Tsunami Mode-Locked Ti:sapphire Laser
8-18
b. The system enters “locked” mode, and the PZT locking loop is
engaged. The “acquisition” bit of the status byte is cleared, the
“loop on” bit stays set.
c. The PZT voltage is continuously monitored, and the motor mike is
servoed to keep it in range. The status byte remains unchanged.
Examples:
LOOP 0 turns loop off
LOOP 1 turns loop on
:LOOP?—returns a “1” if the loop is on, a “0” if it is off. If the system is in
acquisition mode, this query returns a “1”. (This query mirrors the “loop
on” bit in the status byte.)
:LMON:DC? and :LMON:AC?—return the DC and AC portions of the loop
monitor signal. These are essentially meaningless when the loop is off.
When the loop is on, the absolute value of the DC portion is typically less
than about 40, while the AC component is typically 5 or less. The loop
monitor is a more sensitive indicator of loop operation than the PZT volt-
age.
:PZT:DC? and :PZT:AC?—return the DC and AC portions of the PZT volt-
age. These are essentially meaningless when the loop is off. When the loop
is on, the DC value is 0 when the PZT is centered. Auto-centering will keep
the absolute value of the DC value less than about 400. The AC reading is
typically less than 10.
:DLY <parameter>—sets the value of the timing adjustment, with parame-
ter values from 0 to 4095 adjusting the timing by approximately 2 ns.
This setting is added to the timing adjustment set by the front panel knobs.
For consistent results, the front panel coarse and fine timing adjustment
controls should be set fully clockwise.
:DLY?—returns the delay set by the DLY command (which is zero at power-
up).
:LDLY <parameter> and :LDLY?—are similar to the :DLY and :DLY? com-
mand and query. The difference is that the values of the parameter and
reply range from 0 to 65535 and the timing adjustment range is greater than
or equal to 12.5 ns (2π radians at 80 MHz).
The DAC used is not guaranteed to be monotonic beyond 14 bits, and
the phase shifter itself is not perfect. It is possible that small changes in
the LDLY setting will not move the delay in the expected direction.
Note
If this command is issued to the Model 3930, a “Hardware not present”
error will be generated. This command is only valid if the Model 3931 is
present.
Note
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