Detector, Single Photon, Infrared
Wednesday, October 11, 2006
The id201. is a complete photon counting system based on a cooled InGaAs/InP avalanche photodiode (APD). The operation temperature is set to -50°C to optimise the signalto-noise performance. A temperature variation of less than 0.1°C is achieved through a thermoelectric cooler controlled by a PID regulator. The APD is operated in the so-called gated mode.
The id201 offers advanced functionalities, including:
A trigger unit providing the timing signal for the gate generation. The user can choose from external or internal trigger sources:
• The external trigger source can have NIM, TTL and a Var input types. The Var input type lets the user select three parameters: level, slope, load. The id201 accepts external trigger frequencies up to 4 MHz. Larger frequencies can be used, but the id201 will automatically limit the trigger frequency to 4 Mhz.
• An internal trigger source is also available. Trigger frequencies of 1kHz, 10 kHz, 100 kHz and 1 MHz can be selected. The trigger signal is also available on a front panel connector for the synchronization of other devices (e.g. pulsed laser source, such as the id300).
A delay function providing a delay between the trigger and the gate signals. This allows the user to scan the gate and synchronize the gate and the optical signals. Coarse synchronization should be done using cables and optical fibers, while fine adjustment can be obtained with the internal adjustable delay line. The delay can be adjusted from 0 to 25ns in 100ps increments.
A generator unit and a pulser unit produce a gate with the appropriate duration and amplitude. A variable deadtime can be selected to suppress afterpulse occurences. The following parameters can be selected using an intuitive graphical user interface:
Dead Time. At high trigger frequencies, afterpulsing may significantly deteriorate the performance. To suppress detrimental afterpulsing effects, the id201 allows one to set a dead time after a detection. The dead time duration can be chosen between 1μs, 2μs, 5μs or 10μs. When this mode is enabled, the module will ignore trigger signals during a time equal to the deadtime after each registered avalanche event. The unit displays the actual trigger rate.
Gate Width. Five different values of the gate can be set: 2.5ns, 5ns, 20ns, 50ns or 100ns. A user-defined gate duration can also be entered. Gate widths of 2.5ns and 5ns result in an effective gate of typically 500ps and 1.5ns. These short gates provide a very low noise level for applications where the arrival time of the photon is known with high accuracy.
Photon detection probability at 1550nm that can be chosen between 10%, 15%, 20% and 25%, independently of the gate width and trigger frequency. A user-defined detection probability can also be entered. Large detection probability levels allow one to obtain oustanding timing resolution.
An internal counter whose result is displayed on the front panel to monitor the detection and the trigger signals. For each detection, the module also produces electronic pulses (NIM and TTL) available on front panel connectors. These pulses can, for example, be registered by an external counter or sent to a processing unit, such as a time-to-amplitude converter.
An auxiliary counter, which offers the possibility to count external signals. The result of the counter can then be displayed on the LCD screen.
The electronic circuit of the id201 has been designed to reach outstanding timing resolution of less than 300 ps at25% detection probability.
All the user-adjustable parameters can be easily entered from the front panel or when this option is selected from a computer connected to the RS232 port. The graphical user interface offers several display modes: 1) display the internal and auxiliary counters as frequencies, 2) display the number of counts of the internal and auxiliary counters, 3) display the trigger rate and the internal counter as frequencies, 4) display the ratio of the internal counter over the trigger counter as well as the auxiliary counter frequency, and 5) display all the important detector parameters.
For more information regarding this product please contact:id Quantique SA
de la Marbrerie 3
Tel: +41(0)22 301 83 71
Fax: +41(0)22 301 83 79
posted by JD52 @ 9:21 PM,