Burleigh WAVEMETER JR WA-2500, Operating Manual, Page: 6 / 47

Wavemeter
jr
Operating Manual 1. Introduction
Burleigh Instruments, Inc. (04659-M-00 Rev E) page 1-1
Burleigh Park, Fishers, NY 14453
1. INTRODUCTION
1.1 APPLICATIONS
The WA-2500 Wavemeter
jr
is an instrument for wavelength measurement of CW
laser sources that combines accuracy with ease of use. The accuracy is
±
1 part in
10,000 over the full wavelength range.
The primary application for Model WA-2500 is measurement of the wavelength or
the frequency of tunable lasers that operate from 400 to 1800 nanometers,
particularly dye lasers, Ti:Sapphire lasers and diode lasers. Two detectors are
provided to cover this range with high sensitivity. The VIS detector is used for
lasers operating from 400 to 1100 nanometers, and the IR detector for lasers that
operate from 600 to 1800 nanometers.
1.2 THEORY OF OPERATION
Laser light enters the Wavemeter
jr
through a fiber optic cable. Lasers that emit a
collimated beam can be easily coupled into the fiber by a beam receiver consisting of
an Input Beam Coupler (BC-1) and an FC connector terminated 3 meter patch cord
(PC-F). The beam receiver can be mounted in a simple optical mount that provides
rotation about 2 axes. The efficiency of coupling laser light into the fiber is
optimized by small angular adjustments of the beam receiver in
q
and
f
. The
opposite end of the fiber optic cable connects at the rear panel of the Wavemeter
jr
and injects the light into the chassis.
Inside the chassis of the Wavemeter
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is a compact scanning Michelson
interferometer. The incoming laser beam is split into two paths, with one path
length varied by a scan mechanism. The two paths are recombined, producing
interference fringes that are detected by a photodiode. Simultaneously, the
displacement of the scan mechanism is measured by a high resolution Moiré gauge.
The microprocessor computes the correct wavelength or frequency from these two
signals, and transmits this data to the front panel display and RS-232 port. The
units of measurement are selected by a push button on the front panel.
The Moiré gauge attached to the scan mechanism of the Michelson interferometer
must be calibrated against a red HeNe laser. This is accomplished by introducing a
HeNe laser beam into the beam receiver and depressing the CALIBRATION button
on the front panel. The calibration value is stored in non-volatile memory that is
unaffected by power interruption.
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