Abstract
An avalanche photodiode with a ratio of hole-to-electron ionization coefficients, k = 0, is known to produce negligible excess noise irrespective of the avalanche gain. The low noise amplification process can be utilized to detect very low light levels. In this work, we demonstrated InAs avalanche photodiodes with high external quantum efficiency of 60% (achieved without antireflection coating) at the peak wavelength of 3.48 µm. At 77 K, our InAs avalanche photodiodes show low dark current (limited by 300 K blackbody background radiation), high avalanche gain and negligible excess noise, as InAs exhibits k = 0. They were therefore able to detect very low levels of light, at 15-31 photons per 50 µs laser pulse at 1550 nm wavelength. These correspond to the lowest detected average power by InAs avalanche photodiodes, ranging from 19 to 40 fW. The measurement system's noise floor was dominated by the pre-amplifier. Our results suggest that, with a lower system noise, InAs avalanche photodiodes have high potential for optical detection of single or few-photon signal levels at wavelengths of 1550 nm or longer.
Highlights
The ability to detect light efficiently is increasingly important for applications in communications, security, medicine and metrology
Unlike avalanche photodiodes (APDs) for optical fiber communications, low photon or single photon detection demands APDs operating with gains in excess of 104 in tandem with a low noise preamplifier
Beyond −1.0 V, dark currents increase with reverse bias rapidly
Summary
The ability to detect light efficiently is increasingly important for applications in communications, security, medicine and metrology. Unlike APDs for optical fiber communications, low photon or single photon detection demands APDs operating with gains in excess of 104 in tandem with a low noise preamplifier. At such a high gain, achieving F →1, below the conventional excess noise theory is desirable. Superconducting Nanowire Single Photon Detectors (SNSPDs) offer much higher SPDE (typically > 80%), but with the significant disadvantage of cryogenic cooling down to ~2 K Since such cooling requirement is incompatible with practical, large-scale adoption of quantum communication (optical fiber-based [18] or air-ground [19]) and quantum imaging [20,21], high performance SPADs for wavelengths of 1.0-1.6 μm are highly desirable. The lower detection limit, currently imposed by electronic noise, was found to be ~15 photons within a 50 μs pulse
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