Diatoms are single cellular algae encapsulated in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very species dependent with huge variety in size, shape, and microstructure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with common traits, effects and differences between the different frustules. We have observed, when incident light interacts with the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine analysis software. The software uses parameters which are extracted from experimental images as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule parameters, maybe by altering growth conditions of the diatoms tailor their optical properties.
{"title":"Comparing optical properties of different species of diatoms","authors":"C. Maibohm, S. Friis, Yanyan Su, Karsten Rottwitt","doi":"10.1117/12.2078822","DOIUrl":"https://doi.org/10.1117/12.2078822","url":null,"abstract":"Diatoms are single cellular algae encapsulated in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very species dependent with huge variety in size, shape, and microstructure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with common traits, effects and differences between the different frustules. We have observed, when incident light interacts with the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine analysis software. The software uses parameters which are extracted from experimental images as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule parameters, maybe by altering growth conditions of the diatoms tailor their optical properties.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"29 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114023442","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. Riziotis, A. El Sachat, C. Markos, P. Velanas, A. Meristoudi, Aggelos Papadopoulos
Lately the demand for in situ and real time monitoring of industrial assets and processes has been dramatically increased. Although numerous sensing techniques have been proposed, only a small fraction can operate efficiently under harsh industrial environments. In this work the operational properties of a proposed photonic based chemical sensing scheme, capable to monitor the ageing process and the quality characteristics of coolants and lubricants in industrial heavy machinery for metal finishing processes is presented. The full spectroscopic characterization of different coolant liquids revealed that the ageing process is connected closely to the acidity/ pH value of coolants, despite the fact that the ageing process is quite complicated, affected by a number of environmental parameters such as the temperature, humidity and development of hazardous biological content as for example fungi. Efficient and low cost optical fiber sensors based on pH sensitive thin overlayers, are proposed and employed for the ageing monitoring. Active sol-gel based materials produced with various pH indicators like cresol red, bromophenol blue and chorophenol red in tetraethylorthosilicate (TEOS), were used for the production of those thin film sensitive layers deposited on polymer's and silica's large core and highly multimoded optical fibers. The optical characteristics, sensing performance and environmental robustness of those optical sensors are presented, extracting useful conclusions towards their use in industrial applications.
{"title":"Assessment of fiber optic sensors for aging monitoring of industrial liquid coolants","authors":"C. Riziotis, A. El Sachat, C. Markos, P. Velanas, A. Meristoudi, Aggelos Papadopoulos","doi":"10.1117/12.2079988","DOIUrl":"https://doi.org/10.1117/12.2079988","url":null,"abstract":"Lately the demand for in situ and real time monitoring of industrial assets and processes has been dramatically increased. Although numerous sensing techniques have been proposed, only a small fraction can operate efficiently under harsh industrial environments. In this work the operational properties of a proposed photonic based chemical sensing scheme, capable to monitor the ageing process and the quality characteristics of coolants and lubricants in industrial heavy machinery for metal finishing processes is presented. The full spectroscopic characterization of different coolant liquids revealed that the ageing process is connected closely to the acidity/ pH value of coolants, despite the fact that the ageing process is quite complicated, affected by a number of environmental parameters such as the temperature, humidity and development of hazardous biological content as for example fungi. Efficient and low cost optical fiber sensors based on pH sensitive thin overlayers, are proposed and employed for the ageing monitoring. Active sol-gel based materials produced with various pH indicators like cresol red, bromophenol blue and chorophenol red in tetraethylorthosilicate (TEOS), were used for the production of those thin film sensitive layers deposited on polymer's and silica's large core and highly multimoded optical fibers. The optical characteristics, sensing performance and environmental robustness of those optical sensors are presented, extracting useful conclusions towards their use in industrial applications.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"9359 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131350621","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}
The third-order nonlinear susceptibility of crystalline Cadmium Magnesium Telluride (CdMgTe) was studies using a spatially resolved Irradiance Scan method including picosecond and nanosecond laser pulse widths at 1064nm. The samples were placed in a loosely focused beam, and a series of individual laser pulses at different energies were collected. The transmitted beam was reimaged to a CCD with a microscope objective providing a detailed objective function for numerical simulations. The nonlinear transmission results were modeled by way of a split-step nonlinear beam propagation method including diffraction, nonlinear absorption, and refraction arising from bound electrons and light-generated free carriers. The angular dependence of the third order susceptibility with respect to the electric field is also represented along with laser-induced damage thresholds.
{"title":"Nonlinear optical properties of single crystal cadmium magnesium telluride","authors":"D. Lombardo, S. Trivedi, S. Guha","doi":"10.1117/12.2079877","DOIUrl":"https://doi.org/10.1117/12.2079877","url":null,"abstract":"The third-order nonlinear susceptibility of crystalline Cadmium Magnesium Telluride (CdMgTe) was studies using a spatially resolved Irradiance Scan method including picosecond and nanosecond laser pulse widths at 1064nm. The samples were placed in a loosely focused beam, and a series of individual laser pulses at different energies were collected. The transmitted beam was reimaged to a CCD with a microscope objective providing a detailed objective function for numerical simulations. The nonlinear transmission results were modeled by way of a split-step nonlinear beam propagation method including diffraction, nonlinear absorption, and refraction arising from bound electrons and light-generated free carriers. The angular dependence of the third order susceptibility with respect to the electric field is also represented along with laser-induced damage thresholds.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131993584","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}
We present a semiclassical theory of an optically pumped quantum dot phonon laser, based on a system of N quantum dots coupled to a high-Q acoustic phonon cavity. Based on a theory developed earlier [J. Kabuss, A. Carmele, and A. Knorr, Phys. Rev. B 88, 064305 (2013)], that was limited to the single emitter limit, a set of phonon laser equations is generalized to the many emitter regime and solved analytically. Similar to the optical laser it is possible to overcome the adverse effect of a phonon cavity loss with respect to entering the phonon laser regime by the number of quantum dots, that are coupled to the phonon resonator mode. Especially in the case of the proposed quantum dot phonon laser, which exhibits self-quenching, a shift of the laser threshold to lower pump powers and an inhibition of the self-quenching can be essential for entering the phonon lasing regime in the first place.
我们提出了一种基于N个量子点耦合到高q声子腔的光泵浦量子点声子激光器的半经典理论。基于早期发展的理论[J]。卡布斯，A.卡梅尔和A.诺尔，物理学家。Rev. B 88, 064305(2013)]，将一组声子激光方程推广到多发射极区并解析求解。与光学激光器类似，它可以克服声子腔损失的不利影响，通过量子点的数量，这是耦合到声子谐振器模式进入声子激光体制。特别是在提出的量子点声子激光器中，它表现出自猝灭，将激光阈值转移到较低的泵浦功率和抑制自猝灭对于首先进入声子激光状态是必不可少的。
{"title":"Theory of an optically driven quantum-dot phonon laser","authors":"Leon Droenner, J. Kabuss","doi":"10.1117/12.2081870","DOIUrl":"https://doi.org/10.1117/12.2081870","url":null,"abstract":"We present a semiclassical theory of an optically pumped quantum dot phonon laser, based on a system of N quantum dots coupled to a high-Q acoustic phonon cavity. Based on a theory developed earlier [J. Kabuss, A. Carmele, and A. Knorr, Phys. Rev. B 88, 064305 (2013)], that was limited to the single emitter limit, a set of phonon laser equations is generalized to the many emitter regime and solved analytically. Similar to the optical laser it is possible to overcome the adverse effect of a phonon cavity loss with respect to entering the phonon laser regime by the number of quantum dots, that are coupled to the phonon resonator mode. Especially in the case of the proposed quantum dot phonon laser, which exhibits self-quenching, a shift of the laser threshold to lower pump powers and an inhibition of the self-quenching can be essential for entering the phonon lasing regime in the first place.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115222497","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}
The laser-generation of micro-optical volume elements is a promising approach to decrease the optical shadowing of front side metal contacts of solar cells. Focusing a femtosecond laser beam into the volume of the encapsulation material causes a local modification its optical constants. Suchlike fabricated micro-optical elements can be used to decrease the optical shadowing of the front side metallization of c-Si solar cells. Test samples comprising of a sandwich structure of a glass sheet with metallic grid-lines, an Ethylene-vinyl acetate (EVA) encapsulant and another glass sheet were manufactured in order to investigate the optical performance of the volume optics. Transmission measurements show that the shadowing of the metalling grid-lines is substantially decreased by the micro-optical volume elements created in the EVA bulk right above the grid-fingers. A detailed investigation of the optical properties of these volume elements was performed: (i) experimentally on the basis of goniometric measurements, as well as (ii) theoretically by applying optical modelling and optimization procedures. This resulted in a better understanding of the effectiveness of the optical volume elements in decreasing the optical shadowing of metal grid lines on the active cell surfaces. Moreover, results of photovoltaic mini-modules with incorporated micro-optical volume elements are presented. Results of optical simulation and Laser Beam Induced Current (LBIC) experiments show that the losses due to the grid fingers can be reduced by about 50%, when using this fs-laser structuring approach for the fabrication of micro-optical volume elements in the EVA material.
{"title":"Laser-assisted manufacturing of micro-optical volume elements for enhancing the amount of light absorbed by solar cells in photovoltaic modules","authors":"G. Peharz, L. Kuna, C. Leiner","doi":"10.1117/12.2077118","DOIUrl":"https://doi.org/10.1117/12.2077118","url":null,"abstract":"The laser-generation of micro-optical volume elements is a promising approach to decrease the optical shadowing of front side metal contacts of solar cells. Focusing a femtosecond laser beam into the volume of the encapsulation material causes a local modification its optical constants. Suchlike fabricated micro-optical elements can be used to decrease the optical shadowing of the front side metallization of c-Si solar cells. Test samples comprising of a sandwich structure of a glass sheet with metallic grid-lines, an Ethylene-vinyl acetate (EVA) encapsulant and another glass sheet were manufactured in order to investigate the optical performance of the volume optics. Transmission measurements show that the shadowing of the metalling grid-lines is substantially decreased by the micro-optical volume elements created in the EVA bulk right above the grid-fingers. A detailed investigation of the optical properties of these volume elements was performed: (i) experimentally on the basis of goniometric measurements, as well as (ii) theoretically by applying optical modelling and optimization procedures. This resulted in a better understanding of the effectiveness of the optical volume elements in decreasing the optical shadowing of metal grid lines on the active cell surfaces. Moreover, results of photovoltaic mini-modules with incorporated micro-optical volume elements are presented. Results of optical simulation and Laser Beam Induced Current (LBIC) experiments show that the losses due to the grid fingers can be reduced by about 50%, when using this fs-laser structuring approach for the fabrication of micro-optical volume elements in the EVA material.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122884500","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. Valdivia, M. Wilkins, B. Bouzazi, A. Jaouad, V. Aimez, R. Arès, D. Masson, S. Fafard, K. Hinzer
The high-efficiency conversion of photonic power into electrical power is of broad-range applicability to many industries due to its electrical isolation from the surrounding environment and immunity to electromagnetic interference which affects the performance and reliability of sensitive electronics. A photonic power converter, or phototransducer, can absorb several watts of infrared laser power transmitted through a multimode fiber and convert this to electrical power for remote use. To convert this power into a useful voltage, we have designed, simulated, and fabricated a photovoltaic phototransducer that generates >5 V using a monolithic, lattice-matched, vertically-stacked, single-cell device that eliminates complex fabrication and assembly steps. Experimental measurements have demonstrated a conversion efficiency of up to 60.1% under illumination of ~11 W/cm2 at a wavelength of 835 nm, while simulations indicate that efficiencies reaching 70% should be realistically achievable using this novel design.
{"title":"Five-volt vertically-stacked, single-cell GaAs photonic power converter","authors":"C. Valdivia, M. Wilkins, B. Bouzazi, A. Jaouad, V. Aimez, R. Arès, D. Masson, S. Fafard, K. Hinzer","doi":"10.1117/12.2079824","DOIUrl":"https://doi.org/10.1117/12.2079824","url":null,"abstract":"The high-efficiency conversion of photonic power into electrical power is of broad-range applicability to many industries due to its electrical isolation from the surrounding environment and immunity to electromagnetic interference which affects the performance and reliability of sensitive electronics. A photonic power converter, or phototransducer, can absorb several watts of infrared laser power transmitted through a multimode fiber and convert this to electrical power for remote use. To convert this power into a useful voltage, we have designed, simulated, and fabricated a photovoltaic phototransducer that generates >5 V using a monolithic, lattice-matched, vertically-stacked, single-cell device that eliminates complex fabrication and assembly steps. Experimental measurements have demonstrated a conversion efficiency of up to 60.1% under illumination of ~11 W/cm2 at a wavelength of 835 nm, while simulations indicate that efficiencies reaching 70% should be realistically achievable using this novel design.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123900903","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}
Optimization of non-planar antireflective coating and back- (or front-) surface texturing are widely studied to further reduce the reflection losses and increase the sunlight absorption path in solar cells. Back reflectors have been developed from perfect mirror to textured mirror in order to further increase light path, which can significantly improve the efficiency and allow for much thinner devices. A Lambertian surface, which has the most random texture, can theoretically raise the light path to 4n2 times that of a smooth surface. It’s a challenge however to fabricate ideal Lambertian texture, especially in a fast and low cost way. In this work we have developed a method to overcome this challenge that combines the use of laser interference lithography (LIL) and selective wet etching. The approach allows for a rapid wafer scale texture processing with sub-wavelength (nano)- scale control of the pattern and the pitch. The technique appears as being particularly attractive for the development of ultra-thin III-V devices, or in overcoming the weak sub-bandgap absorption in devices incorporating quantum dots or quantum wells. Preliminary results on the application of the technique for the development of back reflector for 1-1.3 eV (MQW bearing) GaAs solar cells are presented.
为了进一步降低太阳能电池的反射损失，增加太阳能电池的吸收路径，人们对非平面减反射涂层的优化和背面(或正面)表面纹理进行了广泛的研究。为了进一步增加光路，后反射镜已经从完美镜发展到纹理镜，这可以显着提高效率并允许更薄的设备。一个具有最随机纹理的朗伯曲面，理论上可以将光路提高到光滑表面的4n2倍。然而，制造理想的兰伯氏纹理是一个挑战，特别是在快速和低成本的方式。在这项工作中，我们已经开发了一种方法来克服这一挑战，结合使用激光干涉光刻(LIL)和选择性湿法蚀刻。该方法允许快速晶圆尺度纹理处理与亚波长(纳米)尺度控制的图案和间距。该技术对于超薄III-V器件的开发，或在克服包含量子点或量子阱的器件的弱亚带隙吸收方面显得特别有吸引力。介绍了该技术在1-1.3 eV (MQW轴承)GaAs太阳能电池背反射器研制中的初步应用结果。
{"title":"Design and development of back reflectors for improved light coupling and absorption enhancement in thin MQW solar cells","authors":"Wei Wang, A. Freundlich","doi":"10.1117/12.2078669","DOIUrl":"https://doi.org/10.1117/12.2078669","url":null,"abstract":"Optimization of non-planar antireflective coating and back- (or front-) surface texturing are widely studied to further reduce the reflection losses and increase the sunlight absorption path in solar cells. Back reflectors have been developed from perfect mirror to textured mirror in order to further increase light path, which can significantly improve the efficiency and allow for much thinner devices. A Lambertian surface, which has the most random texture, can theoretically raise the light path to 4n2 times that of a smooth surface. It’s a challenge however to fabricate ideal Lambertian texture, especially in a fast and low cost way. In this work we have developed a method to overcome this challenge that combines the use of laser interference lithography (LIL) and selective wet etching. The approach allows for a rapid wafer scale texture processing with sub-wavelength (nano)- scale control of the pattern and the pitch. The technique appears as being particularly attractive for the development of ultra-thin III-V devices, or in overcoming the weak sub-bandgap absorption in devices incorporating quantum dots or quantum wells. Preliminary results on the application of the technique for the development of back reflector for 1-1.3 eV (MQW bearing) GaAs solar cells are presented.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125555132","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}
Equivalent circuit models of a transistor laser are used to investigate the suitability of this relatively new device for analog microwave photonic links. The three-terminal nature of the device enables transistor-based circuit design techniques to be applied to optoelectronic transmitter design. To this end, we investigate the application of balanced microwave amplifier topologies in order to enable low-noise links to be realized with reduced intermodulation distortion and improved RF impedance matching compared to conventional microwave photonic links.
{"title":"Circuit-level simulation of transistor lasers and its application to modelling of microwave photonic links","authors":"S. Iezekiel, A. Christou","doi":"10.1117/12.2079306","DOIUrl":"https://doi.org/10.1117/12.2079306","url":null,"abstract":"Equivalent circuit models of a transistor laser are used to investigate the suitability of this relatively new device for analog microwave photonic links. The three-terminal nature of the device enables transistor-based circuit design techniques to be applied to optoelectronic transmitter design. To this end, we investigate the application of balanced microwave amplifier topologies in order to enable low-noise links to be realized with reduced intermodulation distortion and improved RF impedance matching compared to conventional microwave photonic links.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126430489","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. Asahi, H. Teranishi, N. Kasamatsu, T. Kada, T. Kaizu, T. Kita
We have studied detailed carrier generation process in the two-step photon absorption and influence of thermal carrier escape in quantum-dot intermediate-band solar cells (QD-IBSC). The photocurrent created by the two-step photon absorption shows saturation as the inter-band excitation intensity becomes strong, and the inter-band excitation intensity showing the saturation behavior strongly depends on the inter-subband excitation intensity. To interpret this phenomenon, we carried out a theoretical simulation based on carrier dynamics considering carrier generation, energy relaxation and thermal carrier escape. The results indicate that the photocurrent saturation is caused by filling the intermediate states. The shift of the saturation point depending on the inter-subband excitation intensity is caused by the shift of the quasi-Fermi level for the intermediate states.
{"title":"Suppression of thermal carrier escape and enhanced two-step photon absorption in quantum-dot intermediate-band solar cells with a high-potential barrier","authors":"S. Asahi, H. Teranishi, N. Kasamatsu, T. Kada, T. Kaizu, T. Kita","doi":"10.1117/12.2081302","DOIUrl":"https://doi.org/10.1117/12.2081302","url":null,"abstract":"We have studied detailed carrier generation process in the two-step photon absorption and influence of thermal carrier escape in quantum-dot intermediate-band solar cells (QD-IBSC). The photocurrent created by the two-step photon absorption shows saturation as the inter-band excitation intensity becomes strong, and the inter-band excitation intensity showing the saturation behavior strongly depends on the inter-subband excitation intensity. To interpret this phenomenon, we carried out a theoretical simulation based on carrier dynamics considering carrier generation, energy relaxation and thermal carrier escape. The results indicate that the photocurrent saturation is caused by filling the intermediate states. The shift of the saturation point depending on the inter-subband excitation intensity is caused by the shift of the quasi-Fermi level for the intermediate states.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124791499","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}
Solar concentration is using optics in order to minimize the amount of expensive photovoltaic cell material needed. For concentration factors higher than approximately 4, tracking the sun’s position is needed to keep the focal spot on the solar cell. Based on recent developments using a waveguide slab to concentrate sunlight we propose and demonstrate a light responsive, self-tracking solar concentrator. Using a phase change material acting at the focal spot, it is possible to maintain efficient coupling into the waveguide, up to an angular range of +/- 20 degrees. The system uses the unused infrared part of the solar spectrum as energy for the phase change actuator to achieve its high acceptance angle. With a spectrally matched custom silicon solar cell attached to the waveguide slab, in which light is coupled, the visible part of the solar spectrum can be efficiently converted to electricity. A proof-of-concept single lens device was demonstrated in our previous work. Here we extend the principle to a 3x3 lens array demonstration device. The current demonstration device features an acceptance angle of +/- 16 degrees and an effective concentration factor of up to 20x.
{"title":"Demonstration of a 5x5 cm2 self-tracking solar concentrator","authors":"V. Zagolla, E. Tremblay, C. Moser","doi":"10.1117/12.2078775","DOIUrl":"https://doi.org/10.1117/12.2078775","url":null,"abstract":"Solar concentration is using optics in order to minimize the amount of expensive photovoltaic cell material needed. For concentration factors higher than approximately 4, tracking the sun’s position is needed to keep the focal spot on the solar cell. Based on recent developments using a waveguide slab to concentrate sunlight we propose and demonstrate a light responsive, self-tracking solar concentrator. Using a phase change material acting at the focal spot, it is possible to maintain efficient coupling into the waveguide, up to an angular range of +/- 20 degrees. The system uses the unused infrared part of the solar spectrum as energy for the phase change actuator to achieve its high acceptance angle. With a spectrally matched custom silicon solar cell attached to the waveguide slab, in which light is coupled, the visible part of the solar spectrum can be efficiently converted to electricity. A proof-of-concept single lens device was demonstrated in our previous work. Here we extend the principle to a 3x3 lens array demonstration device. The current demonstration device features an acceptance angle of +/- 16 degrees and an effective concentration factor of up to 20x.","PeriodicalId":432115,"journal":{"name":"Photonics West - Optoelectronic Materials and Devices","volume":"9358 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130777029","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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