In this work, a dynamic metallic filamentary resistive switch (MFRS) is used to quench the avalanche in a single photon avalanche photodiode (SPAD). The experimental results and simulations are consistent with an interpretation that, the MFRS is in a high resistance state when the avalanche occurs. This enables the quenching of the avalanche sufficiently within a short time. This increases the voltage drop across the MFRS, which switches the MFRS to its low resistance on-state and the recharging process is greatly accelerated because of the lowered R-C time constant. This leads to a sharp avalanche pulse shape and a fast detection speed.
In this work, a novel smart quenching approach for a Geiger-mode single-photon avalanche diode is proposed. The avalanche photodiode is connected in series with a metallic filamentary resistive switch (MFRS). The hysteresis behavior of the MFRS makes it suitable to operate as a quenching resistor. Initially the MFRS is in the off state and it quenches an avalanche event triggered by an incident photon. After quenching, the MFRS switches to the low-resistance on-state, which reduces the R-C time constant of the recharging process. A sharp avalanche pulse shape, continuous detection, and fast detection speed have been achieved. Our observations are consistent with a model where the MFRS adaptively changes its resistance state from high to low during quenching and recharging.
Freedom Photonics and the University of Virginia have developed high power, wide-bandwidth balanced photodetectors based on vertically-illuminated modified uni-traveling carrier (MUTC) photodiode technology. These balanced pairs are based on single photodiodes which achieve 3-dB bandwidths of 25 GHz, coupled with output powers above 23 dBm, as well as 35 GHz photodiodes with output powers greater than 19 dBm. A balanced configuration of these devices offers advantages in common-mode noise reduction, increasing the signal-to-noise ratio. In a photonic link, high-power, balanced photodiodes support high link gain and large bandwidths, while the high linearity of these devices maximizes spurious-free dynamic range (SFDR).
Links at 1 micron offer key advantages over longer wavelength links. Both ultra-stable, low noise Nd:YAG lasers and high power efficiency, temperature-stable GaAs lasers operate at wavelengths around 1 micron. These components are particularly beneficial for quantum optical systems and links which require stability over a wide range of temperatures, such as are required in avionics. However, a key component missing in these 1 micron photonic links is a high-power photodiode receiver with high linearity and high quantum efficiency. Freedom Photonics and the University of Virginia have collaborated to develop photodiodes which fill this need. The photodetectors are based on an optimized vertically illuminated modified uni-traveling carrier (MUTC) photodiode technology. We report devices with quantum efficiencies in excess of 80% at 1064 nm, with a 3-dB bandwidth of 28 GHz, for a 20µm diameter device. The same device size handles very high power, with a 1-dB compression of >16 dBm RF power at a 64-mA photocurrent. These photodiodes have a major impact on peak performance of a photonic link, supporting high link gain and large bandwidths. Additionally, the high linearity of these devices minimizes noise and signal distortion, maximizing spurious-free dynamic range (SFDR). These are the first photodiodes of this type which have been packaged and made commercially available for this target wavelength.
High frequency analog RF photonic links are desirable to reduce the size, weight and power of RF systems by offering the replacement of lossy, bulky coaxial RF cabling for lightweight, low loss and broadband optical fiber, particularly in applications such as avionics and naval RADAR systems, electronic warfare and distribution of low-jitter clocks or local oscillator signals. Freedom Photonics and the University of Virginia have developed high power, wide-bandwidth optical photodetectors operating in the 1550-nm wavelength range. These photodetectors are based on vertically illuminated modified uni-traveling carrier (MUTC) photodiode technology. The devices have been developed into fully packaged, fiber-pigtailed modules with optimization for high powers or high speeds. This paper will present the architecture and experimental results of our range of photodiodes. One family of devices focuses on high power applications. These include high-power photodiodes with 3-dB bandwidths of 25 GHz coupled with output powers in excess of 23 dBm, as well as 35 GHz photodiodes with output powers greater than 19 dBm. Another family of devices focuses on high speed applications, including photodiodes with 3-dB bandwidths of >65 GHz and >100 GHz. These photodiodes, used in a photonic link, have a major impact on peak performance. The high power-handling capability and high speeds of these devices support high link gain and large bandwidths, while the high linearity of these devices minimizes noise and signal distortion, maximizing spurious-free dynamic range (SFDR).
High-performance photodetectors (HPPDs), with high output power and bandwidth, are needed for RF photonics links. Applications for these HPPDs range from high-power remote antennas, low-duty-cycle RF pulse generation, linear photonic links, high dynamic range optical systems, and radio-over-fiber (ROF). Freedom Photonics is a manufacturer of high-power photodetectors (HPPD) for the 1480 to 1620nm wavelength range, now being offered commercially. In 2016, Freedom has developed a HPPD for similar applications extending into the V-band. The basic device structure used for these photodetectors can achieve over 100-GHz bandwidths with slight variations. This work shows data for RF power and bandwidth performance for various size photodiodes, between 10 μm and 28 μm in diameter. Measurement data will be presented, which were collected at both assembly level and for fully packaged detectors. For detector devices with bandwidth performance over 50 GHz, the generated RF power achieved is expected to be over 15 dBm. This performance is exceptional considering the photodiode is fully integrated into a hermetic package designed for 65 GHz. Improvements in the coplanar waveguide (CPW) transmission line and flip-chip bonding design were integral in achieving the higher saturation at the higher bandwidth performance. Further development is required to achieve a >100 GHz packaged photodetector module.
A method of doping germanium using 1064 nm pulsed fiber laser was demonstrated. The secondary ion mass
spectrometry showed a p-n junction of 800 nm deep with a peak phosphorus concentration of 2×1019 cm-3. Germanium
photodiodes were fabricated on the laser-doped p-n junctions. Low bulk and surface leakage current values were
obtained which were comparable to diodes fabricated by rapid thermal diffusion. Laser doping allows low thermal
budget, minimization of surface desorption and selective doping without requiring photolithography. Laser doping was
shown to be an effective method for fabrication of electronic and optoelectronic devices.