Laser Diode PWM Control and Its Consequences on Optical Characteristics

This article deals with frequency PWM (pulse-width modulation) control methodology and experiments related to a deep characterization of InGaN (Indium gallium nitride) EELs (Edge Emitting Lasers) and the influence of drive current shape on power and spectral characteristics. The aim is to study wavelength tuning possibility and near-threshold region behavior that is usually not described in device datasheets. The publication consists of three main parts where different possible methods of output control are discussed. The CW (continuous wave) characteristics are displayed in the first part which describes the behavior of the LDUT (laser diode under test) in more detailed manner than in the available datasheets. The following part shows PWM control with a delayed rising edge of the drive current which enables frequency control. The third part ultimately shows the behavior using PWM with a rectangular drive current shape.