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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) - A Ps-Pulse Laser for Ultrafast Entanglement Generation at 42.66 Ghz Repetition Rate
摘要： Entangled-photon sources are a key element for most quantum-information applications, ranging from quantum communication systems to quantum simulators and full photonic quantum computers. Spontaneous parametric downconversion (SPDC), requiring a pump laser and a nonlinear medium, is up-to-date still the preferred technique to generate such photonic entanglement. To scale the transmission rates or gate operations of the aforementioned applications, high clock rates of the pump lasers are needed. Moreover, photonic quantum-processing algorithms require photons with not only high entanglement visibility but also high spectral indistinguishability and purity. This can either be achieved by narrow spectral filtering, costly in rate, or by suitable choice of the pump pulse length (typically in the ps range). Attempts have been made to increase the rate of conventional fs-lasers by adding multiple spatial-paths [1] but this method cannot be used to go beyond GHz repetition rates. This results in the quest to produce pump lasers with very high repetition rate, ps-pulse width and high enough power to drive the weak SPDC process. We report here on an implementation of a compact and fast ps-pump laser setup which can generate entangled photon pairs at repetition rates up to 42.66 GHz. Our entangled-photon source can be operated at these high generation rates and is basically only limited by the jitter of the detectors. In addition, we achieve a high spectral purity without narrow bandpass-filtering by mutually matching the length of the PDC crystal and the pump laser‘s pulse length [2], yielding polarisation-entangled photon pairs with minimal spectral correlations. The pump laser consists of a monolithically integrated mode locked DBR laser emitting pulses with a fixed repetition rate of 42.66 GHz at 1554 nm with 1.8 ps length. A pulse picker, made of an intensity modulator and driven by the same controller as the pump laser, allows adjusting the repetition rate used in the experiment, as depicted in Fig. 1. The power of the laser pulses is boosted with a series of optical amplifiers to 25 dBm. Conversion to the proper wavelength for the PDC process takes place in a second-harmonic-generation module, which finally generates output pulses of (cid:79)=777 nm to pump the entangled-photon source. Our entanglement source is based on a Sagnac-interferometer, where a ppKTP crystal is pumped by two pulsed laser beams from opposed directions. The generated photon pair at 1554 nm is split into different spatial modes by a polarizing beamsplitter, collected in optical fibers and detected with InGaAs detectors (10% efficiency). An experimental analysis of the entangled polarisation state yields an average visibility of 0.95 ± 0.01, corresponding to a CHSH parameter of S=2.685 which is in good agreement with theoretical calculations. Two-photon interference based on the Hong-Ou-Mandel effect also shows a high degree of purity.
关键词： ppKTP crystal,quantum-information applications,high clock rates,Sagnac-interferometer,InGaAs detectors,entangled-photon sources,ps-pump laser,spectral purity,spontaneous parametric downconversion
更新于2025-09-11 14:15:04
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Noise characteristics improvement of submicron InP/InGaAs avalanche photodiode for laser detection system
摘要： InP/InGaAs avalanche photodiodes have attracted much attention in optoelectronics and long distance optical communication systems due to their high bit rate and gain-bandwidth. In this paper, to improve the noise characteristics in laser detection systems, separate absorption, grading, charge, and multiplication InP/InGaAs avalanche photodiode (SAGCM APD) with double guard rings and three thin layers of InGaAsP has been simulated. In addition, the multiplication width of SAGCM APD has been optimized which enhances the noise characteristics. The Photocurrent and dark current are acquired as and resulting in superior electrical properties among the other works. The excess noise factor in the constant mean gain of has been reduced 10.3% in comparison with recent SAGCM APDs. The calculated results show that the reduction of dark current and the excess noise factor increase the SNR for about orders of magnitude.
关键词： InP/InGaAs avalanche photodiode,SAGCM APD,Noise characteristics,Multiplication width,Laser detection system,Signal-to-noise ratio
更新于2025-09-11 14:15:04
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Epitaxy || Epitaxy and Device Properties of InGaAs Photodetectors with Relatively High Lattice Mismatch
摘要： In this chapter, our works on the developments of wavelength-extended InGaAs photodetectors with cutoff wavelength >1.7 μm are reviewed. Various InGaAs/InAlAs p-i-n heterojunction structures have been grown on InP and GaAs substrates by gas source molecular beam epitaxy, some details on the InGaAs photodetector structures and the techniques of metamorphic buffer layer such as linearly, step, and one-step continuously InAlAs graded buffer, and dislocation restraint methods of compositional overshoot and digital alloy are introduced. The material characteristics and device properties were evaluated by atomic force microscopy, high-resolution X-ray diffraction and reciprocal space mapping, cross-sectional transmission electron microscopy, and current-voltage measurements, etc. The results provide clues to the development of metamorphic device structures on lattice-mismatched material systems.
关键词： photodetector,X-ray diffraction,InGaAs,metamorphic,atomic force microscopy,photoluminescence,lattice mismatch
更新于2025-09-11 14:15:04
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Low damage patterning of In <sub/>0.53</sub> Ga <sub/>0.47</sub> As film for its integration as n-channel in a fin metal oxide semiconductor field effect transistor architecture
摘要： One of the challenges of InGaAs integration as a channel in a fin field effect transistor architecture is the patterning of the III–V fin with nanometer scale definition, vertical sidewalls, and undamaged surfaces. In this work, the authors propose a two-step process to etch anisotropically and with minimal damage thin layers of InGaAs material. The first step of the process aims to modify the InGaAs surface on a well-defined thickness with limited sputtering by implanting light ions generated by a low pressure He/O2 plasma. The depth of the material modification is well controlled by the ion energy and saturates with process time, giving to this step a self-limited behavior. The second step uses aqueous HF solution to remove the modified oxidized InGaAs layer with infinite selectivity over the nonmodified InGaAs layer. The repetition of cycles of the two-step process was applied to etch the thin film of InGaAs as well as pattern using a SiN hard mask. Blanket experiments show that each cycle of the two-step process allows to remove a fixed and reproducible InGaAs thickness of 5.7 nm, while blanket SiN films are not consumed. After the process, the InGaAs surface roughness is kept intact, but the surface stoichiometry is slightly degraded with Arsenic enrichment because of the wet chemical reactions between the III-As semiconductors and the acids. The results on the pattern show that it is possible to transfer the SiN hard mask into the InGaAs layer using cycles of the two-step process with a reproducible consumed InGaAs thickness at each cycle and low sidewalls surface damage. However, the process leads to tapered InGaAs profile because of the lateral consumption of the SiN hard mask due to preferential sputtering at grazing incidence angle.
关键词： FinFET,atomic layer etching,stoichiometry,plasma etching,InGaAs,surface damage
更新于2025-09-10 09:29:36
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Research on residual gas adsorption on surface of InGaAs photocathode
摘要： The negative electron a?nity InGaAs photocathode is an important part of the infrared vacuum detector. The article focuses on the adsorption of residual gas in the preparation of InGaAs photocathodes. The impact of the adsorbates on the generation of negative electron a?nity was calculated and discussed. Models of InGaAs surface with residual gas were built and the work function, charge transfer, dipole and the formation energy have been analyzed based on the ?rst principles. The dipole from the surface to the residual gas molecule was generated by the charge transfer. The surface work function went up followed. The biggest increment came up to 0.410 eV, which is caused by the adsorption of CO2. The photoelectrons escape was restrained. As a result, three chemical cleaning methods were proposed to clean the InGaAs surface. It is found that oxide is more stable to be wiped o? than the other residual gas molecule. So a further treatment needs to be raised.
关键词： Adsorption energy,InGaAs surface,Residual gas,Charge transfer
更新于2025-09-10 09:29:36
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Enhanced Interface Characteristics of PA-ALD HfO <sub/>x</sub> N <sub/>y</sub> /InGaAs MOSCAPs Using IPA Oxygen Reactant and Cyclic N <sub/>2</sub> Plasma
摘要： This letter reports high-quality plasma-assisted atomic-layer-deposited HfOxNy by using isopropyl alcohol (IPA) oxidant and cyclic N2 plasma treatment demonstrated on n-type In0.53Ga0.47As. Improved interface characteristics, with suppressed frequency dispersion and surface oxidation, were demonstrated and resulted in significantly decreased interface trap density (Dit) of 4.5 × 1011 eV?1cm?2 at the mid-gap level with outstanding inversion behaviors. In addition, to verify true inversion, transition frequency (ωm) of 4 kHz was extracted. The improvement mechanism of the proposed technology is assumed to be that nitrogen plasma reduces oxygen vacancies that act as oxygen diffusion paths and with the use of IPA oxidant the interface would be strongly protected during pre- and post-dielectric deposition.
关键词： IPA oxidant,inversion,nitridation,Hafnium oxintride,InGaAs MOS
更新于2025-09-10 09:29:36
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Ultrawide strain-tuning of light emission from InGaAs nanomembranes
摘要： Single-crystal semiconductor nanomembranes provide unique opportunities for basic studies and device applications of strain engineering by virtue of mechanical properties analogous to those of flexible polymeric materials. Here, we investigate the radiative properties of nanomembranes based on InGaAs (one of the standard active materials for infrared diode lasers) under external mechanical stress. Photoluminescence measurements show that, by varying the applied stress, the InGaAs bandgap energy can be red-shifted by over 250 nm, leading to efficient strain-tunable light emission across the same spectral range. These mechanically stressed nanomembranes could therefore form the basis for actively tunable semiconductor lasers featuring ultrawide tunability of the output wavelength.
关键词： strain-tuning,nanomembranes,photoluminescence,light emission,InGaAs
更新于2025-09-10 09:29:36
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Facet-selective group-III incorporation in InGaAs Template Assisted Selective Epitaxy
摘要： InGaAs is a potential candidate for Si replacement in upcoming advanced technological nodes because of its excellent electron transport properties and relatively low interface defect density in dielectric gate stacks. Therefore, integrating InGaAs devices with the established Si platforms is highly important. Using template-assisted selective epitaxy (TASE), InGaAs nanowires can be monolithically integrated with high crystal quality, although the mechanisms of group III incorporation in this ternary material have not been thoroughly investigated. Here we present a detailed study of the compositional variations of InGaAs nanostructures epitaxially grown on Si(111) and Silicon-on-insulator substrates by TASE. We present a combination of XRD data and detailed EELS maps and find that the final Ga/In chemical composition depends strongly on both growth parameters and the growth facet type, leading to complex compositional sub-structures throughout the crystals. We can further conclude that the composition is governed by the facet-dependent chemical reaction rates at low temperature and low V/III ratio, while at higher temperature and V/III ratio, the incorporation is transport limited. In this case we see indications that the transport is a competition between Knudsen flow and surface diffusion.
关键词： TASE,nanowires,facet-selective incorporation,InGaAs,compositional variations
更新于2025-09-09 09:28:46
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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
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An Accurate Experimental Investigation of an Optical Sensing Microwave Amplifier
摘要： This paper deals with an accurate experimental investigation of the optical sensing behavior of a microwave low-noise amplifier (LNA). The tested amplifier, employing a commercial InGaAs pHEMT has been analyzed in terms of the scattering parameters and the noise figure. The analysis has been carried out by observing how the device behavior is influenced by a continuous wave laser illumination for different optical wavelengths, power levels, and bias conditions. It has been assessed that the LNA performance is significantly influenced by the light exposure with optical effects more pronounced at higher wavelengths for a fixed incident power. Upon applying the recommended bias conditions of the sensing amplifier, the main changes consist of a degradation of the noise figure and gain. As opposite to this, an overall performance enhancement is clearly recognizable with the amplifier biased at the transistor pinch-off. The results obtained in the present work fully confirm a theoretical analysis previously carried out by employing different devices and LNA design.
关键词： low-noise amplifier,noise and scattering parameters,InGaAs pHEMT,Optical sensing
更新于2025-09-09 09:28:46