Quantum Wire Lasers Research Articles

Study of Multiple Quantum Wire Hg0.8Cd0.2Te/CdTe Laser

The optoelectronic properties of Hg0.8Cd0.2Te/CdTe quantum wire laser are investigated, with emphasis on the effect of wire width (W) and barrier width (B) on the optical confinement factor (Г), the optical threshold gain (gth ) and the effect number of well (Nw ) on the confinement factor have been calculated. The laser operation system has been studied in the two cases; the number of well (2 and 3). It found that in our theoretical study, the values affect the work of a multiple laser system operating a number of well 2 was (W= 65nm, B = 40 nm), the value of optical confinement factor equals (Г= 0.055) and the amount of optical threshold gain was (gth = 38 cm −1). Further, the suitable values for multi quantum wire system is running a number of well 3 was (W= 42 nm, B = 60 nm), optical confinement factor equal to (Г= 0.048) and the threshold gain (gth = 42 cm −1). Theoretically, the principle of operation of a laser device depends on the resonator, the effective medium, and the stimulated emission of light radiation which is represented the important process in the work of device. It is found that the effect of optical confinement factor causes an increase in the reflectivity of laser beam in the cavity therefore decrease in the amount of optical threshold gain, noted that the amount of reflection was installed to study the change of other electronic characteristics of the multiple quantum wire.

Research progress of low-dimensional semiconductor materials in field of nonlinear optics

Since the first ruby laser was invented, researchers have focused their attention on how to achieve a strong laser light source, which cannot be produced by the ordinary light sources. Since then, the rich and colorful characteristics of nonlinear optical materials have been discovered, such as the saturation absorption, reverse saturation absorption and nonlinear refraction. They are applied to optoelectronic devices, optical switching devices and optical communication. At the same time, with the increase of the requirements for device integration performance in industrial production, ordinary three-dimensional devices are difficult to meet the production requirements, and the advent of low-dimensional semiconductor devices effectively solves this problem. Therefore, the combination of nonlinear optics and low-dimensional semiconductor materials is a general trend. The emergence of quantum dots, quantum wire lasers, and amplifiers confirms this. In this paper, we summarize the frontier work on nonlinear optics by selecting several special low-dimensional structures and several materials, providing some references for future research. However, due to the fact that the instability and low filling ratio of low-dimensional materials remain to be improved, further relevant research is still required.

Mid-infrared emission in InxGa1−xAs/GaAs T-shaped quantum wire lasers and its indium composition dependence

In this work, the emission wavelength has been extended out to 1.3, 1.5, and 2.2 μm for InxGa1−xAs/GaAs T-shaped quantum wire (TQWR) using multi-band k.p model and variational formalism. We have investigated the impact of the indium composition on the performance of a series of TQWR through a calculation of the optical gain and transition energies. It is found that the optical gain and the emission wavelength are more influenced taking into account the effect of the indium concentration and persisted up at room temperature (RT). The results could open the way to the development of laser communication systems operating at long wavelengths and fabricated from TQWRs structure.

Laser Processing For Nanoscale Size Quantum Wires of AlGaAs/GaAs

In this work we investigate and calculate theoretically the variation in a number of optoelectronic properties of AlGaAs/GaAs quantum wire laser, with emphasis on the effect of wire radius on the confinement factor, density of states and gain factor have been calculated. It is found that there exist a critical wire radius (rc) under which the confinement of carriers are very weak. Whereas, above rc the confinement factor and hence the gain increase with increasing the wire radius.

An Optimized ICP Etching Process for Pyramidal C-QWIP FPAs

ABSTRACTWe developed an optimized inductively coupled plasma (ICP) etching process to produce GaAs pyramidal corrugated quantum well infrared photodetector focal plane arrays. A statistically-designed experiment was performed to optimize the etching parameters. The resulting parameters are discussed in terms of the effect on the etching rate and profile. This process uses a small amount of mask corrosion and the control of the etching mask gap to give a 45-50 degree V-groove etching profile, which is independent on the crystal orientation of GaAs. In the etching development, scanning electron microscope (SEM) was used to observe the surface morphology and the pattern profile. In addition, X-ray photoelectron spectroscopy (XPS) was utilized to obtain the elemental composition and the contamination of the etching surface. It is found that extremely small stoichiometric change and surface damage of the etching surface can be achieved while keeping relatively high etching rate and ~45 degree V-groove etching profile. This etching process is applied to the fabrication of pyramidal C-QWIP FPAs, which is expected to have better performance than the regular prism-shaped C-QWIPs according to electromagnetic (EM) modeling. The expected results will be verified by optical and electrical measurements. In addition to infrared detectors, this process technology can also be applied to GaAs V-groove solar cell, quantum wire light-emitting diodes, quantum wire lasers, and other GaAs –based devices.

Electronic Tuning of Intersubband Transition of Inverted Core-Shell Cylindrical Quantum Wire for Novel Lasing Performance

A novel quantum wire laser structure is presented by designing inverted core-shell cylindrical quantum wire using AlxGa1-xAs/GaAs type-I heterostructure. The energy eigenvalues with corresponding density of states are numerically computed using finite difference technique. Intersubband transition energies are computed considering the lowest three energy states only where material composition of core material is changed to observe the effect on it. Dimensional effect is also studied for suitability of application in case of optical tuning. This analysis is carried out by taking into consideration the conduction band discontinuity and effective mass mismatch at boundaries following BenDaniel duke boundary condition. Results reflect that accuracy of control can be achieved on lasing performance by combining the dimensional variation effect with material parameter adjustment.

Robust Carrier-Induced Suppression of Peak Gain Inherent to Quantum-Wire Lasers

Gain spectra modified by many-body Coulomb interactions were quantitatively calculated for one-dimensional (1D) quantum-wire lasers at various carrier densities and temperatures to investigate, in particular, robustness and 1D inherence of the gain suppression effect at the band edge. We found that the gain suppression at the band edge in the 1D case gets stronger at higher density, in a manner insensitive to temperature or spectral broadening, and results in a robust peak-gain bowing effect at all temperatures. The gain suppression is in stark contrast to the gain/absorption enhancement at the Fermi edge, which commonly occurs in 1D, 2D, and 3D and is temperature sensitive and quenches at higher temperatures. We numerically calculated gain spectra for various types of electron-hole interaction potentials and found that similar gain spectra are reproduced even when the original screened Coulomb potential is replaced by a simple contact-type potential, for which an analytical solution is available. The analysis clarified that the gain suppression effect at the band edge is a unique and inherent feature in 1D resulting from the 1D density of states.

Coulomb‐modulated gain spectra in current‐injection T‐shaped quantum‐wire lasers

AbstractWe measured gain spectra of highly uniform current‐injection T‐shaped quantum wire lasers and investigated the physics of gain‐spectral‐shape modulation due to strong Coulomb interactions by comparing current‐injection and optical‐pumping measurements and additional calculations including screened Coulomb interaction.We found remarkable features for current injection: redshifts and long high‐ and low‐energy tails of the gain peak. These characteristic current‐injection features were ascribed to band‐gap renormalization, state‐filling, and carrier‐carrier scattering inherent to charge‐imbalanced electron‐hole systems (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Temperature insensitivity of the threshold current density in exciton-dominated wide energy gap quantum wire lasers

We present simulations on temperature dependence of the threshold current density (J_th) in InGaN-AlGaN and ZnCdSe-ZnMgSSe quantum wire lasers having exciton transitions. We find that J_th in a quantum wire laser is insensitive to temperature variation when exciton binding energies are in the range of 30 to 50 meV. This behavior is similar to quantum dot lasers having free carrier transitions. We show that the temperature dependence of the threshold current density is greatly reduced in lasers having exciton transitions in comparison to the ones having free carrier transitions. The reduced dependence of J_th on the temperature is attributed to the inherent confinement of electron-hole pairs within the exciton radius along the wire axis, whereas the quantum wire cross section provides confinement of carriers in the plane perpendicular to the wire axis. The large exciton binding energies give rise to high exciton density of states and narrow spectral line width, thus confining the carriers into a pseudoquantum dot-like structure. The effect of exciton localization due to the randomness in quantum wire fabrication, causing exciton inhomogeneous line broadening, is also discussed.

Photonic-crystal microcavity laser with site-controlled quantum-wire active medium

Site-controlled quantum-wire photonic-crystal microcavity laser is experimentally demonstrated using optical pumping. The single-mode lasing and threshold are established based on the transient laser response, linewidth narrowing, and the details of the non-linear power input-output characteristics. Average-power threshold as low as approximately 240 nW (absorbed power) and spontaneous emission coupling coefficient beta approximately 0.3 are derived.

GaInAsP/InP Quantum Wire Lasers

Present status of GaInAsP/InP long-wavelength quantum wire lasers, fabricated by a method using electron beam exposure, dry etching, and two-step organometallic vapor-phase epitaxy, is described from aspects of low-damage interface formation and size uniformity of quantum wire structures. Even though superior lasing properties attributed to sharper gain spectrum over that of quantum well structure have not been realized yet, polarization anisotropic feature of the quantum wire structure and formation of good interfaces by this fabrication method were confirmed. Single-wavelength lasers consisting of quantum wire structure as the active and/or the passive regions have been realized as possible candidates for future integrated photonics.

Growth and Device Applications of GaAs and InGaAs Quantum Wires on Patterned Substrates

A GaAs/AlGaAs quantum wire (QWR) with optical characteristics superior to those of a quantum well (QWL) was realized by employing metal-organic chemical-vapor deposition (MOCVD) selective growth on a patterned substrate by using ow-rate-modulation epitaxy (FME) and tertiary butyl arsine (TBA) as a V element precursor. A narrow (25 10 nm2) InGaAs/InP QWR was also fabricated on a (311)A InP V-groove substrate by using hydrogen-assisted molecular-beamepitaxy (MBE) selective growth, the QWR exhibited enhanced negative di erential resistance e ects even at temperatures near room temperature. The lasing spectra of a Fabry-Perot QWR laser, together with the optical and electronic characteristics of these QWRs, indicate an extension of the coherent electron wave function along the QWR and the formation of sharp density states as a result of reduced dimensionality. As regards QWR devices, a QWR eld-e ect transistor (FET) was found to work as a highly sensitive photo-detector. This is because the QWR and the surrounding QWL work as a small charge-sensitive ampli er and a photo-absorbing region, respectively. A gain-coupled distributed feedback (DFB) laser was realized by using a high-density buried quantum wire (QWR) array, that restricted minority carrier di usion along the QWR within a ridge.

Progress in Epitaxial Growth and Performance of Quantum Dot and Quantum Wire Lasers

We report on interplay of epitaxial growth phenomena and device performance in quantum dot (QD) and quantum wire (QWW) lasers based on self-organized nanostructures. InAs QDs are the most explored model system for basic understanding of near-ideal QD devices. Vertically-coupled growth of QDs and activated phase separation allow ultimate QD wavefunction engineering enabling GaAs lasers beyond 1400 nm and polarization-insensitive optical amplification. A feasibility of QD semiconductor optical amplifiers at terabit frequencies using InAs QDs is manifested at 1300 and 1500 nm. 1250-1300 nm QD GaAs edge emitters and VCSELs operate beyond 10 Gb/s with ultimate temperature robustness. Furthermore, temperature-insensitive operation without current or modulation voltage adjustment at >20 Gb/s is demonstrated up to ~90 degC. Light-emitting devices based on InGaN-QDs cover ultraviolet (UV) and visible blue-green spectral ranges. In these applications, InN-rich nanodomains prevent diffusion of nonequilibrium carries towards crystal defects and result in advanced degradation robustness of the devices. All the features characteristic to QDs are unambiguously confirmed for InGaN structures. For the red spectral range InGaAlP lasers are used. Growth on misoriented surfaces, characteristic to these devices, leads to nano-periodi- cally-step-bunched epitaxial surfaces resulting in two principal effects: 1) step-bunch-assisted alloy phase separation, leading to a spontaneous formation of ordered natural super lattices; 2) formation of quantum wire-like structures in the active region of the device. A high degree of polarization is revealed in the luminescence recorded from the top surface of the structures, in agreement with the QWW nature of the gain medium. QD and QWW lasers are remaining at the frontier of the modern optoelectronics penetrating into the mainstream applications in key industries.

Analysis of Compressively Strained GaInAsP–InP Quantum-Wire Electro-Absorption Modulators

Performance of compressively strained (CS) GaInAsP-InP quantum-wire (QWR) electro-absorption modulators (EAMs) is theoretically studied using an eight-band kldrp model. An empirical relationship is proposed for the quantum-confined Stark shift in QWR EAMs. The accuracy of this relationship is verified by comparing with numerical data. The effects of the variation of different device parameters on the absorption spectra are investigated. The absorption peaks are found to be stronger in narrower QWRs with strain-compensating barriers. Comparison of the extinction ratio with that of similar quantum-well EAMs show that, in spite of the lower in-plane filling factor, QWR EAMs exhibit a higher extinction ratio. Effect of fluctuation of wire width on the absorption spectrum of QWRs has been studied. The proposed QWR EAMs are suitable for photonic integrated circuits (PICs) fabricated by electron-beam lithography, reactive-ion etching, and two-step epitaxial growth. Due to the nature of the integration in such structures, the QWR EAMs are not required to be polarization-insensitive. On the contrary, the QWR EAMs are naturally tuned to the polarization of the output of the CS QWR lasers, fabricated on the same PIC, leading to an enhancement of the absorption strength. Moreover, the QWR EAMs, integrated with QWR lasers, offer low insertion loss.

Exciton–biexciton-plasma crossover and formation of optical gain in quantum wires

T-shaped GaAs quantum-wire lasers were measured to study origin of laser gain and the exciton Mott transition in one dimension. Origin of laser gain was ascribed not to free excitons, or localized excitons, but to biexciton–exciton population inversion near the threshold, or to the electron–hole (e–h) plasma at a high-density regime well above the threshold. Systematic micro-PL study revealed that dominant PL evolves with e–h density from a sharp free-exciton peak, via a biexciton peak, to an e–h plasma PL band. These demonstrated important roles of biexcitons in the Mott transition and in the initial formation of optical gain. Comparison with microscopic theories raised a question for arguments based on large renormalized band-edge shift before the Mott transition.

Current-injection T-shaped quantum wire lasers with perpendicular doping layers operating at 100 K

We demonstrated lasing from current-injection T-shaped GaAs/AlGaAs quantum wire (T-wire) lasers with perpendicular p- and n-doping layers. The T-wire laser showed lasing between 5 and 110 K, and showed the optimal threshold current of 2.1 mA and differential quantum efficiency of 0.9% at 100 K. In microscopic-EL imaging measurements, we observed the emissions from the outside of optical core region, which indicated overflow of holes from the active region.

Electronic structure and efficient carrier injection in low-threshold T-shaped quantum-wire lasers with parallel p- and n-doping layers

We report on the electronic structure, efficient carrier injection, and quantitative lasing characteristics of T-shaped GaAs/AlGaAs quantum-wire-laser diodes with parallel p- and n-doping layers grown by a cleaved-edge-overgrowth method with molecular-beam epitaxy. Continuous single-mode lasing from the ground subband of the quantum wires was demonstrated between 30 and 70 K in laser diodes with high-reflectivity Au coating on both cavity facets. The lowest threshold of 0.27 mA and the highest differential quantum efficiency of 12% were achieved at 30 K. Micro-photoluminescence measurements demonstrated the high optical quality of the quantum wires with narrow linewidth of 0.9 meV and provided electronic structures of surrounding layers. Microscopic electroluminescence (EL) imaging measurements demonstrated the efficient carrier injection into the quantum wires at 30 K. These two factors, i.e., high material quality and efficient carrier injection, contribute to the low threshold current and high efficiency of the laser device. The result of EL imaging at 5 K indicates an inefficient carrier injection into the active region, which limits the operating temperature of the devices.

Quantum-wire laser keeps cool, a picosecond switchable-wavelength device, and more

Quantum-wire laser keeps cool, a picosecond switchable-wavelength device, and more

T-shaped GaAs quantum-wire lasers and the exciton Mott transition

T-shaped GaAs quantum-wire (T-wire) lasers fabricated by the cleaved-edgeovergrowth method with molecular beam epitaxy on the interface improved by agrowth-interrupt high-temperature anneal are measured to study the laser device physicsand fundamental many-body physics in clean one-dimensional (1D) systems. Acurrent-injection T-wire laser that has 20 periods of T-wires in the active regionand a 0.5 mm long cavity with high-reflection coatings shows a low thresholdcurrent of 0.27 mA at 30 K. The origin of the laser gain above the lasing threshold isstudied with the high-quality T-wire lasers by means of optical pumping. The lasingenergy is about 5 meV below the photoluminescence (PL) peak of free excitons,and is on the electron–hole (e–h) plasma PL band at a high e–h carrier density.The observed energy shift excludes the laser gain due to free excitons, and itsuggests a contribution from the e–h plasma instead. A systematic micro-PL studyreveals that the PL evolves with the e–h density from a sharp exciton peak, via abiexciton peak, to an e–h-plasma PL band. The data demonstrate an importantrole of biexcitons in the exciton Mott transition. Comparison with microscopictheories points out some problems in the picture of the exciton Mott transition.

(InP) 5/(Ga 0.47In 0.53As) 4 short-period superlattices waveguides for InAs quantum wires lasers

Waveguides formed by (InP) 5/(Ga 0.47In 0.53As) 4 short-period superlattices (SPSL) have been grown and characterized for their use as waveguides in InAs self-assembled quantum wires (QWR) lasers. Atomic force microscopy has been used to characterize both the SPSL and the QWR morphology quality. It is demonstrated that the shape of the QWR strongly depends on the roughness of the SPSL surface and that an atomically flat surface is necessary to obtain a uniform QWR size and shape morphology. Photoluminescence (PL) spectroscopy is also employed as a feedback to achieve the optimum growth parameters in order to obtain high-quality QWR confined by SPSL.