Single Photon Avalanche Photodetectors Research Articles

Engineering the gain and bandwidth in avalanche photodetectors.

Avalanche and Single-Photon Avalanche photodetectors (APDs and SPADs) rely on the probability of photogenerated carriers to trigger a multiplication process. Photon penetration depth plays a vital role in this process. In silicon APDs, a significant fraction of the short visible wavelengths is absorbed close to the device surface that is typically highly doped to serve as a contact. Most of the photogenerated carriers in this region can be lost by recombination, get slowly transported by diffusion, or multiplied with high excess noise. On the other hand, the extended penetration depth of near-infrared wavelengths requires thick semiconductors for efficient absorption. This diminishes the speed of the devices due to the long transit time in the thick absorption layer that is required for detecting most of these photons. Here, we demonstrate that it is possible to drive photons to a critical depth in a semiconductor film to maximize their gain-bandwidth performance and increase the absorption efficiency. This approach to engineering the penetration depth for different wavelengths in silicon is enabled by integrating photon-trapping nanoholes on the device surface. The penetration depth of short wavelengths such as 450 nm is increased from 0.25 µm to more than 0.62 µm. On the other hand, for a long-wavelength like 850 nm, the penetration depth is reduced from 18.3 µm to only 2.3 µm, decreasing the device transit time considerably. Such capabilities allow increasing the gain in APDs by almost 400× at 450 nm and by almost 9× at 850 nm. This engineering of the penetration depth in APDs would enable device designs requiring higher gain-bandwidth in emerging technologies such as Fluorescence Lifetime Microscopy (FLIM), Time-of-Flight Positron Emission Tomography (TOF-PET), quantum communications systems, and 3D imaging systems.

Dynamic-quenching of a single-photon avalanche photodetector using an adaptive resistive switch

One of the most common approaches for quenching single-photon avalanche diodes is to use a passive resistor in series with it. A drawback of this approach has been the limited recovery speed of the single-photon avalanche diodes. High resistance is needed to quench the avalanche, leading to slower recharging of the single-photon avalanche diodes depletion capacitor. We address this issue by replacing a fixed quenching resistor with a bias-dependent adaptive resistive switch. Reversible generation of metallic conduction enables switching between low and high resistance states under unipolar bias. As an example, using a Pt/Al2O3/Ag resistor with a commercial silicon single-photon avalanche diodes, we demonstrate avalanche pulse widths as small as ~30 ns, 10× smaller than a passively quenched approach, thus significantly improving the single-photon avalanche diodes frequency response. The experimental results are consistent with a model where the adaptive resistor dynamically changes its resistance during discharging and recharging the single-photon avalanche diodes.

Measurement of the biphoton second-order correlation function with analog detectors.

An experimental scheme and data processing approaches are proposed for measuring by analog photo detectors the normalized second-order correlation function of the biphoton field generated under spontaneous parametric down-conversion. Obtained results are especially important for quantum SPDC-based technologies in the long-wave spectral ranges, where it is difficult to use the single-photon detector at least in one of the two biphoton channels. The methods of discrimination of analog detection samples are developed to eliminate the negative influence of the detection noises and get quantitatively true values of both the correlation function and the detector quantum efficiency. The methods are demonstrated depending on whether two single-photon avalanche photo detectors are used in both SPDC channels, or at least one single-photon detector is replaced by a photo-multiplier tube which cannot operate in the photon counting mode.

Temporal Encoding to Reject Background Signals in a Low Complexity, Photon Counting Communication Link.

Communicating information at the few photon level typically requires some complexity in the transmitter or receiver in order to operate in the presence of noise. This in turn incurs expense in the necessary spatial volume and power consumption of the system. In this work, we present a self-synchronised free-space optical communications system based on simple, compact and low power consumption semiconductor devices. A temporal encoding method, implemented using a gallium nitride micro-LED source and a silicon single photon avalanche photo-detector (SPAD), demonstrates data transmission at rates up to 100 kb/s for 8.25 pW received power, corresponding to 27 photons per bit. Furthermore, the signals can be decoded in the presence of both constant and modulated background noise at levels significantly exceeding the signal power. The system’s low power consumption and modest electronics requirements are demonstrated by employing it as a communications channel between two nano-satellite simulator systems.

Measurement of two-mode squeezing with photon number resolving multipixel detectors

The measurement of the two-mode squeezed vacuum generated in an optical parametric amplifier (OPA) was performed with photon number resolving multipixel photon counters (MPPCs). Implementation of the MPPCs allows for the observation of noise reduction in a broad dynamic range of the OPA gain, which is inaccessible with standard single photon avalanche photodetectors.

Characterization of InP Based SAGCM Avalanche Photodetector for Single Photon Fiber Optic Communications

This paper presents fabrication and characterization of InP-based separate absorp- tion, grading, charge, and InP/InAlAs hetro-multiplication (SAGCM) single photon avalanche photo-detectors (SPADs) for application of single photon flber optic communications. The dark current (ID) of SPAD at 90% of the breakdown voltage (VBR) was 37.8pA and 18.8nA at 200K and 300K, respectively. Under i40 - C and gate repetition frequency of 10kHz with pulse width of 2ns, the performance of dark count probability Pdc = 0:02, single-photon detection e-ciency ·det = 11:5%, noise equivalent power NEP = 5£10 i14 W/(Hz) 1=2 , a factor of quantum bit-error rate of Pdc=·det = 0:16 were simultaneously achieved. In addition, both the dark current and the dark count exhibited activation energy of 0.24eV in temperature below 240K which shown the dominant generation sources were band-to-band tunneling and fleld-enhanced band-traps-band tunneling.

Single photon avalanche photodetector with integrated quenching fabricated in TSMC 0.18 [micro sign]m 1.8 V CMOS process

The design and testing of a single photon avalanche detector with integrated quenching circuit fabricated in the TSMC 0.18 mum CMOS technology are reported. A 78 mum device exhibits an average dark count rate of 100 counts/s without cooling. Photon detection probability of approximately 14% is measured at 670 nm.

Erratum for ‘Single photon avalanche photodetector with integrated quenching fabricated in TSMC 0.18 [micro sign]m 1.8 V CMOS process’

Erratum for ‘Single photon avalanche photodetector with integrated quenching fabricated in TSMC 0.18 [micro sign]m 1.8 V CMOS process’