Arroyo Instruments LaserSource 4400 Series, Руководство пользователя

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Page 30 · 4400 Series LaserSource User’s Manual
Po mode (also referred to as APC, or automatic power control, mode) is simply
Im mode with a mathematical constant applied to the set point, providing a
convenient way of operating in milliwatts. Using the PD Resp factor (in
μ
A/mW),
a Po set point is internally converted to an equivalent Im set point by the driver,
which is then used to control the photodiode feedback. For example, if the PD
Resp factor was 10, then a set point of 1mW would be the same as a set point of
10
μ
A.
Vf mode (also referred to as AVC, or automatic voltage control, mode) is used to
control the voltage driven through the device. Unlike ACC mode, AVC mode
allows the current to drive to whatever current is necessary to achieve the
voltage set point, so long as it does not exceed the current limit. As with
Im
mode, only low frequency modulation (10Hz or less) is possible in Vf mode.
Modulation
The instrument supports external analog modulation using the
Modulation BNC
on the front panel of the instrument. Modulation rates vary by model, so see
your model’s specification for the maximum modulation rates. Only
Io HiBW
mode supports high speed modulation. All other modes of operation have a
modulation bandwidth of 10Hz or less.
Using QCW Modes
Io (Pulse), Io (Ext Trig) , and Io (Burst) are quasi-CW (QCW) modes, where the
laser is turned on and off, typically with very short on times and long off times to
minimize the thermal loading of the laser. Measurements are taken only during
the on cycle (although at a reduced accuracy and resolution), and external
instruments can by synchronized using the trigger input and trigger output
signals.
In pulse
( Io Pulse ) mode, the current pulses are based on the pulse width, duty
cycle, and frequency, as defined in the main menu. To use this mode, set the
Mode to Io (Pulse) , and then set the QCW Width , QCW Duty , and QCW Freq
as needed for your application. These three parameters are interrelated as
defined by the following equation:
Width Pulse
DutyCycle
Frequency

However, if you take the values directly from the menu, then a modified version
of this equation that takes the various decimal places of the menu values into
account could be written this way: