Fluorescence Spectroscopy


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Picosecond photon detection made easy.

The PPD Series is a range of miniaturized single-photon counting detectors containing all the electronics necessary to detect single photons with picosecond accuracy.

Each module contains a fast rise-time photomultiplier (PMT), GHz pre-amplifier, constant fraction discriminator (CFD) , regulated high voltage supply and in cooled detectors the thermoelectric cooler - all in one compact, fully integrated and factory optimized package.

The PPD series offers very high time resolution at an affordable price.  When used in time-resolved fluorescence applications, lifetimes as short as 20ps can be resolved using reconvolution.  Furthermore, unlike some more costly photon counting detectors, the PPD can also be used at very high counting rates without distortion. This makes the PPD not only an ideal time resolved detector, but also suitable for phosphorescence and general spectroscopic applications. Finally one photon counting detector that can be used for most applications without compromise.

The PPD's board is housed in a precision milled, nickel-plated casing to provide the highest level of electromagnetic shielding.  Optical coupling is via a convenient circular bayonet mount which at the same time provides a light-tight seal.

Simultaneous TTL-compatible and NIM-compatible signal outputs are provided, along with a Gate input that allows the HV to be disabled if required e.g. to protect the PMT when it is possibly going to be exposed to ambient light.

The TTL output may be connected to general purpose counter/timer apparatus, while the NIM output is compatible with TCSPC instrumentation.

Three models of PPD are available to suit different spectral ranges. (See the specification table.) The PPD-850 and PPD-900 versions have extended red sensitivity and feature integral thermoelectric cooling of the PMT to reduce the dark count rate.  Both these versions include the DPS-1 power supply module.  The uncooled PPD-650 version requires only 15V, so the DPS-1 is an optional power supply in this case.

The PPD is an ideal retrofit to existing fluorescence lifetime systems that still use side-window (e.g. R1527) and linear-focused (e.g. XP2020Q) photomultipliers, and is easer to use than SPADs (solid state), detectors because the active detection area is many thousand times larger.

Applications include:

  • Time-resolved fluorescence detection
  • Chemi-luminescence detection
  • Bioluminescence
  • Single molecule detection
  • Photon correlation spectroscopy
  • Particle sizing
  • Adaptive optics
  • Microscopy
  • General purpose photon counting and low light level detection

Manufactured by HORIBA





Spectral response




Peak wavelength




Typical dark counts

<80 cps

<200 cps

<3000 cps

Transit Time Spread

<180 ps typical at 405nm

Thermoelectric cooling




DPS-1 included





77 x 107 x 48 mm


0.6 kg

Power requirements

+15V @ 330mA



Specifications and appearance are subject to change without notice

PPD spectral response