Photodiode Module Research Articles

An Energy-Efficient FD-fNIRS Readout Circuit Employing a Mixer-First Analog Frontend and a Σ-Δ Phase-to-Digital Converter.

This paper presents a low-power frequency-domain functional near-infrared spectroscopy (FD-fNIRS) readout circuit for the absolute value measurement of tissue optical characteristics. The paper proposes a mixer-first analog front-end (AFE) structure and a 1-bit Σ-Δ phase-to-digital converter (PDC) to reduce the required circuit bandwidth and the laser modulation frequency, thereby saving power while maintaining high resolution. The proposed chip achieves sub-0.01° phase resolution and consumes 6.8 mW of power. Nine optical solid phantoms are produced to evaluate the chip. Compared to a self-built high-precision measurement platform that combines a network analyzer with an avalanche photodiode (APD) module, the maximum measuring errors of the absorption coefficient and reduced scattering coefficient are 10.6% and 12.3%, respectively.

High-power MUTC Photodiode Module for Photonics-assisted Beyond 100 Gb/s Wireless Sub-THz Communications in the F-band

High-power MUTC Photodiode Module for Photonics-assisted Beyond 100 Gb/s Wireless Sub-THz Communications in the F-band

Малогабаритный лазерно-волоконный флуориметр ик-спектрального диапазона для люминесцентной фотодиагностики опухолей

The results of the development of a small-sized laser fiber fluorimeter in the IR spectral range for a luminescent photodiagnostics of superficial localization tumors are presented. This device, working in conjunction with the “Fluroscan” type pharmaceutical composition based on the 2,4-di(α-methoxyethyl)deuteroporphyrin IX ytterbium complex dipotassium salt, ensures the achievement of high values of the luminescent diagnostic contrast index for a neoplasm/normal tissue. Import substitution of some basic design elements of the developed device, in particular the photodiode module, was carried out with a domestic analogue.

Dynamic performance of a membrane-based variable focus lens with a large aperture.

Dynamic performance is one of the most important characteristics of a variable focus lens. However, there are few studies investigating the dynamic response of a membrane-based variable focus lens. In this paper, we present a mathematical model to describe spring-damping phenomena in theory. The first order natural frequencies with different scales were confirmed via finite element analysis. We also built a dynamic response experiment platform with changeable optical apertures, which was driven by a high-speed piezo stack actuator. A photodiode module was placed behind the lens to measure the variation of light luminance as the lens changed, and a laser displacement sensor was used to measure the deformation of the membrane. A series of data was collected with different optical apertures (20mm, 30mm, 50mm) and different pre-stretching ratios (200%, 300%) under different driving frequencies (from 5Hz to 25Hz in every 5Hz step). The experimental results were consistent with the mathematical model, which showed that the first order natural frequency increased as the aperture decreased or the membrane stiffness increased. This frequency-dependent characteristic of the variable focus lens provides a basis for further research on its dynamic performance.

A 56-Gb/s PAM-4 Transmitter/Receiver Chipset With Nonlinear FFE for VCSEL-Based Optical Links in 40-nm CMOS

This article presents a 56-Gb/s four-level pulse amplitude modulation (PAM-4) transmitter/receiver (TX/RX) chipset for optical link. The optical transmitter (TX) adopts a digital-to-analog converter (DAC)-based structure with a two-tap nonlinear PAM-4 feed-forward equalizer (FFE) implemented in the digital domain to compensate for the asymmetric responses from the vertical cavity surface-emitting laser (VCSEL). The 56-Gb/s PAM-4 receiver (RX) is connected to the photodiode (PD) and transimpedance amplifier (TIA) module for optical application. The interconnection loss from the RX chip to the PD+TIA module is compensated by the RX continuous-time linear equalizer (CTLE) and the one-tap decision-feedback equalizer (DFE). The pattern-filter-based bang-bang phase detector in the RX improves the jitter performance. Both TX and RX are fabricated in the 40-nm CMOS. The VCSEL TX demonstrates a 56-Gb/s compensated PAM-4 waveform with −0.9-dBm outer optical modulation amplitude (OMA) while consuming only 97 mW of power (1.73 pJ/b). The RX achieves 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−12</sup> bit error rate (BER) with 0.08 UI margin under 10-dB interconnection loss while dissipating 278 mW of power (4.96 pJ/b).

A 77-dB Dynamic-Range Analog Front-End for Fine-Dust Detection Systems with Dual-Mode Ultra-Low Noise TIA.

This paper presents an analog front-end for fine-dust detection systems with a 77-dB-wide dynamic range and a dual-mode ultra-low noise TIA with 142-dBΩ towards the maximum gain. The required high sensitivity of the analog signal conditioning path dictates having a high sensitivity at the front-end while the Input-Referred Noise (IRN) is kept low. Therefore, a TIA with a high sensitivity to detected current bio-signals is provided by a photodiode module. The analog front end is formed by the TIA, a DC-Offset Cancellation (DCOC) circuit, a Single-to-Differential Amplifier (SDA), and two Programmable Gain Amplifiers (PGAs). Gain adjustment is implemented by a coarse-gain-step using selective loads with four different gain values and fine-gain steps by 42 dB dynamic range during 16 fine steps. The settling time of the TIA is compensated using a capacitive compensation which is applied for the last stage. An off-state circuitry is proposed to avoid any off-current leakage. This TIA is designed in a 0.18 µm standard CMOS technology. Post-layout simulations show a high gain operation with a 67 dB dynamic range, input-referred noise, less than 600 fA/√Hz in low frequencies, and less than 27 fA/√Hz at 20 kHz, a minimum detectable current signal of 4 pA, and a 2.71 mW power consumption. After measuring the full path of the analog signal conditioning path, the experimental results of the fabricated chip show a maximum gain of 142 dB for the TIA. The Single-to-Differential Amplifier delivers a differential waveform with a unity gain. The PGA1 and PGA2 show a maximum gain of 6.7 dB and 6.3 dB, respectively. The full-path analog front-end shows a wide dynamic range of up to 77 dB in the measurement results.

Infrared neurostimulation in ex-vivo rat sciatic nerve using 1470 nm wavelength

Objective. To design and implement a setup for ex-vivo optical stimulation for exploring the effect of several key parameters (optical power and pulse duration), activation features (threshold, spatial selectivity) and recovery characteristics (repeated stimuli) in peripheral nerves. Approach. A nerve chamber allowing ex-vivo electrical and optical stimulation was designed and built. A 1470 nm light source was chosen to stimulate the nerve. A photodiode module was implemented for synchronization of the electrical and optical channels. Main results. Compound neural action potentials (CNAPs) were successfully generated with infrared light pulses of 200–2000 µs duration and power in the range of 3–10 W. These parameters determine a radiant exposure for stimulation in the range 1.59–4.78 J cm−2. Recruitment curves were obtained by increasing durations at a constant power level. Neural activation threshold is reached at a mean radiant exposure of 3.16 ± 0.68 J cm−2 and mean pulse energy of 3.79 ± 0.72 mJ. Repetition rates of 2–10 Hz have been explored. In eight out of ten sciatic nerves (SNs), repeated light stimuli induced a sensitization effect in that the CNAP amplitude progressively grows, representing an increasing number of recruited fibres. In two out of ten SNs, CNAPs were composed of a succession of peaks corresponding to different conduction velocities. Significance. The reported sensitization effect could shed light on the mechanism underlying infrared neurostimulation. Our results suggest that, in sharp contrast with electrical stimuli, optical pulses could recruit slow fibres early on. This more physiological order of recruitment opens the perspective for specific neuromodulation of fibre population who remained poorly accessible until now. Short high-power light pulses at wavelengths below 1.5 µm offer interesting perspectives for neurostimulation.

A Luminescence Signal Detector for Oncofluorometry of the Near Infrared Region

A portable high-sensitivity device for recording weak luminescence signals in the near infrared (NIR) region (900–1100 nm) has been developed for applications in laser oncofluorometry. The device consists of a housing with optical lenses, interference filters, and a high-sensitivity NIR photodiode module with a preamplifier, protection circuit, and power supply. It is shown that the use of interference filters of the SL 930–1100 type can significantly increase the efficiency of the device. The use of a photodiode module unit with a sensitivity peak near 960 nm, which maximally coincides with the luminescence peak of ytterbium porphyrin complexes, ensures the sensitivity of detecting weak luminescence signals at the level of several fW.

Ultraflexible Integrated Organic Electronics for Ultrasensitive Photodetection

AbstractFlexible organic photodetectors can form seamless contact with human skin, enabling continuous health monitoring. However, developing flexible photodetectors with high detectivity remains challenging because of the high theoretical dark current of photodetectors using a bulk heterojunction (BHJ) structure. Herein, a simple approach is reported that integrates a field‐effect transistor (FET) and an organic photodiode (OPD) module on the same substrate to achieve an ultralow dark current density (3.0 × 10−8 mA cm−2), ultrahigh detectivity (1.7 × 1015 Jones), and excellent flexibility. In the integrated sensor, the light‐sensing process occurs in the OPD module, whose signal is used to control the gate of the FET where the current output process occurs, enabling to utilize the light‐sensing properties of the OPD's BHJ structure while bypassing its high dark current. The ultraflexible integrated sensor amplifies the photoplethysmogram signal intensity from the OPD module by a factor of ≈10, thereby confirming its potential as an indoor wearable biosensor.

Numerical Considerations for Neutral Beam Spectroscopy Based Diagnostics in the Stellarator TJ-II

Two neutral-beam based diagnostic techniques are numerically evaluated for the stellarator TJ-II. The evaluation considers the beam from a dedicated diagnostic neutral beam injector that provides a 5 ms pulse of hydrogen accelerated to 30 keV as well as the light throughput of a dual purpose optical system that views the beam as it traverses the microwave, or neutral beam, heated plasmas of this magnetic confinement device. In the first instance, in which the implementation of the beam emission spectroscopy technique is considered for characterizing medium to long wavelength plasma turbulence, detailed estimates are made to determine the Balmer Hα light intensity reaching avalanche photodiode modules. In the second instance, similar detailed estimates are made for the spectrograph-based experimental set-up used for the Motional Stark Emission technique that has been successfully employed to determine the magnitude and direction of the internal magnetic field in TJ-II plasmas. In addition, optical measurements made to evaluate beam energy and composition are described. Finally, estimates and measurements are compared and discussed in order to complete this work.

Transmission of data, audio and text signal using Li-fi technology

The light fidelity technology refers to visible light communication that uses light as a medium to deliver high speed data which is much greater than that of WiFi. LiFi data is transmitted in several bit streams and the receiver side consisting an IR detector decodes the message. The transmission happens in the form of binary data where 0 means LED in ‘OFF’ state and 1 means that the LED is in the ‘ON’ state. Transmitter and receiver sections contain Arduino which is programmed using Arduino IDE. High power intensity led’s are used in the LiFi transmitter. In receiver section photodiode module is used to detect the light signal generated by the LiFi transmitter. In this we are transmitting the 2 different data using light they are Audio signal and Text signal. Hence the study of various topologies to understand the characteristics a LiFi system.

Underwater laser communication with sloped pulse modulation in turbid water

In this article, we propose the demonstration of an underwater wireless laser communication link operating at data rates of up to 100 Mbps over a band-limited turbid water channel using a modified pulse position modulation scheme with a sloped pulse. The communication link uses an avalanche photodiode module as the receiver. The bit error rate of a 5.4 × 10−6 by 450-nm blue laser diode in turbid water with 1.4 Nephelometric Turbidity Unit was below the forward error correction limit. Our demonstrated underwater wireless laser communication system is simple to use and maintains a high data transmission rate.

Influence of slit alignment and slit width on the luminosity measurement of arc discharge channel

The luminosity of lightning channel is closely related to the lightning current. In the present paper, a lightning channel luminosity detection system (LCLDS), comprising of an avalanche photodiode module, a neutral density filter, an extension tube and an adjustable horizontal slit, is assembled. By using the impulse current generator, lightning impulse currents with different amplitudes and also different waveforms were produced in a 15-mm open-air gap between two graphite-rod electrodes. The luminosity and the current of discharge channel were measured synchronously. The experiments looking into the influencing factors of luminosity measurement, including the alignment of the silt and the slit width, were carried out. Obtained results show that the slit opening center of LCLDS should be aligned to the center of the discharge gap. Otherwise, in the case of improper alignment, the measured luminosity waveforms associated with the same injected current might be quite different in the amplitudes as well as in the waveforms. Moreover, the peak luminosity increases linearly with increasing slit width, whereas the luminosity waveforms are practically unaffected, implying that, in the practical application, the slit width can be adjusted to alter the luminosity signal output according to the actual need. Obtained results here can establish the foundation to develop the correlation between the current and the corresponding luminosity in the future.

Remote Sensing of Lower Tropospheric Aerosols and Clouds over Islamabad Region Using a Self-Engineered Mie Scattering Lidar

Atmospheric changes in the lower troposphere have been remotely studied using a self-engineered Mie scattering lidar with special emphasis on aerosols and clouds profiling over Islamabad region in Pakistan. The lidar is based on a Nd:YAG laser operating at 1064 nm, with maximal energy of 350 mJ at 20-Hz repetition rate and 5-ns pulse length. A silicon avalanche photodiode (Si-APD, C30950E) module is used as a detector. A higher resolution of the lidar revealed time evolution of thermal transport phenomena in the convective boundary layer. Regions of incessant wind speed, temperature, and particulates concentration have been detected through band-like structures at altitudes above 900 m. Strong backscattering (β) and extinction (α) due to a partially invisible thin cloud layer falling in the field-of-view of the lidar beyond 4 km have been identified.

Thermal Management Study of LTCC PIN Photodiode Module

Multilayer low temperature co-fired ceramic (LTCC) is well known in usage as interconnect substrate, especially in high frequency application due to high electrical conductivity of the conductors and low loss of the LTCC dielectric. As substrate and packaging materials, there are many chips or devices placed on the multilayer LTCC board. In this paper, multilayer LTCC is implemented as the packaging at PIN photodiode (PD) module of the Radio over Fiber (RoF) system with the reason to increase thermal dissipation capacity of the PD module.

Development of a time-of-flight low-energy neutral particle analyzer for EAST tokamak

To understand the erosion effect of neutral particles on the first wall, a low energy neutral particle analyzer (LENPA), based on the time-of-flight method, has been developed for the Experimental Advanced Superconducting Tokamak (EAST). The LENPA to be installed in the EAST mid-plane mainly consists of a chopper sub-system, a 3 m long flight tube, two sets of detector assemblies, and data acquisition and processing, vacuum, power supply, and control sub-systems. The neutral outflux is gated in bunches of 1 μs time scale by a slotted rotating disc which is driven by a vacuum compatible motor modified from a turbomolecular pump. A He-Ne laser beam is projected through the disc slit to record the instants of chopper slits opening with an avalanche photodiode module. An on-axis electron multiplier detects chopped neutrals, and a central perforated Cu-Be plate is employed to channel the emitted secondary electrons into an off-axis electron multiplier. The radiation peaks of on-axis electron multiplier caused by UV photons projected through the central hole of the Cu-Be plate provide an alternative way to record the chopper slits' opening time. With an additional 4 TB fast memory card, 1 GS/s sampling rate has been realized by using a GaGe acquisition card continuously. The LENPA data from the EAST together with neutral particle material erosion experiments will be used to benchmark the simulation results for better predictions on future fusion reactors, such as ITER and China Fusion Engineering Test Reactor (CFETR).

Over 300 GHz bandwidth UTC‐PD module with 600 GHz band rectangular‐waveguide output

A hollow-waveguide-output uni-travelling-carrier photodiode (UTC-PD) module operating at frequencies from 400 to 900 GHz has been developed. The module consists of a UTC-PD, a photodiode-to-waveguide coupler, and a metallic package with a waveguide rectangular (WR)-1.5 rectangular waveguide. The coupler is monolithically integrated with the UTC-PD chip. The fabricated module exhibits the output power as high as −19 dBm at 500 GHz and the 3 dB bandwidth of 340 GHz, which is the widest among ever-reported photodiode modules.

(Invited) Indium Gallium Phosphide Photodiode with 50% Increased External Quantum Efficiency and Higher Signal to Noise Ratio for Blood Pressure Measurement

Measurement of blood pressure is one of the most important parameters for personal healthcare. Arteries are responsible for carrying blood from the heart to all parts of the body and the pressure of blood in arteries is measured in many abnormalities. The blood pressure is explained by two parameters. The highest blood pressure during heart pumping is measured by systolic pressure whereas the diastolic pressure measures the lowest blood pressure when the heart is not pumping the blood. For current work, the principle of light absorption is used to measure blood pressure in arteries. Light is more strongly absorbed by blood compared to skin or tissues and therefore, blood flow change can be detected by the change in intensity of light. This blood flow change is proportional to blood pressure and hence the blood pressure can be measured by measurement of change in light intensity. In this work, we have developed the InGaP photodiode module with higher signal to noise ratio for blood pressure measurement. The InGaP photodiode External Quantum Efficiency (EQE) is 50% higher than Silicon (Si) photodiode. The EQE is ever higher than Si photodiode equipped with the filter as shown in Fig. 1(a). The newly developed InGaP photodiode has the advantage of selective EQE at different wavelength. The photodiode has almost zero EQE outside the desired region of wavelength (300 nm- 700 nm) where the Si photodiode EQE is spread in the longer wavelength region (300 nm - 1200 m). This higher region of EQE can lower the signal to noise ratio. The InGaP photodiode has an increased signal to noise ratio (24.8) compared to other photodiodes (24.0) due to the smaller wavelength region of EQE. Both systolic blood pressure and diastolic blood pressure measurement was compared for actual value and predicted value. The R2 correlation value for systolic and diastolic blood pressure is measured to be 0.86 and 0.91 respectively as shown in Fig. 1(b) and Fig. 1(c). This works explore new doorway for LED and photodiode application in the field of biomedical sensors. The application of our new photodiode with enhanced EQE and the wide range of LED has numerous possibilities. The higher possibility of multichip design with Flip chip packaging technique can provide a single module for measurement of blood pressure, blood glucose, blood lipid and other parameters using LED of different wavelength. Figure 1

UHD Video Transmission Over Bidirectional Underwater Wireless Optical Communication

In this paper, we experimentally demonstrate for the first time a bidirectional underwater wireless optical communication system that is capable of transmitting an ultrahigh definition real-time video using a downlink channel while simultaneously receiving the feedback messages on the uplink channel. The links extend up to 4.5 m using QPSK, 16-QAM, and 64-QAM modulations. The system is built using software defined platforms connected to TO-9 packaged pigtailed 520 nm directly modulated green laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter for video streaming on the downlink, and an avalanche photodiode (APD) module as the downlink receiver. The uplink channel is connected to another pigtailed 450 nm directly modulated blue LD with 1.2 GHz bandwidth as the optical uplink transmitter for the feedback channel, and to a second APD as the uplink receiver. We perform laboratory experiments on different water types. The measured throughput is 15 Mb/s for QPSK, and 30 Mb/s for both 16 QAM and 64 QAM. We evaluate the quality of the received live video streams using peak signal-to-noise ratio and achieve values up to 16 dB for 64 QAM when streaming UHD video in harbor II water and 22 dB in clear ocean.

Evaluation of InGaAs/InP photodiode for high-speed operation at 4 K

An optically controlled high-speed current source located at 4 K is likely to improve the performance of pulse-driven Josephson junction arrays. A custom photodiode module with an Albis PDCS24L InGaAs/InP PIN photodiode is investigated in order to determine the suitability at 4 K. The DC and frequency response were tested at room temperature and at temperatures down to 4 K. For continuous wave optical input, photocurrents above 15 mA were produced at both room temperature and 4 K. I–V measurements show that the threshold voltage increased from 0.5 V at room temperature to 0.8 V at 4 K. The transmission coefficient S21 of the optoelectronic system, including cables and modulated laser source, was measured using a vector network analyzer. Up to 14 GHz, the results showed that the frequency response at 4 K was not degraded compared to room temperature. At room temperature, reverse bias voltages of up to 3 V was required for the highest bandwidth, while at 4 K, the photodiode was operated at nearly full speed even at 0 V reverse bias.