High-speed Photodetectors Research Articles

Optical Generation and Transmission of mmWave Signals in 5G ERA: Experimental Evaluation Paradigm

We demonstrate the generation, of a mmWave signal via the injection of an optical frequency comb (OFC) into an integrated tunable dual distributed Bragg reflector (DBR) laser as well as the fiber transmission and the processing of this signal by an optical beamforming network (OBFN). The dual DBR laser is based on a hybrid indium phosphide (InP) – polymer photonic integrated circuit (PIC). Two different cases have been examined in which the microwave signal is centered around 39 GHz and 60 GHz respectively, carrying quadrature amplitude modulation (QAM) formats at 0.5 Gbaud. In this proof-of-concept scenario, the OBFN consists of two optical paths, where the relative true time delay is induced by an optical delay line (ODL). Extensive comparison between the back-to-back (B2B) case and scenarios with transmission over 25 km of standard single-mode fiber (SSMF) has been made using the error-vector magnitude (EVM) and the bit-error ratio (BER) as evaluation criteria. In all cases, error-free transmission was suggested for all QPSK signals, whereas a worst-case EVM of 11.8% was observed for 16-QAM transmission, successfully showcasing the concept’s potential. The generated microwave signal’s frequency can be set arbitrarily high, provided that high-speed photodetection equipment is available for the detection and down-conversion of the signal. Extension to higher antenna elements (AEs) numbers is straight-forward, relying only on the number of available photodetectors.

Van der Waals semiconductor embedded transparent photovoltaic for broadband optoelectronics

Van der Waals and wide bandgap materials are essential for developing fast solar energy-activated photoelectric devices and power electronics. The high absorption coefficient of van der Waals materials and intermediate band defects states of wide bandgap materials can be used for photoactivated charge carrier generation. This study develops a novel heterojunction of van der Waal and wide bandgap materials with SnS and Ga2O3 for transparent photovoltaics (TPV). The TPV is a transparent electrical power generator comprised of nontoxic materials, making it a sustainable advanced optoelectronic device. This study reports an attempt to deploy wide bandgap (Ga2O3) and van der Waals layered (SnS) materials for TPVs. By tuning the thickness of SnS with Ga2O3, a notable open-circuit voltage (∼500 mV) with impressive short-circuit current density >1 mA/cm2 under AM1.5 G illumination condition is achieved. The device is highly optically transparent, with an average visible transmittance of 48%, enabling it as an on-site power supplier. Extensive investigation on van der Waal layer thickness features was given for optimum junction property, light absorption, and optical transmittance, which offers an outstanding dark to photocurrent ratio of 106, attributed to lower dark current. The Ga2O3/SnS heterojunction device also demonstrates a responsivity up to 79 mA/W under broadband light illumination from 365 nm to 623 nm and a fast photoresponse speed of 0.6 ms, suitable for self-biased, high-speed transparent photovoltaic photodetector.

Ultrafast two-dimensional imaging for surface defects measurement of mirrors based on a virtually imaged phased-array.

Single-shot measurement of surface defects of mirrors is vital for monitoring the operating states of high power lasers systems. While conventional methods suffer from low speed and small dynamic range. Here, we demonstrate a method for high speed two-dimensional (2D) surface amplitude-type defects measurement based on ultrafast single-pixel imaging assisted by a virtually imaged phased-array. Together with an optical grating, 2D wavelength to space mapping is achieved based on Fraunhofer far field diffraction, and the uniform broad spectrum of a home-made dissipative soliton is uniformly dispersed into the targeted mirror with one-to-one wavelength-to-space mapping. The surface amplitude-type defects are modulated into the intensity variation of the reflected spectrum. Then, we build a dispersive Fourier transform module for wavelength to time mapping, through which modulated spectral information is time stretched into the temporal domain, and recorded by a high speed photodetector together with a real time oscilloscope. Finally, to diminish the distortions induced by nonlinear dispersion during the wavelength-time mapping, we utilize the interpolation, and reconstruct the 2D surface with a frame rate of 7.6 MHz. A two-dimensional image with widths of 1.5 × 2 mm can be obtained within 10 ns, with a y direction spatial resolution of 180 µm and a x direction spatial resolution of 140 µm. This ultrafast 2D surface defects measurement scheme is promising for real-time monitoring of surface defects mirrors with large aperture, which are widely utilized in various high power laser systems.

Fast-Response Photodetector Based on Hybrid Bi2Te3/PbS Colloidal Quantum Dots.

Colloidal quantum dots (CQDs) as photodetector materials have attracted much attention in recent years due to their tunable energy bands, low cost, and solution processability. However, their intrinsically low carrier mobility and three-dimensional (3D) confinement of charges are unsuitable for use in fast-response and highly sensitive photodetectors, hence greatly restricting their application in many fields. Currently, 3D topological insulators, such as bismuth telluride (Bi2Te3), have been employed in high-speed broadband photodetectors due to their narrow bulk bandgap, high carrier mobility, and strong light absorption. In this work, the advantages of topological insulators and CQDs were realized by developing a hybrid Bi2Te3/PbS CQDs photodetector that exhibited a maximum responsivity and detectivity of 18 A/W and 2.1 × 1011 Jones, respectively, with a rise time of 128 μs at 660 nm light illumination. The results indicate that such a photodetector has potential application in the field of fast-response and large-scale integrated optoelectronic devices.

Simulation Study of High-Speed Ge Photodetector Dark and Light Current Degradation

The reliability of Ge photodetectors used in the framework of Si photonics is studied using TCAD simulation, in order to better understand the physical origin of dark current and responsivity degradation observed in Sy <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2019). It is shown that bulk and interface recombination mainly modify the SRH dominated dark and light currents, while fixed charge and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{D}_{\mathrm{ it}}$ </tex-math></inline-formula> strongly impacts band-to-band tunneling dark currents. This essential distinction shows the necessity to discriminate the dominating transport mechanisms in photodetectors using activation energy measurement, in order to better identify the origin of performance degradation. It also strengthens the requirement for adequate passivation of all interfaces to reach higher lifetime of photodetectors.

Fiber-optic amplitude bend direction and magnitude sensor

A variant of the implementation of a fiber-optic sensor for the direction and magnitude of the bend is proposed. Unlike existing spectral measuring systems, the solution under consideration involves the use of an amplitude polling technique which makes it possible to increase the speed of the sensor when using simpler and more affordable components. A sensitive element based on special diffraction structures consisting of pairs of chirped fiber Bragg gratings has been studied. The sensing elements are mounted on a tooling — a steel rod subjected to bending. The ability of the sensor to determine the magnitude and direction of bending in the deviation range from 0 to 30 mm was demonstrated with a standard deviation of the measured values from the real values of 0.536 mm. This measurement result is achieved by processing data obtained from three measuring devices and by the neural network with a hidden layer of 10 neurons and the sigmoid as the activation function. The research results are essential for modern monitoring systems. The implementation of the direction and magnitude of the bend sensor in the format of a fiber-optic device allows you to overcome the limitations of piezoelectric sensors, due to high noise immunity and resistance to environmental influences. The proposed technological solution makes it possible to avoid the spectral measurement technique that has become widely used in fiber-optic sensor systems. The use of an amplitude sensor for the magnitude and direction of bending will allow its use in devices where there is a need for precise positioning of control elements or structural components subjected to bending. Also, due to the measurement of the desired bending effect by estimating the optical power of the signal, the design of the sensor does not require the presence of a complex measuring device, and the sensor’s performance can be ensured using a cascade of inexpensive, but at the same time high-speed and durable photodetectors.

Revealing charge carrier dynamics and transport in Te-doped GaAsSb and GaAsSbN nanowires by correlating ultrafast terahertz spectroscopy and optoelectronic characterization

Recent advances in the growth of III-V semiconductor nanowires (NWs) hold great promise for nanoscale optoelectronic device applications. It is established that a small amount of nitrogen (N) incorporation in III-V semiconductor NWs can effectively red-shift their wavelength of operation and tailor their electronic properties for specific applications. However, understanding the impact of N incorporation on non-equilibrium charge carrier dynamics and transport in semiconducting NWs is critical in achieving efficient semiconducting NW devices. In this work, ultrafast optical pump-terahertz probe spectroscopy has been used to study non-equilibrium carrier dynamics and transport in Te-doped GaAsSb and dilute nitride GaAsSbN NWs, with the goal of correlating these results with electrical characterization of their equilibrium photo-response under bias and low-frequency noise characteristics. Nitrogen incorporation in GaAsSb NWs led to a significant increase in the carrier scattering rate, resulting in a severe reduction in carrier mobility. Carrier recombination lifetimes of 33 ± 1 picoseconds (ps) and 147 ± 3 ps in GaAsSbN and GaAsSb NWs, respectively, were measured. The reduction in the carrier lifetime and photoinduced optical conductivities are due to the presence of N-induced defects, leading to deterioration in the electrical and optical characteristics of dilute nitride NWs relative to the non-nitride NWs. Finally, we observed a very fast rise time of ∼2 ps for both NW materials, directly impacting their potential use as high-speed photodetectors.

Integrated photonics approach to radio-frequency self-interference cancellation

An integrated photonics based scheme for radio-frequency self-interference cancellation is proposed and demonstrated. It is achieved using a dual-parallel Mach-Zehnder modulator that eliminates the interference signal in the optical domain. The output of the modulator is a carrier suppressed double-sideband waveform that contains only the signal of interest. Finally, the signal of interest is recovered by combining the modulator output with a local optical carrier and detecting it at a high-speed photodetector. We present a detailed theoretical analysis and derive the optimal condition for self-interference cancellation for small modulation indices. The modulators were designed and fabricated on IMEC’s Silicon-on-Insulator iSiPP50G platform. Using this technique, we experimentally obtain a cancellation depth of 30 dB and a signal to interference ratio of 25 dB for frequencies up to 20 GHz, limited only by the equipment used. This is the first demonstration of self-interference cancellation on a silicon photonics platform and a further expansion of the functionalities offered by integrated microwave photonics.

A High-Speed Grating-Assistant SOA-PIN Photodetector With High Sensitivity

With an increased demand for high speed and high sensitivity in optical communication system applications, semiconductor optical amplifier (SOA)-PIN photodetectors and AlInAsSb, InGaAs/InAlAs, or Ge/Si based avalanche photodiodes (APDs) have attracted extensive attentions. Nevertheless, their gain-bandwidth products and sensitivities are limited either by the amplified spontaneous emission (ASE) noise of the SOA or by the long avalanche buildup time in the avalanche multiplication process. In this paper, we have proposed a grating-assistant SOA-PIN photodetector (GA-SOA-PIN) aiming at raising its sensitivity by filtering out the ASE noise. Our simulation result shows that it can achieve a sensitivity close to −25 dBm under a transmission data rate of 100 Gbps at 1.55 μm with a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−12</sup> . With a simulated gain-bandwidth product reaches 2.62 THz, for systems with their data rates beyond 40 Gbps, the performance of the proposed GA-SOA-PIN is superior as compared to that achievable by the best available APD and SOA-PIN photodetectors.

Graded multilayer triple cation perovskites for high speed and detectivity self-powered photodetector via scalable spray coating process

Rapid advancements in perovskite materials have led to potential applications in various optoelectronic devices, such as solar cells, light-emitting diodes, and photodetectors. Due to good photoelectric properties, perovskite enables low-cost and comparable performance in terms of responsivity, detectivity, and speed to those of the silicon counterpart. In this work, we utilized triple cation perovskite, well known for its high performance, stability, and wide absorption range, which is crucial for broadband photodetector applications. To achieve improved detectivity and faster response time, graded multilayer perovskite absorbers were our focus. Sequential spray deposition, which allows stacked perovskite architecture without disturbing lower perovskite layers, was used to generate single, double, and triple-layer perovskite photodetectors with proper energy band alignment. In this work, we achieved a record on self-powered perovskite photodetector fabricated from a scalable spray process in terms of EQE and responsivity of 65.30% and 0.30 A W-1. The multilayer devices showed faster response speed than those of single-layer perovskite photodetectors with the champion device reaching 70 µs and 88 µs for rising and falling times. The graded band structure and the internal electric field generated from perovskite heterojunction also increase specific detectivity about one magnitude higher in comparison to the single-layer with the champion device achieving 6.82 × 1012 cmHz1/2 W−1.

High-speed and high-power germanium photodetector based on a trapezoidal absorber.

A compact high-power germanium photodetector (Ge PD) is experimentally demonstrated by re-engineering light distribution in the absorber. Compared with a conventional Ge PD, the proposed structure shows a DC saturation photocurrent improved by 28.9% and 3 dB bandwidth as high as 49.5 GHz at 0.1 mA. Under the same photocurrent of 10.5 mA, the proposed Ge PD shows a 3 dB bandwidth of 11.1 GHz, which is almost double the conventional Ge PD (5.6 GHz). The 25 Gb/s eye-diagram measurement verifies the improved power handling capability. The compact size and manufacturing simplicity of this structure will enable new applications for integrated silicon photonics.

Monolithic integration of electro-absorption modulators and photodetectors on III-V CMOS photonics platform by quantum well intermixing.

Quantum well intermixing (QWI) on a III-V-on-insulator (III-V-OI) substrate is presented for active-passive integration. Shallow implantation at a high temperature, which is essential for QWI on a III-V-OI substrate, is accomplished by phosphorus molecule ion implantation. As a result, the bandgap wavelength of multi-quantum wells (MQWs) on a III-V-OI substrate is successfully tuned by approximately 80 nm, enabling the monolithic integration of electro-absorption modulators and waveguide photodetectors using a lateral p-i-n junction formed along the InP/MQW/InP rib waveguide. Owing to the III-V-OI structure and the rib waveguide structure, the parasitic capacitance per unit length can be reduced to 0.11 fF/µm, which is suitable for high-speed and low-power modulators and photodetectors. The presented QWI can extend the possibility of a III-V complementary metal-oxide-semiconductor (CMOS) photonics platform for large-scale photonic integrated circuits.

40 GHz waveguide-integrated two-dimensional palladium diselenide photodetectors

Hybrid integration of two-dimensional (2D) materials with photonic integrated circuits can enable additional functionality in planar waveguides based on excellent optical and electrical properties of 2D materials. 2D layered palladium diselenide (PdSe2) has a narrow energy bandgap and high carrier mobility, and its stability under normal laboratory environment conditions makes it of interest for use as high-performance infrared photodetectors. In this work, we propose and experimentally demonstrate a high-speed waveguide-integrated photodetector which uses chemical vapor deposition grown PdSe2 transferred onto a silicon waveguide. At 1550 nm wavelength, the photodetector can be operated without external bias with a responsivity of 0.57 mA/W and a responsivity of 20 mA/W at 6 V bias voltage. The detector had an impulse response full-width-half-maximum pulse width of about 11 ps, corresponding to a 3-dB bandwidth of 40 GHz.

High-performance modified uni-traveling carrier photodiode integrated on a thin-film lithium niobate platform

Lithium niobate on insulator (LNOI) has become an intriguing platform for integrated photonics for applications in communications, microwave photonics, and computing. Whereas, integrated devices including modulators, resonators, and lasers with high performance have been recently realized on the LNOI platform, high-speed photodetectors, an essential building block in photonic integrated circuits, have not been demonstrated on LNOI yet. Here, we demonstrate for the first time, heterogeneously integrated modified uni-traveling carrier photodiodes on LNOI with a record-high bandwidth of 80 GHz and a responsivity of 0.6 A/W at a 1550-nm wavelength. The photodiodes are based on an n-down InGaAs/InP epitaxial layer structure that was optimized for high carrier transit time-limited bandwidth. Photodiode integration was achieved using a scalable wafer die bonding approach that is fully compatible with the LNOI platform.

Self-powered, low-noise and high-speed nanolayered MoSe2/p-GaN heterojunction photodetector from ultraviolet to near-infrared wavelengths

Integration of nanolayered metal chalcogenides with wide-bandgap semiconductors forming pn heterojunction leads to the way of high-performance photodetection. This work demonstrates the fabrication of a few nanometer thick Molybdenum diselenide (MoSe2)/Mg-doped Gallium Nitride (p-GaN) heterostructure for light detection purposes. The device exhibits low noise broadband spectral response from ultraviolet to near-infrared range (300–950 nm). The band-alignment and the charge transfer at the MoSe2/p-GaN interface promote self-powered photodetection with high photocurrent to dark current ratio of 2000 and 1000 at 365 nm and 640 nm, respectively. A high responsivity of 130 A W−1, detectivity of 4.8 × 1010 Jones, and low noise equivalent power of 18 fW/Hz1/2 at 365 nm is achieved at an applied bias of 1 V. Moreover, the transient measurements reveal a fast rise/fall time of 407/710 μsec for the fabricated device. These outcomes exemplify the viability of MoSe2/p-GaN heterostructure for high-speed and low-noise broadband photodetector applications.

High-Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector Based on InAs/InAsSb Type-II Superlattice

High-speed photodetectors operating at mid-wave infrared are crucial for free-space optical communication and frequency comb spectroscopy. In this letter, we report a high-speed mid-wave infrared uni-traveling carrier photodiode based on InAs/InAsSb type-II superlattice at room temperature for the first time. The device exhibits a cut-off wavelength of around 5.5 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> at room temperature. The responsivity of the device is about 0.6 A/W (at 4.5 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>) under &#x2212;1 V at room temperature. The frequency response of the device is characterized by an optical parametric amplification system generating mid-infrared femtosecond pulses. A device with a 20 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> diameter has a 3-dB bandwidth of 12.8 GHz at &#x2212;4 V. These promising results suggest that the device could be potential candidates to be employed in the emerging high-speed MWIR applications.

Waveguide-Integrated van der Waals Heterostructure Mid-Infrared Photodetector with High Performance.

Extending the operation wavelength of silicon photonics to the mid-infrared (mid-IR) band will significantly benefit critical application areas, including health care, astronomy, and chemical sensing. However, a major hurdle for mid-IR silicon photonics has been the lack of high-speed, high-responsivity, and low noise-equivalent power (NEP) photodetectors. Here, we demonstrate a van der Waals (vdW) heterostructure mid-IR photodetector integrated on a silicon-on-insulator (SOI) waveguide. The detector is composed of vertically stacked black phosphorus (BP)/molybdenum ditelluride (MoTe2). We measured high responsivity (up to 0.85 A/W) over a 3-4 μm spectral range, indicating that waveguide-confined light could strongly interact with vdW heterostructures on top. In addition, the waveguide-integrated detector could be modulated at high speed (>10 MHz) and its switching performance shows excellent stability. These results, together with the noise analysis, indicate that the NEP of the detector is as low as 8.2 pW/Hz1/2. This reported critical missing piece in the silicon photonic toolbox will enable the wide-spread adoption of mid-IR integrated photonic circuits.

High performance Photodetector Based on PdSe2/MoS2 heterojunction

Abstract Photodetectors are devices that instantaneously convert optical signals into electrical signals. With the advancement of science and technology, they are being widely used in various fields. Two-dimensional materials possess many unique and important properties, such as tunable band gap, etc., and have been widely used in photodetectors, and have been widely used in photodetectors in terms of responsivity (R), detectability (D*) and external quantum efficiency (EQE) Shows excellent performance. By building heterojunctions, 2D materials can serve as excellent photodetector components. Herein, We prepared two-dimensional multilayer PdSe2 thin films by a simple one-step direct selenization method and a high performance photodetector was fabricated based on vertically stacked MoS2/PdSe2 heterojunctions via a Van der Waals force mechanical transfer method. The fabricated device displays current rectification characteristics in darkness (on/off ratio &gt; 102) and superior photovoltaic behavious under illumination. In addition, the MoS2/PdSe2 heterojunctions exhibits a remarkable responsivity of 2.7A·W-1 and a fast response time at 193/96 μs under 532nm laser irradiation. These results provide new opportunities for developing highly responsive and high-speed photodetectors to address integrated applications.

High-Bandwidth Extended-SWIR GeSn Photodetectors on Silicon Achieving Ultrafast Broadband Spectroscopic Response

The availability of high-frequency pulsed emitters in the 2–2.5 μm wavelength range paved the way for a wealth of new applications in ultrafast spectroscopy, free-space and fiber-optical communications, surveillance and recognition, artificial intelligence, and medical imaging. However, developing these emerging technologies and their large-scale use depend on the availability of high-speed, low-noise, and cost-effective photodetectors. With this perspective, here we demonstrate GeSn photodiodes grown on silicon wafers featuring a high broadband operation covering the extended-SWIR range with a peak responsivity of 0.3 A/W at room temperature. These GeSn devices exhibit a high bandwidth reaching 7.5 GHz at 5 V bias with a 2.6 μm cutoff wavelength, and their integration in ultrafast time-resolved spectroscopy applications is demonstrated. In addition to enabling time-resolved electroluminescence at 2.3 μm, the high-speed operation of GeSn detectors was also exploited in the diagnostics of ultrashort pulses of a supercontinuum laser with a temporal resolution in the picosecond range at 2.5 μm. Establishing these capabilities highlights the potential of manufacturable GeSn photodiodes for silicon-integrated high-speed extended-SWIR applications.

High-Speed 850 nm Photodetector for Zero-Bias Operation

High-speed photodetector operating at 850 nm wavelength with a large diameter and high quantum efficiency is desirable to meet the growing demands of short-reach optical links for high-performance computing systems. Zero-bias operation of the high-speed photodetectors can reduce power consumption, minimize system complexity of the optical transceivers and reduce the radiation damage in a harsh environment. Traditional p-i-n photodetectors for 850 nm applications often require a high reverse bias to accelerate the carrier transport for high-speed data transmission. In this work, we demonstrate a high-speed and low dark current modified uni-traveling-carrier photodiode based on GaAs/AlGaAs at 850 nm wavelength operating under zero bias with a quantum efficiency of 73%. The 3-dB bandwidth of the 20 μm and 40 μm diameter devices is 22.5 GHz and 13.3 GHz, respectively. A clear eye pattern is demonstrated at a 25.8 Gbit/s data rate for the device under zero-bias operation. To the best of our knowledge, this photodetector demonstrates the highest 3-dB bandwidth among all the zero-bias 850 nm photodetectors reported to date.