Thorlabs' Correlated Photon-Pair Sources use spontaneous parametric down-conversion (SPDC) to generate a pair of photons near 810 nm. Each source is self-contained, features an integrated 405 nm pump laser, and is capable of high-brightness photon-pair generation rates.

The SPDC810N narrowband source provides output with a 0.25 nm photon bandwidth, generates photon pairs at a rate of >100 kHz, and has a high-efficiency heralding ratio of >0.30. Comparatively, the SPDC810 source produces output with a wider photon bandwidth of ~10 nm, but generates photon pairs at a rate of >450 kHz and has an even higher heralding ratio of 0.45. A zero-time delay second-order correlation function [g⁽²⁾ (τ = 0)] value of <0.1 can be achieved with these sources, making them high-brightness heralded single-photon sources ideal for quantum optics applications. For complete performance specifications, please see the Specs tab; note that the heralding ratio, pair rate, and g⁽²⁾(0) values are given for the pump laser operating at 40 mW and the observed statistics will vary with the pump power and detector specifications.

• Heralded Single-Photon Sources with g⁽²⁾(τ = 0) < 0.1
• Photon-Pair Generation at 810 nm
• Integrated 405 nm Pump Laser
• Sources with <0.25 nm or 10 nm Photon Bandwidths

In each SPDC source, a nonlinear crystal [periodically poled potassium titanyl phosphate (PPKTP)] converts one 405 nm pump photon into two 810 nm photons (the signal and idler) in a single event. The resulting signal and idler photons have type-II phase matching, which means they propagate with orthogonal polarizations (extraordinary and ordinary); see the schematics to the right. As a source that emits photon-pairs in a simultaneous event, it can be used as a heralded single-photon source. This is when the detection of one photon (idler) heralds the presence of the second photon (signal). More information about single-photon verification can be found in the Single-Photon Output tab.

Collinear Type-II SPDC of one 405 nm pump photon entering a PPKTP crystal and exiting as two 810 nm output photons.

To efficiently collect the down-converted light, the signal and idler channel outputs are FC/PC coupled.

• Spontaneous Parametric Down-Conversion (SPDC) Sources (Collinear Type-II) 
• <0.25 nm (Item # SPDC810N) or ~10 nm (Item # SPDC810) Photon Bandwidth
• High-Efficiency Heralding Ratio: 
  • SPDC810N: >0.30
  • SPDC810: >0.45 
• Room Temperature Operation
• Remote Operation of 405 nm Pump Laser 
• Two AR-Coated FC/PC to Uncoated FC/PC Patch Cables Included
• Fiber Bulkhead and Connector Cleaners Included

Typical Applications:

• Heralded g⁽²⁾ Measurements
• Absorption Spectroscopy
• Quantum Metrology
• Waveguide Characterization

• Sub-Shot-Noise Imaging
• 2-Photon Interference
• Single-Photon Sensor Characterization
• Quantum Key Distribution

Model Details:

SPDC810N Narrowband Correlated Photon-Pair Source

• >0.30 High-Efficiency Heralding Ratio
• >100 kHz Pair Generation Rate
• Pump Laser Power Adjustable up to 40 mW
• ±0.1 nm Wavelength Stability
• <0.25 nm Photon Bandwidth
• Wavelength Tuning Range up to 8 nm
• Control via the Front Panel or Remotely through USB

The SPDC810N Narrowband Correlated Photon-Pair Source features a single-frequency integrated 405 nm pump laser and generates photon pairs at a rate of >100 kHz with a high-efficiency heralding ratio of >0.3. The photon-pair output at 810 nm has a photon bandwidth of <0.25 nm. A resistive heater oven maintains the crystal temperature and the wavelength of the down-converted photons, resulting in a wavelength stability of ±0.1 nm. For adequate cooling, the unit requires 1" of clearance on all sides. To tune in and out of degeneracy, the temperature of the nonlinear crystal can be adjusted to change the output photon wavelength by more than 8 nm.

The pump laser's power and the crystal temperature can be adjusted and monitored directly with the on-unit controls and display. Alternatively, a type B USB port on the back of the unit allows it to be connected to a PC and controlled remotely using the SPDC810 Software.

SPDC810 Correlated Photon-Pair Source

• >0.45 High-Efficiency Heralding Ratio
• >450 kHz Pair Generation Rate
• Pump Laser Power Adjustable up to 150 mW
• ±2.5 nm Wavelength Stability
• Photon Bandwidth: ~10 nm
• Remote Operation via Serial RS232

The SPDC810 Correlated Photon-Pair Source has an integrated 405 nm pump laser, generates photon pairs at a rate of >450 kHz, and has a high-efficiency heralding ratio of >0.45. It also contains an oven to maintain the temperature of the nonlinear crystal and the wavelength of the down-converted photons, resulting in a wavelength stability of ±2.5 nm. For adequate cooling, the unit requires 1" of clearance on all sides.