light equally and maximally into the plus first and minus first orders. Self-interference between these two orders creates an interference pattern with half the pitch of the phase mask pitch. As the diagram illustrates, a +1/-1 order phase mask can generate additional unwanted orders. Ibsen phase masks have highly suppressed zero order noise. The main advantage of this +1/-1 order principle (relative to the 0/-1 order principle) is its ease of use with normally incident illumination.
Documentation
Product range and specifications
| Parameter | Specification |
|---|---|
| Grating periods | 260 nm - 2600 nm |
| Illumination wavelengths | 193 nm - 800 nm |
| Material | UV grade fused silica |
| Period accuracy | +/- 0.01 nm |
| Period uniformity | +/- 0.01 nm |
| Chirp rates | 0 - 30 nm/cm |
| Standard grating sizes | 10 mm x 10 mm 25 mm x 10 mm 50 mm x 10 mm 100 mm x 10 mm |
| Guaranteed 0. order suppression | <3% (lower spec optional) |
| Typical 0. order suppression | 0-2 % |
| 0. order uniformity | |
| Grating length 10 mm | +/- 0.5 % |
| Grating length 25 mm | +/- 0.75 % |
| Grating length 50 mm | +/- 1.0 % |
| Grating length 100 mm | +/- 1.5 % |
Which phase mask to use?
For further information or to request a quotation please contact us.