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Spoof Plasmon Interconnects— Communications beyond RC Limit
摘要： T HE inception of spoof surface plasmon polariton (SSPP) mode realized in planar, patterned conductors to manage light beyond diffraction limit at a chosen frequency garnered significant attention of late. We show that, an SSPP channel can be chosen to act in two distinct ways: first, as a regular RC limited electrical interconnect at low frequencies; and second, as an exotic, beyond RC limit communication channel near its resonant frequency by binding the electromagnetic field on its surface to the elimination of capacitance C. A dynamic transformation between these two modes can constitute an energy economic, tera-scale inter-chip hybrid communication network. We have investigated theoretical limits on the information transfer capability of SSPP interconnects. We show that, a geometry dependent trade-off relation between cross-talk limited bandwidth density and information traveling length emerges in SSPP based communication networks. According to our analysis, a bandwidth density of 1 Gbps/μm is attainable in SSPP communication network with ～ 10 mm information transfer distance, where each channel can carry ～ 300 Gbps information with nominal cross-talk.
关键词： Interconnect,Spoof Plasmon,bandwidth,Terahertz,thermal noise,information capacity
更新于2025-09-23 15:23:52
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Amorphous Silicon with Extremely Low Absorption: Beating Thermal Noise in Gravitational Astronomy
摘要： Amorphous silicon has ideal properties for many applications in fundamental research and industry. However, the optical absorption is often unacceptably high, particularly for gravitational-wave detection. We report a novel ion-beam deposition method for fabricating amorphous silicon with unprecedentedly low unpaired electron-spin density and optical absorption, the spin limit on absorption being surpassed for the first time. At low unpaired electron density, the absorption is no longer correlated with electron spins, but with the electronic mobility gap. Compared to standard ion-beam deposition, the absorption at 1550 nm is lower by a factor of ≈100. This breakthrough shows that amorphous silicon could be exploited as an extreme performance optical coating in near-infrared applications, and it represents an important proof of concept for future gravitational-wave detectors.
关键词： amorphous silicon,thermal noise,gravitational-wave detection,ion-beam deposition,optical absorption
更新于2025-09-23 15:21:01
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Silicon nitride and silica quarter-wave stacks for low-thermal-noise mirror coatings
摘要： This study investigates a multilayer high reflector with new coating materials for next-generation laser interferometer gravitational wave detectors operated at cryogenic temperatures. We use the plasma-enhanced chemical vapor deposition method to deposit amorphous silicon nitride and silica quarter-wave high-reflector stacks and studied the properties pertinent to the coating thermal noise. Room- and cryogenic-temperature mechanical loss angles of the silicon nitride and silica quarter-wave bilayers are measured using the cantilever ring-down method. We show, for the first time, that the bulk and shear loss angles of the coatings can be obtained from the cantilever ring-down measurement, and we use the bulk and shear losses to calculate the coating thermal noise of silicon nitride and silica high-reflector coatings. The mechanical loss angle of the silicon nitride and silica bilayer is dispersive with a linear weakly positive frequency dependence, and, hence, the coating thermal noise of the high reflectors show a weakly positive frequency dependence in addition to the normal 1/sqrt(f) dependence. The coating thermal noise of the silicon nitride and silica high-reflector stack is compared to the lower limit of the coating thermal noise of the end test mirrors of ET-LF, KAGRA, LIGO Voyager, and the directly measured coating thermal noise of the current coatings of Advanced LIGO. The optical absorption of the silicon nitride and silica high reflector at 1550 nm is 45.9 ppm. Using a multimaterial system composed of seven pairs of ion-beam-sputter deposited Ti:Ta2O5 and silica and nine pairs of silicon nitride and silica on a silicon substrate, the optical absorption can be reduced to 2 ppm, which meets the specification of LIGO Voyager.
关键词： quarter-wave stacks,silica,silicon nitride,gravitational wave detectors,thermal noise,mechanical loss,cryogenic temperatures,optical absorption,mirror coatings
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 1st International Conference on Energy, Systems and Information Processing (ICESIP) - Chennai, India (2019.7.4-2019.7.6)] 2019 IEEE 1st International Conference on Energy, Systems and Information Processing (ICESIP) - Improved ANN Model for Predicting the AC Energy Output of a Realistic Photovoltaic Grid Connected PV System
摘要： A sub-0.5 electron read noise VGA (640H×480V) CMOS image sensor has been integrated in a standard 0.18 μm 4PM CMOS process. The low noise performance is achieved exclusively through circuit optimization without any process refinements. The presented imager relies on a 4T pixel of 6.5 μm pitch with a properly sized and biased thin oxide PMOS source follower. A full characterization of the proposed image sensor, at room temperature, is presented. With a pixel bias of 1.5 μA the sensor chip features an input-referred noise histogram from 0.25 e? rms peaking at 0.48 e? rms. The imager features a full well capacity of 6400 e? and its frame rate can go up to 80 fps. It also features a fixed pattern noise as low as 0.77%, a lag of 0.1% and a dark current of 5.6 e?/s. It is also shown that the implementation of the in-pixel n-well does not impact the quantum efficiency of the pinned photo-diode.
关键词： image sensor,thick oxide,thin oxide,CIS,thermal noise,1/f noise,low noise,sub-electron,low light,CMOS
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Thermal Noise in Optically Pumped DF-VECSELs
摘要： Over the last decades, the low noise properties of Vertical–External–Cavity Surface–Emitting Lasers (VECSELs) have aroused interest for various applications. The dual–frequency (DF) VECSELs can generate a very low noise RF signal resulting from the beatnote of two orthogonal linear polarizations as sketched in Fig.1(a). For example, the very high spectral purity and class–A operation of DF–VECSELs are of interest for ultrastable atomic clocks [1] or microwave electronics for optically-carried RF signal processing or wide-band RADARs. The sources of noise of optically pumped VECSELs are well identi?ed : (i) the intensity noise induced by the pump through the laser dynamics, (ii) the spontaneous emission contribution, (iii) technical noises such as mechanical vibrations, and (iv) the thermal noise. The two ?rst sources of noise are well modeled and understood. But in [2] a simple second–order low-pass ?lter behaviour is assumed for the thermal contribution to the frequency noise power spectral density (PSD) spectra. Yet, de?ning unequivocally a cut–off frequency is not obvious since different time scales are actually involved. Moreover, this over–simpli?ed model fails at low frequencies in [3] as displayed in Fig.1(b). Indeed, below 200 kHz the slope of the beatnote phase–noise spectrum of a DF–VECSEL at 852 nm obeys a f ?3 scaling law instead of the f ?4 expected behaviour. The aim of the present work is to microscopically model the thermal noise contribution. First, we describe the layers of the optically pumped emitting–surface, which is glued to a Peltier cooler. The heat equations take into account transverse and longitudinal diffusion processes. Assuming a gaussian pro?le for the pump, we obtain the temperature ?eld inside the structure using Hankel transformation formalism and we investigate the transient thermal response. The pump intensity ?uctuations induce heat ?uctuations inside the structure leading to changes of the refractive index and the material thermal–expansion, which are responsible for frequency ?uctuations of the laser mode. We ?nd an analytical expression of the frequency noise PSD induced by these thermo-optic effects, which allows to model the beatnote phase noise PSD of DF-VECSELs. We ?nd a very good agreement with the f ?3 slope of the experimental datas and we evidence the fundamental thermal ?uctuations contribution at room temperature. Such thermodynamics ?uctuations were already investigated for VCSEL structures in [4], starting from a stochastic heat equation. We extend it to a full study of the frequency noise PSD spectrum for DF-VECSELs. We obtain a fully analytical expression and discuss its validity.
关键词： Thermal noise,frequency noise PSD,thermal fluctuations,optically pumped,DF-VECSELs
更新于2025-09-16 10:30:52
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Measurement and Analysis of Noise Spectra in Terahertz Wave Detection Utilizing Low-Temperature-Grown GaAs Photoconductive Antenna
摘要： Noise power spectral density (NPSD) in time domain terahertz (THz) wave detection systems utilizing GaAs-based photoconductive antennas (PCAs) was investigated quantitatively. The contributions of the PCA noise and the amplifier noises at the amplifier output depend strongly on the resistance of the PCA, the circuit parameters, and the frequency. The PCA has two types of noise: one can be modeled by the Johnson-Nyquist (thermal) noise for the PCA resistance, while the other has an NPSD inversely proportional to the frequency with its intensity dependent on the properties of the GaAs and the metallization. At a high frequency range ~ 100 kHz, voltage-type amplifier noise could appear if the cable capacitance between the PCA and the amplifier is large. As a result, a low-noise range tends to appear in the intermediate frequency range. In comparison with the PCAs with Ti/Au metallization, the PCAs with Pd/Ge/Ti/Au having lower contact resistance lead to lager influence of the Johnson-Nyquist noise at the output.
关键词： Thermal noise,Noise spectra,Photoconductive antenna,Low-temperature-grown GaAs,1/f noise
更新于2025-09-12 10:27:22
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High signal-to-noise ratio for high-impedance-loaded nano-photodetector toward attojoule optical reception
摘要： We demonstrate a high signal-to-noise ratio (SNR) for a photonic-crystal nanophotodetector (PD). The ultralow-capacitance nano-PD can be terminated with a load resistor with a resistance as high as 59 kX for ef?cient light-to-voltage conversion, and its strong thermal-noise suppression leads to an SNR that is 30 dB higher than that of the conventional p-i-n PD terminated with a 50-X load. The noise equivalent power is only 500 fW/(cid:2)Hz, while a gigahertz-level bandwidth can be maintained when considering that the PD capacitance is only 1 fF. Theoretically, this allows optical reception at less than 100 aJ to obtain a bit error rate of 10–9. The resistor-loaded nano-PD requires a small electrical biasing energy comparable to the optical energy, which is remarkably energy saving compared with avalanche PDs or other PDs integrated with ampli?ers. Such a receiver promises a dense optical interface with CMOS electronics in photonic networking and processing chips.
关键词： high signal-to-noise ratio,attojoule optical reception,thermal-noise suppression,nano-photodetector,photonic-crystal
更新于2025-09-12 10:27:22
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Comparative Simulation of Thermal Noise Effects for Photodetectors on Performance of Long-Haul DWDM Optical Networks
摘要： Long-haul 16-channel dense-wavelength division multiplexing networks employing two different avalanche photodiode (APD) structures (Si and InGaAs) and positive-intrinsic-negative (PIN) photodetectors are simulated and compared under thermal noise effects for different fiber lengths. The effect of thermal noise level on the transmission quality with a variation of amplifying section length, number of amplifying sections and channel speed is discussed. The impact of thermal noise on the system performance is analyzed by varying input power from ?5dBm to 20dBm for both 25 km and 50 km amplifying section at 100 km fiber length. The performance is evaluated for both 5 Gb/s and 10 Gb/s data rates over transmission distances up to 500 km. A comprehensive comparison is developed based on signal-to-noise ratio (SNR), quality factor (Q-factor) and bit error rate (BER). It is found that both APD structures achieve superior performance up to distance of 350 km comparing to PIN photodetectors for 50 km amplifying section. input The system provides optimum performance at power Pin = 10dBm in case of 50 km amplifying section, but then afterwards, the performance is degraded rapidly due to nonlinearities. The results revealed that the worst performance scenario is at 10–18 W/Hz thermal noise in terms of higher BER and lower Q-factor.
关键词： PIN,Q-factor,thermal noise,APD,amplifying section
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Thermal Noise Metrology with Time-Based Synthesis
摘要： We present a new measurement technique for quantifying noise temperature based on temperature and time. A single-pole, double-throw (SPDT) ultra-fast switch combines signals from outputs of two synchronized electromechanical (EM) switches. The input ports of EM switches are terminated by one unknown noise source, one known cold noise source, and two known noise references at ambient temperature. The magnitude of the combined noise signal can be adjusted by the duty cycle of the transistor-transistor logic (TTL) pulse that controls the fast switch. The measurement approaches the balanced mode by regulating the TTL duty cycle in order to minimize the difference between the combined noise signal and the ambient noise reference. In comparison to conventional total-power radiometers, this new instrumentation is more efficient and potentially provides a wider dynamic range.
关键词： thermal noise,feed-back loop,Balanced radiometer,noise synthesis,switch
更新于2025-09-10 09:29:36
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - Measuring Thermal Acoustic Radiation with an Optomechanical Antenna
摘要： We optically probe the SiN membrane nanomechanical resonator modes that are strongly coupled to acoustic radiation into the substrate. We use this optomechanical system for temperature metrology by detecting the ballistic transport of thermal excitations from a remote bath.
关键词： Metrology,Temperature Sensors,Optomechanics,Photonics,Thermal Noise,Nanophotonics
更新于2025-09-09 09:28:46