multi-quantum well laser

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Self-Consistent Analysis of Barrier Characterization Effects on Quantum Well Laser Internal Performance

Self-Consistent Analysis of Barrier Characterization Effects on Quantum Well Laser Internal Performance

Simulation is a very helpful and valuable work tool in manufacturing. It can be used in the industrial field allowing the system’s behavior to be learned and tested. Simulation provides a low cost, secure, and fast analysis tool. It also provides benefits that can be achieved with many different system configurations [4]. In this study, first, we will simulate typical InGaAsP-InP multi-quantum well laser with lattice match barriers using Photonic Integrated Circuit Simulator in 3D (PICS3D), which self- consistently combines 3D simulation of carrier transport, self-heating, and optical wave- guiding; then, the same structure will be investigated with different barrier characterizations.
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Excitonic localization in AlN-rich AlxGa1-xN/AlyGa1-yN multi-quantum-well grain boundaries

Excitonic localization in AlN-rich AlxGa1-xN/AlyGa1-yN multi-quantum-well grain boundaries

was grown. The quantum barriers (QBs) had a fixed nominal AlN molar fraction of 0.73, while the nominal molar frac- tions of AlN content in quantum wells (QWs) of the four samples (A, B, C, and D) varied from 35% to 65% in 10% increments, as shown in Table I. The widths of the quantum barrier and QW were estimated by scanning transmission electron microscopy (STEM). In the STEM measurements, the samples were first prepared using an FEI Helios 400S dual beam focused ion beam (FIB) system and were subse- quently characterized using an FEI TITAN microscope. Atomic force microscopy (AFM) was employed to analyze the morphological structures of the samples on an Agilent Technologies 5400 scanning probe microscope operated in the tapping mode. All photoluminescence (PL) measure- ments were excited using a frequency doubled Ar þ laser operating at 244 nm wavelength, with a beam power of 11 mW. The samples were mounted in a He-closed cycle cryo- stat system for low-temperature PL measurement (5 K). An Andor spectrograph with a UV-visible charge coupled device (CCD) camera was used to detect and analyze the PL spec- tra. To investigate luminescence properties across the samples, secondary electron (SE) images and cathodolumi- nescence (CL) hyperspectral imaging were carried out at room temperature (RT) using an FEI Quanta 250 environ- mental FEGSEM. The electron beam energy was fixed at 5 keV, with an acquisition time of 40 ms per pixel, and 0.1 Torr of water vapor pressure was introduced into the chamber to prevent sample charging.
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Photovoltaic and Photo-emissive Properties of InGaNGaN Multi Quantum Well Structure on Sapphire

Photovoltaic and Photo-emissive Properties of InGaNGaN Multi Quantum Well Structure on Sapphire

III-Nitride semiconductor materials have showing promising materials for optoelectronics and power applications. These materials have direct bandgap ranging from 0.7eV to 6.2 eV which covers entire visible and UV spectra of solar radiation (Pankove J. I., and Moustakas T.D., ;Shur M. S., and Davis R. F.,). InGaN materials whose band gap varies from 0.7 eV to 3.4 eV are suitable for photovoltaic and photoemissive applications (Chitnis A., Chen C., Adivarahan V., Shatalov M.,Kuokstis E., Mandavilli V.,Yang J., and Khan M.A., 2004; Dahal R., Pantha B., Lin j.Y. and Jiang H.X., 2009). Many photo emissive cells from these materials like LEDs, Laser diode are successfully commercialized. But very few works on photovoltaic application are reported in literature (Sheu J.K., Yang C.C., Tu S.J., Chang K.H., Lee M.L., Lai W.C., Peng L.C., 2009 ; Nawaz M., and Ahmad A.,).
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Reversed Effects of Quantum Well Numbers and Temperature on Optical Power and Wavelength of a Designed Ultraviolet Semiconductor Laser Based on GaN/InGaN

Reversed Effects of Quantum Well Numbers and Temperature on Optical Power and Wavelength of a Designed Ultraviolet Semiconductor Laser Based on GaN/InGaN

In recent years, Gallium-nitride optoelectronic devices have been the most attractive productions because of their performance near UV, blue and green wavelengths. In addition, GaN and related alloys are also being used in high power, high frequency, high temperature bipolar and field effect transistors and multi-junction solar cells [1]. There is a strong interest in development of multi quantum well semiconductor lasers based on GaN/InGaN in some applications like high density optical power and energy efficient lighting [2]. Usage of quantum well lasers to increase the output power in semiconductor devices has been started science many years ago. However rise in quantum well numbers is one of the well known approaches to increase the optical power in optical semiconductor devices, sometimes increase in number of quantum wells more than a limited number will contribute to some reversed effects, such as rise in threshold current and reduction in optical power.
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Elimination of Bimodal Size in InAs/GaAs Quantum Dots for Preparation of 1 3 μm Quantum Dot Lasers

Elimination of Bimodal Size in InAs/GaAs Quantum Dots for Preparation of 1 3 μm Quantum Dot Lasers

InAs/GaAs heterostructures grown by molecular beam epitaxy (MBE) have been paid much attention in order to fabricate low dimensional nanostructures, such as self-assembled QDs due to large lattice (~ 7%) mismatch between InAs layers and GaAs substrate [8]. The growth of InAs on GaAs (001) substrate results in the formation of a three-dimensional (3D) island shape on the InAs with the Stranski-Krastanov (SK) growth mode. The SK growth technique is expected to be a convenient fabrication method of the high-density coherent QDs and is still an open challenge [9, 10]. However, SK QDs have some prob- lems, such as the large inhomogeneous broadening of the QD energy levels and the bimodal size problem [11–15]. For MBE growing high-density quantum dots, the conven- tional way is to increase the deposition rate of InAs and lower the growth temperature. The purpose of this approach is to reduce the migration rate that can make the formation of the island quickly. However, low-temperature growth may reduce the lattice quality of the epitaxial mater- ial. On the other hand, rapid growth can increase the
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Hitting statistics from quantum jumps

Hitting statistics from quantum jumps

Our appeal to photon counting as a way of thinking about quantum jumps for the hitting problem raises another interesting question related to the use of measurements in quantum walks. This is related to our allusion to other unravellings made earlier in Sec. 1.1. In general, an unravelling is a specific decomposition of the master equation into stochastic trajectories such that the ensemble average of them recovers the dynamics of the master equation. Two classes of unravellings have special significance in quantum optics—the jump unravellings used in our paper, and the so-called diffusive unravellings—because they turn out to have concrete interpretations in terms of quantum optical measurements (as already seen with the jump unravellings in our work) [13]. Canonical examples of quantum-optical measurements that give rise to (or essentially realise) diffusive unravellings are the homodyne and heterodyne detection schemes [57, 58]. Since we are defining the graph of a continuous-time open quantum walk by a master equation, and we know that a master equation can be unravelled in different ways, one might wonder if another type of unravelling can be used to study a hitting problem. Given that diffusive unravellings form the second major class of unravellings in quantum optics we might then ask if they can be used for the hitting problem in this paper. The short answer is that there is not much motivation to do so because they are unhelpful for solving hitting problems with discrete-state quantum walks. To understand this we recall that in our quantum-jump approach we imagined the incoherent transitions in the graph gave off photons which were measured by photodetectors. Using a diffusive unravelling is equivalent to superimposing the stream of photons coming from an incoherent transition with a local-oscillator field (a laser in a coherent state) on a beam splitter before it is detected by the photodetector. In this case the photodetector actually measures a quadrature of the stream of photons determined by the phase of the local oscillator. A diffusive unravelling thus gives us information about a continuous variable that does not directly reveal to us if the walker has reached a prescribed state or not. To get around this one can then try to introduce the fidelity between ρ f (here taken to be a parameter) and the walker’s state to define when ρ f is reached
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Optically pumped intersublevel midinfrared lasers based on InAs-GaAs quantum dots

Optically pumped intersublevel midinfrared lasers based on InAs-GaAs quantum dots

Therefore, we propose the following scheme which gives the largest values of gain among all the schemes explored. The elec- trons are optically pumped from level 1 to level 7. The distance between levels 5 and 7 is close to an LO-phonon energy and consequently the transition rate between these two levels ex- ceeds all other LO-phonon interaction transition rates by more than an order of magnitude, enabling a fast depopulation of level 7. Consequently, the occupancy of level 7 in steady state is small and thus the undesirable stimulated emission from level 7 to level 1 is almost completely avoided in this scheme. The main difference between this and the previous scheme is that in this scheme there exists a fast depopulation mechanism from the level to which the electrons are being pumped, which pre- vents backfilling of level 1 by stimulated emission of photons. Almost all the electrons from level 7 therefore go into level 5, which implies that level 6 remains almost unpopulated. The electrons are further distributed to levels 2–4 and if the pump flux is sufficiently large, a population inversion between any of the levels 2–5 and level 1 occurs. As will be shown later, the largest population inversion occurs between levels 2 and 1, as well as between 3 and 1. Since the transition linewidth is of the same order of magnitude as the energy difference between states 2 and 3, laser emission is caused by both transitions and . Due to selection rules on the transition , the pump needs to be -polarized, while the emitted radiation is in-plane polarized, since the selection rules on both transitions and allow only such emission. Therefore, a laser based on these transitions can operate either as an edge emitter or as a surface emitter.
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IMPROVING QUANTUM MICROSCOPY VIA RAMAN PHOTON PAIRS

IMPROVING QUANTUM MICROSCOPY VIA RAMAN PHOTON PAIRS

Photon correlation interferometry [1] is a powerful tool with applications ranging from the macro- to the micro- cosmos. For example, it is well-known that it is possible to improve our ability to measure stellar diameters and resolve binary stars via the Hanbury Brown-Twiss effect. It is also known that it is possible to improve the reso- lution of optical microscopy [2] and lithography [3] by us- ing photon correlation interferometry [4]. This has been demonstrated in the elegant experiment of D’Angelo, Chekhova and Shih [5] via two photon down conversion. We here apply the geometry and physics of the orig- inal [2] Raman quantum erasure [6] scheme to resolve molecular markers separated by distances smaller than the wavelength of the probing radiation. As a case in point we note that in many biophysical studies, the shape or conformation of a protein or a DNA strand is moni- tored as a function of various parameters. One way of making such measurements involves attaching markers, such as dye molecules or quantum dots, to two known points on the protein and observing their fluorescence as they move apart. We here propose and analyze a new, photon-correlation approach, see Fig. 1, to measure the distance between the markers.
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M-VCR : Multi-View Consensus Recognition for Real-Time Experimentation

M-VCR : Multi-View Consensus Recognition for Real-Time Experimentation

This work uses a traditional approach for gesture recognition in terms of its system architecture and then proposes a new architecture inspired by N-versioning [15], [16]. The proposed framework is then benchmarked against previous state-of-the-art and the results demonstrated in section VI show an improvement of 47% in classification whilst meeting the original timeliness constraints. It is vital to note that all the results demonstrated in this paper are entirely through the integration approach of M-VCR that utilises quantum super-positioning to achieve consensus and no modification of the classification algorithms has been attempted. The significance of treating the algorithms as commercial-off-the-shelf (COTS) tools allows us to evaluate the mathematical framework at an abstraction away from the problem of gesture recognition. It is therefore expected that the M-VCR framework could be applied to other scientific and engineering domains.
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Investigation of Ultra-Wide Reflection Bands in UV Region by Using One-Dimensional Multi Quantum Well Photonic Crystal

Investigation of Ultra-Wide Reflection Bands in UV Region by Using One-Dimensional Multi Quantum Well Photonic Crystal

obtained by employing the transfer matrix method (TMM). From the analysis of the proposed structure it is observed that by applying the combination of multi quantum well structure with a suitable value of thickness of unit cell in each case, one gets very enlarged range of reflection bands. The range of reflection bands can be further increased by increasing the thickness of the unit cell. We have also investigated the ODR band up to incident angle 50 ◦ and found that there is significant enhancement in ODR band by using three MQWs in comparison with single MQW structure for the same number of layers. The proposed MQW photonic crystals can be used to design the ultraviolet reflector to protect the DNA from damage, in ultraviolet shielding for drugs, in skin diseases especially for skin cancer and in the detection of charged particle.
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Effects of an intense, high frequency laser field on bound states in Ga1 − xInx
              Ny
              As1 − y/GaAs double quantum well

Effects of an intense, high frequency laser field on bound states in Ga1 − xInx Ny As1 − y/GaAs double quantum well

Recently, the evolution of the growth techniques such as molecular beam epitaxy and metal-organic chemical vapor deposition combined with the use of the modulation- doped technique made it possible the fabrication of low- dimensional heterostructures such as single and multiple quantum wells, quantum wires, and quantum dots. In these systems, the restriction on the motion of the charge carriers allows us to control the physical properties of the structures. The studies on these systems offer a wide range of potential applications in the development of semicon- ductor optoelectronic devices [1-5].
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Graphene Electron States in a Quantum Well

Graphene Electron States in a Quantum Well

Graphene is a mono-atomic layer of carbon atoms arranged on a 2D honeycomb lattice. Near each corner of the hexagonal first Brillouin zone (also called Dirac points or K-points) the quasiparticle excitations obey a 2D linear dispersion relation and behave like massless “relativistic” particles. That leads to a number of unusual electronic properties; one of them is so called Klein paradox [5] well known in quantum electrodynamics. It predicts that the electron can perfectly pass through the potential barrier independently of its height in contrast to the conventional nonrelativistic tunneling where the transmission probability exponentially decays with the barrier height increasing. As was shown in [6,7] the similar phenomenon takes place in graphene (see also [8]). So some electron states in graphene with a quantum well (which can be considered as a barrier for holes) are those corresponding just to that Klein (or “chiral”) tunneling in both directions. Klein chiral tunneling
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Quantum backreaction in laser driven plasma

Quantum backreaction in laser driven plasma

plasma. Hence, multi-particle considerations are included from the outset. The underpinning ingredients rely on standard approximations in classical laser-plasma theory; the slowly-varying envelope approximation for the laser pulse, and the ponderomotive approximation for the force exerted by the laser on the plasma electrons [6]. We exploit results established in the context of quantum field theory on curved spacetime to obtain the quantum corrections to the classical field equations. As the first application of our new theory, we show that the quantum fluctuations lead to the relationship
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High-Coherence Hybrid Si/III-V Semiconductor Lasers

High-Coherence Hybrid Si/III-V Semiconductor Lasers

The relentlessly increasing demand for network bandwidth, driven primarily by In- ternet -based services such as mobile computing, cloud storage and video-on-demand, calls for more efficient utilization of the available communication spectrum, as that afforded by the resurging DSP-powered coherent optical communications. Encoding information in the phase of the optical carrier, using multilevel phase modulation formats, and employing coherent detection at the receiver allows for enhanced spec- tral efficiency and thus enables increased network capacity. The distributed feedback semiconductor laser (DFB) has served as the near exclusive light source powering the fiber optic, long-haul network for over 30 years. The transition to coherent commu- nication systems is pushing the DFB laser to the limits of its abilities. This is due to its limited temporal coherence that directly translates into the number of different phases that can be imparted to a single optical pulse and thus to the data capacity. Temporal coherence, most commonly quantified in the spectral linewidth ∆ν, is lim- ited by phase noise, result of quantum-mandated spontaneous emission of photons due to random recombination of carriers in the active region of the laser.
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Fast modulation of terahertz quantum cascade lasers using graphene loaded plasmonic antennas

Fast modulation of terahertz quantum cascade lasers using graphene loaded plasmonic antennas

Recently, an impressive advancement has been achieved by terahertz (THz) solid-state sources in terms of performance with the quantum cascade laser (QCL) 1,2 and by time-domain spectroscopic (TDS) systems, in terms of costs, compactness and bandwidth. However, the lack of suitable optoelectronic devices, both passive and active, has so far hindered technology in this spectral region from reaching its full potential in many demanding sectors, such as spectroscopy or communications. The realization of a tuneable external THz amplitude/phase/frequency modulator would allow for fast reconfigurable spectroscopic systems, e.g. to be implemented for amplitude, frequency or phase stabilization. 3 Terahertz communications represent a fast evolving research area. Wireless communications always strive for broader bandwidths and the THz range represents a non-allocated frequency range. Further to this, because of the high carrier frequency, THz radiation has the potential to yield high transmission rates, as high as 100 Gbit s -1 , as recently
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NIST-F1 and Systematic Frequency Tuning

NIST-F1 and Systematic Frequency Tuning

NIST is collaborating with the Jet Propulsion Laboratory, the University of Colorado, the Havard-Smithsonian Center for Astrophysics, and the Politecnico di Torino to develop the Primary Atomic Reference Clock in Space (PARCS), a NASA-sponsored program to operate a laser-cooled cesium atomic clock on the International Space Station (ISS) [5]. The PARCS mission objectives include (1) sensitive tests of general and special relativity by measuring the frequency shift of PARCS; (2) measure local position invariance by comparing the PARCS frequency to that of a hydrogen maser assumed to be part of the PARCS package; (3) improve the realization of the second through the reduced frequency uncertainty of PARCS afforded by the long atom drift time; (4) use PARCS to study the performance of GPS timing and time transfer. NIST and University of Colorado staff serve as co-principal investigators for the experiment, with the Jet Propulsion Laboratory providing the Project Scientist, Project Manager, and construction of the flight hardware. Other partners provide key input to the design of the systems.
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Physical model of quantum-well infrared photodetectors

Physical model of quantum-well infrared photodetectors

In the past decade quantum well infrared photodetectors (QWIPs) have reached a technologi- cal maturity as devices offering excellent performance in the mid- (3 − 5µm) and long-wavelength (8 − 14µm) infrared spectral range [1]. A large number of papers have been published, covering different aspects of QWIP design, modelling and characterization, delivering tunable, broadband and multicolor operation [2–8]. Moreover, large, highly uniform QWIP focal plane arrays have been reported with a wide range of possible applications [9, 10]. However, despite the extensive amount of experimental and theoretical efforts, not much work has been done on a microscopic quantum description of the processes that govern both vertical and parallel electron transport in periodic quantum structures, involving bound-bound and bound-continuum intersubband transi- tions [6, 11–13]. In order to ensure further improvement of the QWIP technology, primarily by using novel structures and material systems, a thorough understanding of fundamental physical procesess in QWIPs, as well as a first principles simulation tool are neccesary.
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NIR Broadband LED. Si-Based MOEMS Filter. Diode Array

NIR Broadband LED. Si-Based MOEMS Filter. Diode Array

47. M. H. Shih, K. S. Hsu, Wan Kunag, Y. C. Yang, Y. C. Wang, S. K. Tsai, Y. C. Liu, Z. C. Chang, and M. C. Wu, "Compact optical curvature sensor with a flexible microdisk laser on a polymer substrate", Opt. Lett., 34, 2733-2735, 2009,09.(SCI) 48. Wei-Hsun Lin, Chi-Che Tseng, Kuang-Ping Chao, Shih-Yen Lina*, Meng-Chyi

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Controlling the optical properties of a laser pulse at λ = 1.55μm in InGaAs\InP double coupled quantum well nanostructure

Controlling the optical properties of a laser pulse at λ = 1.55μm in InGaAs\InP double coupled quantum well nanostructure

In Fig. 1 we consider a compact double coupled quantum well nanostructure which is fabricated using InGaAs/ InP nanostructures in material grown by an attractive growth technique i.e. organometallic vapor phase epi- taxy (OMVPE). The QWs consist of two periods of alternating 10 nm InGaAs and 10 nm InP layers. The sample can be grown in a horizontal OMVPE system at atmospheric pressure. The growth chamber should contain a system that allows the growth of a QW as narrow as 10 A° with an average roughness of half the lattice constant of InGaAs. Typical growth rates are 10 A° ∕s for lnGaAs and 5 A° ∕s for InP [44]. An inco- herent pumping field and weak probe field are ap- plied to first quantum well (QW 1 ). According to the
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Threshold characteristics and intensity fluctuations of lasers with excess quantum noise

Threshold characteristics and intensity fluctuations of lasers with excess quantum noise

In lasers with nonorthogonal transverse eigenmodes the spontaneous-emission noise in the laser mode is enhanced by the transverse excess-noise factor, or K factor @ 1–12 # . Ex- perimental values of transverse K factors realized in unstable cavities range from K 5 200 to 500 @ 2,6,7 # . The longitudinal K factor, which arises due to nonorthogonality of the longi- tudinal eigenmodes, usually stays close to unity @ 11,12 # . So far, all studies of the K factor, both theoretically and experi- mentally, have concentrated on its consequences for the laser phase noise. In this paper we investigate, both theoretically and experimentally, the appearance of K in the intensity noise. This automatically brings up the laser threshold char- acteristics, being intimately linked to intensity noise. In our analysis we include bad-cavity aspects since, in practical cases, excess noise occurs in lasers with relatively large losses, so that the cavity bandwidth often exceeds the gain bandwidth @ 13 # .
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