The HydraHarp 400 is a high-end, easy-to-use, plug and play Time-Correlated Single Photon Counting (TCSPC) system with scalability for multiple channels*. It is connected to a PC through a USB 2.0 high speed interface. It provides identical synchronized but independent input channels. They can be used as detector inputs for coincidence correlation experiments as well as independent stop inputs for TCSPC. A dedicated common sync input is provided for TCSPC with fast excitation sources. This allows forward start-stop operation at the full repetition rate of mode locked lasers with stable repetition rate up to 150 MHz. Experiments with low repetition rate benefit from the HydraHarp's multi-stop capability.

The HydraHarp 400 offers 65536 histogram bins per input channel and allows to collect more than 4 billion counts (32 bits) per bin. Each input channel even has an internal adjustable delay with ±100 ns range at picosecond resolution. This unique feature eliminates the need for specially adapted cable lengths or cable delays for different experimental setup. The design of the HydraHarp 400 allows high measurement rates up to 12.5 million counts/sec per channel and provides a highly stable, crystal calibrated time resolution of 1 ps. Along with the extremely low differential non-linearity of the instrument, excellent data quality can be obtained. As a special feature, an external time base can be used to synchronize the internal clock in relation to other timing devices. The instrument's timing resolution is well matched to SPAD detectors of the PDM series or micro-channel plate photomultiplier tubes (MCP). Overall IRF widths down to 50 ps can be attained even with pulsed diode lasers.

All input channels are equipped with constant fraction discriminators (CFD), sensitive on the falling edge. A Time-Tagged mode for recording of individual photon events with their arrival time on all channels allows the most sophisticated offline analysis of the photon dynamics. TTTR data can also be correlated in real-time for monitoring of FCS experiments at count rates up to 1.000.000 counts/sec. In TTTR mode, the device can be synchronized with other hardware such as scanners. External hardware such as monochromators can be controlled via CAN bus.

The HydraHarp software provides functions such as the setting of measurement parameters, display of results, loading and saving of measurement parameters and measurement curves. Important measurement characteristics such as count rate, count maximum, position and peak width are displayed continuously. A comprehensive online help function shortens the users' learning curve. A driver library for custom programming e.g. with LabVIEW™ will also be available as an option, both for Windows™ and Linux™.

*patent pending

• Integration mode
• Oscilloscope mode
• Time-Resolved Emission Spectra (TRES)
• Time-Tagged Time-Resolved mode (listing each event arrival time)
• On-line ("real-time") correlator for FCS

Current software and Developer's Library version: 1.0