Modern Pulsed Diode Laser Sources for Time-Correlated Photon Counting

Time-correlated single-photon counting applications require pulsed excitation sources at various wavelengths from the UV to the IR that feature a short pulse width (usually picoseconds or femtoseconds) as well as repetition rates in the kilohertz to megahertz range. The repetition rate should ideally be tunable in order to adapt the pulse period to the required measurement window. In the blue, red, and IR spectral range, such pulses with energies of up to 100 pJ can be readily provided by single gain-switched laser diodes which can be housed in compact and robust packages. Laser pulses in the UV or green-yellow spectral range are, however, not directly accessible and require more elaborate setups that are based on power amplification and frequency conversion. An alternative excitation source that has also become popular in the recent years is the supercontinuum laser as it gives direct access to a broad wavelength spectrum that spans from the blue to the IR.

This chapter provides an overview about the fundamental aspects and parameters of pulsed diode lasers as well as a short introduction into pulsed LEDs and supercontinuum lasers that are usually used for time-correlated single-photon counting applications.