2021/04/17 23:32
5/18
Reconfigurable Laser Servo
Product Manuals - https://www.vescent.com/manuals/
Fig. 3: Monitor output logic
Error In
The ERROR IN monitor is a buffered and filtered version of the ERROR INPUT. The monitor has a 300
kHz low-pass filter.
DC Error
The signal from ERROR IN (after demodulation if in PEAK LOCK mode) is amplified by 26 dB (x20). The
amplified signal is summed with both the DC OFFSET as set on the front panel and the back-panel DC
OFFSET INPUT. The DC ERROR is passed through a low pass filter with a roll off of 200 kHz, so that
high frequency noise does not obfuscate the signal. The DC level of the DC ERROR sets the lock-point
and can be adjusted with the DC OFFSET knob. When locked, the Laser Servo acts to drive the DC
ERROR to zero.
AC Error
The AC ERROR monitors the same signal as the DC ERROR, except there is no low-pass filter and the
signal is coupled through a high pass filter to remove DC components (< 10 Hz). It is designed for
spectrum analysis and is also useful for coarse estimates of the laser line-width. The bandwidth of the
AC ERROR is limited by the preceding amplifier stages to greater than 20 MHz.
Servo Out
The SERVO OUT monitors the correction signal that is fed back to the laser, SERVO OUTPUT. The
signal is the output from the tunable loop filter.
Ramp Mon
The RAMP MON is a monitor for the actual ramp signal sent to the SERVO OUTPUT when the laser is in
RAMP mode.
Ramp TTL
