Datasheet

Chapter A: QCL theory and application notes
A.2. QCL electrical response
The QCL can be modeled with a combination of one resistor and two capacitors. R1
increases from a higher resistance at low biases to 1-4 Ohms at the operating point.
The resistance at low bias varies from 10-20 Ω to 10
2
kΩ for 10 µm and 4 µm wave-
length QCLs respectively. C1 is a 100 pF capacitor (essentially bias independent)
between the cathode and the anode coming from the bonding pads. C2 depends on
the laser mounting; typically, C1<100 pF in the LLH.
As an example, the values given below apply for a 10µm laser wavelength. Note:
Voltage and resistor values may vary according to the type of laser.
R1 : . . . . . . . . . . . . . . 10 to 20Ω when a voltage of less than 4 to 6 Volts is applied
R1 : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 to 4Ω up to 10 - 12 Volts
R1 : . . . . . . . . . . 10 to 20Ω over 12 Volts, after which the laser no longer operates
C1 : . . . . . . . . . . . . . . . . . . . . . 100pF, capacitor between the anode and the cathode
C2 : . . . . . . . . . . . . . . . . . . . . . . . . . <100pF, depending on your mounting of the laser
− −
+
=
+
R1
C1
C2
Figure A.1.: Electrical model for QCL.
98 QCL user’s manual v3.0