Arroyo Instruments LaserSource 4300 Series User manual

Page 2 · 4300 Series LaserSource User’s Manual
Table of Contents
Introduction ...............................................................................................3
Safety Terms and Symbols.......................................................................5
Quick Start ................................................................................................7
Installation .................................................................................................8
Operation ................................................................................................10
Settings and Menus ................................................................................12
Control Modes.........................................................................................17
Using QCW Modes .................................................................................18
Cable Wiring for Modulation and QCW ..................................................20
Using the Cable R Setting.......................................................................21
Using Remote Voltage Sense (4320 Only) .............................................22
Remote Mode Operation.........................................................................23
Installing the USB Drivers .......................................................................24
Rear Panel...............................................................................................25
Connecting to the LaserSource ..............................................................28
Grounding Considerations......................................................................29
Using Limits.............................................................................................30
Thermal Considerations..........................................................................31
Specifications..........................................................................................33
Special Considerations for 12V to 15V Units ..........................................35
Error Messages.......................................................................................35
Maintenance and Service........................................................................37
Warranty..................................................................................................38

4300 Series LaserSource User’s Manual · Page 3
Introduction
Thank you for choosing the LaserSource from Arroyo Instruments. Your
LaserSource is a combination of leading edge technology combined with years
of experience in the field of current control.
With a crystal clear VFD display, both RS232 and USB computer interfaces, and
small footprint, the LaserSource will fit into almost any laser diode control
application.
A key feature of the LaserSource is its optical isolation of both modulation and
photodiode inputs. By isolating these inputs, it prevents unwanted ground loop
problems. No other laser diode driver in the industry has this feature.
Another important feature of the LaserSource is its ability to operate in quasi-
CW (QCW) mode. This mode permits operation of lasers to a higher current and
power, minimizing the thermal load by turning the laser on for only a brief period
of time, taking measurements, then turning off the laser. The LaserSource
supports both internal and external triggering of pulses, and also includes a
trigger out to synchronize the LaserSource with other instruments.
The LaserSource also operates in constant voltage control mode, allowing you
to use it in precision voltage applications, such as EML devices, or for doing V-I
measurement graphs.
The LaserSource includes another feature not found in other products: the
ability to program the photodiode bias level from the front panel or over the
computer interface, to any voltage from 0 to -5V. No more tweaking a
potentiometer with a screwdriver and a DMM. Simply dial in the voltage you
need.
Unlike other laser diode drivers in its class, which use inexpensive 7-segment
displays, the LaserSource takes advantage of its large VFD display to
simultaneously show the set point, laser voltage, and photodiode read back.
The user interface of the LaserSource is engineered to make using the
instrument straightforward. With its text-based menus, there is never any
confusion over which setting is being changed, and parameters are displayed in
clear English (no cryptic numbers or LEDs to decode).
The LaserSource offers all the features you would expect from a modern
precision laser diode driver, including:
 10ppm current stability over one hour
 2A to 20A current ranges

Page 4 · 4300 Series LaserSource User’s Manual
 Comprehensive laser protection circuitry, including hardware voltage
and current limits, and fast transient shutdown.
 External analog modulation
 Power mode control, both in photodiode current (AMC) or computed
photodiode power (APC) modes.
 Simultaneous reading of current set point, voltage measurement, and
photodiode current or power measurement.
What’s in the Box
Along with the LaserSource itself, a CD with electronic copies of this manual,
the Computer Interfacing Manual, and USB drivers are included. For USA
customers, a power cord is included. For non-USA customers, an IEC-60320-
C13 rated AC power cord must be provided.
Accessories
Arroyo Instruments also sells several accessories designed to work with the
LaserSource. These include:
 LaserSource Cable, 2m (p/n 1220B)
This cable has DB-9 male/female connectors for interfacing to the
LaserMount or other connectorized fixtures.
 LaserSource Cable, 2m, Pigtailed (p/n 1221B)
This cable has a female DB-9 connector for plugging into the
LaserSource and tinned leads for wiring into custom solutions.
 LaserSource Cable, 20A, 9W4, 2m (p/n 1228B)
Design for the 4320’s 9W4 connector, this cable is designed for 20A
operation, and has 9W4 male/female connectors.
 LaserSource Cable, 20A, 9W4, Pigtailed, 2m (p/n 1229B)
Design for the 4320’s 9W4 connector, this cable is designed for 20A
operation, and has 9W4 male connector on the instrument end and
bare wire leads connections on the device end for custom wiring.
 LaserSource Cable, Sensor, DB-9, 2m (p/n 1228-S)
Designed for the 4320’s Sensor / Interlock connector, this cable has
DB-9 male and female connectors, and carries the photodiode and
remote voltage sense signals.
 4300/5300 Series 2U Rack Mount Kit, 1 unit (p/n 1401-RM-1)
 4300/5300 Series 2U Rack Mount Kit, 2 units (p/n 1401-RM-2)
For installing your 5300 Series TECSource or 4300 LaserSource into
a standard 19” rack. The 1401-RM-1 is used when installing a single
instrument into a 2U rack space. For mounting two instruments side-by-
side, use the 1401-RM-2 rack mount kit. A 1401-RM-1 cannot be
converted to a 1401-RM-2, or vise versa, to be sure to purchase the
correct rack mount kit.
 RS-232 NULL Cable, 3m (p/n 1200-NULL)

4300 Series LaserSource User’s Manual · Page 5
 USB Cable, 3m (p/n 1201)
Safety Terms and Symbols
The following safety-related terms are used in this manual:
 Warnings (noted by the WARNING heading) explain dangers that
could result in physical injury or death;
 Cautions (noted by the CAUTION heading) explain conditions that
could result in damage to the instrument, other equipment, or your
device.
 Notes (noted by the NOTES heading) are not safety-related, and are
intended simply to point out important information.
If, at any time, any of the following conditions exist, or are suspected of existing,
discontinue use of the unit until it can be inspected by qualified service
personnel:
 Visible damage to the unit, including damage or stress caused during
product shipment;
 Storage of the unit outside the standard storage temperature or
humidity rating, or prolonged storage under harsh conditions;
 Failure to operate properly.
If needed, contact your distributor or Arroyo Instruments for service or repair to
ensure the safety of the product is maintained.
Symbols
Power Off Power On
Caution, refer to manual Earth ground
Caution, risk of electric shock

Page 6 · 4300 Series LaserSource User’s Manual
General Warnings
CAUTION
There are no user-serviceable parts inside. All service
and repair work shall be done by Arroyo Instruments or
personnel authorized by Arroyo Instruments.
Modifications done by non-authorized personnel will
void the warranty. Please see the Service section later
in this manual for instructions on how to obtain service
for this instrument.
WARNING
To avoid electrical shock, ensure a 3-prong power cord
is used, and is plugged into a earth-grounded
receptacle. Failure to do so can result in severe injury or
death.
WARNING
Potentially lethal voltages exist within this instrument.
This instrument is intended for use by qualified
personnel who understand the shock and laser hazards
and are familiar with safety procedures required to avoid
injury. Read this manual completely before attempting
to use this product.

4300 Series LaserSource User’s Manual · Page 7
Quick Start
The LaserSource was designed with ease of use in mind, and you will likely
have little need for this manual for almost all of the features the unit offers. This
section will show how you can quickly get the unit up and running in almost no
time.
After unpacking the unit, ensure that the voltage selection on the Input Power
Connector (IPC) on the back of the unit is set to the correct voltage. This is
critical, as incorrect voltages can damage the unit. The LaserSource is typically
shipped in the 120V configuration from the factory, but always verify the voltage
selection. Change the voltage as needed. For more information, refer to the IPC
section below.
Once the voltage selection has been completed, plug the AC cord into the unit
and into the wall outlet. Turn on the power switch located on the front panel, and
the unit will power up, displaying the model information, serial number, and
firmware version number.
Press the Menu button to enter the menu, and using the knob, turn to the right
until the Io Lim setting is displayed. Press the knob to edit the setting, and
adjust the limit as appropriate to your laser diode. Press the knob again to save
the value. Make the same adjustments to the voltage limit (Vf Lim), as
appropriate for your application. Once you have made all your adjustments,
press the Menu button to exit the menu.
Next, connect the cable between your LaserMount or other fixture and the
Output connector of the LaserSource. We recommend using our cables as they
have been designed to work well with the LaserSource. If using your own
cables, ensure they have been properly wired according to the pin-out of the
LaserSource and your fixture.
Finally, set the set point to an appropriate current and press the Output button.
The output will turn on and you will see the actual voltage and photodiode
current displayed on the second line.
It’s that simple. For more detailed operating and installation instructions, read
on.

Page 8 · 4300 Series LaserSource User’s Manual
Installation
Installation of the LaserSource is very straightforward, as the quick start section
above illustrated. This section will provide additional details and considerations
for installing your LaserSource.
After unpacking the unit, make sure all packing materials have been removed
and nothing obscures the ventilation ports on the side and front of the unit.
Changing the Voltage Selection
Before powering on the unit, ensure that the voltage selection on the IPC is set
correctly. Improper voltage selection can easily damage the unit. Changing the
voltage selection requires that you remove the voltage selection module from
the IPC. You can select from 100V, 120V, and 230V. Choose the voltage that
most closely matches your AC voltage.
Remove the power cord from the unit. Using a small, flat-blade screwdriver,
insert the tip of the screwdriver into the two small openings above and below the
voltage indication to release the voltage selection module from the IPC, as
shown in the picture below.
Input Power Connector (IPC)
Once the module has been removed, remove the small, white voltage selection
tumbler from the module, and then re-insert so that the desired voltage is
shown. Re-insert the module into the IPC.

4300 Series LaserSource User’s Manual · Page 9
Powering Up the Unit
Once the correct voltage selection has been made, connect the AC power cord
to the unit. You must properly ground the unit by plugging the supplied power
cord into a three prong grounded outlet, or using a three-to-two prong adapter
and connecting the ground tab to earth ground.
Turn the power switch, located on the front panel, into the on (|) position. The
unit will display the model, serial number, and firmware version, go through a
quick power-up self-test, and return to the last known operating state.
Ventilation
The LaserSource has vent holes on the side and front of the unit. You must not
block these vent holes, or overheating may occur, causing damage to the unit.
Rack Mounting
Rack mounting kits (p/n 1401-RM-1 or p/n 1401-RM-2) for standard 19” racks
are available for the LaserSource, and supports the rack mount of one (1401-
RM-1) or two (1401-RM-2) units in a 2U (3.5”) high opening. Because the unit
draws air from the side, and therefore inside the rack housing, be sure that the
internal rack ambient temperature (which will typically be several degrees higher
than room ambient) does not exceed the unit’s operating temperature. When
using 1401-RM-2 to rack mount two units, either unit may also be a 5300 Series
TECSource.
CAUTION
Do not exceed 250VAC on the line input.
It is critical to select the proper voltage selection prior to
applying power to the unit. If the actual voltage exceeds
the voltage selection by +/-10%, damage to the unit
may occur.
CAUTION
Do not operate the unit above +40°C ambient, and
ensure the instrument is properly ventilated, or the unit
may overheat and possible damage to the unit may
occur.

Page 10 · 4300 Series LaserSource User’s Manual
Warm-up and Environmental Considerations
In order to achieve the highest level of accuracy, the LaserSource should be
powered on for at least one hour prior to taking measurements. In addition,
ensure that the unit is not operating outside the ambient temperature range or
humidity conditions.
Operation
The Front Panel
Operation of the LaserSource is very straightforward. The sections below will
help familiarize you with the front panel, the display, and the menu structure.
The front panel is designed for simplicity in operation. There are four buttons on
the front panel: Output, Menu, adjustment knob, and the AC power switch.
The output is controlled via the Output button. When turning the output on,
there is a programmable delay (factory default of 3 seconds) where the unit will
indicate that the output is on (the blue output LED will be lit), but the output
stage is, in fact, not on. This is a CDRH safety feature required for some laser
applications. The output will be energized once the delay has expired.
The Menu button is used to enter the LaserSource menu. When in remote
mode, it acts as a Local button, returning the instrument to local mode.
The adjustment knob located on the right hand side of the unit is used to
change the set point or parameters in the menu. It also acts as a push button,
primarily as an enter button, when making changes in the menu.
There are four LEDs: a green power LED that is lit whenever the AC power is
turned on; the blue Output on LED that indicates the LaserSource is actively

4300 Series LaserSource User’s Manual · Page 11
controlling the laser diode; a red Error LED that indicates an error has occurred;
and a yellow Remote LED that indicates the unit is being controlled via a
computer.
Whenever an error is generated, the red Error LED will light, and the error will be
displayed on the VFD display. There may be one or more errors, but only the
first error will be displayed. To display the next error, press Menu button. To
clear all errors, press the knob. A list of error codes can be found in the Error
Messages section below.
When the unit is in remote mode, the yellow Remote LED will be lit. More
information about how the instrument behaves in remote mode can be found in
the Remote Mode Operation section below.
Main Display Screen
On the main display you will find the set point and two measurements. Which set
point and measurements are displayed will depend on the control mode you
have selected. An example display is shown below:
Sample Display
Measurements
One of the advantages of the LaserSource is its ability to display both the set
point and two measurements simultaneously. The table below shows which
values will appear on the display depending on the mode selected:
Mode Setpoint Displayed Measurements
Io Current (mA) PD current or power and voltage
Im PD current (μA) Current and voltage
Po PD power (mW) Current and voltage
Vf Voltage (V) Current and PD current or power
The instrument will show photodiode current or photodiode power, depending
on the value of PD Resp. Photodiode current is shown whenever PD Resp is
zero, while photodiode power will be shown whenever PD Resp is non-zero.
See the Control Modes section below for more information on the various
modes.

Page 12 · 4300 Series LaserSource User’s Manual
Status Messages
The instrument will display status messages in the upper-right corner of the
display indicating several different conditions that may be of interest to the user.
If multiple conditions exist simultaneously, then the instrument will cycle through
each condition, displaying each status message for approximately one second.
Possible condition messages are:
HiBW The unit is in Io (HiBW) mode.
Pulse The unit is in Io (Pulse) mode.
ExtTrig The unit is in Io (Ext Trig) mode.
Burst The unit is in Io (Burst) mode.
Lock The interlock is open and the unit cannot be turned on.
Shrt A short circuit has been detected on the output.
OutT The unit is out-of-tolerance. See the Tol Time and Tol Io settings for
more information.
ILim The unit is in current limit.
MLim The unit is in photodiode current limit.
PLim The unit is in photodiode power limit.
Notice that the mode indicators are in reverse text, and are used to highlight the
operating mode.
Settings and Menus
All parameters of the LaserSource can be viewed and changed within the
menu. The menus are constructed with the most used parameters first. To
change any setting, press Menu to enter the menu then rotate the knob to select
the parameter to change. Press the knob to begin changing the value. As a
visual indication that you are in edit mode, you will see an asterisk appear next
to the value. Once you have made your change, press the knob or Menu button
to store the value. Pressing the Menu button will store and exit the menu, while
pressing the knob will store the value but leave you in the menu to make
additional changes.
Some settings are contained inside a sub menu, such as communications
settings. To access the sub menu, simply press the knob to enter the sub menu
when its name is displayed.

4300 Series LaserSource User’s Manual · Page 13
Menu Description Factory
Default
Root Menu Top Level Menu
Mode As described in the Control Modes section above,
the unit offers seven control modes: Io (ACC), Io
HiBW (ACC), Io (Pulse), Io (Ext Trig), Io (Burst), Im
(AMC), Po (APC), and Vf (AVC). Change this
setting to select a new mode.
Io (ACC)
QCW Const When in Io (Pulse) or Io (Burst) mode, this
controls which parameter (frequency or duty cycle)
is adjusted when the pulse width is adjusted. This
setting will only be displayed when in Io (Pulse) or
Io (Burst) modes.
Freq
QCW Width Sets the pulse width in QCW mode. See QCW
Mode below for more details. This setting will only
be displayed when in Io (Pulse), Io (Ext Trig), or
Io (Burst) modes.
0.1ms
QCW Duty Sets the duty cycle in QCW mode. See QCW Mode
below for more details. This setting will only be
displayed when in Io (Pulse) or Io (Burst) modes.
10%
QCW Freq Sets the frequency of the QCW pulse. See QCW
Mode below for more details. This setting will only
be displayed when in Io (Pulse) or Io (Burst)
modes.
1000 Hz
QCW Pulses Sets the number of pulses to generate when in Io
(Burst) mode. This setting will only be displayed
when in Io (Burst) mode.
1
DelayIn Sets the delay, in seconds, from the start of trigger
input pulse to the start of the current pulse. This
setting will only be displayed when in Io (Ext Trig)
mode.
0.000015s
DelayOut Sets the delay, in seconds, from the current pulse
to the start of the trigger output pulse. This setting
will only be displayed when in Io (Pulse), Io (Ext
Trig), or Io (Burst) modes.
0.000000s
Io limit This setting controls the maximum amount of
forward current that can be delivered to the laser
diode. This limit is implemented in hardware for
immediate response. For more information about
limits, see Using Limits below.
Maximum

Page 14 · 4300 Series LaserSource User’s Manual
Menu Description Factory
Default
Im limit This setting controls the maximum amount of
monitor photodiode current the unit will allow. This
limit is implemented in software. For more
information about limits, see Using Limits below.
Maximum
Po limit This setting controls the maximum amount of
monitor photodiode power the unit will allow. This
limit is implemented in software. For more
information about limits, see Using Limits below.
Maximum
Vf limit This setting controls the maximum amount of
forward voltage that can be delivered to the laser
diode. This limit is implemented in hardware for
immediate response. For more information about
limits, see Using Limits below.
Maximum
Vf Sense Selects the remote voltage sense lines for diode
voltage measurement. Pins 4 & 5 of the Monitor /
Interlock connector must be wiring to the diode.
See Using Remote Voltage Sense below for more
details. Only available on the 4320.
Internal
Sense Warn When operating in remote voltage sense mode, if
the remote voltage is significantly lower that the
voltage at the Output connector, a warning
message is displayed. Only available when Vf
Sense is set to External. Only available on the
4320.
Yes
Cable R The cable resistance, in ohms. This setting can be
used to compensate for voltage losses in the cable
due to cable and connector resistances. Cable R
is ignored in Vf (AVC) Mode. For more information
about this feature, see Using the Cable R Setting
below. Not available when using remote voltage
sense.
0.0000 Ω
Int Contact Enables or disables intermittent contact. Not
available in Io (Pulse), Io (Ext Trig), or Io (Burst)
modes
Off
PD Resp This factor is used by the unit to convert from
monitor photodiode current into optical power. The
value is in terms of microamps per milliwatt
(μA/mW), such that power = photodiode current
divided by the factor.
0.00μA/mW
PD Bias This is the photodiode bias voltage, which is
applied to the PD+/PD- pins of the output
connector.
5.0V

4300 Series LaserSource User’s Manual · Page 15
Menu Description Factory
Default
Tol Time Tolerance time is the amount of time, in seconds,
that the measured value (current, voltage, etc.)
must be within the set point +/- the tolerance for
the unit to be considered in tolerance. In Io modes,
the tolerance is defined by Tol Io. For Im/Po
modes, the tolerance is fixed at 50uA. For Vf
mode, the tolerance is fixed at 50mV.
5 seconds
Tol Io Tolerance current is a band (in mA) around the set
point. When the actual current is within this band
for longer than the Tol Time setting, then the unit is
considered to be in tolerance.
10.0mA
On Delay The delay, from the time the Output button is
pressed to when the output is actually energized.
3000ms
Comm Menu Communications Menu
Baud This sets the baud rate for the RS-232 serial port.
See the Computer Interfacing Manual which is
included on the CD that accompanied this
product.
9600
Err While
Rmt
To turn off the display of errors while in remote
mode, set this value to “No”. To display errors
while in remote mode, set this value to “Yes”.
Yes
Terminal
Mode
Terminal mode simply echoes any characters
received over the serial or USB interfaces.
No
Msg Term This controls the output message termination, and
can be set to CR/LF, CR, LF, or None.
CR/LF
Sys Menu System Settings Menu
Disp Mode Display mode, which is used to control the layout
on the main screen. Normal will display three
values, typically the set point current, photodiode
or power readback and voltage. Large will display
the read back current, depending on the mode (Io,
Im, Po, VF mode, respectively). When changing
the set point, the set point will be displayed during
the set point change.
Normal
Brightness The vacuum florescent display can be set to one of
eight brightness levels.
100%
Audible
Beep
This setting controls when the unit produces
audible feedback. Set to No to prevent sound, or
Yes or audible alerts such an error messages.
Yes

Page 16 · 4300 Series LaserSource User’s Manual
Menu Description Factory
Default
Lockout
Knob
Lockout knob allows you to disable knob
operation from the main display. This prevents
accidental changes of the set point. The knob will
always work in the menus regardless of this
setting.
No
Knob Speed Controls the adjustment speed of the knob.
Possible values are slow, medium, and fast.
Slow
Advanced Advanced Settings Menu
Off on I Lim Enables output shutdown on current limit. Adjusts
the OUTOFF register.
No
Off on Im
Lim
Enables output shutdown on photodiode current
limit. Adjusts the OUTOFF register.
No
Off on Po
Lim
Enables output shutdown on photodiode power
limit. Adjusts the OUTOFF register.
No
Off on Out
of Tolerance
Enables output shutdown on out of tolerance.
Adjusts the OUTOFF register.
No
Active
VTune
Enables active power supply tuning. See thermal
considerations, page 31. Not available on all units.
Yes

4300 Series LaserSource User’s Manual · Page 17
Control Modes
The LaserSource offers up to eight laser control modes: Io (ACC), Io HiBW
(ACC), Io (Pulse), Io (Ext Trig), Io (Burst), Im (AMC), Po (APC), and Vf
(AVC). The Io (Pulse), Io (Ext Trig), and Io (Burst) modes are only available on
QCW-equipped units.
Changing the control mode is done through the menu by changing the Mode
parameter in the menu to one of these values.
Io and Io HiBW modes (referred to collectively as ACC, or automatic current
control modes) are used to drive a specific current through the laser diode.
When in this mode, the set point will be in milliamps, and the LaserSource will
drive the desired current through the laser diode as long as the voltage at the
chosen set point does not exceed the voltage limit. In Io mode, you will be
limited to less than a 10 Hz bandwidth. To modulate above that rate, use the Io
HiBW, which is a high bandwidth current mode supporting modulation.
Io (Pulse), Io (Ext Trig), and Io (Burst) are quasi-CW (QCW) modes, where the
laser output is pulsed on based on the pulse width, duty cycle, and frequency,
as defined in the menu. See Using QCW Modes section below for more details.
Im mode (also referred to as AMC, or automatic monitor photodiode control,
mode) is used to control the laser diode using the monitor diode feedback. You
select the target monitor diode current, and the LaserSource will drive exactly
enough forward current through the laser diode to generate the selected monitor
diode current. Only low frequency modulation (10Hz or less) is possible in Im
mode due to the feedback latencies of the photodiode itself.
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 μA/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
10μA.
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.

Page 18 · 4300 Series LaserSource User’s Manual
Modulation
The instrument supports external analog modulation using the Modulation BNC
on the back 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:
WidthPulse
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:
10*
WidthQCW
DutyQCW
FreqQCW 
As an example, a 0.6ms pulse width and 30% duty cycle results in a frequency
of 500 Hz. Put into the formula above, it would be written:
10*
6.0
30
500 
Because of this relationship, when adjusting any of these parameters, it requires
a change in one of the others. To achieve this, when adjusting frequency, duty
cycle is adjusted and when adjusting duty cycle, the frequency is adjusted. For

4300 Series LaserSource User’s Manual · Page 19
pulse width adjustments, the frequency or duty cycle is adjusted based on the
setting of QCW Hold. For example, if QCW Hold is set to Duty, then when the
pulse width is adjusted, the frequency is adjusted (the duty cycle is held
constant).
In external trigger mode (Io Ext Trig), only the pulse width is defined by the
instrument. The frequency and duty cycle are defined by the trigger input. For
each rising edge of the trigger input, one current pulse will be generated with the
pulse width defined by the QCW Width setting.
Burst mode (Io Burst) operates as a combination of pulse and external trigger
modes. Like pulse mode, the pulse train is defined in terms of frequency and
duty cycle, but only a defined number of pulses is generated, which can be as
few as one, or as many as 60,000. Like external trigger mode, no pulses are
generated until a trigger is received. As in external trigger mode, this trigger can
be generated from the trigger input, but unlike external trigger mode, it can also
be generated from the front panel using the Output button. When in burst mode,
the BURST icon will be displayed in the upper right corner of the display.
Burst mode operation from the front panel is distinctly different from the other
operating modes. Normally, you will use the Output button to turn the output on
or off. This is true of burst mode, but the Output button does double-duty: it
serves both as an output on/off button as well as a trigger button. To turn the
output on in burst mode, press and hold the Output button for at least one
second, then release. When you release the button, you will hear an audible
click inside the unit, and the blue LED will start flashing. This indicates the output
is ready to start producing pulses. To generate a pulse train, press and release
the Output button quickly (holding it down for less than one second). On the
button release, the pulse train will start. The blue LED will remain lit solid until the
pulse train has completed, at which point it will begin flashing again to indicate
it’s ready to start the next pulse train. To turn the output off, press and hold the
Output button for at least one second, then release.
When triggering remotely (or via the LASER:TRIGGER command), the LED will
also remain lit solid during the pulse train. Also, the LASER:OUTPUT command
is only used to turn the output on or off; use the LASER:TRIGGER command to
start a pulse train.
Laser measurements are made just before the falling edge of the pulse,
maximizing the time the laser has to settle. A hardware sample and hold
samples current, voltage, and power simultaneously, ensuring all three
measurements are made at the same point in time.
Note that QCW mode is not designed to operate below approximately 3% of the
range of the instrument. When operating below this point, the accuracy of the
pulse degrades, overshoot increases, and the rise time of the pulse increases.

Page 20 · 4300 Series LaserSource User’s Manual
These errors can be overcome somewhat by operating at longer pulse widths,
but actual performance can only be determined through empirical
measurements using an oscilloscope and current probe.
Trigger In and Trigger Out Delay
Using the trigger in delay (DelayIn), you can delay the beginning of the current
pulse up to 1 second, and only applies in Io (Ext Trig) mode. Likewise, using
the trigger out delay (DelayOut), you can delay when the trigger output up to 1
second from the start of the current pulse.
When setting the trigger in or trigger out values, another pulse cannot start until
the current pulse (which starts after the trigger input delay) and the trigger
output have both completed. This can limit the range of the frequency or duty
cycle if the trigger delays are large.
For example, if the trigger output delay is 10 milliseconds and the pulse width is
1 millisecond, then the minimum duty cycle is about 10%, because the next
pulse cannot start until after the trigger output is complete.
Cable Wiring for Modulation and QCW
When modulating at higher frequencies (>1 kHz) or operating in QCW modes, it
is critical that high quality, shielded twisted pair cabling be used, and wire size
suitable for the applied current (or the equivalent if using a multi-conductor
cable). See the chart below for suggested sizes. Failure to do so may result in
current oscillations that may damage your laser. When operating in these
modes, always use shielded cable and never use individual wires to connect the
instrument to your laser. If in doubt, use a current probe attached to an
oscilloscope to monitor actual performance.
Arroyo Instruments’ cables are shielded, twisted-pair cables, and designed to
support these applications. For questions, contact the factory or your local
representative for additional help.
Current (A) Recommend Wire Gauge
2 22 AWG
4 20 AWG
8 18 AWG
20 14 AWG