Frequently asked questions

Are the output photons single polarization or not?

Yes, they are single polarized.

What is the coherence length of the output light?

Typically 500 MHz

For the resonant chip, if the customer use 1GHz or 10 GHz laser to pump it the Single- photon efficiency in the fiber will be proportional increased or not?

We have an overall efficiency of around 20% currently (i.e 0.1 GHz single photons with 0.5 GHz excitation rate). With our typical devices that we have tested (this includes the standard 3 GHz etalon spectral filter used in collection), we prefer to keep the quantum dot
lifetime ~200-300 picoseconds. Therefore, for the quantum dot to be fully reset, it would be good to excite every 500 – 600 picoseconds (i.e. < 2 GHz repetition rate). 

Thus, for sources below 2 GHz, the Single Photon rate will increase proportionally with the pump frequency. Above 2 GHz the total efficiency will drop below 20% as the quantum dot might not always reset between two consecutive excitation pulses.

What is the lifetime of the chip?

Our own chip has now been working for 2 years in the lab. We will give one year guarantee
and 50% discount when exchanging a used chip with a new improved chip.

Is the single photon count detected by an APD?

The count rate is measured with a fiber coupled superconducting detector. We correct for the detection efficiency of the detector (about 90%) to find the efficiency in the fiber of 20%, i.e. 0.1 GHz when excited with a 0.5 GHz pump.

How about the linewidth of the emission. Is the emission linewidth near the transform limited?

Yes, the emission lines are generally near-transform limited. For details, see:
https://pubs.acs.org/doi/10.1021/acsphotonics.0c00758

What's the charge state of the dot that is resonantly coupled to the cavity mode in the (pre/post) fabrication process? It would be useful for us to have the possibility of the cavity mode to be resonant to the exciton, trions (negatively and postiively charged), as well as biexciton. Is this something feasible?

Our technology is based on waveguides and hence broadband, which is a major asset. For that reason simultaneously exciton, trion, and biexciton states can be well coupled.

What's the Purcell enhancement of your sample?

Typically about 5, can be up to 10.

Has the chip electrical access? And what degree of tunability does it have?

Yes. The tuning range is typically about 0.5 nm.

I have seen from your leaflet that the emission wavelength is 920-980nm. Are the performances of the dot similar across the whole wavelength range? And what range of wavelength does a single sample span?

If you want to target a specific wavelength in this range that would have to be custom made.

What is the price of the chip?

Please contact sales@sparrowquantum.com