{"title":"Prediction of optically-triggered amplification in phototransistor with SPICE circuit simulators","authors":"Chiara Rossi, J. Sallese","doi":"10.1117/12.2545771","DOIUrl":"https://doi.org/10.1117/12.2545771","url":null,"abstract":"","PeriodicalId":115816,"journal":{"name":"Physics and Simulation of Optoelectronic Devices XXVIII","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131074023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Schulz, D. Chaudhuri, M. O’Donovan, M. O’Donovan, S. Patra, T. Streckenbach, P. Farrell, O. Marquardt, T. Koprucki
In this work we outline our multiscale approach for modeling electronic, optical and transport properties of III-N-based heterostructures and light emitting diodes (LEDs). We discuss our framework for connecting atomistic tight-binding theory and continuum-based calculations and how finite element and finite volume meshes are generated for this purpose. Utilizing this framework we present an initial comparison of the electronic structure of an (In,Ga)N quantum well carried out within tight-binding theory and a single band effective mass approximation. We show that for virtual crystal approximation studies, a very good agreement between tight-binding and effectivemass model results is achieved. However, for random alloy fluctuations noticeable deviations in the electronic ground and excited states are found when comparing the two methods. In addition to these electronic structure calculations, we present first LED device calculations, using a drift-diffusion model.
{"title":"Multi-scale modeling of electronic, optical, and transport properties of III-N alloys and heterostructures","authors":"S. Schulz, D. Chaudhuri, M. O’Donovan, M. O’Donovan, S. Patra, T. Streckenbach, P. Farrell, O. Marquardt, T. Koprucki","doi":"10.1117/12.2551055","DOIUrl":"https://doi.org/10.1117/12.2551055","url":null,"abstract":"In this work we outline our multiscale approach for modeling electronic, optical and transport properties of III-N-based heterostructures and light emitting diodes (LEDs). We discuss our framework for connecting atomistic tight-binding theory and continuum-based calculations and how finite element and finite volume meshes are generated for this purpose. Utilizing this framework we present an initial comparison of the electronic structure of an (In,Ga)N quantum well carried out within tight-binding theory and a single band effective mass approximation. We show that for virtual crystal approximation studies, a very good agreement between tight-binding and effectivemass model results is achieved. However, for random alloy fluctuations noticeable deviations in the electronic ground and excited states are found when comparing the two methods. In addition to these electronic structure calculations, we present first LED device calculations, using a drift-diffusion model.","PeriodicalId":115816,"journal":{"name":"Physics and Simulation of Optoelectronic Devices XXVIII","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116797838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Hantschmann, Zizhuo Liu, M. Tang, A. Seeds, Huiyun Liu, I. White, R. Penty
The growth of reliable III-V quantum well (QW) lasers on silicon remains a challenge as yet unmastered due to the issue of carrier migration into dislocations. We have recently compared the functionality of quantum dots (QDs) and QWs in the presence of high dislocation densities using rate equation travelling-wave simulations, which were based on 10-μm large spatial steps, and thus only allowed the use of effective laser parameters to model the performance degradation resulting from dislocation-induced carrier loss. Here we increase the resolution to the sub-micrometer level to enable the spatially resolved simulation of individual dislocations placed along the longitudinal cavity direction in order to study the physical mechanisms behind the characteristics of monolithic 980 nm In(Ga)As/GaAs QW and 1.3 μm QD lasers on silicon. Our simulations point out the role of diffusion-assisted carrier loss, which enables carrier migration into defect states resulting in highly absorptive regions over several micrometers in QW structures, whereas QD active regions with their efficient carrier capture and hence naturally reduced diffusion length show a higher immunity to defects. An additional interesting finding not accessible in a lower-resolution approach is that areas of locally reduced gain need to be compensated for in dislocation-free regions, which may lead to increased gain compression effects in silicon-based QD lasers with limited modal gain.
由于载流子迁移到位错的问题，在硅上生长可靠的III-V量子阱(QW)激光器仍然是一个尚未掌握的挑战。我们最近使用速率方程行波模拟比较了高位错密度下量子点(QDs)和量子点(QWs)的功能，该模拟基于10 μm大的空间步长，因此只允许使用有效的激光参数来模拟由位错引起的载流子损耗导致的性能下降。为了研究单片980 nm in (Ga)As/GaAs QW和1.3 μm QD激光器特性背后的物理机制，我们将分辨率提高到亚微米级别，以实现沿纵向腔方向放置的单个位错的空间分辨模拟。我们的模拟指出了扩散辅助载流子损失的作用，它使载流子迁移到缺陷状态，从而在量子阱结构中形成几微米的高吸收区域，而量子阱活性区域具有有效的载流子捕获，因此自然减少了扩散长度，对缺陷具有更高的免疫力。另一个在低分辨率方法中无法获得的有趣发现是，局部增益降低的区域需要在无位错区域进行补偿，这可能导致具有有限模态增益的硅基QD激光器的增益压缩效应增加。
{"title":"Impact of dislocations in monolithic III-V lasers on silicon: a theoretical approach","authors":"C. Hantschmann, Zizhuo Liu, M. Tang, A. Seeds, Huiyun Liu, I. White, R. Penty","doi":"10.1117/12.2547327","DOIUrl":"https://doi.org/10.1117/12.2547327","url":null,"abstract":"The growth of reliable III-V quantum well (QW) lasers on silicon remains a challenge as yet unmastered due to the issue of carrier migration into dislocations. We have recently compared the functionality of quantum dots (QDs) and QWs in the presence of high dislocation densities using rate equation travelling-wave simulations, which were based on 10-μm large spatial steps, and thus only allowed the use of effective laser parameters to model the performance degradation resulting from dislocation-induced carrier loss. Here we increase the resolution to the sub-micrometer level to enable the spatially resolved simulation of individual dislocations placed along the longitudinal cavity direction in order to study the physical mechanisms behind the characteristics of monolithic 980 nm In(Ga)As/GaAs QW and 1.3 μm QD lasers on silicon. Our simulations point out the role of diffusion-assisted carrier loss, which enables carrier migration into defect states resulting in highly absorptive regions over several micrometers in QW structures, whereas QD active regions with their efficient carrier capture and hence naturally reduced diffusion length show a higher immunity to defects. An additional interesting finding not accessible in a lower-resolution approach is that areas of locally reduced gain need to be compensated for in dislocation-free regions, which may lead to increased gain compression effects in silicon-based QD lasers with limited modal gain.","PeriodicalId":115816,"journal":{"name":"Physics and Simulation of Optoelectronic Devices XXVIII","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125333472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Sande, K. Harkhoe, A. Katumba, P. Bienstman, G. Verschaffelt
Currently, multiple photonic reservoir computing systems show great promise for providing a practical yet powerful hardware substrate for neuromorphic computing. Among those, delay-based systems offer a simple technological route to implement photonic neuromorphic computation. Its operation boils down to a time-multiplexing with the delay length limiting the processing speed. As most optical setups end up to be bulky employing long fiber loops or free-space optics, the processing speeds are ranging from kSa/s to tens of MSa/s. Therefore, we focus on external cavities which are far shorter than what has been realized before in such experiments. We present experimental results of reservoir computing based on a semiconductor laser, operating in a single mode regime around 1550nm, with a 10.8cm delay line. Both are integrated on an active/passive InP photonic chip built on the Jeppix platform. Using 23 virtual nodes spaced 50 ps apart in the integrated delay section, we increase the processing speed to 0.87GSa/s. The computational performance is benchmarked on a forecasting task applied to chaotic time samples. Competitive performance is observed for injection currents above threshold, with higher pumps having lower prediction errors. The feedback strength can be controlled by electrically pumping integrated amplifiers within the delay section. Nevertheless, we find good performance even when these amplifiers are unpumped. To proof the relevance and necessity of the external cavity on the computational capacity, we have analysed linear and nonlinear memory tasks. We also propose several post-processing methods, which increase the performance without a penalty to speed.
{"title":"Integrated photonic delay-lasers for reservoir computing","authors":"G. Sande, K. Harkhoe, A. Katumba, P. Bienstman, G. Verschaffelt","doi":"10.1117/12.2550576","DOIUrl":"https://doi.org/10.1117/12.2550576","url":null,"abstract":"Currently, multiple photonic reservoir computing systems show great promise for providing a practical yet powerful hardware substrate for neuromorphic computing. Among those, delay-based systems offer a simple technological route to implement photonic neuromorphic computation. Its operation boils down to a time-multiplexing with the delay length limiting the processing speed. As most optical setups end up to be bulky employing long fiber loops or free-space optics, the processing speeds are ranging from kSa/s to tens of MSa/s. Therefore, we focus on external cavities which are far shorter than what has been realized before in such experiments. We present experimental results of reservoir computing based on a semiconductor laser, operating in a single mode regime around 1550nm, with a 10.8cm delay line. Both are integrated on an active/passive InP photonic chip built on the Jeppix platform. Using 23 virtual nodes spaced 50 ps apart in the integrated delay section, we increase the processing speed to 0.87GSa/s. The computational performance is benchmarked on a forecasting task applied to chaotic time samples. Competitive performance is observed for injection currents above threshold, with higher pumps having lower prediction errors. The feedback strength can be controlled by electrically pumping integrated amplifiers within the delay section. Nevertheless, we find good performance even when these amplifiers are unpumped. To proof the relevance and necessity of the external cavity on the computational capacity, we have analysed linear and nonlinear memory tasks. We also propose several post-processing methods, which increase the performance without a penalty to speed.","PeriodicalId":115816,"journal":{"name":"Physics and Simulation of Optoelectronic Devices XXVIII","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132369875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Our group is developing a guided-wave optical pressure sensor to detect minute pressure fluctuations occurring during tsunami formation. The sensor consists of a diaphragm as a pressure-sensitive structure and a semi-closed structure with a small hole under the diaphragm which provides a unique high-pass filter function. Cutoff frequency of the high-pass characteristic is an important factor to detect pressure fluctuations due to tsunami formation. In this study, investigations were carried out on frequency characteristics and cutoff frequencies, which vary according to the semiclosed structure dimensions and pressure vibration amplitude, by numerical simulations and experiments in order to further establish design details of the sensor
{"title":"Frequency characteristics of a semi-closed structure in a guided-wave optical pressure sensor for detection of tsunami formation: investigation based on numerical simulations and experiments","authors":"Taiju Triyama, H. Ono, Naoto Takaoka, M. Ohkawa","doi":"10.1117/12.2541707","DOIUrl":"https://doi.org/10.1117/12.2541707","url":null,"abstract":"Our group is developing a guided-wave optical pressure sensor to detect minute pressure fluctuations occurring during tsunami formation. The sensor consists of a diaphragm as a pressure-sensitive structure and a semi-closed structure with a small hole under the diaphragm which provides a unique high-pass filter function. Cutoff frequency of the high-pass characteristic is an important factor to detect pressure fluctuations due to tsunami formation. In this study, investigations were carried out on frequency characteristics and cutoff frequencies, which vary according to the semiclosed structure dimensions and pressure vibration amplitude, by numerical simulations and experiments in order to further establish design details of the sensor","PeriodicalId":115816,"journal":{"name":"Physics and Simulation of Optoelectronic Devices XXVIII","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130859020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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