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These two LEDs indicate the status of the TEC under the laser crystal. The red LED indicates
the TEC is heating, while the green LED indicates it is cooling. When the laser is initially turned
on, one of these lights may be very bright as the crystal temperature stabilizes. After the crystal
temperature stabilizes both LEDs should be on, although the intensities of the two LEDs will be
different in most cases.
3.2.2 Diode Current LED
This LED indicates that current is flowing to the diode, and that the diode should be on.
Unlike the emission indicator, the Diode Current LED indicates that the seeder is lasing. There
should be laser emission unless the aperture shutter is closed.
3.2.3 Dither Potentiometer
This potentiometer sets the dither magnitude of the piezo in the host laser. Turning the
potentiometer clockwise will increase the dither magnitude.
3.2.4 Diagnostic Connector
The optional Lightwave Electronics Diagnostic Box attaches at this connector.
3.2.5 Laser Frequency Potentiometer
Turning this potentiometer will alter the temperature of the laser crystal, and consequently the
seed laser's frequency. The crystal temperature range is from ³20°C to ³60°C. Turning the
potentiometer clockwise increases the crystal's temperature, and decreases the laser's frequency. As
discussed in Section 2.1.7, adjusting the frequency of the seed laser may require adjusting the
temperature of the host laser's cooling water.
3.2.6 System Status LED
As indicated on the top of the laser head, this LED will be on when the laser is lasing, will
flash at a 1 Hz rate when the laser is in Standby Mode, and will flash at 5 Hz when there is a fault.
3.2.7 Trigger and Photodiode LED
This LED should flash at half the host laser's pulse repetition rate. If this is not happening,
either the Q-switch trigger input into the seeder's locking electronics is faulty or missing, or the
photodiode in the seeder is not "seeing" the pulse which is rejected back to the seeder.
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