Optical Coatings

Fundamental Optics
Material Properties Optical Specifications Gaussian Beam Optics
HEBBAR Coatings
Our HEBBAR (high-efficiency broadband antireflection)
coatings provide a very low reflectance over a broad spectral
bandwidth. These multilayer films, comprising alternate layers of
various index materials, are combined to reduce overall reflectance
to an extremely low level for the broad spectral range covered.
These coatings exhibit a characteristic, double-minimum reflectance
curve covering a range of some 300 nm in wavelength. The
reflectance does not exceed 1.0% and is more typically below 0.6%
over this entire range. Within a more limited spectral range on
either side of the central peak, reflectance can be held well below
0.4%. HEBBAR coatings are somewhat insensitive to angle of
incidence. The effect of increasing the angle of incidence, however,
is to shift the curve to slightly shorter wavelengths and to increase
the long wavelength reflectance slightly. These coatings are extremely
useful for high-numerical-aperture (low f-number) lenses or steeply
curved surfaces. In these cases, incidence angle varies significantly
over aperture.
Six versions of HEBBAR coatings are offered (see figures 5.20
through 5.25). Many of our components are carried in stock with
a HEBBAR coating. The /078 covers most of the visible spectrum
(415–700 nm) and is optimized for normal incidence. A 45-degreeincidence
version of this coating (/079) is available. The infraredshifted
/077 covers the range from 700 nm to 1100 nm. Two
HEBBAR coatings, the /075 and the /076, are specifically optimized
for diode laser wavelengths. The /074 is a modified HEBBAR
coating intended for use in the range from 300 nm to 500 nm. Over
this range, the reflectance is less than 1% and typically does not
exceed 0.5%. Due to the special nature of the /074 coating, it is
designed to be used only at an angle of incidence of 0±15 degrees,
and it is not suitable for use on lenses with steeply curved surfaces.
For these coatings, reflectance values apply to indices 1.47–1.55
only. Other indices, while having their own designs, will have
reflectance values approximately 20% higher for incidence angles
from 0 to 15 degrees and 25% higher for incidence angles of 30
degrees. The typical reflectance curves shown for the HEBBAR
coatings are for BK7 substrates, except for /074 which is for fused
silica.
HEBBAR Coatings
Wavelength
Range
(nm)
440–660
415–685
415–700
415–680
632.8
632.8
425–670
425–670
440–670
440–670
750–1100
700–1100
700–1150
700–1100
650–850
650–850
780–850
780–850
725–875
300–500
300–500
Maximum
Reflectance
(%)
0.6 Abs
0.4 Avg
1.0 Abs
1.0 Abs
0.3 Abs
0.4 Abs
0.6 Avg
1.0 Abs
0.4 Abs
1.0 Abs
0.6 Abs
0.4 Avg
1.0 Abs
1.0 Abs
0.6 Avg
1.0 Abs
0.25 Abs
0.40 Abs
1.0 Abs
1.0 Abs
0.5 Avg
Angle of
Incidence
(degrees)
0–15
0–15
0–15
0–30
0–15
0–30
45
45
30–45
45–50
0–15
0–15
0–15
0–30
0–15
0–15
0–15
0–30
0–30
0–15
0–15
COATING
SUFFIX
/078
/079
/077
/075
/076
/074
Note: To order, append coating suffix to product number and specify which surfaces are
to be coated.
Optical Coatings
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