Terahertz Metasurface Quantum Cascade Laser

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Terahertz Metasurface Quantum Cascade Laser

Author : Luyao Xu
Publisher :
ISBN 13 :
Total Pages : 231 pages
Book Rating : 4.:/5 (17 download)

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Book Synopsis Terahertz Metasurface Quantum Cascade Laser by : Luyao Xu

Download or read book Terahertz Metasurface Quantum Cascade Laser written by Luyao Xu and published by . This book was released on 2017 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz (THz) frequency range (0.3-10 THz, 30-1000 m) is the least explored region in the electromagnetic spectrum, mostly due to a relative lack of convenient, ecient and economical THz sources. However, THz frequency range has the potential for various applications including but not limited to: astrophysics and space science, biological and medical imaging and spectroscopy, and non-destructive evaluation. This Ph.D. research builds upon the growing request for compact and ecient THz sources with both high power and high-quality beam pattern. Since its invention in 2001, the THz quantum cascade laser (QCL) has emerged as a compact semiconductor THz source capable of delivering milliwatt-level power or higher at various frequencies from 1.2 to 5.6 THz. In the best devices, the operating temperature has reached 200 K in pulsed mode and 129 K in continuous wave (cw) mode. However, the state-of-the-art THz QCLs almost exclusively use sub-wavelength metallic and/or plasmonic waveguides, which leads to highly divergent beams. Achieving high power in combination with an excellent beam pattern for THz QCLs remains a longstanding challenge. Vertical external-cavity-surface-emitting-laser (VECSEL) has been demonstrated as a very successful approach to achieve high power and good beam pattern for semiconductor lasers in the visible and near-infrared. A typical VECSEL configuration consists of a quantum well (or dot) semiconductor active medium grown monolithically on a Bragg reflector and an output coupler to form a cavity. Output power is scalable with the active medium area and the cavity can be readily engineered to support only the fundamental Gaussian mode. However, the VECSEL concept has been impossible to implement for QCLs owing to "intersubband selection rule": the intersubband transitions in cascaded quantum wells -- the gain medium of QCLs -- are only allowed to interact with and provide gain to the electric field polarized perpendicular to the wells. This is incompatible with the natural polarization for surface incident waves in a VECSEL cavity. This thesis reports the development of a new class of THz QCL to achieve high-power output with an excellent beam pattern -- THz metasurface quantum-cascade VECSEL (QC-VECSEL). The enabling component of QC-VECSEL is an active metasurface reflector composed of a sub-wavelength array of metallic microcavity antennas; each antenna efficiently couples in THz radiation, amplifies it and re-radiates into the free space. Lasing is possible when an active metasurface is paired with an output coupler form a low-loss cavity. This new architecture gives the ability to scale up output power with the metasurface area while maintaining a good beam pattern shaped by the external cavity. Moreover, this approach can leverage ongoing advances in novel metasurfaces to realize versatile functionality for QC-VECSELs, such as engineerable polarization/wavefront, spectral tunability. The demonstration of THz QC-VECSEL marks the two "firsts": the first VECSEL in the THz frequency range and the first laser built around an active metasurface. The concept of metasurface QC-VECSEL is potentially applicable beyond the terahertz and can be applied to shorter wavelengths. This thesis describes the theory, design, fabrication, testing and analysis of THz meta- surface QC-VECSELs. Electromagnetic simulations for various active metasurfaces are presented, including the dependence of reflective gain on the antenna size, periodicity and shape, the suppression of metasurface self-lasing. A laser model is laid out for QC-VECSELs to relate the performance metrics with the metasurface and cavity design parameters, providing a tool for metasurface optimization. Numerical methods are also developed to compute the mode profile and diffraction loss of various external cavities. Experimental results and analysis are presented on a wide variety of THz metasurface QC-VECSELs varying in metasurface and cavity designs, which have yielded considerable high-performance results, including high power combined with excellent beam pattern, record-high cw power at >77 K, polarization and wavefront engineering. Finally, prospects are considered for QC-VECSELs with higher power, better temperature performance and capability to generate complex beams and versatile functionality.

Vertical External Cavity Surface Emitting Lasers

Author : Michael Jetter
Publisher : John Wiley & Sons
ISBN 13 : 3527807977
Total Pages : 584 pages
Book Rating : 4.5/5 (278 download)

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Book Synopsis Vertical External Cavity Surface Emitting Lasers by : Michael Jetter

Download or read book Vertical External Cavity Surface Emitting Lasers written by Michael Jetter and published by John Wiley & Sons. This book was released on 2021-09-16 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vertical External Cavity Surface Emitting Lasers Provides comprehensive coverage of the advancement of vertical-external-cavity surface-emitting lasers Vertical-external-cavity surface-emitting lasers (VECSELs) emit coherent light from the infrared to the visible spectral range with high power output. Recent years have seen new device developments – such as the mode-locked integrated (MIXSEL) and the membrane external-cavity surface emitting laser (MECSEL) – expand the application of VECSELs to include laser cooling, spectroscopy, telecommunications, biophotonics, and laser-based displays and projectors. In Vertical External Cavity Surface Emitting Lasers: VECSEL Technology and Applications, leading international research groups provide a comprehensive, fully up-to-date account of all fundamental and technological aspects of vertical external cavity surface emitting lasers. This unique book reviews the physics and technology of optically-pumped disk lasers and discusses the latest developments of VECSEL devices in different wavelength ranges. Topics include OP-VECSEL physics, continuous wave (CW) lasers, frequency doubling, carrier dynamics in SESAMs, and characterization of nonlinear lensing in VECSEL gain samples. This authoritative volume: Summarizes new concepts of DBR-free and MECSEL lasers for the first time Covers the mode-locking concept and its application Provides an overview of the emerging concept of self-mode locking Describes the development of next-generation OPS laser products Vertical External Cavity Surface Emitting Lasers: VECSEL Technology and Applications is an invaluable resource for laser specialists, semiconductor physicists, optical industry professionals, spectroscopists, telecommunications engineers and industrial physicists.

Mid-Infrared and Terahertz Quantum Cascade Lasers

Author : Dan Botez
Publisher : Cambridge University Press
ISBN 13 : 1108570607
Total Pages : 552 pages
Book Rating : 4.1/5 (85 download)

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Book Synopsis Mid-Infrared and Terahertz Quantum Cascade Lasers by : Dan Botez

Download or read book Mid-Infrared and Terahertz Quantum Cascade Lasers written by Dan Botez and published by Cambridge University Press. This book was released on 2023-09-14 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how the rapidly expanding area of mid-infrared and terahertz photonics has been revolutionized in this comprehensive overview. State-of-the-art practical applications are supported by real-life examples and expert guidance. Also featuring fundamental theory enabling you to improve performance of both existing and future devices.

Theory and Design of Terahertz Quantum-Cascade Littrow Metasurface External Cavity Lasers

Author : Parastou Mortazavian
Publisher :
ISBN 13 :
Total Pages : 105 pages
Book Rating : 4.:/5 (116 download)

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Book Synopsis Theory and Design of Terahertz Quantum-Cascade Littrow Metasurface External Cavity Lasers by : Parastou Mortazavian

Download or read book Theory and Design of Terahertz Quantum-Cascade Littrow Metasurface External Cavity Lasers written by Parastou Mortazavian and published by . This book was released on 2020 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum-cascade vertical-external-cavity surface-emitting-laser (QC-VECSEL) is a recently developed compact and coherent source of THz radiation which has demonstrated excellent beam quality and scalable high-power. The key component of the QC-VECSEL is an amplifying reflectarray metasurface made up of an array of sub-wavelength metal-metal waveguides loaded with quantum-cascade (GaAs/AlGaAs) laser gain material. To further the usefulness of this technology for many applications, including spectroscopy, heterodyne detection, and multispectral imaging, broadband and tunable THz QCLs are required. In this work, I investigate the feasibility of two techniques for tuning THz metasurface-based QCLs. First, A Littrow metasurface external cavity laser (ECL) is modeled and studied. We also propose and evaluate a novel method to implement Littrow ECL based upon blazed metasurface gratings. Electromagnetic simulations show that these metasurfaces can provide up to 15% fractional tunability around the center frequency of the laser at 3.3 THz. Preliminary results on several active resonant-phonon quantum-cascade materials are also obtained. Current progress on actual fabrication and device testing is reported.

Development of Terahertz Quantum-cascade VECSELs

Author : Christopher Curwen
Publisher :
ISBN 13 :
Total Pages : 184 pages
Book Rating : 4.:/5 (112 download)

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Book Synopsis Development of Terahertz Quantum-cascade VECSELs by : Christopher Curwen

Download or read book Development of Terahertz Quantum-cascade VECSELs written by Christopher Curwen and published by . This book was released on 2019 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz (THz) quantum-cascade lasers (QCLs) are an emerging semiconductor source of compact, high-power THz radiation. Though first realized more than 15 years ago, THz QCLs continue to suffer from poor beam quality and outcoupling efficiency due to the subwavelength nature of the semiconductor ridge-waveguides typically used. In this thesis, a new technique is discussed for obtaining high power and good beam quality from THz QCLs, the THz quantum-cascade external cavity surface emitting laser (QC-VECSEL). The concept of the QC-VECSEL is to use THz QC-gain material to design a millimeter-scale reflective amplifying surface, or metasurface, for free space THz waves and incorporate it into a free-space THz resonant cavity to provide feedback to the amplification and form a laser. In this manner, the beam shape is determined by the external cavity, which supports fundamental Gaussian solutions. Further, the metasurface itself is composed of a subwavelength array (to prevent diffraction) of surface-coupled QC-elements whose properties, such as phase and polarization response, can be engineered on a unit cell basis allowing for a variety of unique experiments. The power output power of the QC-VECSEL can be scaled by either increasing the size of the metasurface, or increasing the density (or fill factor) of QC-elements across the surface. In this work, large area metasurfaces with high fill-factor have been studied and demonstrated up to 1.35 W of peak output power for a QC-VECSEL operating at 3.4 THz at a heat sink temperature of 4 K. A peak wall-plug efficiency of ~2% is demonstrated, but observation of self lasing from the metasurface at high bias (when no external cavity is provided) in combination with a simultaneous roll-off in VECSEL output power suggests even higher efficiency can be achieved with improved suppression of self-lasing modes. The output beam is well fit to a Gaussian distribution with a 4 degree full-width half-maximum divergence angle. In addition to power and beam quality, the QC-VECSEL opens the door to many interesting and unique studies via engineering of the metasurface properties and external cavity. Much of this thesis describes frequency tuning of QC-VECSELs based on broadband metasurfaces by varying the length of the external cavity. By making the external cavity extremely short (comparable to the operating wavelength), we are able to push all other external cavity modes outside of the gain bandwidth of the metasurface and demonstrate more than 20% fractional single-mode tuning around a center operating frequency of 3.5 THz. Because there are almost no diffraction losses at such a short cavity, the size of the metasurface could be reduced, allowing for continuous wave lasing with up to 20 milliwatts of output power at a heatsink temperature of 77 K, though the output power is highly variable as the reflectance of the output coupler has a strong frequency dependence. At the time of writing this, these are record performances in both frequency tuning and high-temperature continuous wave operation for lasers based on THz QC-gain material. The amount of tuning that be achieved with this approach is limited by the phase response of the metasurface, which squeezes the external cavity modes closer together in the spectral domain. Development of metasurfaces with lower electrical power consumption and higher conversion efficiency for the purpose of improving continuous wave performance. A sparse, patch-based metasurface with reduced power consumption is demonstrated, though the design was not optimal and only showed a 20% reduction in current draw compared to the previously demonstrated metasurfaces. Routes towards improving the performance are discussed. The last subject discussed is the design of a mid-infrared (IR) QC-VECSEL. Due to the large metal losses at mid-IR frequencies compared to THz, the technique used to develop THz QC-VECSELs cannot be directly extended to the mid-IR. We propose a scheme based on a diffraction grating to provide surface coupling of the QC-gain material. Progress on experimental realization is discussed, but lasing has not yet been observed.

Spectroscopic Applications of Terahertz Quantum-Cascade Lasers

Author : Tasmim Alam
Publisher : Cuvillier Verlag
ISBN 13 : 3736962975
Total Pages : 132 pages
Book Rating : 4.7/5 (369 download)

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Book Synopsis Spectroscopic Applications of Terahertz Quantum-Cascade Lasers by : Tasmim Alam

Download or read book Spectroscopic Applications of Terahertz Quantum-Cascade Lasers written by Tasmim Alam and published by Cuvillier Verlag. This book was released on 2020-10-29 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum cascade lasers (QCLs) are attractive for high-resolution spectroscopy because they can provide high power and a narrow linewidth. They are particularly promising in the terahertz (THz) range since they can be used as local oscillators for heterodyne detection as well as transmitters for direct detection. However, THz QCL-based technologies are still under development and are limited by the lack of frequency tunability as well as the frequency and output power stability for free-running operation. In this dissertation, frequency tuning and linewidth of THz QCLs are studied in detail by using rotational spectroscopic features of molecular species. In molecular spectroscopy, the Doppler eff ect broadens the spectral lines of molecules in the gas phase at thermal equilibrium. Saturated absorption spectroscopy has been performed that allows for sub-Doppler resolution of the spectral features. One possible application is QCL frequency stabilization based on the Lamb dip. Since the tunability of the emission frequency is an essential requirement to use THz QCL for high-resolution spectroscopy, a new method has been developed that relies on near-infrared (NIR) optical excitation of the QCL rear-facet. A wide tuning range has been achieved by using this approach. The scheme is straightforward to implement, and the approach can be readily applied to a large class of THz QCLs. The frequency and output stability of the local oscillator has a direct impact on the performance and consistency of the heterodyne spectroscopy. A technique has been developed for a simultaneous stabilization of the frequency and output power by taking advantage of the frequency and power regulation by NIR excitation. The results presented in this thesis will enable the routine use of THz QCLs for spectroscopic applications in the near future.

Fundamentals of Terahertz Devices and Applications

Author : Dimitris Pavlidis
Publisher : John Wiley & Sons
ISBN 13 : 1119460719
Total Pages : 580 pages
Book Rating : 4.1/5 (194 download)

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Book Synopsis Fundamentals of Terahertz Devices and Applications by : Dimitris Pavlidis

Download or read book Fundamentals of Terahertz Devices and Applications written by Dimitris Pavlidis and published by John Wiley & Sons. This book was released on 2021-08-02 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: An authoritative and comprehensive guide to the devices and applications of Terahertz technology Terahertz (THz) technology relates to applications that span in frequency from a few hundred GHz to more than 1000 GHz. Fundamentals of Terahertz Devices and Applications offers a comprehensive review of the devices and applications of Terahertz technology. With contributions from a range of experts on the topic, this book contains in a single volume an inclusive review of THz devices for signal generation, detection and treatment. Fundamentals of Terahertz Devices and Applications offers an exploration and addresses key categories and aspects of Terahertz Technology such as: sources, detectors, transmission, electronic considerations and applications, optical (photonic) considerations and applications. Worked examplesbased on the contributors extensive experience highlight the chapter material presented. The text is designed for use by novices and professionals who want a better understanding of device operation and use, and is suitable for instructional purposes This important book: Offers the most relevant up-to-date research information and insight into the future developments in the technology Addresses a wide-range of categories and aspects of Terahertz technology Includes material to support courses on Terahertz Technology and more Contains illustrative worked examples Written for researchers, students, and professional engineers, Fundamentals of Terahertz Devices and Applications offers an in-depth exploration of the topic that is designed for both novices and professionals and can be adopted for instructional purposes.

THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface

Author : Yue Shen
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)

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Book Synopsis THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface by : Yue Shen

Download or read book THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface written by Yue Shen and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz (THz) quantum cascade lasers (QCLs) are compact electrically pumped unipolar semiconductor laser which can produce a continuous wave radiation of high output power in the range of 1.2 to 5.6 THz. The QC vertical-external-cavity surface-emitting-laser (QC-VECSEL) is an external cavity configuration that supports high-power operation with excellent beam quality and broadband tunability. The key component of the QC-VECSEL is an amplifying reflectarray metasurface, based on a subwavelength array of surface-radiating metal-metal waveguide antenna elements loaded with QC-laser gain material. Despite its importance, up to now the spectral properties of the QC-metasurface have been designed by simulations and have only been verified indirectly through observation of the QC-VECSEL lasing characteristics, or by passive FTIR reflectance measurements at room temperature. Furthermore, design takes place using simulations based upon simplified models for the material loss and the QC-gain, where uncertain Drude model parameters for material losses are used, and the detailed interaction of the intersubband transition with the metasurface is neglected. In the past decade, THz time domain spectroscopy (THz-TDS) has been widely used to investigate gain spectra and laser dynamics of THz QC-lasers based on various ridge waveguide geometries. During my doctoral studies, I designed and built up a reflection-mode THz-TDS system to study amplifying quantum-cascade (QC) metasurface samples as a function of injected current density. The first direct spectral measurements were performed on QC-metasurfaces using reflection-mode THz-TDS. Several different kinds of metasurface were designed that were suitable for study by the THz-TDS system. Extremely strong absorption features for QC-metasurfaces whose resonance frequency designed below 3 THz is measured at zero bias, which is associated with coupling between the metasurface resonance and an intersubband transition within the QC material. In one case, nearly perfect absorption is observed due to the transition from weak to strong light-matter coupling condition. Increase in reflectance are observed as the devices are biased, both due to reduction in intersubband loss and the presence of intersubband gain. Significant phase modulation associated with the metasurface resonance is observed via electrical control for some certain metasurfaces, which may be useful for electrical tuning of QC-VECSEL. These results provide insight into the interaction between the intersubband QC-gain material and the metasurface and modify the design rules for QC-VECSELs for both biased and unbiased regions.

Terahertz Time-domain Characterization of Amplifying Quantum Cascade Metasurface

Author : Yue Shen
Publisher :
ISBN 13 :
Total Pages : 67 pages
Book Rating : 4.:/5 (113 download)

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Book Synopsis Terahertz Time-domain Characterization of Amplifying Quantum Cascade Metasurface by : Yue Shen

Download or read book Terahertz Time-domain Characterization of Amplifying Quantum Cascade Metasurface written by Yue Shen and published by . This book was released on 2019 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: The THz quantum-cascade vertical-external-cavity surface-emitting-laser (QC-VECSEL) is a recently developed approach for designing high-power, electrically pumped THz lasers with excellent beam quality and broadband tunability. The key component of the QC-VECSEL is an amplifying reflectarray metasurface, based on a subwavelength array of surface radiating metal-metal waveguide antenna elements loaded with QC-laser gain material. Despite its importance, the gain properties of the QC-metasurface are designed by simulation and have only been verified indirectly through observation of the QC-VECSEL lasing characteristics, or by passive FTIR reflectance measurements at room-temperature. THz time-domain spectroscopy (TDS) has been widely used to investigate gain spectra and laser dynamics of THz QC-lasers based on various ridge waveguide geometries. In this thesis, I describe my construction of a THz TDS system and present the first direct spectral measurement using reflection-mode THz TDS of an amplifying QC-metasurface resonant at 2.6 THz under different conditions. The large surface-radiating aperture of the metasurface (1.5 1.5 mm2 in this case) eases free-space TDS measurements compared to ridge waveguide QC-devices with sub-wavelength sized facets.

Towards Actively Mode-locked Terahertz Quantum-cascade VECSELs

Author : Yu Wu
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (141 download)

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Book Synopsis Towards Actively Mode-locked Terahertz Quantum-cascade VECSELs by : Yu Wu

Download or read book Towards Actively Mode-locked Terahertz Quantum-cascade VECSELs written by Yu Wu and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The invention of optical frequency combs generated by mode-locked lasers revolutionized time and frequency metrology in the late 1990s. This concept has been explored in several laser systems; the quantum cascade laser (QCL) is one such system that operates in the terahertz (THz) frequency range.THz QCL was first invented in 2001 as a reliable semiconductor source for compact, high-power THz radiation. The inherently strong third-order nonlinearity in its QC-gain medium allows for spontaneous frequency comb formation as a result of spatial hole burning induced by Fabry-Perot cavities and four-wave mixing, which synchronizes the dispersed cavity modes. It was noticed that the self-generated combs are naturally frequency-modulated with quasi-continuous power output, whereas amplitude-modulated combs, i.e., mode-locking, are considered challenging in THz QCLs because of the inherent fast gain recovery time. One effective method to trigger active mode-locking is RF injection locking. It involves injecting RF current modulation into the QC-device at a frequency that is close to the cavity round-trip frequency. This locks the spacing between adjacent lasing modes, and pulses with a duration of 4-5 ps have been reported. In recent years, the study of frequency comb/mode-locking in THz QCLs has raised increasing interest because of its potential for a number of applications, including astronomy, biomedicine, fast spectroscopy, non-invasive imaging, and non-destructive evaluation. So far, research has concentrated on ridge-waveguide and ring QCLs. On the other hand, THz quantum-cascade vertical-external-cavity surface-emitting-laser (QC-VECSEL) was introduced in 2015 as a novel external cavity configuration of THz QCLs.The key concept of THz QC-VECSEL is to engineer its gain chip into a millimeter-scale reflectarray metasurface for free-space THz radiation and further incorporation into a resonant laser cavity as an active reflector. This enables watt-level output power with near-Gaussian distributed beam quality; versatile functionality may be incorporated into the amplifying metasurface; and broadband frequency tunability is provided by the VECSEL architecture. Despite the fact that VECSELs are widely used for mode-locking at near-infrared and optical frequencies, THz QC-VECSELs have not yet been exploited in frequency comb and mode-locking applications. In this thesis, we report for the first time the techniques utilized to achieve frequency comb/mode-locking operations in THz QC-VECSELs. Both the metasurface design and VECSEL cavity geometry are optimized for this purpose. The double-patch metasurface design is considered optimal for broadband frequency response and low dispersion, and a well-designed RF package is needed for efficient RF signal injection and extraction. On the other hand, an off-axis parabolic (OAP) mirror is introduced to build a V-shaped intra-cryostat focusing VECSEL cavity. This OAP-focusing cavity design eliminates most of the intra-cavity diffraction losses and, therefore, enables lasing in an ultra-long external cavity using a small-sized metasurface that supports continuous wave (CW) biasing. It is highly suited for frequency comb/mode-locking applications as the cavity round-trip frequency is lowered to a typical value of 3-5 GHz. In contrast to ridge-waveguide or ring QCLs, self-generated frequency combs have not been observed in THz QC-VECSELs --- in fact, they prefer to lase in a single-mode regime primarily due to a lack of spatial hole burning.To promote multimode operation in THz QC-VECSELs, we present a technique based on a specific combination of output coupler thickness and external cavity length. Through Vernier selection and reflectance compensation in a cascaded Fabry-Perot cavity, we are able to perform simultaneous nine modes lasing with a free-spectral range (FSR) of ~21 GHz. The number of lasing modes that can be generated using this method is limited by the maximum available output coupler thickness. A more effective way to promote multimoding, as well as possible frequency comb or even mode-locking operations, is through RF injection locking.The successful demonstration of RF injection locking in THz QC-VECSELs for the first time is the main focus of this thesis. Lasing spectral broadening has been observed under strong RF modulation, with a maximum bandwidth of around 100-300 GHz. An intermodal beat-note is produced as a result of beating between each of the two lasing modes. It is locked to the RF injection signal as the injection frequency is tuned around the cavity round-trip frequency. This suggests that the lasing modes are equally spaced, which is a prerequisite of frequency comb/mode-locking. Several impacting factors, including metasurface design, external cavity length, and optical feedback, are experimentally investigated in the RF-injection locked QC-VECSELs, which may help control and tune the laser states. THz QC-VECSEL is consequently considered to be a superior platform that enables a more thorough investigation of the fundamental physics of mode-locking/frequency comb operation in QCL systems. Our research on mode-locked THz QC-VECSELs opens the way for future development of semiconductor lasers operating in the 2-5 THz region that produce picosecond-scale pulses.

Theory and Design of Tunable Terahertz Metamaterials for Application to Tunable Terahertz Quantum Cascade Lasers

Author : Christopher Curwen
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (97 download)

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Book Synopsis Theory and Design of Tunable Terahertz Metamaterials for Application to Tunable Terahertz Quantum Cascade Lasers by : Christopher Curwen

Download or read book Theory and Design of Tunable Terahertz Metamaterials for Application to Tunable Terahertz Quantum Cascade Lasers written by Christopher Curwen and published by . This book was released on 2014 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz quantum cascade lasers are compact, coherent sources of THz power that have drawn considerable attention in the past 10-15 years for their potential use in THz applications such as spectroscopy and imaging. One of the key developments required to further the usefulness of THz QCLs is robust, broadband tenability. In this work, I describe a new technique for tuning THz QCLs by incorporation MEMS fixed-fixed and fixed-free cantilever beams into a THz transmission line metamaterial resonant cavity. An analytic model for such THz transmission line metamaterials is demonstrated using transmission line theory and is supported by 2-D and 3-D finite element simulations. Proposed processes for fabricating tunable THz transmission line metamaterials are outlined and current progress on actual fabrication and device testing is reported.

Terahertz Quantum-cascade Transmission-line Metamaterials

Author : Amir Ali Tavallaee
Publisher :
ISBN 13 :
Total Pages : 146 pages
Book Rating : 4.:/5 (828 download)

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Book Synopsis Terahertz Quantum-cascade Transmission-line Metamaterials by : Amir Ali Tavallaee

Download or read book Terahertz Quantum-cascade Transmission-line Metamaterials written by Amir Ali Tavallaee and published by . This book was released on 2012 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Terahertz quantum-cascade (QC) lasers operating at 0.6 − 5 THz (λ ∼ 60 − 500 μm) are poised to become the dominant solid-state sources of continuous-wave (cw) far-infrared radiation enabling applications in terahertz spectroscopy, imaging, and sensing. QC-lasers are the longest wavelength semiconductor laser sources in which terahertz gain is obtained from electronic intersubband radiative transitions in GaAs/AlGaAs heterostructure quantum wells. Since their invention in 2001, rapid development has enabled demonstration of cw powers greater than 100 mW. However, challenges still remain in the areas of operating temperature, laser efficiency and power, and beam quality to name a few. The highest-temperature operation of terahertz quantum-cascade lasers (200 K pulsed, 117 K cw) depends on the use of a low-loss "metal-metal" waveguide where the active gain material is sandwiched between two metal cladding layers; a technique similar, in concept, to microstrip transmission line technology at microwave frequencies. Due to the subwavelength transverse dimensions of the metal-metal waveguide, however, obtaining a directive beam pattern and efficient out-coupling of THz power is non-trivial. This thesis reports the demonstration of a one-dimensional waveguide for terahertz quantum-cascade lasers that acts as a leaky-wave antenna and tailors laser radiation in one dimension to a directional beam. This scheme adapts microwave transmission-line metamaterial concepts to a planar structure realized in terahertz metal-metal waveguide technology and is fundamentally different from distributed feedback/photonic crystal structures that work based on Bragg scattering of propagating modes. The leaky-wave metamaterial antenna operates based on a propagating mode with an effective phase index smaller than unity such that it radiates in the surface direction via a leaky-wave mechanism. Surface emission (∼ 40◦ from broadside) with a single directive beam (FWHM ∼ 15◦) at 2.74 THz was demonstrated from terahertz QC-lasers with leaky-wave coupler antennas which exhibited slope efficiencies ∼ 4 times greater than conventional Fabry-Perot metal-metal waveguides. Using this technique the first demonstration of beam scanning for a terahertz QC-laser was reported (from 35◦ − 60◦) as the emission frequency varied from 2.65 − 2.81 THz. Towards the bigger goal of realizing an active terahertz metamaterial to ultimately develop "zero-index" terahertz quantum-cascade lasers immune to spatial hole burning, or "negative-index" metamaterials for superresolution terahertz imaging, a composite right-/left-handed transmission-line metamaterial based upon subwavelength metal waveguide loaded with terahertz QC material was demonstrated. Due to the addition of distributed series capacitors (realized by introducing gaps in top metallization) and shunt inductors (realized by operating in the higher-order lateral mode of the waveguide), the transmission-line metamaterial exhibits left-handed (backward waves or negative index) leaky-wave propagation from 2.3 − 2.45 THz in addition to the conventional right-handed leaky-wave behavior (from 2.6 − 3.0 THz).

Focusing Metasurface Quantum-cascade Laser with a Near Diffraction-limited Beam

$Download Focusing Metasurface Quantum-cascade Laser with a Near Diffraction-limited Beam PDF Online Free$

Author :
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (971 download)

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Book Synopsis Focusing Metasurface Quantum-cascade Laser with a Near Diffraction-limited Beam by :

Download or read book Focusing Metasurface Quantum-cascade Laser with a Near Diffraction-limited Beam written by and published by . This book was released on 2016 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A terahertz vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated using an active focusing reflectarray metasurface based on quantum-cascade gain material. The focusing effect enables a hemispherical cavity with flat optics, which exhibits higher geometric stability than a plano-plano cavity and a directive and circular near-diffraction limited Gaussian beam with M2 beam parameter as low as 1.3 and brightness of 1.86 × 106 Wsr-1m-2. As a result, this work initiates the potential of leveraging inhomogeneous metasurface and reflectarray designs to achieve high-power and high-brightness terahertz quantum-cascade VECSELs.

External Modulation of Terahertz Quantum Cascade Lasers Using Metamaterials

Author :
Publisher :
ISBN 13 :
Total Pages : 19 pages
Book Rating : 4.:/5 (957 download)

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Book Synopsis External Modulation of Terahertz Quantum Cascade Lasers Using Metamaterials by :

Download or read book External Modulation of Terahertz Quantum Cascade Lasers Using Metamaterials written by and published by . This book was released on 2008 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Physics and Applications of Terahertz Radiation

Author : Matteo Perenzoni
Publisher : Springer
ISBN 13 : 9400738374
Total Pages : 257 pages
Book Rating : 4.4/5 (7 download)

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Book Synopsis Physics and Applications of Terahertz Radiation by : Matteo Perenzoni

Download or read book Physics and Applications of Terahertz Radiation written by Matteo Perenzoni and published by Springer. This book was released on 2013-10-16 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the latest advances in the techniques employed to manage the THz radiation and its potential uses. It has been subdivided in three sections: THz Detectors, THz Sources, Systems and Applications. These three sections will allow the reader to be introduced in a logical way to the physics problems of sensing and generation of the terahertz radiation, the implementation of these devices into systems including other components and finally the exploitation of the equipment for real applications in some different field. All of the sections and chapters can be individually addressed in order to deepen the understanding of a single topic without the need to read the whole book. The THz Detectors section will address the latest developments in detection devices based on three different physical principles: photodetection, thermal power detection, rectification. The THz Sources section will describe three completely different generation methods, operating in three separate scales: quantum cascade lasers, free electron lasers and non-linear optical generation. The Systems and Applications section will take care of introducing many of the aspects needed to move from a device to an equipment perspective: control of terahertz radiation, its use in imaging or in spectroscopy, potential uses in security, and will address also safety issues. The text book is at a level appropriate to graduate level courses up to researchers in the field who require a reference book covering all aspects of terahertz technology.

Frontiers in Optics and Photonics

Author : Federico Capasso
Publisher : Walter de Gruyter GmbH & Co KG
ISBN 13 : 3110710684
Total Pages : 783 pages
Book Rating : 4.1/5 (17 download)

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Book Synopsis Frontiers in Optics and Photonics by : Federico Capasso

Download or read book Frontiers in Optics and Photonics written by Federico Capasso and published by Walter de Gruyter GmbH & Co KG. This book was released on 2021-06-08 with total page 783 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a cutting-edge research overview on the latest developments in the field of Optics and Photonics. All chapters are authored by the pioneers in their field and will cover the developments in Quantum Photonics, Optical properties of 2D Materials, Optical Sensors, Organic Opto-electronics, Nanophotonics, Metamaterials, Plasmonics, Quantum Cascade lasers, LEDs, Biophotonics and biomedical photonics and spectroscopy.

Beam Pattern Engineering of Metamaterial Terahertz Quantum-cascade Devices

Author : Philip Wing-Chun Hon
Publisher :
ISBN 13 :
Total Pages : 199 pages
Book Rating : 4.:/5 (868 download)

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Book Synopsis Beam Pattern Engineering of Metamaterial Terahertz Quantum-cascade Devices by : Philip Wing-Chun Hon

Download or read book Beam Pattern Engineering of Metamaterial Terahertz Quantum-cascade Devices written by Philip Wing-Chun Hon and published by . This book was released on 2013 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generation and detection of microwave radiation is done with electronic systems where the underyling processes involve oscillating free charges (such as on an antenna or within a transistor or diode). On the higher energy side of the spectrum, generation and detection of near infrared and visible radiation is achieved via quantum transitions with emission wavelengths that are dictated by the material. Solutions moving up towards the THz regime using microwave based solutions are limited by carrier transit time and RC time-constant limitations. Techniques and solutions moving down toward the THz regime using photonic techniques have emission wavelengths naturally limited by the band gap of the material. However, THz quantum-cascade (QC) lasers, which are an extension of photonic concepts to lower energies, have artificially engineered energy levels and hence emission wavelengths. THz QC-lasers have been demonstrated to operate at frequencies between 1.2 and 5.0 THz and the best high-temperature operation is based upon the metal-metal (MM) waveguide configuration, in which the multiple-quantum well active region is sandwiched between two metal cladding layers, typically separated by 2-10 [mu]m. Soon after the demonstration of MM waveguide QC-lasers, it was recognized that the beam pattern from a conventional cleaved-facet Fabry Pérot (FP) ridge cavity produced a highly divergent beam pattern, characterized by concentric rings in the far field. This thesis presents work on a new approach to tailor the beam pattern of THz MM waveguide QC-devices. Namely, dispersion engineering using metamaterials based on the composite right/left-handed (CRLH) transmission line formalism is adapted to the MM waveguide configuration to realize an entirely new class of devices. Dispersion, radiative loss, and radiation patterns are presented for many newly designed 1-D and 2-D THz QC transmission line metamaterial designs. The first ever active 1-D THz QC transmisison line metamaterial is experimentally characterized and its radiation pattern and polarization closely match theoretical and full-wave finite element method (FEM) simulated predictions. Proven microwave techniques such as circuit, antenna cavity modeling and array factor theory are used to understand the radiative properties of conventional THz QC-lasers. We predict far-field beam patterns and polarizations, approximate cavity quality factors, and associate these properties with individual surfaces or structures of the device. The analysis technique is also applied to the project's 1-D and 2-D THz CRLH QC-devices yielding qualitative agreement with experiments. The first THz design, analysis and experimental verification of a metasur face comprised of an array of passive THz QC transmission lines is presented. By using the cavity model, array factor, circuit and electromagnetic theory a surface impedance model is developed to characterize the metasurface. The surface impedance model reveals waveguide mode dependent radiative coupling with the light line and capacitve/inductive surface impedance. Polarization dependent angle-resolved Fourier transform infrared reflection spectroscopy measurements match the model and full-wave FEM predictions, further assisting the understanding of such devices. To address the broader goal of a directive and scalable THz QC-device, thefeasibility of a 2-D metamaterial inspired QC-laser and an active reflectarray is considered. Finally, preliminary work on a technology enabling active metasurface reflector for a QC vertical external cavity surface emitting laser is discussed.