technical reference
34
Synrad
Series 48Series 48
Series 48Series 48
Series 48 operator’s manual
Technical overview
The output wavelength remains at or near 10.6 µm (typically 10.57 µm to 10.63 µm). Beam shape is
square at the laser output aperture, changing to circular at distances of approximately one meter or more
from the laser with a near gaussian profile in the far field (0.6 m or more). The internal structure and
optics of the resonator combine to produce a mode quality of TEM
00
, 95% purity with an M
2
factor less
than 1.2. As shown in Figure 3-3, beam waist diameter is 3.5 mm at the output aperture and full angle
divergence due to diffraction is 4 mrad (a 4 mrad full angle divergence means that beam diameter
increases 4 mm over every one meter distance traveled).
Figure 3-3 Beam characteristics
Ø
RF DISCHARGE REGION
1.5 cm
GAP
3 METER RADIUS
Si TOTAL REFLECTOR
ZnSe FLAT
OUTPUT COUPLER
37 cm FOR 10W LASER or
75 cm FOR 25W LASER
FULL ANGLE
DIVERGENCE ~ 4 mrad
OUTPUT
1.5 cm
GAP
BEAM
BEAM WAIST DIA. ~ 3.5 mm
Control circuitry
Electrical description
Control of laser operation and power output levels is essentially performed using a single PCB. The
Control PCB connects the modulated signal to the RF amplifier. It also provides electronics to monitor
performance of RF control, output circuitry, input power, temperature, PWM accuracy, provides outputs
to an externally accessible connector, and incorporates reverse polarity protection.
Functional differences between model types generally relate to the number of RF channels. Model 48-1
lasers use a single RF electrode requiring a single modulated RF drive input from the Control PCB. The
48-2 uses 2 RF electrodes and requires 2 RF channels, while the 48-5 uses 4 electrodes and 4 RF channels
(2 Control PCB’s). For the purpose of this description, a single channel will be described. Model specific
details relating to differences in electrical characteristics are individually discussed.
The modulated input Command signal is generated externally to the laser and connected to the panel-
mounted BNC connector labeled CTRL. This signal is connected to an optoisolator, the output of which
is applied to the PWM switch control circuit. The PWM switch control circuit gates the PWM switch off
and on at the frequency and duty cycle controlled by the modulation source. When the PWM switch
closes, a potential of +30 VDC is applied to the RF Driver. The PWM control circuit provides on/off
gating of the PWM switch unless disabled by the five-second delay, Shutter Switch, or the fault shutdown
circuits.
The five-second delay disables PWM output to the RF amplifier for a period of approximately five
seconds after the panel-mounted Keyswitch and Remote Keyswitch link are closed (power ON). On OEM
models, the five-second delay period begins on DC power up of the laser.
The Shutter Switch allows the operator to temporarily interrupt laser output during active lase modes. A
mechanical lever physically blocks the exit aperture and at the same time actuates independent micro-
switches that electrically interrupt power to the RF module by disabling the PWM input optoisolator,
forcing an “off” state.
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