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[IEEE 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Rome (2018.6.19-2018.6.21)] 2018 International Symposium on Networks, Computers and Communications (ISNCC) - Design of a Photoconductive Antenna for Pulsed-Terahertz Spectroscopy with Polarization Diversity
摘要： In the present paper, a photoconductive antenna is designed to work as both pulse-terahertz emitter and receiver. The proposed two-port antenna benefits from polarization diversity with high sensitivity of polarization detection. The antenna electrodes consist of three arms and two gaps that can be excited by laser illumination. An 800 nm wavelength laser beam with output power of 80 mW, 100 MHz repetition rate, and 100 fs laser pulse duration is considered as optical excitation. Each port stimulates a pulse that its polarization is orthogonal to that of the other one according to their arrangement. Along with GaAs as photoconductive substrate beneath the antenna electrodes, an anti-reflection coating of Taconic RF-35 is used for depreciating unwanted terahertz echoes. The simulated results clarify that the proposed antenna shows polarization diversity and also, proper broadband behavior.
关键词： spectroscopy,polarization diversity,pulsed terahertz,photoconductive antenna
更新于2025-09-23 15:23:52
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Intense THz Source of Sub-Cycle Pulses with Tunable Elliptical Polarization
摘要： We propose a new THz source based on a large aperture photoconductive antenna for the generation of intense THz waves with tunable elliptical polarization. We designed an interdigitated structure with vertical and horizontal electrodes to produce half-cycle THz pulses with horizontal and vertical polarizations, respectively. A time delay between the two polarizations is introduced using a quartz window deposited onto the parts of the antenna with horizontal electrodes forming a phase mask. We demonstrate the generation of sub-cycle THz pulses with tunable elliptical polarization and a 70 kV/cm electric field. We show that the polarization state can be varied from linear to quasi-circular.
关键词： elliptical polarization,photoconductive antenna,sub-cycle pulses,THz source,tunable polarization
更新于2025-09-23 15:22:29
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Up to 70 THz bandwidth from an implanted Ge photoconductive antenna excited by a femtosecond Er:fibre laser
摘要： Phase-stable electromagnetic pulses in the THz frequency range offer several unique capabilities in time-resolved spectroscopy. However, the diversity of their application is limited by the covered spectral bandwidth. In particular, the upper frequency limit of photoconductive emitters - the most widespread technique in THz spectroscopy – reaches only up to 7 THz in the regular transmission mode due to absorption by infrared-active optical phonons. Here, we present ultrabroadband (extending up to 70 THz) THz emission from an Au-implanted Ge emitter that is compatible with mode-locked ?bre lasers operating at wavelengths of 1.1 and 1.55 μm with pulse repetition rates of 10 and 20 MHz, respectively. This result opens up the possibility for the development of compact THz photonic devices operating up to multi-THz frequencies that are compatible with Si CMOS technology.
关键词： photoconductive antenna,Si CMOS technology,THz emission,Ge emitter,femtosecond fiber lasers
更新于2025-09-19 17:13:59
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Multi-Energy Valley Scattering Characteristics for a SI-GaAs-Based Terahertz Photoconductive Antenna in Linear Mode
摘要： In this paper, the relationship between the terahertz radiation and the spatial distribution of photogenerated carriers under different bias electric field is studied. Terahertz pulses and the photocurrent of SI-GaAs photoconductive antenna are measured by the terahertz time-domain spectroscopy system. The occupancy rate for photogenerated carriers for different energy valleys is obtained by comparing the photocurrent of terahertz field integrating with respect to time with the photocurrent measured by oscilloscope. Results indicate that 93.04% of all photogenerated carriers are located in the Γ valley when the bias electric field is 3.33 kV/cm, and 68.6% of all photogenerated carriers are transferred to the satellite valley when the bias electric field is 20.00 kV/cm. With the bias electric field increasing, the carrier occupancy rate for the satellite valley tends to saturate at 72.16%. In order to obtain the carrier occupancy rate for the satellite valley and saturate value at the high bias electric field, an ensemble Monte Carlo simulation based on the theory of photo-activated charge domain is developed.
关键词： photoconductive antenna,multi-energy valley scattering,semi-insulating Gallium arsenide (SI-GaAs),terahertz time-domain spectroscopy
更新于2025-09-16 10:30:52
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Enhanced terahertz emission bandwidth from photoconductive antenna by manipulating carrier dynamics of semiconducting substrate with embedded plasmonic metasurface
摘要： In this article, we demonstrate a technique to enhance the Terahertz (THz) emission bandwidth from photo-conductive antenna (PCA) based on semiconducting substrates by manipulating the surface carrier dynamics of the semiconductor. Bandwidths in PCAs are limited by the decay of the photogenerated charge carriers, which in case of SI-GaAs is in the orders of 50 picoseconds. We show, with an embedded design of plasmonic meta-surface in the photoconductive gap of a PCA, it is possible to enhance the emission bandwidths by more than 50 percent. This is due to the fact that these nano-structures act as local recombination sites for the photogenerated carriers, effectively reducing the carriers’ lifetime. Additionally, the defect sites reduce the terminal current, thereby reducing the Joule heating in the device. Furthermore, the meta-surface also facilitates higher in-coupling of the exciting infrared light on to the PCA, thereby increasing the optical-to-THz conversion efficiency of the device.
关键词： carrier dynamics,plasmonic metasurface,bandwidth enhancement,photoconductive antenna,Terahertz
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Tail-Suppressed THz Photocurrent by a Bi-Polar Photoconductive Antenna Fabricated on Semi-insulating GaAs
摘要： We designed and fabricated a bi-polar type photoconductive antenna (PCA) for efficient generation of broadband terahertz (THz) radiation. The falling time of overlyingly generated photocurrent from bi-polar PCA can achieve 200 fs via superimposing two primarily opposite polarity photocurrent pulses having falling time of 100 ps with time delay of 200 fs. The simulation results disclosed a possibility to shift the central frequency from 0.1 to 1.3 THz and enhance the THz power by twice in the range 1.5 - 3.3 THz by using low cost substrate with long carrier life time such as semi-insulating gallium arsenide (SI-GaAs).
关键词： photocurrent,terahertz radiation,bi-polar photoconductive antenna,SI-GaAs
更新于2025-09-12 10:27:22
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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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Enhanced terahertz radiation of photoconductive antenna fabricated on GaAs-on-sapphire
摘要： The terahertz (THz) radiation properties of a photoconductive antenna (PCA) fabricated on a GaAs-on-sapphire (GoS) substrate are reported at sub-THz band. The GaAs layer with a thickness of approximately 1 μm was directly deposited on a sapphire wafer by means of molecular beam epitaxy. A butterfly-shaped antenna structure was then fabricated on the GoS substrate by photolithography, and the device was tested as the emitter of an in-house built THz time-domain spectrometer. The performance of this antenna was compared with a commercial one, which had an identical antenna structure but was fabricated on low-temperature-grown GaAs (LT-GaAs). The results showed that the GoS-based PCA radiated an enhanced THz field, which could be as much as 1.9 times that of the LT-GaAs-based PCA, indicating that GoS could be a promising photoconductive material. In addition, the optical transparency of the sapphire substrate allows the device to be illuminated from the backside, which is crucial for THz near-field imaging applications where the sample is usually in close proximity to the front surface of the PCA device.
关键词： photoconductive antenna,molecular beam epitaxy,THz time-domain spectrometer,terahertz,GaAs-on-sapphire
更新于2025-09-12 10:27:22
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An advanced approach to control the electro-optical properties of LT-GaAs-based terahertz photoconductive antenna
摘要： This work reports on an advanced approach to the design of THz photoconductive antenna (PCA). The LT-GaAs thin films used for the PCA fabrication were synthesized by MBE method on GaAs (100) substrate by adjusting the As pressure, As/Ga fluxes ratio, growth/annealing temperatures and annealing time. These parameters crucially affect electro-optical properties of the PCA samples as evidenced by the THz radiation power and time-domain spectroscopy measurements. The annealing temperature of 670 °C was found to be optimal for constructing a PCA possessing high amplitude of the THz radiation over the spectral range up to 1 THz at the resonance of 0.1 THz. The comparison of this PCA with the reference ZnTe crystal reveals a 2-fold increase in THz power. Furthermore, this antenna attains a 1.5-, 3-, and 2-fold increase in THz power, photocurrent efficiency, and actuating dc BV, as compared with the commercial ZOMEGA antenna. These results pave the way towards the creation of highly efficient LT-GaAs-based PCAs.
关键词： THz-antenna,Terahertz (THz) radiation,Photoconductive antenna (PCA),Low temperature-grown gallium arsenide (LT-GaAs),THz-spectroscopy
更新于2025-09-11 14:15:04
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Photoconductive antennas based on epitaxial films In <sub/>0.5</sub> Ga <sub/>0.5</sub> As on GaAs (1?1?1)A and (1?0?0)A substrates with a metamorphic buffer
摘要： The terahertz (THz) wave generation by the spiral photoconductive antennas fabricated on the low-temperature and high-temperature grown undoped and Si-doped In0.5Ga0.5As films is studied by the terahertz time-domain spectroscopy method. The In0.5Ga0.5As layers were grown by molecular beam epitaxy on GaAs substrates with (1 0 0) and (1 1 1) A crystallographic orientations utilizing step-graded InxGa1?xAs metamorphic buffer. The antennas are excited by radiation of Er3+-fiber laser at 1.56 μm wavelength in two regimes: with pulse durations of 2.5 ps or 100 fs. It is found that the THz wave generation is 3–4 times more effective in the case of InGaAs-based antennas on (1 1 1)A GaAs substrates as compared to the (1 0 0) substrates. Power-voltage characteristic of the LT-InGaAs antenna up to and beyond threshold breakdown voltage are reported.
关键词： time-domain spectroscopy,terahertz wave generation,photoconductive antenna,GaAs (1 1 1)A,InGaAs,molecular beam epitaxy
更新于2025-09-09 09:28:46