LD250MTC5 LAB datasheet(21/31 Pages) WAVELENGTH

21 / 31 page

CHOOSE OPERATION MODE,

SETPOINT & LASER TYPE

1. Press to access the LD Control Screen.

2. Press the

Mode type to toggle between

Constant Current and Constant Power. This

control cannot be modified if output current to

the laser is enabled.

3. Press the

Setpoint value and turn the adjustment knob

until the desired operating current is displayed.

Note: For added safety, if the setpoint is set to the value

of the current limit, actual current will be ~43 mA below

setpoint.

CC setpoint & CP setpoint are separate, independent

stored values. CC setpoint is LD current and CP setpoint

can be PD current or power. If the PD range changes, the

CP setpoint is zeroed.

4. Press the

Laser Type value to toggle between A/B and

C type lasers (see

Figure 37 for elaboration on laser

types). This control cannot be modified if output current

to the laser is enabled.

Figure 35. LD Control Screen

CONSTANT CURRENT MODE

In Constant Current mode, the setpoint chosen corresponds

to actual current through the laser. This mode does not require

the user to configure photodiode settings.

CONSTANT POWER MODE

In Constant Power mode, the setpoint chosen corresponds to

actual current through the photodiode (proportional to output

power). This mode requires the user to configure additional

photodiode settings:

1. Press the photodiode icon to access the

Photodiode Screen.

2. Press the blue text next to

PD Biasing:

to toggle whether the bias voltage for

the photodiode is enabled or disabled.

Biasing puts photodiode in photoconductive mode, while

unbiased operation will be in photovoltaic mode. Use bias

if the laser diode datasheet recommends it or for faster

PD response. See the Photodiode Basics App Note for

more detail.

3. Press the blue text next to

PD Range until the value

matches the appropriate current range for the photodiode.

The available options are 500 μA, 5 mA, and 10 mA.

4. If the transfer function from photodiode current to optical

power is known, input this using the

Transfer Function

field. Units for the transfer function are W/mA.

Figure 36. Photodiode Screen

Type A Laser Diode

Type B Laser Diode

Type C Laser Diode

Common

Cathode

Laser Diode Anode &

Photodiode Cathode Common

Isolated Photodiode

Short the

Laser Diode Anode

to Photodiode Cathode

Common

Anode

Laser Diode Cathode &

Photodiode Anode Common

Figure 37. Laser Type Diagrams

LD250MTC5 LAB Datasheet(PDF) 21 Page - Wavelength Electronics, Inc.

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