2
1
Introduction
This operator’s manual contains useful information about the Clarity
TM
family of locked lasers. It
contains all the information you will need to operate and maintain your laser.
If you have just received your laser, refer to section 1.3 for instructions on initial inspection. For routine
operation, section 4 will be most informative.
This manual is intended to coincide with firmware version 1.00. For other firmware versions, please
consult the appropriate manual or contact Wavelength References for information.
1.1
Product Overview
The Clarity is a semiconductor laser that is locked to a molecular absorption line. Lasers can be offered
with wavelengths chosen from the spectra of acetylene, hydrogen cyanide, hydrogen fluoride, carbon
monoxide, carbon dioxide and other gases, please inquire. The standard product configurations are
available locked to a line of C12 acetylene in the 1530nm region, C13 acetylene in the 1540nm region,
and hydrogen fluoride at 1312nm. Other wavelengths can be available on special order.
The laser is available as Precision Frequency Reference (PFR) and/or a Narrowed Line Laser (NLL).
The PFR is designed to function as a primary frequency reference and offers an output that can be
used to wavelength-calibrate optical instruments. The NLL version includes PFR functionality but
additionally locks to the side of the line to provide narrowed linewidth capability.
The locking process is fully automatic and extremely robust. The fully digital architecture also allows for
correction of many errors that could creep into a design based on older analog techniques.
This locking process can be considered as a primary frequency standard since the locked frequency is
traceable to a physical constant. The absolute accuracy of the wavelength is limited only by the
measurements (literature values or measurements made at standards bodies) made on the energy
level and the small jitter inherent in the locking process.
1.2
Application
A typical application for the Clarity laser is to provide an extremely accurate and stable wavelength
standard in the DWDM band. This can be used as a calibration source for an OSA (optical spectrum
analyzer) or to verify operation of a wavelength meter. Most wavelength meters are actually frequency
ratio meters which measure the wavelength of the unknown signal as a ratio to the built-in standard.
Generally the built-in standard is a helium neon laser. These lasers are available with absolute
frequency accuracy nearly as accurate as the Clarity but the wavelength at 632nm is very far from the
DWDM band. Vendors of wavelength meters have developed correction algorithms to compensate for
the difference of index of refraction of air and other factors that might affect the transfer of this accuracy
to the DWDM band by the wavelength meter. These techniques all add a measure of uncertainty. The
Clarity provides a means, heretofore unavailable, to verify the correct operation of a wavemeter up to
its full capabilities with a signal in the DWDM band.
Another application of the laser is in the area of interferometric sensing. Fiber optic based
hydrophones, for example, require a laser with very narrow linewidth and stable wavelength. The
Clarity laser is available with a semiconductor laser with a linewidth of <30KHz. Other interferometric
applications are surface roughness characterization, down-hole sensing, LIDAR wind detection, and
perimeter security. For applications requiring extremely narrow kHz linewidth the Clarity platform is can
be offered with extended cavity lasers from several vendors. Here we can combine the very narrow
linewidth of the extended cavity laser with the long term stability of a gas line. The Clarity can be made
available at several different wavelengths determined by the absorption spectra of the gases suitable
for your application. Also contact factory for inquiries relating to any OEM applications as a low cost
board level product is also available.
The Clarity laser is also a useful tool in gas sensing. We can provide a laser locked to many species of
gases in the near IR region. This includes the greenhouse gases carbon dioxide, methane, and nitrous
