Vescent Photonics D2 Series Product Manual
optimized to a wide variety of plants and servo loops. With the Peak Lock option, the Laser Servo can
demodulate a system-provided 4 MHz dither signal to enable slope-detection for locking to signal minima
and maxima. The Laser Servo can be used to lock a laser's current or PZT to an interferometer or an
optical transition. With peak-lock, the Laser Servo can perform Pound-Drever-Hall (PDH) locking to an
optical cavity. The Reconfigurable Laser Servo uses basic voltage inputs and outputs. As a result, it can
be used with lasers or with any voltage-tunable device with an error signal.
The Laser Servo can be unlocked by a computer (via TTL control) to jump the output voltage to a set
voltage difference from the current lock point, or to a specific voltage. This feature can be used to jump
the laser frequency a known distance away and then relock to the original or a new lock-point frequency.
This feature can be used for auto-locking or relocking routines.
The Laser Servo has an internal sweep generator to sweep the laser frequency prior to lock. It also
optionally contains a temperature control circuit to maintain constant temperature for the Spectroscopy
Module (D2-110) or other TEC-controlled environments.
1.1.1. Options
The D2-125 can be purchased with five options1:
•-PL – Peak Lock option
•-T – Temp stabilization option
•-RC – Ramp Offset option
•-IP-X – Internal Power (where X=100 AC, 120 AC, or 230 AC)
•-LG – Lock Guard option
The Peak Lock option generates a 4 MHz dither signal that can be used to modulate the laser current. The
amplitude and phase of this modulation can be adjusted via front panel controls. The Error Signal input
will be demodulated relative to the dither signal which will generate a derivative of the input Error Signal.
This derivative signal will be used to lock the laser to a minima or maxima of the input Error Signal. This
is often referred to as peak-locking. If purchased with the Peak Lock option, the Laser Servo can still be
used in side-lock mode. A front panel switch controls whether the D2-125-PL is in side-lock or peak-lock
mode. When in side-lock mode the modulation / demodulation circuitry is disabled. In this manual,
sections that are only relevant to the Peak Lock option are printed in red.
The Temp option is designed for use with the escent Spectroscopy Module (D2-110). It provides power
(±12 ) to the photo-detector board and stabilizes the module's temperature via the TEC's and a thermistor
in the D2-110 module. In this manual, sections that are only relevant to the Temp stabilization Lock
option are printed in blue.
The Ramp Offset option provides the user with two front-panel knobs to adjust the voltage of the center
of the ramp. Without this option, the ramp is always centered at 0 and when the servo goes from unlock
mode to lock mode, it engages the integrators starting from 0 . With the Ramp Offset option, the user
can turn Ramp Offset knobs (coarse and fine) to adjust the center of the ramp and the initial voltage point
from which the servo begins integrating. This option is typically not used when Servoing escent DBR
lasers as this functionality is redundant with the current adjust knobs on the D2-105 Laser Controller.
1 Not all combinations of options are available. For example, the “-T” option cannot be combined with the “-IP”
option. Please contact sales for details.
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