Wide bandwidth modulation techniques for laser diodes and current noise investigations of laser diode drivers

We report on methods for widening modulation bandwidths of commercial laser diode drivers Inexpensive commercial laser diode drivers have many important characteristics but unfortunately their modulation bandwidths are often restricted to below kHz Here techniques involving p channel and n channel JFETs have been tested to enhance the modulation bandwidth of drivers suitable for common laser anode photodiode cathode laser diodes A scheme using a p channel JFET has extended the electronic bandwidth of a commercial current driver to kHz To illustrate the e ectiveness of the technique an optical phase locked loop has been implemented in which the optical beat exhibits an residual phase noise of rad and a frequency instability of mHz at s Furthermore the coherent bisection of a THz frequency interval has been carried out showing that the modulation technique can be employed in optical frequency synthesis The current noise of three commercial laser diode drivers has been measured and compared to that of a purpose built low noise current driver We show that the current noise of the commercial current drivers is su ciently low so as not to a ect the frequency noise of an extended cavity laser diode E mail mcferran physics uwa edu au Submitted to Meas Sci Technol z Present address Laboratoire Primaire du Temps et des Fr equences Observatoire de Paris Av de l Observatoire F Paris France Modulation techniques and current noise measurements of laser diode drivers