Configure Heralded g² Measurements in PicoQuant UniHarp Software

Heralded g²(τ) measurements are used when a SYNC (pump) signal defines when photons should be considered for correlation. UniHarp enables this via Herald manipulators, which create virtual channels containing only photons inside a defined time window after each SYNC pulse.

1. Enable and Configure Herald Manipulators

Open the Manipulators Panel

1. Click the Manipulators icon on the left toolbar.
2. Turn on Enable Manipulators.

Add a Herald Manipulator

1. In Type, select Herald.
2. Click ➕ Add.
3. A block like Herald_5 will appear.

Configure the Herald Manipulator

Inside the Herald block:

Virtual Channel Output

UniHarp creates two virtual channels:

• Herald_5_1 → heralded version of channel 1
• Herald_5_2 → heralded version of channel 2

(The index “5” is used because it is the first virtual channel number after the real channels.)

2. Timing Parameters

Delay Time

Set delay so the gate starts when heralded photons arrive.

Example:

• SYNC at 0 ns
• Photons at ~6 ns
• → Delay = 6000 ps

Gate Time

Window width that accepts photons.

Typical:

• 200–1000 ps for pulsed sources
• Larger gates may let in background

3. Configure the Correlation Method (g²)

1. Go to Measurement Settings → Method.
2. Select Correlation (FCS / g²).
3. Choose Correlation Type: g²(τ).

Select the Heralded Virtual Channels

• Channel A = Herald_5_1
• Channel B = Herald_5_2

⚠️ Do not use real detector channels (1,2).

Use only virtual heralded channels.

Additional correlation settings:

4. Run the Measurement

1. Check HW-Countrate to confirm the virtual channels receive events.
2. Click Start.
3. UniHarp computes heralded g²(τ) using only gated photon events.