Achromatic self-referencing interferometer

Patent · 01 January 1994

OSTI ID:869244

Feldman, Mark ^[1]

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1. Pleasanton, CA

A self-referencing Mach-Zehnder interferometer for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and registers the resulting interference pattern ("first" interferogram) at a first detector. Optionally, subportions of the measurement portion are diverted to second and third detectors, which respectively register intensity and interferogram signals which can be processed to reduce the first interferogram's sensitivity to input noise. The reference arm includes a spatial filter producing a high quality spherical beam from the reference portion, a tilted wedge plate compensating for off-axis aberrations in the spatial filter output, and mirror collimating the radiation transmitted through the tilted wedge plate. The apparatus includes a thermally and mechanically stable baseplate which supports all reference arm optics, or at least the spatial filter, tilted wedge plate, and the collimator. The tilted wedge plate is mounted adjustably with respect to the spatial filter and collimator, so that it can be maintained in an orientation in which it does not introduce significant wave front errors into the beam propagating through the reference arm. The apparatus is polarization insensitive and has an equal path length configuration enabling measurement of radiation from broadband as well as closely spaced laser line sources.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• DOE Contract Number: W-7405-ENG-48
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 5305074
• OSTI ID: 869244
• Country of Publication: United States
• Language: English

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600
900
aberrations
accurately
accurately measuring
achromatic
adjustably
apparatus
arm
arms
baseplate
beam
beams
broad
broadband
closely
closely spaced
collimating
collimator
compensating
configuration
detector
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directs
diverted
enabling
equal
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filter
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front
input
input beam
insensitive
intensity
interference
interference pattern
interferogram
interferometer
introduce
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line
line source
mach-zehnder
mach-zehnder interferometer
maintained
measurement
measuring
measuring laser
mechanically
mechanically stable
mirror
mounted
nm
noise
off-axis
optics
optionally
orientation
output
output beam
output beams
path
path length
pattern
plate
polarization
portion
processed
producing
propagating
quality
radiation
radiation transmitted
range
recombines
reduce
reference
reference portion
register
registers
respect
respectively
resulting
self-referencing
sensitivity
signals
significant
sources
spaced
spatial
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spherical
stable
subportions
supports
thermally
third
tilted
transmitted
wave
wave front
wavefronts
wavelength
wavelength range
wedge