Detection Of Weak Optical Signals Research Articles

Facile synthesized Sb2S3 based high-performance visible photodetector for weak optical signal detection

This report is enlightening a novel approach to fabricating Sb2S3-based photodetector that can be used as an efficient receiver with the capability to detect weak optical signals in the visible light communication system. In place of several limitations posed by traditional wireless fidelity networks, this study also provides further evidence supporting the application of the new Light Fidelity technology. The solid-state reaction method was used to synthesize Sb2S3 material. A thin film of Sb2S3 was then deposited on a SiO2 substrate via thermal evaporation, and then MSM (metal semiconductor metal) type device was fabricated. The fabricated photodetector demonstrated excellent performance with a responsivity of 2635 mAW−1, detectivity of 1011 Jones order, and external quantum efficiency of 615%. This device is remarkable for its ability to detect optical signals with low power, with an estimated detection capability of up to 2.8 × 10−12 WHz−1/2 The device also boasts a faster response time, with a rise and decay time of approximately 130 ms. Additionally, it is highly durable and can withstand high voltages, making it an ideal device for visible light communication, even with weak optical signals.

Fabrication of highly sensitive visible photodetector based on SnS2 Terrazzo-like structure for weak signal detection

Chemically inert and van der Waal-structured tin-disulfide (SnS2) has become a potential candidate for optoelectronics due to its ultra-sensitivity and high performance resulting from high light absorption coefficient and thickness-dependent electrical properties. We report the facile synthesis of SnS2 Terrazzo-like structure using the CVD technique. A highly responsive MSM SnS2-based device is designed to detect optical radiation ranging from 300 to 800 nm. The fabricated device exhibits excellent responsivity (external quantum efficiency) of 2240 mAW−1 (522%) under 532 nm wavelengths for a 5 μW optical signal. The other merits, like detectivity and noise equivalent power, are 1.4 × 1010 Jones and 2.6 × 10−12 WHz−1/2, respectively, with a linear dynamic range (LDR) of ∼41 dB. The low LDR plays a vital role in evaluating light intensity from the corresponding generated photocurrent. The weak optical signal detection capability of SnS2-based photodetector paves the way for its application in astronomy, communication systems, and biomedical imaging.

Sb-Based Low-Noise Avalanche Photodiodes

Accurate detection of weak optical signals is a key function for a wide range of applications. A key performance parameter is the receiver signal-to-noise ratio, which depends on the noise of the photodetector and the following electrical circuitry. The circuit noise is typically larger than the noise of photodetectors that do not have internal gain. As a result, a detector that provides signal gain can achieve higher sensitivity. This is accomplished by increasing the photodetector gain until the noise associated with the gain mechanism is comparable to that of the output electrical circuit. For avalanche photodiodes (APDs), the noise that arises from the gain mechanism, impact ionization, increases with gain and depends on the material from which the APD is fabricated. Si APDs have established the state-of-the-art for low-noise gain for the past five decades. Recently, APDs fabricated from two Sb-based III-V compound quaternary materials, AlxIn1-xAsySb1-y and AlxGa1-xAsySb1-y, have achieved noise characteristics comparable to those of Si APDs with the added benefit that they can operate in the short-wave infrared (SWIR) and extended SWIR spectral regions. This paper describes the materials and device characteristics of these APDs and their performance in different spectral regions.

High-performance graphene/Si hybrid photodetector with a PMMA coating layer

Photodetectors with ultrahigh responsivity are meaningful for weak optical signal detection in the fields of biomedicine science and environmental monitoring. Graphene/Si hybrid photodetectors with ultrahigh photoresponsivity have already been reported. However, with all atoms exposed to the environment, graphene-based devices often show low stability. Here, the PMMA layer assisting the graphene transfer process has been retained on the surface of graphene during the fabrication process of the graphene/Si hybrid photodetector, and a high stability graphene photodetector with ultrahigh responsivity (>106 A W−1 for white LED illumination) has been successfully demonstrated. The fabricated graphene/Si hybrid photodetectors may have the potential to be utilized in functional near-infrared spectroscopy systems or underwater wireless optical communication systems for weak optical signal detection.

A Highly Sensitive Deep-Sea In-Situ Turbidity Sensor With Spectrum Optimization Modulation-Demodulation Method

This paper focuses on the design and development of a high sensitivity, low-power consumption deep-sea in-situ turbidity sensor with low-cost electronic design. A pseudo-random sequence modulation is applied to the amplitude measurement of the light diffuse radiation for the first time. This method can improve the detection sensitivity of turbidity sensors without increasing LED light intensity or building complex optical path structures in deep-sea application scenarios. The stability and anti-interference ability of the sensor has also been improved. To meet field requirements of deep-sea and long term detection, we also designed a light-scattering path and watertight mechanical structure. The limit of detection of the sensor was improved to 0.0036 FTU with a concentration range of 0 to 20 FTU and an R-square of 0.9991. The sensor has low power consumption with a supply current of 18.9 mA in operation mode and 25.4 μA in sleep mode. The bottom lander experiments in South China Sea indicated that the sensors successfully completed in-situ measurement tasks and can detect small changes in turbidity. The maximum dive depth reaches 3,413 meters. Thus, the experimental results show that the specifications of our turbidity sensor are comparable to those of commercial in-situ turbidity sensor products at these turbidity levels. The results also show that the PRS modulation method can be applied to weak optical signal detection with different optical principles.

High-Sensitivity Visible-Near Infrared Organic Photodetectors Based on Non-Fullerene Acceptors.

Highly sensitive solution-processed organic photodetectors (OPDs) with a broadband response ranging from visible to near infrared (NIR) and excellent overall device performance are demonstrated. The OPDs were fabricated from a blend consisting of a wide-band gap polymer donor and a newly developed fused octacylic small-molecule electron acceptor with an acceptor-donor-acceptor structure, which shows relatively high and balanced hole/electron mobility and allows for a thicker photo-active layer (∼300 nm). In conjunction with the use of an optimized inverted device structure, the dark current density of the OPDs was suppressed to an ultralow level of (8.3 ± 5.5) × 10-10A cm-2 at a bias of -1 V and the capability to direct weak light intensity is down to 0.24 pW cm-2; both are among the lowest reported values for OPDs. Owing to the low shot noise enabled by the inverted structure and the low thermal noise due to the high shunt resistance of the device, the obtained OPDs show a spectrally flat photoresponse in the range of 350-950 nm (UV-vis-NIR) and a maximal specific detectivity (D*) of (2.1 ± 0.1) × 1013 Jones at 800-900 nm, which are among the best results of NIR OPDs reported to date and represents a highly sensitive photodetector for weak optical signal detection. Besides, the OPDs show a wide bandwidth of 30 kHz, a fast temporal response time around 12 us ∼14 us, and a large linear dynamic range of 106 dB.

Design of weak optical signal detection system for measuring eye axial length

Since the reflectivity of two reflective surfaces of the corneal surface and the retinal pigment cortex is greatly different when measuring the axial length of eye, the intensity of the reflected optical signal belonges to the weak signal category under the premise of the incident light safety in the eye. In order to remove the noise and quickly extract the peak value of the signal for the calculation of the starting and ending point of the eye axial length, a weak optical signal detection system was designed. This system used PIN photodiode to receive weak optical signal and a weak light signal detection system was built coordinated with the I-V conversion circuit, automatic gain control circuit as well as the post-processing circuit. The experiment used ZIESS simulation eye to test. The results show that the designed detection system can detect the weak optical signal of about 0.77 nW at least, the maximum photoelectric conversion capacity can reach 4.5×108 V/W, the signal-to-noise ratio is more than 9 dB, and the maximum error between the measured eye length and the actual value can reach 0.05%. This system is characterized by low noise, high gain and large dynamic range, which provides an effective solution for accurate measurement of the eye axial length.

Imaging enhancement based on stimulated Brillouin amplification in optical fiber.

The detection of weak optical signals embedded in strong background illumination has broad application prospects. We propose an imaging enhancement method based on stimulated Brillouin scattering (SBS) in a single-mode fiber, which is capable of amplifying the weak optical signal while neglecting the broadband background noise because of its narrow gain bandwidth. In experiment, a high gain of 60 dB was achieved. An imaging enhancement experiment was carried out, where a target which cannot be seen because of transmission loss could be clearly captured with the amplification of SBS in the fiber. Because of the employment of continuous pump rather than a pulsed pump, this system has wide application in the monitoring of non-cooperative targets.

Design and Analysis of Weak Optical Signal Detection System Based on Photoelectric Detection Technology

Design and Analysis of Weak Optical Signal Detection System Based on Photoelectric Detection Technology

Modern photodetector arrays for detection of weak signals by spacecraft astroorientation instruments

We describe three classes of modern detector arrays for detection of weak optical signals—traditional CCD photoconverters (CCDs), electron-multiplied CCD photoconverters (EMCCDs), and CMOS photoconverters (CMOS arrays). Specific characteristic properties are provided for each class of detector in terms of functionality, architecture, and photoelectric/operational specifications; this information in turn determines the effectiveness of each detector class for application to a specific instrument. We cite several examples of photodetector arrays currently in production that demonstrate the capabilities of each class of photodetector discussed in this paper.

High-detectivity ultraviolet photodetectors based on laterally mesoporous GaN.

Photodetectors for the ultraviolet (UV) range of the electromagnetic spectrum are in great demand for several technologies, but require the development of novel device structures and materials. Here we report on the high detectivity of UV photodetectors based on well-ordered laterally mesoporous GaN. The specific detectivity of our devices under UV-illumination reaches values of up to 5.3 × 1014 Jones. We attribute this high specific detectivity to the properties of the mesoporous GaN/metal contact interface: the trapping of photo-generated holes at the interface lowers the Schottky barrier height thus causing a large internal gain. High detectivity along with a simple fabrication process endows these laterally mesoporous GaN photodetectors with great potential for applications that require selective detection of weak optical signals in the UV range.

Interview

Dr Niksa Tadic from the University of Montenegro talks to us about the work behind the paper ‘A 100 MHz current generator with T/(T-t) time waveform in 0.35 μm BiCMOS technology model’, page 744. Dr Niksa Tadic In 1995, after three years of industrial experience, I joined the University of Montenegro, Faculty of Electrical Engineering. I am interested in optoelectronic integrated circuit design including optical receivers with variable transimpedances, red-green-blue optical sensors, and current drivers for laser diodes in both CMOS and BiCMOS technologies. At the moment, together with my colleagues from the EMCE Institute in Vienna and the University of Montenegro in Podgorica, I am working on negative resistance based voltage amplifiers. The small-signal amplification approach based on the shifting of a DC operating point along the linear part of the voltage amplifier's transfer characteristic has become questionable in deep submicron technologies. The slope of the linear part of the amplifier's transfer characteristic reduces with the decrease of transistors dimensions, causing decrease of the voltage gain. The nonlinear small-signal amplification method based on negative resistance could be used as an alternative to the linear approach. I have reported in Electronics Letters a design of a current generator suitable for optical quantum random number generation (OQRNG), designed in 0.35 mm BiCMOS technology, with T/(T-t) time dependence. Logarithmic converter and differentiator used in an existing design have been avoided in the proposed design by using the BJT translinear loop. The achieved frequency bandwidth of the current pulses of 100 MHz is 5 times larger in comparison to the state-of-the-art, with at least 20 times smaller power consumption. The relative error of the measured waveform at 20 MHz is less than 3% in 97.5% of the time interval in which the current pulses have a rising slope. A generator based on a random physical phenomenon is the only method to obtain true random numbers. OQRNG based on the randomness of detecting single photons is of special interest because of its fast generation of random numbers and reliability. Hence, the proposed current generator with T/(T-t) time dependence can be applied in all those fields where true random numbers are needed, such as cryptography, statistical analysis, numerical simulations, or lottery games. In addition to the mentioned negative resistance based voltage amplifiers, I am working on further improvement of the OQRNG based on the proposed current generator with T/(T-t) time dependence. During the last 12 years of my research in optoelectronics, among the other specific applications in the field, there have been efforts toward research and development of optical detectors of various types (especially photodiodes), optical receivers with variable transimpedances intended for the universal optical storage systems (CD, DVD, Blu-Ray), colour sensors, and optical distance measurement systems. In the future, without any doubt, one of the main research interests in the field of optoelectronics will be the systems for detection of weak optical signals based on single photon avalanche diodes (SPADs). When a single photon is absorbed in the space-charge region of the SPAD, an electron-hole pair is generated. Due to the high electric field, additional electron-hole pairs are generated causing the rapid rise of the avalanche current. The avalanche current must be quenched to allow the detection of the next photon. To provide data transfer based on weak optical signals in the GHz region, the quenching of the avalanche current should be performed very fast, typically within 1 ns. This task is a great challenge for researchers in this area.

Detection performance of trigger-controlled Geiger-mode avalanche photodiodes in weak optical signal detection

This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode (GM-APD). A hierarchical look-back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection (impulse noise and continuous noise situations). Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.

Improved Circuits for Single-photon Avalanche Photodiode Detectors

A CMOS photo detection bias quenching circuit is developed to be used with single photon avalanche photodiodes (SPADs) operating in Geiger mode for the detection of weak optical signals. The proposed bias quenching circuits for the performance improvement reduce the circuit size as well as improve the performance of the quenching operation. They are fabricated in a 0.18-㎛ standard CMOS technology to verify the effectiveness of this technique with the chip area of only 300 ㎛², which is about 60 % of the previous reported circuit. Two types of proposed circuits with resistive and capacitive load demonstrated improved performance of reduced quenching time. With a commercial APD by HAMAMATSU, the dead time can be adjusted as small as 50 ㎱.

近红外微弱光信号检测镜头的研制

A weak optical signal detection lens is designed by optical design software – ZEMAX.The optical system requires small distortion and large relative aperture,which can match with the near-infrared CCD image sensor,in order to realize real-time,fast,high-precision detection of the weak singlet oxygen signal.The optical system parameters are relative aperture 1∶0.86,semi-image high 6.3 mm,spectral range(1 250~1 290 nm),magnification 1X,distortion0.1%,and manual focus.On the other hand,the mechanical structure of the optical system is design using the software-Auto CAD.The symmetrical structure is used to reduce costs and independent filter switching mechanism to facilitate the adjustment of the experiment.The detected lens successfully collects better weak singlet oxygen signals in the research experiments.

Detection of weak optical signals in lidar measurements under noise conditions

An algorithm of weak optical signal processing in lidar measurements under intensive background radiation is described. The algorithm is based on transformation of the Poisson photoelectron flow forming at the output of the photodetector photocathode into a flux with sub-Poisson statistics due to its stochastic-determined “rarefaction.” The quality coefficients of the proposed algorithm are estimated.

Specific features of the quantum picture of laser detection of optical signals

The physical picture of laser detection of weak optical signals is refined by theoretical consideration of the quantum nature of radiation detected. The basic equations describing the processes occurring in the detector are solved numerically and the detector sensitivity is estimated.

Optical Detection Using Multi-Wavelength Modulation

In this paper, we proposed a method to attain a high sensitivity of weak optical signal detection by using the multi-wavelength modulation principle. In this method, the optical phase carrying the measurand is obtained by averaging the phases obtained in various orders of heterodyne harmonics. The employment of higher heterodyne harmonics reduces the drift effect in optical detection. The proposed method is demonstrated on the nano-scale displacement measurement by using a single channel fiber interferometer. In the experiment, the displacement is simulated by moving a mirror with a piezoelectric tube. The results show that more repeatable measurements with a resolution of 35nm can be obtained by using the proposed method.

Detection of weak optical signals with a laser amplifier

Detection of weak and extremely weak light signals amplified by linear and four-wave mixing laser amplifiers is analyzed. Photoelectron distributions are found for different input photon statistics over a wide range of gain. Signal-to-noise ratios are calculated and analyzed for preamplification schemes using linear and four-wave mixing amplifiers. Calculations show that the high signal-to-noise ratio (much higher than unity), ensuring reliable detection of weak input signals, can be attained only with a four-wave mixing preamplification scheme. Qualitative dependence of the signal-to-noise ratio on the quantum statistical properties of both signal and idler waves is demonstrated.

Photocounts and laser detection of weak optical signals

Spatial localization of a photon, admissible within the framework of quantum electrodynamics, cannot explain the photocounts observed. Photocounts are shown to result from Coulomb instability of a weak electron flow in a photodetector. It is also shown that the use of bound electrons, i.e., electrons bound in atoms, ions, molecules, and so on, in detectors makes laser detection of weak optical signals without photocounts possible, in other words, with suppressed shot noise.