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Detectors and Recording Materials
Published in Rajpal S. Sirohi, Optical Methods of Measurement, 2018
Detectors are compared by the use of several defined parameters. These are (i) responsivity R, (ii) detectivity D or D*, (iii) noise equivalent power (NEP), (iv) noise, (v) spectral response, and (vi) frequency response. The responsivity is the ratio of the output signal (in amperes or volts) to the incident intensity, and is measured in μA/(mW/cm2). For photodiodes, the quantum efficiency, which is the number of electron-hole pairs per incident photon, is sometimes given. Responsivity is proportional to quantum efficiency. The detectivity is the ratio of the responsivity to the noise current (voltage) produced by the detector. This, therefore, is the signal-to-noise ratio (SNR) divided by intensity. A parameter that is often used is D*, which includes the dependence on noise frequency bandwidth Δf and detector area A, and is connected to the detectivity through the relation () D*=D(AΔf)1/2
THz Photonics
Published in Chi H. Lee, Microwave Photonics, 2017
Albert Redo-Sanchez, X.-C. Zhang
With regard to detection systems, the main characteristic parameters are the signal-to-noise ratio (SNR), dynamic range (DR), noise equivalent power (NEP), and responsivity (Figure 10.2). They can be used to characterize both CW and pulsed systems. SNR is defined as the ratio between the signal and the noise measured within the system bandwidth. DR is defined as the ratio between the largest to the smallest signal. The smallest is usually related to the noise floor and the largest to the maximum signal that the system can handle without damage or saturation. The NEP is defined as the input signal that produces a SNR equal to one at the output of a detector at a given modulation frequency, operating wavelength, and noise bandwidth. The unit is expressed in power for incoherent detector. For coherent detection systems, NEP is defined as the minimum detectable power per square root bandwidth. The NEP gives the theoretical detection limit of the system and, in an optimal situation, the noise floor should be lower than the NEP. Responsivity and sensitivity are confused very often and sometimes they are used indistinctly. The responsivity is the ratio of the electrical output with respect to the excitation signal and it is usually expressed in units of voltage (or current) divided by input power. The sensitivity is defined as the minimum input signal required to produce an output signal with a specific SNR. Sensitivity and responsivity usually depend on the frequency of the radiation being detected and the bandwidth of the system.
Two-Dimensional Materials in Photoconductive Detectors
Published in Sam Zhang, Materials for Devices, 2023
Yu Duan, Shuanglong Feng, Sam Zhang
Responsivity is a physical quantity that describes the intensity of the output signal of a device under unit radiation. Its calculation formula is as follows:[22]R=Ilight-IdarkP
Levenberg–Marquardt-Based Non-Invasive Blood Glucose Measurement System
Published in IETE Journal of Research, 2018
Jyoti Yadav, Asha Rani, Vijander Singh, Bhaskar Mohan Murari
Monolithic photodiode/preamplifier integrated circuits housed in a clear 8-pin DIP package (OPT101, Texas Instruments) are used to detect the attenuated light. This photodiode has sensitivity starting from 300 to 1100 nm. Photodiode has high responsivity of 0.5 A/W at 940 nm. Figure 2 represents the block diagram of the proposed experimental system utilized in this pilot study. LM 324 IC used for filters, consists of four independent high-gain frequency-compensated operational amplifiers, designed specifically to operate on single supply over a wide range of voltages. The invivo prototype is designed to assess the feasibility of proposed blood glucose measurement technique.
Pyro-phototronic effect enhanced self-powered photodetector
Published in International Journal of Optomechatronics, 2022
Previous devices generally consist of two layers including a pyroelectric semiconductor and another semiconductor or metal. This kind of device can only utilize polarization charges on one end of the semiconductor. Taking advantage of polarization charges induced on two ends of a pyroelectric semiconductor will make more excellent devices.[42] Pyro-phototronic effect has been investigated in a PEDOT: PSS/ZnO NWs/n-Si tri-layer heterojunction whose photoresponse performance to 648 nm laser illumination is significantly enhanced. responsivity increases from 0.823 (photovoltaic effect) to 22.054 mA/W (pyro-phototronic effect) under illumination (0.04 mW). Moreover, the photocurrent first increases and then reaches a plateau as the chopper frequency rises. The devices with short ZnO NWs have the more powerful current than those with long ZnO NWs. The authors also demonstrate a visible light communication system based on the as-fabricated devices that transmit and decrypt the encrypted light input signal. It is worthy of extensive attention to realize pyro-phototronic effect in this ZnO NWs based tri-layer heterojunction, which is beneficial for detecting ultrafast pulsed light and constructing light communication systems. Another tri-layer device with n-Si/p-SnOx/n-ZnO can also make use of the pyro-phototronic effect to boost the photoresponse of the device.[43] When illuminated under a 405 nm laser (36 mW/cm2), the devices display peak responsivity and detectivity, 36.7 mA/W and 1.5 × 1011 Jones, at a chopper frequency of 400 Hz. Ultrafast response and recovery time are also obtained as 3 µs and 2 µs, respectively. Furthermore, under 650 nm laser illumination, the responsivity and detectivity can be obtained as 64.1 mA/W and 2.4 × 1011 Jones.
Progress in semiconductor diamond photodetectors and MEMS sensors
Published in Functional Diamond, 2022
Responsivity or sensitivity: Responsivity, Rλ, is characterized by the output signal per radiant power, P, in watts (W). Usually, the photocurrent, Ip (A), is the measured. Rλ is then described as [58] where λ is the light wavelength λ. As a general, one can add gain, g, in the expression as