Origin of Anomalously Low SPCM Detection Efficiency

Quantitative loss budget analysis for single-photon detection at 737 nm in diamond quantum photonics

3.27%
Computed Efficiency
35%
Measured Efficiency
60%
Expected QE
14.9 dB
Total Loss

Loss Budget by Source (dB)

Mitigation Strategies

Efficiency Comparison

Fiber Coupling Breakdown

Top Loss Sources

SourceCategoryTransmissionLoss [dB]
Fiber NA matchingFiber0.1189.30
Detector base QEDetector0.6002.22
ObjectiveOptical0.8500.71
Bandpass filterOptical0.9000.46
DichroicOptical0.9200.36
PolarizerOptical0.9200.36
Connector/prop.Fiber0.9310.31

Mitigation Strategy Details

StrategyImproved etaImprovementCost
Free-space detection32.1%+883%Medium
SNSPD upgrade5.1%+55%High
Improved alignment3.4%+3.9%Low
AR coatings3.3%+2.4%Medium
Fewer mirrors3.3%+1.0%Low