Infrared detectors - Special interest bibliography with abstracts

Bibliography and abstracts of literature related to infrared detectors used in geoscience researc

All-Fiber Centralized Architecture for Parallel Terahertz Censors

(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.The use of optical fiber for signal distribution and remote operation of a set of parallel inspection units based on THz time-domain spectroscopy is presented and analyzed. A centralized approach with optical source-sharing simplifies the implementation and cost of nondestructive inspection platforms, where several sensing units have to work in the same facility, such as factories and security controls. The cost of such a distribution system is evaluated, its feasibility experimentally demonstrated, and key features relevant to the system performance are discussed.This work was supported in part by the Spanish Ministry of Economy and Competitiveness through Project TEC2012-35797 and FPU Grant 12/02847.Bockelt, AS.; Palací López, J.; Vidal Rodriguez, B. (2015). All-Fiber Centralized Architecture for Parallel Terahertz Censors. IEEE Transactions on Terahertz Science & Technology. 5(1):137-144. https://doi.org/10.1109/TTHZ.2014.2373313S1371445

Terahertz (THz) Generator and Detection

In the whole research process of electromagnetic wave, the research of terahertz wave belongs to a blank for a long time, which is the least known and least developed by far. But now, people are trying to make up the blank and develop terahertz better and better. The charm of terahertz wave originates from its multiple attributes, including electromagnetic field attribute,photon attribute and thermal attribute, which also attracts the attention of researchers in different fields and different countries, and also terahertz technology have been rated as one of the top ten technologies to change the future world by the United States. The multiple attributes of terahertz make it have broad application prospects in military and civil fields, such as medical imaging,astronomical observation, 6G communication, environmental monitoring and material analysis. It is no exaggeration to say that mastering terahertz technology means mastering the future. However, it is because of the multiple attributes of terahertz that the terahertz wave is difficult to be mastered. Although terahertz has been applied in some fields,controlling terahertz (such as generation and detection) is still an important issue. Nowadays, a variety of terahertz generation and detection technologies have been developed and continuously improved. In this paper, the main terahertz generation and detection technologies (including already practical and developing) are reviewed in terms of scientific and engineering principles,in order to provide a systematic and up-to-date reference for researchers in terahertz field

Ultrafast Laser-Based Spectroscopy and Sensing: Applications in LIBS, CARS, and THz Spectroscopy

Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), coherent Raman spectroscopy, and terahertz (THz) spectroscopy. Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications

New Materials for Photoconductive Terahertz Antennas

In this thesis, we have first introduced a new setup for the reliable characterization of photoconductive antennas to be used in THz time-domain spectroscopy. Using this setup one can benchmark THz antennas with high precision. The intra-day reproducibility error is in the range of 1.9% while the reproducibility within 9 days is 2.6%. This includes not only absolute power stability but also reproducibility of the spectra by eliminating alignment errors that alter the transfer function from sender to receiver. In order to demonstrate the full capabilities of the system, we investigated samples from five LT-GaAs wafers, grown at temperatures between 200°C and 300°C, in a systematic manner. The obtained results are in good agreement with previous studies on the same material system. These results prove that the system allows for quality control of photoconductors with minimum comparison error. We have also investigated the correlation between THz emission strength and the surface properties of the LT-GaAs photoconductive antenna. The THz characteristics were measured with the highly stable setup mentioned above, which allowed exciting a 10-mm long CPS antenna along the gap without changing the alignment of the optical or THz beam path. The surface properties were quantified regarding roughness and grain size. The roughness was extracted from AFM measurements and the grain size from SEM measurements. A comparison of the THz emission strength in form of the peak-to peak THz amplitude and the surface properties showed a strong nonlinear correlation: a smaller grain size and a smoother surface increase the THz amplitude. These results can be used in the future to optimize the performance of THz antennas. Additionally, we have successfully prepared TiN-nanoparticles using ultrasonic and pulsed laser ablation techniques. The two techniques provide with a different distribution of Zeta-potential and particle size. Within our experimental conditions, pulsed laser ablation can give lower particle size and greater Zeta-potential. TiN-nanoparticles prepared by these techniques have a high and flat absorbance in the spectral range 600 -1000 nm. LT-GaAs covered with dispersed TiNnanoparticles has enhanced THz emission when the average particle size is about 62 nm. More investigations are needed on how to develop preparation and deposition techniques in such a way that control the shape, size, distance between the particles. This may lead to a further improvement of the THz power emitted from such devices. Finally, we demonstrated that coating with MnFe2O4 nanoparticles could be used to improve the performance of photoconductive antennas in the THz region. Our experiments demonstrate that coatings with MnFe2O4−particles provided a new approach to increase the photocurrent density on silicon under CW illumination. In order to understand the effect ofMnFe2O4 nanoparticles on photo-excited silicon, a semiconductor model was proposed to describe this phenomenon. We used this model to calculate the transmission amplitudes of THz pulses transmitted through bare silicon substrates and silicon substrates covered by MnFe2O4 nanoparticles under laser irradiation with different powers. Because the effect of MnFe2O4 nanoparticles on silicon significantly provides an enhanced attenuation of terahertz wave, silicon substrates covered by MnFe2O4 nanoparticles have the potential to be used as an optical modulator in the THz region. This may lead to a costefficient component for THz systems operating in transmission mode. Furthermore, MnFe2O4 nanoparticles could be used for the implementation of novel optical devices

Dielectric-based Components and Methods for Terahertz Sensing

[ES] En el presente trabajo, se investigan algunos aspectos de la interacción de los materiales dieléctricos con ondas de THz. La banda de THz, que incluye las frecuencias de 100 GHz a 30 THz, ha despertado un gran interés sobre todo por su baja energía y su buena capacidad de penetración en materiales de uso diario como tejidos y plásticos. Las características peculiares de estas ondas permiten su aplicación en diversos campos tecnológicos, especialmente como herramientas científicas y para la inspección de control de calidad. Para avanzar en la aplicación práctica de la radiación THz, la presente tesis doctoral investigó varios caminos. En primer lugar, se trataron métodos alternativos de bajo coste para la fabricación de componentes pasivos de THz, centrándose en los polarizadores. El interés en el control de la polarización nace de la demanda de un mayor control sobre las características físicas de los haces de THz. Asimismo, se han investigado los polarizadores wire grid flexible basados en el efecto de absorción dicroica. Se han fabricado polarizadores con grafito y GaIn24,5 depositados en materiales ordinarios utilizados como sustratos (papel y polímeros como PVA y PVC). Mediante la colaboración con el grupo de investigación chino dirigido por el profesor Liu de la Universidad de Tsinghua, se investigaron procesos de fabricación alternativos. Todos los componentes se simularon mediante un simulador comercial basado en la técnica de integrales finitas FIT (CST Microwave Studio). En segundo lugar, se investigó el potencial de la técnica de fixed delay para la detección rápida de elementos homogéneos y transparentes con posible aplicación en la inspección de calidad industrial. En este esquema, la variación de corriente del haz de THz en un punto específico está relacionada con la variación de sus parámetros ópticos, por lo que se demostró la capacidad de detectar defectos, así como de estimar sus volúmenes bajo ciertas condiciones. Por último, un enfoque diferente para el beam profile basado en un slit dieléctrico fue evaluada como alternativa a los métodos convencionales utilizados en la región de THz y la óptica. Todas las mediciones, tanto la espectroscopia como el control de la polarización, se hicieron por medio de un sistema basado en fibra TDS-THz, con antenas fotoconductoras (PCA), tanto para la generación como para la detección de THz.[EN] In the present work, some aspects of the role of dielectric materials when interacting with THz waves were investigated. The THz bandgap, which covers the frequencies from 100 GHz to 30 THz, has aroused great interest mainly due to its low energy and its good penetration capacity in some materials of daily use such as fabrics and plastics. The peculiar features of terahertz waves enable their application in various technological fields, especially as scientific tools and for quality control inspection. To advance in the practical application of THz radiation, the present doctoral thesis researched several paths. Firstly, alternative low-cost methods for manufacturing THz passive components, in particular, THz polarizers was treated. The interest in polarization control is derived from the demand for greater control over the physical characteristics of THz beams. Flexible wire grid polarizers based on the dichroic absorption effect have been investigated. The polarizers have been manufactured using graphite and GaIn24.5 deployed on ordinary materials used as substrates (paper and polymers such as PVA and PVC). Through a collaboration undertaken with the Chinese research group led by Professor Liu at Tsinghua University, alternative manufacturing processes were researched. All components were simulated through a commercial simulator based on the FIT finite integrals technique (CST Microwave Studio). Secondly, the potential of the fixed delay technique was investigated for rapid sensing of homogeneous and transparent items with possible application to industrial quality inspection. In this scheme, the current variation of the THz beam at a specific point is related to the variation of its optical parameters, thus it was demonstrated the ability of the method in detecting voids as well as in roughly estimating their volumes under certain conditions. Finally, a different approach for beam profiling based on a dielectric slit aperture was evaluated, as an alternative to the conventional methods used in the THz region and optics All measurements, both spectroscopy and polarization control, were made by means of a TDS-THz fibre-based system, with photoconductive antennas (PCA), both for the generation and detection of THz.[CA] En el present treball, s'investiguen alguns aspectes del paper dels materials dielèctrics quan interactuen amb ones de THz. El bandgap de THz, que cobreix les freqüències de 100 GHz a 30 THz, ha despertat un gran interés principalment a causa de la seua baixa energia i la seua bona capacitat de penetració en alguns materials d'ús diari com els teixits i els plàstics. Les característiques peculiars de les ones de terahertz permeten la seua aplicació en diversos camps tecnològics, especialment com a eines científiques i per a la inspecció de control de qualitat. Per a avançar en l'aplicació pràctica de la radiació THz, la present tesi doctoral investiga diversos camins. En primer lloc, es s'han tractat mètodes alternatius de baix cost per a la fabricació de components passius de THz, centrant-se principalment en polaritzadors de THz. L'interés en el control de la polarització es deriva de la demanda d'un major control sobre les característiques físiques dels feixos de THz. Així mateix, s'han investigat els polaritzadors amb reixes de filferro flexible basats en l'efecte d'absorció dicroica. Els polaritzadors s'han fabricat utilitzant grafit i GaIn24,5 desplegats en materials ordinaris utilitzats com a substrats (paper i polímers com el PVA i el PVC). Mitjançant una col·laboració empresa amb el grup d'investigació xinés dirigit pel professor Liu de la Universitat de Tsinghua, es van investigar processos de fabricació alternatius. Tots els components es van simular mitjançant un simulador comercial basat en la tècnica d'integrals finites FIT (CST Microwave Studio). En segon lloc, s'ha investigat el potencial de la tècnica de retard fix per a la detecció ràpida d'elements homogenis i transparents amb possible aplicació a la inspecció de qualitat industrial. En aquest esquema, la variació actual del feix de THz en un punt específic està relacionada amb la variació dels seus paràmetres òptics, per la qual cosa es va demostrar la capacitat del mètode per a detectar els buits així com en l'estimació aproximada dels seus volums sota certes condicions. Finalment, un enfocament diferent per al perfil de feix basat en una obertura d'escletxa dielèctrica ha sigut avaluada, com a alternativa als mètodes convencionals utilitzats a la regió de THz i l'òptica.Tots els mesuraments, tant l'espectroscòpia com el control de la polarització, es van fer per mitjà d'un sistema basat en fibra TDS-THz, amb antenes fotoconductores (PCA), tant per a la generació com per a la detecció de THz.Colleoni, MPM. (2020). Dielectric-based Components and Methods for Terahertz Sensing [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/149569TESI

Possibility of electric arc detection in power transformers by directly embedded photoconductive elements in the transformer tank

In this article, an application of potential light-sensitive semiconductive elements, including photoresistors and photodiodes as electric arc detection sensors in the transformer tank, is comprehensively investigated. Conventionally, a Buchholz relay (BHR) is implemented for arc fault detection in power transformers. Unfortunately, in some cases, the tripping of the transformer is not fast enough in order to prevent a tank rupture and catastrophic collateral damages. Therefore, an application of light-sensitive elements as optical sensors is investigated for detecting an arc inside a transformer tank faster under various operational conditions. This contribution focuses on the performance of sensors, which are inserted in the transformer tank. Apart from consideration of different factors such as stochastic nature of light in the arc, thermal cycling, the distance effect on the light sensitivity and possibility of light reflection by the tank, challenges and limitations of arc sensing with light sensors in the mentioned approach are comprehensively discussed. The deficiencies and limitations of the arc sensors are revealed through the experimental investigations conducted

Possibility of electric arc detection in power transformers by directly embedded photoconductive elements in the transformer tank

In this article, an application of potential light-sensitive semiconductive elements, including photoresistors and photodiodes as electric arc detection sensors in the transformer tank, is comprehensively investigated. Conventionally, a Buchholz relay (BHR) is implemented for arc fault detection in power transformers. Unfortunately, in some cases, the tripping of the transformer is not fast enough in order to prevent a tank rupture and catastrophic collateral damages. Therefore, an application of light-sensitive elements as optical sensors is investigated for detecting an arc inside a transformer tank faster under various operational conditions. This contribution focuses on the performance of sensors, which are inserted in the transformer tank. Apart from consideration of different factors such as stochastic nature of light in the arc, thermal cycling, the distance effect on the light sensitivity and possibility of light reflection by the tank, challenges and limitations of arc sensing with light sensors in the mentioned approach are comprehensively discussed. The deficiencies and limitations of the arc sensors are revealed through the experimental investigations conducted

Fiber-based Terahertz Time-Domain Spectroscopy Systems Operated in the Telecom Band

The aim of the doctoral thesis is the study of Terahertz time domain spectrometers relying on telecommunication fiber technology. Optical fiber offers low losses, high stability and compactness, features that ease the deployment of this kind of sensing instruments in industrial scenarios. The development of terahertz signal sources working at telecom wavelengths has enabled the employment of mature, telecom-related photonic components that allowed a transition within THz research from being mainly object of scientific interest to an application-oriented technology. In this thesis, fiber terahertz systems utilizing ultrafast photoconductors with integrated antenna structures have been investigated at different levels, including the control of the photoconductor structure, as well as at instrument and system levels. The carrier transport in InGaAs-InAlAs multilayer hetero-structures, present in the employed photoconductive antennas, has been investigated under the additional injection of a continuous optical wave. By varying the amplitude level of the respective optical signal injected into either the emitter or the receiver, it has been shown that the amplitude of the detected photocurrent could be controlled without affecting its bandwidth. Unlike increasing the optical power of the pulsed signal, raising the continuous optical power results in a reduction of the measured photocurrent. This lowering of the conductivity is related to changes in the instantaneous carrier momentum relaxation time in the photoactive material, rather than to variations of the free carrier density level. This behavior affects systems including continuous-wave optical components, as, for instance, optical amplifiers. The effect has been further exploited to modulate the operation conditions of photoconductive antennas, enabling an all-optical control of the THz amplitude. This represents a method to implement a signal modulation, necessary, for instance, for lock-in signal detection. Different industrial applications and THz imaging systems require fast data acquisition. Slow, stepwise working mechanical optical delay lines are about to be replaced by faster schemes. A fast THz-time-domain spectroscopy system using a coil-based rapid mechanic delay line has been set up and analyzed. A convenience of usage of optical fibers is the simplicity of signal multiplication and distribution. It can be exploited to allow centralized operation of a set of parallel terahertz sensing units. A centralized architecture with optical source sharing simplifies the implementation as well as the cost of nondestructive inspection platforms, where several sensing units would have to work in the same facility, for example at quality control in factories or security checkpoints. The cost of such a distribution system is evaluated, its feasibility experimentally demonstrated, and key features relevant to the system performance are discussed. The present document is formally structured in a brief introduction, Chapter 2, which review common terahertz technology as a whole, with the focus on optoelectronic schemes and respective technology in the telecom band. Chapter 3 includes work carried out dealing with the carrier dynamics under continuous optical wave irradiation of the photoconductive antenna modules and the application of the effect as modulation method. Chapter 4 deals with the implementation of the fast delay in the system and Chapter 5 describes and analyses architecture for parallel, remotely controlled sensing. Finally, Chapter 6 provides conclusion and future work perspectives.El objetivo de la presente Tesis Doctoral es el estudio de espectroscopios temporales de Terahercios basados en tecnología de fibra óptica para telecomunicaciones. La fibra óptica ofrece bajas pérdidas de propagación, alta estabilidad y la capacidad de implementar sistemas robustos y compactos, características que facilitan el despliegue de este tipo de instrumentos de sensado en escenarios industriales. El desarrollo de fuentes de THz que operan en la banda infrarroja empleada en telecomunicaciones permite el uso de componentes maduros de la industria de las comunicaciones ópticas, lo que a su vez se ha traducido en una transición desde el uso de la banda de THz básicamente para intereses científicos al desarrollo de sistemas para aplicaciones industriales. En la presente tesis se investigan sistemas de THz basados en antenas fotoconductivas y fibra óptica a distintos niveles: control de la estructura fotoconductiva, instrumento y sistema. El transporte de portadores en heteroestructuras multicapa InGaAs-InAlAs, empleadas actualmente en antenas fotoconductivas, se ha investigado bajo la inyección de una onda óptica continua. Se ha observado que variando el nivel de amplitud de esta onda continua tanto en el emisor como en el receptor es posible controlar la fotocorriente detectada sin afectar a su ancho de banda. A diferencia de un incremento en la potencia óptica de la señal pulsada, elevar el nivel de continua resulta en una reducción de la fotocorriente medida. Esta reducción de la conductividad se relaciona con cambios en el tiempo de relajación del momento de los portadores en el material fotoactivo en lugar de variaciones de la densidad de portadores libres. Este comportamiento puede tener un efecto en sistemas que introduzcan componentes ópticos continuos como por ejemplo sistemas de sensado que empleen amplificadores ópticos. Este efecto puede ser usado para modular las condiciones de operación de las antenas fotoconductivas permitiendo el control todo-óptico del sistema. Este método permite modular la señal, lo que resulta necesario por ejemplo para realizar detección lock-in. Tanto diferentes aplicaciones industriales como los sistemas de imagen en THz requieren sistemas rápidos de captura. Para ello es necesario sustituir las líneas de retardo ópticas tradicionales basadas en motores paso-a-paso por otros sistemas de mayor velocidad. Se ha implementado y caracterizado un sistema THz-TDS usando una línea de retardo rápida basada en bobinas de voz. Una característica fundamental de la fibra óptica es su extraordinaria simplicidad para realizar la distribución de señales ópticas. Esta característica puede ser explotada para permitir la operación centralizada de un conjunto paralelo de sensores de THz. Una arquitectura centralizada en la que la fuente óptica se comparte entre muchos sensores simplifica la implementación y reduce el coste de sistemas de inspección no destructiva que requieran de múltiples sensores en paralelo, como, por ejemplo, en control de calidad industrial o en controles de seguridad. Se ha evaluado el coste de estos sistemas distribuidos, se ha validado experimentalmente su viabilidad y se han identificado y estudiado sus prestaciones. El documento de la tesis doctoral se estructura formalmente en una breve introducción, el capítulo 2, en el que se revisa la tecnología de THz en su conjunto, los esquemas optoelectrónicos y el uso de tecnologías ópticas basadas en la banda de las telecomunicaciones. El capítulo 3 incluye el estudio realizado sobre la dinámica de los portadores bajo la irradiación dela antena fotoconductiva con una onda óptica continua y su uso como técnica de modulación. El capítulo 4 trata con la implementación de un sistema THz-TDS rápido mientras que el capítulo 5 describe y analiza una arquitectura de sensado paralela para reducir costes. Finalmente el capítulo 6 recoge las conclusiones y futuras líneas de actuación.L'objectiu de la present Tesi Doctoral és l'estudi d'espectroscopis temporals de terahertzs basats en tecnologia de fibra òptica per a telecomunicacions. La fibra òptica ofereix baixes pèrdues de propagació, alta estabilitat i la capacitat d'implementar sistemes robustos i compactes, característiques que faciliten el desplegament d'aquest tipus d'instruments de sensat en escenaris industrials. El desenvolupament de fonts de THz que operen a la banda infraroja emprada en telecomunicacions permet l'ús de components madurs de la indústria de les comunicacions òptiques, el que al seu torn s'ha traduït en una transició des de l'ús de la banda de THz bàsicament per interessos científics al desenvolupament de sistemes per a aplicacions industrials. En la present tesi s'investiguen sistemes de THz basats en antenes fotoconductivas i fibra òptica a diferents nivells: control de l'estructura fotoconductiva, instrument i sistema. El transport de portadors en heteroestructures multicapa InGaAs-InAlAs, emprades actualment en antenes fotoconductivas, s'ha investigat sota la injecció d'una ona òptica contínua. S'ha observat que variant el nivell d'amplitud d'aquesta ona contínua tant en l'emissor com en el receptor és possible controlar la fotocorriente detectada sense afectar el seu ample de banda. A diferència d'un increment en la potència òptica del senyal polsada, elevar el nivell de contínua resulta en una reducció de la fotocorrent mesurada. Aquesta reducció de la conductivitat es relaciona amb canvis en el temps de relaxació del moment dels portadors en el material fotoactiu en lloc de variacions de la densitat de portadors lliures. Aquest comportament pot tenir un efecte en sistemes que introdueixin components òptics continus com ara sistemes de sensat que utilitzen amplificadors òptics. Aquest efecte pot ser usat per modular les condicions d'operació de les antenes fotoconductivas permetent el control tot-òptic del sistema. Aquest mètode permet modular el senyal, el que resulta necessari per exemple per realitzar detecció lock-in. Tant diferents aplicacions industrials com els sistemes d'imatge en THz requereixen sistemes ràpids de captura. Per a això és necessari substituir les línies de retard òptiques tradicionals basades en motors pas-a-pas per altres sistemes de major velocitat. S'ha implementat i caracteritzat un sistema THz-TDS usant una línia de retard ràpida basada en bobines de veu. Una característica fonamental de la fibra òptica és la seua extraordinària simplicitat per realitzar la distribució de senyals òptiques. Aquesta característica pot ser explotada per a permetre l'operació centralitzada d'un conjunt paral·lel de sensors de THz. Una arquitectura centralitzada en la qual la font òptica es comparteix entre molts sensors simplifica la implementació i redueix el cost de sistemes d'inspecció no destructiva que requereixin de múltiples sensors en paral·lel, com, per exemple, en control de qualitat industrial o en controls de seguretat . S'ha avaluat el cost d'aquests sistemes distribuïts, s'ha validat experimentalment la seua viabilitat i s'han identificat i estudiat les seues prestacions. El document de la tesi doctoral s'estructura formalment en una breu introducció, capítol 2, en el qual es revisa la tecnologia de THz en el seu conjunt, els esquemes optoelectrònics i l'ús de tecnologies òptiques basades en la banda de les telecomunicacions. El capítol 4 inclou l'estudi realitzat sobre la dinàmica dels portadors sota la irradiació de la antena fotoconductiva amb una ona òptica contínua i el seu ús com a tècnica de modulació. El capítol 5 tracta la implementació d'un sistema THz-TDS ràpid mentre que el capítol 6 descriu i analitza una arquitectura de sensat paral·lela per reduir costos. Finalment, el capítol 7 recull les conclusions i futures línies d'actuació.Bockelt, AS. (2017). Fiber-based Terahertz Time-Domain Spectroscopy Systems Operated in the Telecom Band [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86148TESI