Synrad 32-1 - Introduction; Plasma Section; Technical Overview

SYNRAD® 32-1 Operator’s Manual Version 2.2
31
Technical Reference
Technical overview
Introduction
Plasma section
Optical resonator
Control circuitry
Optical setup,
Faults, cooling, and DuoLase®
Introduction
32-1 lasers incorporate the latest technology in sealed carbon dioxide devices, combining the
best features of both waveguide and free space CO laser technology. The all-metal laser tube
construction features the ruggedness, stable optical support, and small size of waveguide
lasers. Low cost is achieved by using simple extruded and welded aluminum structures pack-
aged together with compact, state-of-the-art RF power supplies.
32-1 lasers emit a laser beam with a wavelength of 10.6 microns (µm). The laser beam diverges
due to diraction at a full angle of 8 mrad (milliradians), with the beam waist at the output
aperture of the laser.
Power control of the laser beam is achieved by pulse width modulation (PWM) of the RF drive
circuit. Modulation control can be used to gate the laser on and o at time intervals synchro-
nized with automated processing equipment. It can also be used to control instantaneous
power by adjusting the pulse width (PWM duty cycle) at a variable modulation frequency.
Both methods can be used simultaneously.
Plasma section
The laser consists of an RF-excited plasma tube with an adjustable mirror on each end,
mounted together with the RF drive assembly in a single aluminum chassis. The plasma tube
is made of two-inch square cross-section extruded aluminum tubing with pre-machined
ends welded on. RF drive power is applied between the two electrodes. The internal resonant
circuit induces RF drive on the upper electrode that is 180 degrees out of phase with that of
the lower electrode. Thus the voltage between the two RF electrodes is roughly twice that on
either electrode. Waste heat is conducted away to the outer walls of the laser tube, where it is
transferred to the chassis.
Optical resonator
The optical resonator consists of a curved total reector and a at Zinc Selenide (ZnSe) output
coupler. The mirrors are held on with Viton (uorocarbon) elastomeric o-rings for factory ad-
justment by means of three screws that are secured by adhesive after alignment. The ceramic
bore in conjunction with the mirror curvatures selected favors a Gaussian (TEM00) mode.