What is a Phase mask?

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Clarification of Question by bubu1970-ga on 06 Apr 2004 03:11 PDT

I actually know (Ibsen Photonics makes Phase masks) but I think there
should be a definition!

Hi bubu1970,
  
From the Optical Engineering magazine website:
  
"A phase mask is itself a grating, etched in silica, that diffracts UV
light at normal incidence into the +1 and -1 diffractive orders. These
two orders interfere to create the desired interference pattern just
behind the mask, which is where the fiber is placed. Typical exposure
times vary from a few seconds to a few minutes, depending on the type
and strength of grating."
http://oemagazine.com/fromTheMagazine/tutorial/tutorial101.html
  
  
StockerYale Inc. is a world leader in phase mask fabrication. On their
website you'll find detailed information on the function of phase
marks with diagrams and formulas:
  
"Introduction to Phase Masks" 
http://www.stockeryale.com/o/lasiris_pm/index.htm
  
  
This paper presents an investigation of a fabricated fiber grating
device characteristics and its applications, using a phase mask
writing technique:
  
"A phase mask fiber grating and sensing applications"
http://www.psu.ac.th/PresidentOffice/EduService/journal/25-5-pdf/07fiber.pdf
  
  
I hope this information is useful.
  
  
   
Google search terms: 
"phase mask"
"phase mask is" OR "phase marks are" gratings

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Request for Answer Clarification by bubu1970-ga on 06 Apr 2004 04:22 PDT

The first definition is good - but it only covers 1 of 2 Phase mask types.

See the principle paragraph on:
http://www.ibsen.dk/ibsen/phasemas.nsf/Framesets)/2A336B79D631BBBFC12567CA003016D1

(Also the similar +1/-1 principle is defined:)
http://www.ibsen.dk/ibsen/phasemas.nsf/Framesets)/F7AA8B52CE66751AC12567CA002FE49A

PLease add the 0/-1 order principle to complete the definition.

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Clarification of Answer by jackburton-ga on 06 Apr 2004 05:01 PDT

"Phase masks are typically employed in one of two configurations:
+1/-1 or 0/-1. In the +1/-1 configuration, the UV radiation is
directed with normal incidence at the phase mask, and the period of
the fringe pattern generated by the interference of the outgoing beams
is exactly one half of the period of the phase mask grating. In the
0/-1 configuration, the UV radiation is directed at the phase mask
with a specially chosen angle of incidence, and the period of the
fringe pattern is exactly equal to the period of the phase mask
grating."
http://www.stockeryale.com/o/lasiris_pm/index.htm
(paragraph 4)