Stabilife®
optical filters and coatings are manufactured using two
patented processes for the deposition of metal oxide thin
film optical coatings; Reactive Ion Plating (RIP) and Hybrid
Plasma Deposition (HPD). Both processes yield highly dense,
thin film coatings with extraordinary hardness, abrasion
resistance, and adhesion to the substrate. Our Stabilife®
processes were developed at our Corion coating facility in
Franklin, Massachusetts, where these products are
manufactured.
Spectral Stability
Optical components which directly
affect the spectral performance of an optical system, must
be able to deliver repeatable and accurate wavelength vs.
transmission response, regardless of the operating
conditions. In some applications, un-stabilized metal oxide
optical coatings or laminated soft-film coatings are
adequate to meet the required performance parameters.
However, for some of the more demanding applications such as
fluorescence detection, wavelength stability is absolutely
critical to insure dependable results. Stabilife®
optical filters and coatings provide the solution for these
high accuracy applications.
Film Density & Spectral Stability
Film density is a critical factor
affecting the spectral stability of an optical coating.
Un-stabilized metal oxide thin film coatings typically
exhibit a significantly lower packing density than Stabilife®
coatings. This occurs as a result of the intrinsic growth
properties of the coating materials when deposited using
methods which do not enhance film densification. The film
structure of un-stabilized metal oxide film tends to be
columnar with a significant number of voids. The presence of
these voids contributes to the occurrence of environmentally
induced spectral shift in un-stabilized external coatings.
Changes in wavelength, which are influenced by the presence
of voids, tend to be elastic in nature and depend upon the
ambient relative humidity in which the coating is being
used. The permeability of the film will determine the degree
to which this phenomena will occur. Spectral shifts in the
range of 2-5% of wavelength are typical of un-stabilized
metal oxide coatings. Stabilife® coatings have a
higher packing density and lower void ratio than
un-stabilized metal oxide coatings and are therefore less
affected by water absorption. They typically exhibit total
wet-to-dry shifts of less than 0.02% of wavelength. The
graph that follows contains measured transmittance scans of
a Stabilife filter at 0% and 100% relative humidity. The
scans are exactly overlaid as no shift is discernible at the
standard scan speed for a 30nm bandwidth filter.
Thermal Properties & Spectral
Stability
Stabilife® films are
typically 5 to 10 times less sensitive to thermal variation
than un-stabilized metal oxide films as a result of film
densification. Temperature change functions as a catalyst
for moisture migration in thin films having a significant
volume of voids. When un-stabilized films are exposed to
high temperatures, moisture migrates out of film voids
contributing to the wavelength change discussed earlier. The
high film density and reduced permeability resulting from
the Stabilife® processes reduces this effect
providing the maximum spectral stability available for all
types of precision coatings including bandpass, dichroic,
edge, notch and polarizer coatings. The graphs that follow
illustrate measured temperature-induced wavelength shift of
an unstabilized metal oxide ultra-narrow bandpass filter
compared to a Stabilife®
ultra-narrow bandpass filter.
Physical Durability
Stabilife® thin-film
optical coatings have demonstrated excellent resistance to
damage due to handling, extreme nuclear and optical
radiation, and severe environmental conditions. In the most
severe applications, such as autoclave immersed nuclear
reactor monitoring, Stabilife®
filters have demonstrated spectrally stable performance
lifetimes exceeding 8,000 hours. Stabilife®
filters have been qualified for telecommunications
applications per the requirements of Telcordia GR-2883.
While most applications are much less demanding than these,
the same robust coatings as are required for extreme
applications, are routinely supplied for all Stabilife®
products. In the course of normal production, Stabilife®
films are tested for adhesion using the snap tape test
specified in MIL-C-48497, for abrasion resistance using the
eraser test specified in MIL-C-675, and for humidity
resistance using the aggravated test specified in
MIL-STD-810E. Stabilife® thin-film optical
coatings require no additional protection such as hermetic
sealing using lamination or other processes, to achieve
their exceptional durability.
Typical Stabilife®
Applications
Stabilife®
films are produced over the wavelength range from 200nm in
the UV to 3 microns in the IR and have been utilized in a
variety of applications including:
Stabilife® is an
effective solution for bandpass filters from 200 nm to 2000
nm where thermal, environmental and spectral stability is of
primary concern. Filter sizes can range from 0.100 inches to
over 15 inches. Typical applications include filters for
clinical laboratory instrumentation, color matching systems,
and fluorescence detection systems. Spectral slopes and
blocking characteristics typical of multi-cavity Stabilife®
narrow bandpass filters are shown on the following graph.
Ultra-narrow Bandpass Filters
The exceptional spectral stability
provided by Stabilife® films is particularly
important for applications requiring ultra-narrow bandpass
filters. This quality, along with the low total loss of the
films, combine to yield high transmittance ultra-narrowband
filters with bandwidths £1 nm
that require no active substrate temperature control during
operation. Typical applications for ultra-narrow bandpass
filters include filters for astronomical observation, point
of care clinical chemistry systems, and environmental
monitoring systems. Filters as large as 10 inches in
diameter can be provided. In the following graph, the
spectral slopes and blocking characteristics of multi-cavity
Stabilife® ultra-narrow bandpass filters are
displayed.
Wide Bandpass Filters
Stabilife® wideband
filters provide extremely steep spectral slopes and very
high transmission, coupled with thermal and environmental
stability for applications requiring wide filter acceptance
angle and/or wide spectral transmission ranges. Wide
bandpass filters are commonly used in fluorescence detection
systems. The graph that follows details the typical band
shape of Stabilife® wide bandpass filters.
Dichroic Edge Filters
For applications such as
fluorescence spectroscopy, steep-edged dichroic filters with
enhanced temperature and environmental stability have been
developed using Stabilife® films. Newport’s
designs provide the very narrow transition zones necessary
for small stokes-shift fluorophores. Paired with Stabilife®
excitation and emission filters, Newport provides
fluorescence filter sets delivering superior spectral
performance, spectral stability, and durability.
Plastics and Semiconductors
Using our RIP Stabilife®
process, dense metal-oxide films can be deposited at near
ambient temperature on a wide variety of
temperature-sensitive substrates such as plastics and
semiconductor wafers. Anti-reflection, conductive, and
mirror coatings have been deposited on plastics such as
polycarbonate, acrylic, and CR39®.
Low Loss Laser Mirrors
Historically, high reflector and
output coupler inter-cavity optics have been produced by Ion
Beam Sputtering (IBS) techniques. Stabilife®
coatings provide similar low defect, low loss coatings in
reduced deposition times, with larger load sizes. Stabilife®
reflectors are routinely built with reflectivity greater
than 99.995% at 632.8 nm resulting from significantly
reduced levels of scatter and absorption in the film
(roughly a factor of ten improvement over coatings
manufactured using un-stabilized evaporation techniques).
Other thin film products currently manufactured using lBS
such as low loss thin film waveguides and high density
passivation layers are good candidates for Stabilife®
technology.
Stable UV Filters
Ultraviolet filters manufactured
using Stabilife® technology provide improved
stability and lifetime over traditional UV bandpass filters
by the inclusion of a band-defining component that requires
no protection from environmental factors.
Excellent Stabilife® film transparency combines
with physical stability to improve transmission, wavelength
precision, blocking, and of course, filter life. Stabilife®
narrow bandpass filters can be provided at wavelengths as
low as 200 nm. The following graph depicts a Stabilife®
UV narrow bandpass filter @ 228nm, fully blocked to 5OD.
Scalability
In addition to enabling the
production of highly stable films, the Stabilife®
processes are highly scalable. In comparison to other
coating technologies that are capable of producing low-loss,
spectrally stable coatings, the Stabilife®
processes are significantly less costly to scale up to very
large coating areas per process cycle. Taking advantage of
this feature, Newport has deployed both small and very large
coating chambers to fulfill orders for Stabilife®
filters in quantities as small as one and as large as one
million at competitive prices and at high monthly delivery
rates for large quantity orders.
Typical Stabilife®
Bandpass Specifications
Specification
Ultra-Narrowband
Narrowband
Wideband
Bandwidth (FWHM)
0.5
nm to 4 nm
5 nm
to 20 nm
20
nm to 200 nm
Center Wavelength (CWL)
300
nm to 2 mm
200
nm to 2 mm
200
nm to 3 mm
CWL
Tolerance (% of FWHM)
±
20%
±
20%
± 10
to 20%
Peak
Transmittance
Up
to 75%
Up
to 80%
Up
to 95%
Out-of-Band Blocking
OD4
to OD6
OD4
to OD8
OD4
to OD8
Cavities (typical)
2 to
3
3 to
5
4 to
8
Typical Stabilife®
General Specifications
Spectral Range
200
nm to 3.0 mm
Surface Quality
F/F
(80/50) per MIL-F-48616 (typical); D/C (40/20) or
C/B (20/10) achievable
Coating Hardness
MIL-C-48497
Coating Abrasion Resistance
MIL-C-48497
Coating Adhesion
MIL-C-48497
Coating Humidity Resistance
MIL-STD-810, Method 507.3, Procedure III, Modified
to 40 cycles**
Coating Operating Temperature Range
-100
º C to 300 º C**
Filter Size Range
1 mm
to 300 mm
Filter Thickness Range
0.5
mm to 20 mm
**The
specifications for humidity resistance and coating operating
temperature range listed above apply to exposed coatings
only. Humidity resistance and operating temperature range of
filters manufactured using Stabilife® coatings
and assembled using epoxy systems revert to the humidity
resistance and operating temperature range of the epoxy
system.
Founded in 1969,
Newport Corporation
is a pioneering single-source solutions provider of laser and photonics components
to the leaders in scientific research, life and health sciences, microelectronics,
industrial manufacturing, and homeland security markets.
