OPERATION
Current Sources and Current Measurements
12 LDM-4990
CHAPTER 2
Current Sources and Current Measurements
Do not exceed the specified current settings of the laser. Excessive drive current may
cause laser failure.
Operate the LDM-4990 Laser Diode Mount using any ILX Lightwave current
source or temperature controller. Operation with other current sources or
temperature controllers is also possible, provided that the correct wiring is
observed (refer to Figures 2.4 and 2.5). If an ILX Lightwave current source is used
with the system interlock feature, the interlock connections are available at pins 1
and 2 of the current source connector (see Figure 2.2). With the ILX Lightwave
interlock feature enabled, the interlock pins must be connected before current can
flow from the source to the laser diode.
Do not exceed the specified maximum drive current of the laser. If you are using
an ILX Lightwave current source, or any other current source which has an
adjustable limit setting, be sure to set the current limit to a safe level for your laser.
If it is necessary to measure the current of your laser during operation, follow
these steps:
1 NEVER connect an ammeter in series with the laser circuit.
2 Place a known resistance (1 ohm works well) in series with the laser diode circuit. Then,
measure the voltage across the resistor. Calculate the current by using Ohm's Law,
I = E/R.
3 NEVER turn the voltmeter on or off, or change the voltage measurement range, while
current is flowing to the laser. These actions could result in failure of your laser diode.
ILX Lightwave current sources allow the user to read the output current during
laser operation. Therefore, if you are using an ILX Lightwave current source, it is
not necessary to measure the laser current as described above.
Temperature Control
Thermoelectric Temperature Control
The operating characteristics of diode lasers vary considerably with temperature.
Emission wavelength, threshold current and operating lifetime all are strong
functions of device temperature. For a typical diode laser emitting 3 mW at 780
nm, the emission wavelength will shift an average of 0.26 nm/°C and the threshold
current will shift an average of 0.3 mA/°C. In addition, the operating lifetime drops
by a factor of two for every 25°C rise in operating temperature. Thermoelectric
