Presented herein is a model for a laser diode exhibiting not only electrical and radiant characteristics, but also the thermal characteristics of droop and crosstalk. Also presented is the model's implementation in SPICE simulation. A behavioral level laser diode model is developed using the SPICE ideal diode, a resistive/capacitive network, and SPICE's ability to accept mathematical relationships to describe simulation schematic components. Modeled were various electrical and thermal dynamic effects that occur during DC and transient operation. The resistive/capacitive network models the thermal resistance and capacitance within the laser diode. The instantaneous input power devoted to heating is separate from the power converted to radiant energy with a relational feedback loop. Equations are used to derive a `droop' current that arises from the heating. The effect of droop then is implemented by the subtraction of the `droop' current from the input driving current to yield an `effective' driving current into the modeled laser diode. The model's parameters are adjusted to achieve a performance match to electrical and radiant energy empirical data. The radiant energy is expressed accurately in magnitude and in units of mA rather than mW. Two parallel laser diode intensity control systems, each containing a laser diode model, are simulated. The two laser diodes were also connected in such a fashion as to model crosstalk between the two lasers. The model provided expected results over a wide range of bias and transient excitations from a step current to low and high duty cycle input pulses representing gray levels.

Date Published: 2 July 1999
PDF: 8 pages
Proc. SPIE 3787, Optical Scanning: Design and Application, (2 July 1999); doi: 10.1117/12.351649

Published in SPIE Proceedings Vol. 3787:
Optical Scanning: Design and Application
Leo Beiser; Stephen F. Sagan; Gerald F. Marshall, Editor(s)