| dc.description.abstract | Single photon detection is crucial to many applications, such as lidar, quantum
key distribution, and quantum computing. This thesis focuses on the study of
InGaAs based single photon avalanche photodiodes (SPAD) which can perform
single photon detection in the near infrared including fiber communication bands.
Due to their advantages of compact, robustness, efficient power consumption and
noncryogenic, the development of SPADs is instrumental for the widespread
application of quantum information science. In photonic quantum communication
and computing, the detectors having both the single photon sensitivity and photon
number resolving capability can definitely make a more secure quantum
communication and facilitate the development of quantum computer.
SPAD is usually operated under the gated Geiger mode for suppressing the
afterpulsing effect caused by defects. Under gated mode operation, the fast rising
and falling edge of pulse will be coupled through the junction capacitance of
SPAD to the output, generating a spikelike capacitive response superimposed with
avalanche signal and may bury weak avalanche pulses. Therefore, it is necessary
to increase the excess bias for discriminating the avalanche signal. Under such
high excess bias, there will be lots of avalanche carriers that induce serious
afterpulsing effect. Hence for high-speed applications, self-differencing circuit is
often used to suppress the spike noise for discriminating weak avalanche signal.
Moreover, for gifting SPAD with photon number resolving capability, the
avalanche process should be regulated such that the avalanche carriers become
proportional to the incident photon number. The most intuitive way to regulate the
avalanche process is to reduce the pulse width, which simultaneously eliminate
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the afterpulsing effect and reduce the dark count rate. However, it also degrades
the single photon detection efficiency.
In order to get the shorter pulse, we design a pulse width modulator. This
modulator input normal pulse signal into comparator and another comparator
which is delayed by a resistor. Then the “and” gate will output the signal when
the two signal from comparator are positive in the same time. Thus we can
generate a pulse signal with effective pulse width of nearly 1.1 ns at the excess
bias of 3 % and at 250 K.
Coordinating the short pulse operation with a self-different circuit, a very weak
avalanche signal can be successfully discriminated with good signal-to-noise ratio.
We further demonstrate a comprehensive study on the performance of
InGaAs/InAlAs SPAD. Under the condition of pulse width of 1.1 ns, excess bias
of 3 % and at 250 K, the dark count rate (DCR) of 2 % and the single photon
detection efficiency of 52 % are obtained, where the DCR is significantly
improved as compared to past work of our lab. With superior DCR performance
and short pulse operation, we anticipate to perform the photon number resolving
with our homemade SPAD. | en_US |