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PurposeIncorporating student voice to improve both academic and institutional performances is the contemporary innovative way to enhance and ensure quality in higher education. Higher education organizations are developing a culture and an encouraging environment for the students where they can express their opinions and be an integral part and partner of educational improvement process. The purpose of this paper is to explore students preferred learning and teaching methods for management education, to study current intended learning outcome and practiced teaching methods, to investigate prerequisites to implement students expected teaching methods in the college-level management education of National University.Design/methodology/approachNature of the study is exploratory and descriptive as well. Primary data were collected using focus group discussions, surveys conducted using structured and closed-ended questions and in-depth, face-to-face interviews employed to collect data from academic staff.FindingsThe key findings include the need for bringing changes in teaching techniques at college-level management education. Furthermore, the study has explored challenging issues which can hinder changes in teaching techniques.Practical implicationsThe study pointed to the need of including student voice to keep improving teaching techniques that can satisfy students' learning needs continuously.Originality/valueThe study adds the body of knowledge on incorporating student voice to improve the quality of higher education teaching techniques and in other services as well in Bangladesh.

A fully-functional photonic integrated circuit (PIC) platform with supporting active and passive components in the green part of the visible spectral regime is of significant research interest for next-generation optical systems. Here we design highly-integrated ∼3.5 mm long PICs at green wavelengths, which consist of on-chip GaAs-based near-infrared pump lasers, SiN-LiNbO3 hybrid waveguides and ring resonators for nonlinear frequency conversion. The waveguides in the PICs are designed to eliminate etching of LiNbO3, reducing fabrication challenges. Efficient wavelength of 1062 nm pump to 531 nm coherent light is achieved by employing modal phase matching. Unlike a quasi-phase matching technique, modal phase matching enables poling-free operation and further eases device fabrication with comparable performance in terms of second harmonic generation efficiency. The effective nonlinear mode-overlap factor between 1062-nm-TE00 and 531-nm-TE01 modes in the hybrid waveguide is calculated to be 26%. For robust on-chip light coupling between pump laser and waveguide, a calculated maximum coupling efficiency of −2.3 dB is achieved. The theoretical work presented is an initial step towards demonstrating complex non-telecom PICs which could offer a comprehensive range of photonic functionalities.

This Letter reports the growth, fabrication, and characterization of molecular beam epitaxy (MBE)-grown quaternary InAlGaAs/GaAs quantum dot (QD) lasers emitting at sub-900 nm. The presence of Al in QD-based active regions acts as the origin of defects and non-radiative recombination centers. Applying optimized thermal annealing annihilates the defects in p-i-n diodes, thus lowering the reverse leakage current by six orders of magnitude compared to as-grown devices. A systematic improvement in the optical properties of the devices is also observed in the laser devices with increasing annealing time. At an annealing temperature of 700°C for 180 s, Fabry–Pérot lasers exhibit a lower pulsed threshold current density at infinite length of 570 A/cm2.

Electrically-pumped AlGaN-based edge-emitting laser diodes with a buried tunnel junction (TJ) for sub-300 nm emission are designed in this paper. Hole injection is one of the major concerns for the design of ultraviolet (UV) lasers based on this material system. The use of a low-resistive TJ as an intracavity contact within the devices will offer an opportunity to replace highly resistive p- type AlGaN-based cladding and contact layers by their n- doped counterparts. This advanced polarization-engineered interband TJs will lead to improved hole injection and a significantly reduced threshold voltage. The thermal properties of the tunnel-injected devices are thoroughly studied theoretically. For the demonstration of continuous-wave operating lasers, possible improvements in terms of better thermal management of the device are also discussed. Our improved design allows CW-operating AlGaN lasers with a threshold current density of 220 mW, yielding a wall-plug efficiency of > 2.8%.

In this paper, we report a low-loss photonic integrated circuits (PICs) platform at blue wavelengths of the visible spectral regime. Silicon nitride (SiN) is a popular passive waveguide material due to its fabrication flexibility, CMOS compatibility and spectral transparency in this wavelength regime. For active devices including lasers, gallium nitride (GaN) and its alloys are considered. Several basic building blocks for the development of a complete integrated platform, including blue diode lasers, in-plane- and out-of-plane light couplers, as well as on-and off-chip coupling between these active and passive components are theoretically investigated. The proposed in-plane and out-of-plane architectures operate through edge- and vertical grating couplers (VGCs), respectively. With edge-coupling, large mode-mismatch between the GaN laser diode and SiN waveguide is alleviated through nanotapers on both the active and passive sections and the calculated peak coupling efficiency is achieved to be 74% at a wavelength of 450 nm. We also separately designed efficient VGCs for coupling light from standard, commercial, off-the-shelf fibers to the SiN chip, and edge couplers for fiber-chip coupling, exhibiting coupling efficiencies of 51% and 83%, respectively. For robust on-chip light-coupling between active and passive circuit elements, with relaxed alignment tolerances, two approaches, i.e., flip-chip based hybrid integration and evanescent coupling based heterogeneous integration are studied. Calculated maximum coupling efficiencies of 40% (−4 dB) are achieved for both the hybrid and heterogeneous schemes. The theoretical work performed is an initial step towards demonstrating complex blue PICs which could offer a comprehensive range of photonic functionalities.

We investigate the disorders of microring resonators caused by conventional microfabrication technologies. Our experimental and theoretical results help understand the degree of the disorders in a ring array and their impact on topological insulator lasers.

Ultra-violet (UV) light emitting diodes operating at 339 nm using transparent interband tunnel junctions are reported. Tunneling-based ultraviolet light emitting diodes were grown by plasma-assisted molecular beam epitaxy on 30% Al-content AlGaN layers. A low tunnel junction voltage drop is obtained through the use of compositionally graded n and p-type layers in the tunnel junction, which enhance hole density and tunneling rates. The transparent tunnel junction-based UV LED reported here show a low voltage drop of 5.55 V at 20 A/cm2 and an on-wafer external quantum efficiency of 1.02% at 80 A/cm2.

Due to its atomic thickness and insulating nature, hexagonal boron nitride (h-BN) is considered to be one of the most promising substrates and gate insulating materials for two-dimensional electronic devices. In this study, polarized Raman spectroscopy was employed to uncover the effects of polarized incident light on the optical properties of h-BN phonon modes. Our measured polarization-resolved Raman spectra indicate that the symmetrical nature and the broken symmetry of degenerate phonon modes from h-BN are induced by linearly and elliptically polarized light, respectively. Moreover, a helicity exchange was observed between the excitation of circularly polarized light and the resulting opposite circular polarization of scattered light from h-BN. The measured phenomena were modeled on the basis of Raman tensors and Jones calculus to eventually calculate the amplitude coefficients of two orthogonal in-plane phonon modes. Hence, our experimental study provides a holistic understanding of the vibrational modes in h-BN, which is expected to enhance the knowledge of physical mechanisms such as heat capacity and thermal and electrical conductivities of this layered material.

InAlGaAs/GaAs quantum dots (QDs) are grown by molecular beam epitaxy and subsequently characterized to achieve emission $\lt 1\ \mu$m. Growth parameters are optimized to grow a new generation of homogeneous quaternary QDs with a PL FWHM of $\sim 60\ \mathrm{meV}$ and a surface density of $\gt10^{10} \mathrm{~cm}^{-2}$.

Extensive post-growth microscopic and spectroscopic characterizations are performed to leverage true potentials of high-quality hexagonal boron nitride (h-BN). Compressive residual strain between h-BN and sapphire is estimated and corroborated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Raman spectroscopy also supported the result.

This experimental study reports the morphological and optical properties of self-organized quaternary InAlGaAs quantum dots (QDs) grown on GaAs substrates. Atomic force microscopy (AFM) revealed the presence of QDs and their geometry across the sample surface, while the optical properties were verified by photoluminescence (PL) spectroscopy. Temperature-dependent PL measurements were performed for a series of samples with different indium compositions. Unlike conventional quantum well materials, the change in PL peak positions in QD structures exhibits a non-monotonic exotic dependence on temperature. Our AFM data confirm a bimodal distribution of dot sizes as corroborated by calculated thermal activation energies. A rapid decrease in the PL signal at elevated temperatures suggests that thermionic emission and interface defects are the two dominant mechanisms of carrier escape and recombination in these QD structures. Such a quaternary QD-based active region is important for realizing next-generation diode lasers with an emission wavelength shorter than 1 μm.

In this work, we study thermal conductivity (k) of BC5, an ultra-hard diamondlike semiconductor material, using first-principles computations and analyze the effect of both isotopic disorder as well as length scale dependence. k of isotopically pure BC5 is computed to be 169 Wm- 1K-1 (along a-axis) at 300K; this high k is found to be due to the high frequencies and phonon group velocities of both acoustic and optical phonons owing to the light atomic mass of Carbon (C) and Boron (B) atoms and strong C-C and B-C bonds. We also observe a dominance of optical phonons (~ 54%) over acoustic phonons in heat conduction at higher temperatures (~500 K). This unusually high contribution of optical phonons is found to be due to a unique effect in BC5 related to a weaker temperature dependence of optical phonon scattering rates relative to acoustic phonons. The effect is explained in terms of high frequencies of optical phonons causing decay into other high frequency phonons, where low phonon populations cause the decay term to become insensitive to temperature. The effect further leads to high nanoscale thermal conductivity of 77 Wm-1K-1 at 100 nm length scale due to optical phonon meanfreepaths being in nanometer regime. These results provide avenues for application of BC5 in nanoscale thermal management., Comment: 14 pages and 14 figures

Nonlinear photonic integrated circuits at green wavelengths with on-chip pump lasers and hybrid waveguides are designed. The calculated nonlinear mode overlap factor and maximum laser-to-waveguide coupling efficiency are 26% and -2.3 dB, respectively.

Photonic integration of GaN and Si-SiN platforms at the shortest visible wavelength is reported. Maximum theoretical coupling efficiencies up to 51% and 24% for a vertical grating coupler (fiber-chip) and hybrid integration, respectively, are achieved.

Two-dimensional hexagonal boron nitride (h-BN) materials have garnered increasing attention due to its ability of hosting intrinsic quantum point defects. This paper presents a photoluminescence (PL) mapping study related to sub-bandgap-level emission in bulk-like multilayer h-BN films. Spatial PL intensity distributions were carefully analyzed with 500 nm spatial resolution in terms of zero phonon line (ZPL) and phonon sideband (PSB) emission-peaks and their linewidths, thereby identifying the potential quantum point defects within the films. Two types of ZPL and PSB emissions were confirmed from the point defects located at the non-edge and edge of the films. Our statistical PL data from the non-edge- and edge-areas of the sample consistently reveal broad and narrow emissions, respectively. The measured optical properties of these defects and the associated ZPL peak shift and line broadening as a function of temperature between 77° and 300° K are qualitatively and quantitatively explained. Moreover, an enhancement of the photostable PL emission by at least a factor of ×3 is observed when our pristine h-BN was irradiated with a 532 nm laser.

This paper aims to investigate how behavioral anomalies manipulate investors" cogent investment decisions into silly decisions and how investors" behavioral anomalies play an imperative role on investment decisions. Regression method was adopted to analyze and interpret investors" behavioral anomalies. The study highlights on how investors" behavioral anomalies (i.e. anchoring, conservatism, endowment, optimism and hindsight) influence investors" investment decisions. To conduct this study, researchers collected primary data from 120 investors under Dhaka Stock Exchange and Chottogram Stock Exchange using structured questionnaire. Conversely, secondary data were collected from different journal articles and books. Basically logistic regression technique was run using SPSS to analyze behavioral anomalies of investors in decision making. The results showed that behavioral anomalies were leading factors to contribute decision making process of investors in Bangladesh. The findings of this paper would help to understand common behavioral anomalies and their effect in investment decisions for the decision makers and researchers.

An inter-cavty contact single mode 850 nm VCSEL was fabricated with a graphene assisted self-assembly curved dielectric bubble Bragg mirror for the first time. Taking the advantage of graphene’s uniform low surface energy, the low cost dielectric bubble DBR (Si 3 N 4 /SiO 2 ) was deposited on top of the graphene/half-VCSEL structure via van der Waals Force (vdWF) without using any additional spacing elements and sacrificial layer release-etch process. The continuous-wave operating VCSELs with an aperture diameter of 7 μm exhibit single-mode output power of more than 1 mW with a slope efficiency of 0.2 W/A. The sidemode suppression ratios are >40 dB. This novel modification into the lasers can also be applied to a variety of other optoelectronic devices, such as resonance photodetecter and super narrow linewidth VCSEL.

We design and experimentally demonstrate two chip-scale and agile heterodyne optical phase-locked loops (OPLLs) based on two types of InP-based photonic-integrated coherent receiver circuits. The system performance of the first-generation OPLL was improved in terms of offset-locking range, and power consumption with the use of a power efficient and compact photonic-integrated circuit (PIC). The second-generation PIC consists of a 60-nm widely tunable Y-branch laser as a local oscillator with a 2 × 2 multimode interference (MMI) coupler and a pair of balanced photodetectors. This PIC consumes only 184-mW power in full operation, which is a factor of 3 less compared to the first-generation PIC. In addition, the sensitivity of these OPLLs was experimentally measured to be as low as 20 μw. A possible solution to increase the sensitivity of these OPLLs is also suggested.

Similar to the area of microelectronics, InP­based photonic integrated circuits (PICs) in the optical domain as a counterpart are also seeing a clear exponential development. This rapid progress can be defined by a number of active/passive components monolithically integrated on a single chip. Given the probability of achieving low-cost, compact, robust, and energy-efficient complex photonic systems, there have been significant achievements made in realizing relatively complex InP­PICs in recent years. The performance of these complex PICs is reaching a stage that can enable a whole new class of applications beyond telecom and datacom. A great deal of effort from both academia and industry has made the significant advances of this technology possible. This development has resulted in a positive and profound impact in many areas including sensing, medical diagnostics, metrology, and consumer photonics. This review paper will mainly discuss the recent, in particular since 2012, progress and findings obtained out of current academic and industry research activities for InP-PICs. Major emphasis will be given to the high-performance and complex PICs that have been reported by the scientific community in this time period. A prospect for further development of this photonic integration in InP-platforms is also briefly described.

The development of electrically pumped semiconductor diode lasers emitting at the ultraviolet (UV)-B and -C spectral bands has been an active area of research over the past several years, motivated by a wide range of emerging applications. III-Nitride materials and their alloys, in particular AlGaN, are the material of choice for the development of this ultrashort-wavelength laser technology. Despite significant progress in AlGaN-based light-emitting diodes (LEDs), the technological advancement and innovation in diode lasers at these spectral bands is lagging due to several technical challenges. Here, the authors review the progress of AlGaN electrically-pumped lasers with respect to very recent achievements made by the scientific community. The devices based on both thin films and nanowires demonstrated to date will be discussed in this review. The state-of-the-art growth technologies, such as molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD); and various foreign substrates/templates used for the laser demonstrations will be highlighted. We will also outline technical challenges associated with the laser development, which must be overcome in order to achieve a critical technological breakthrough and fully realize the potential of these lasers.

The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at 2.3 μm, 2.6 μm and 2.9 μm, are investigated. Temperature characterization techniques and measurements under hydrostatic pressure identify an Auger process as the dominant non-radiative recombination mechanism in these devices. The results are supplemented with hydrostatic pressure measurements from three additional type-I GaInAsSb lasers, extending the wavelength range under investigation from 1.85-2.90 μm. Under hydrostatic pressure, contributions from the CHCC and CHSH Auger mechanisms to the threshold current density can be investigated separately. A simple model is used to fit the non-radiative component of the threshold current density, identifying the dominance of the different Auger losses across the wavelength range of operation. The CHCC mechanism is shown to be the dominant non-radiative process at longer wavelengths (> 2 μm). At shorter wavelengths (< 2 μm) the CHSH mechanism begins to dominate the threshold current, as the bandgap approaches resonance with the spin-orbit split-off band.

Ultra-compact, widely-tunable and low-power InP­based four-section coupled-cavity lasers are designed and analyzed. Two Fabry–Perot cavities of unequal lengths, each containing an amplifier and a phase­tuning section, are coupled together through low-loss Bragg grating. The theoretical analysis of such multisection lasers starts with calculating the poles of a linear transfer function of the entire resonator in order to obtain resonant wavelengths and wavelength-dependent threshold gains. The differential quantum efficiency and the power-current characteristics are then calculated to evaluate the laser performance. The effectiveness of the design procedure is verified by the experimental and proof­of-principle demonstration using simplified three-section lasers. Devices exhibit single-mode operation with a side-mode suppression ratio of over 24 dB and tuning range of 11.2 nm. These telecom-suitable lasers can be used as on-chip local oscillators in low-power integrated optical coherent receivers.

We report the design of electrically-pumped high-power vertical-external-cavity surface-emitting lasers emitting at the mid-wave infrared wavelength regime. The device is designed with a monolithic configuration that can provide multiwatts of continuous-wave output power in a single transverse mode with an excellent beam quality.

Recently, highly-integrated optical phase-locked loops (OPLLs) have been demonstrated for a number of potential applications including coherent optical communications, light detection and ranging (LiDAR) and frequency metrology. Another particularly interesting application is an optical frequency synthesis (OFS) for which OPLL-based offset locking is recently considered to be one of the most attractive techniques. There have been extensive ongoing research efforts to develop low-cost, compact, robust and power-efficient OFS systems using this OPLL-based technology. In this talk, I will discuss about a power-efficient and highly-integrated photonic system, producing low phase-noise coherent optical signal with a wavelength range of 23 nm in the C-band. In fact, the experimental results on the recently-developed highly­integrated OFS based on OPLL technology will be presented. The system includes novel InP-photonic integrated coherent receiver circuits that consume record-low (approximately 184 mW) electrical power. By employing a combination of photonic and electronic integration, this low-cost highly-integrated InP-based OFS with low-energy consumption exhibits both compact size and exceptional stability. This work is a major step towards demonstration of the true chip-scale optical frequency synthesizer with programmable

This paper reports the recent progress on the development of GaSb-based vertical-cavity surface-emitting lasers (VCSELs) with a record-long emission wavelength of above 4 μm using type-II quantum wells. Mid-wave infrared (MWIR) spectral region, covering the 3-6 μm wavelength range, is technologically very interesting for enabling two major application areas such as sensing and defense/security. Among several types of diode lasers, electricallypumped continuous-wave operating VCSELs seem to be the most attractive choice owing to their low-power consumption, inherent longitudinal single-mode emission, and simple electro-thermal wavelength tunability. The applicability of MWIR VCSELs for these two major areas are also discussed in this paper. Single-mode low-power (a few mWs) VCSEL operating at room-temperature with reasonable tunability is essential for the sensing application. For the advanced military application, high optical power (with at least a few watts), high-efficiency and high-brightness (>1 W/mm2) MWIR lasers are important. Given that the MWIR wavelength regime is eye-safe and has a low-loss atmospheric window, the development of next-generation MWIR laser sources is currently in high demand.

We report on the dry etch process parameters and the associated etch rates for target and mask materials, as well as surface roughness in an inductively coupled plasma (ICP) for the (AlGaIn)(AsSb)-compounds. The essential chemistry is based on Cl2 with the addition of N2 for sidewall passivation. The optimized ICP etch process is capable of producing high aspect ratio structures with smooth sidewalls. In situ reflectance monitoring with a 670-nm-wavelength laser was used to enable stop-etching at a material interface with high accuracy. Given the additional need for highly selective wet chemical etchants in the fabrication of GaSb based electronic and optoelectronic devices, an extensive investigation was also performed to examine numerous etch solutions. These etchants were listed with etch rates, selectivities, and surface roughness in order to validate their suitability for intended applications. Despite the frequent use of GaSb or InAsSb materials for etch stop layers against each other, devices where their unique type-II broken bandgap alignment is undesired require new selective wet etchants between GaSb and AlGaAsSb with good selectivity. All of the wet chemical and dry etching processes described here were optimized using an n-type GaSb substrate.

Hexagonal boron nitride (h-BN) is considered as one of the most promising materials for next-generation quantum technologies. In this paper, we report bulk-like multilayer h-BN epitaxially grown using a carbon-free precursor on c-plane sapphire with a strong emphasis on material characterization and analysis. In particular, structural, morphological, and vibrational properties, and chemical bonding of such van der Waals materials are presented. Between as-grown h-BN and c-plane sapphire, a compressive residual strain induced by both lattice mismatch and thermal expansion mismatch is examined by both theoretical and experimental studies. Atomic force microscopy revealed and scanning electron microscopy supported the presence of wrinkles across the entire surface of the film, likely due to biaxial compressive strain further verified by Raman spectroscopy. Stacking orders in h-BN with a clearly layered structure were confirmed by high resolution transmission electron microscopy, showing that the films have crystallographic homogeneity. Chemical analysis of the as-grown films was done by x-ray photoelectron spectroscopy, which confirmed the formation of stoichiometric h-BN films with excellent uniformity. This wafer-scale chemical vapor deposition-grown layered h-BN with 2D morphology facilitates applications in the fields of quantum- and deep ultraviolet-photonics.

Tunnel junction devices grown monolithically by metal organic chemical vapor deposition were optimized for minimization of the tunnel junction voltage drop. Two device structures were studied: an all-GaN homojunction tunnel junction and a graded InGaN heterojunction-based tunnel junction. This work reports a record-low voltage drop in the graded-InGaN heterojunction based tunnel junction device structure achieving a de-embedded tunnel junction voltage drop of 0.17 V at 100 A/cm2. The experimental data were compared with a theoretical model developed through technology computer-aided design (TCAD) simulations that offer a physics-based approach to understanding the key components of the design space, which lead to a more efficient tunnel junction.

We carefully investigate three important effects including postgrowth activation annealing, delta (δ) dose and magnesium (Mg) buildup delay as well as experimentally demonstrate their influence on the electrical properties of GaN homojunction p–n diodes with a tunnel junction (TJ). The diodes were monolithically grown by metalorganic chemical vapor deposition (MOCVD) in a single growth step. By optimizing the annealing parameters for Mg activation, δ-dose for both donors and acceptors at TJ interfaces, and p +-GaN layer thickness, a significant improvement in tunneling properties is achieved. For the TJs embedded within the continuously-grown, all-MOCVD GaN diode structures, ultra-low voltage penalties of 158 mV and 490 mV are obtained at current densities of 20 A cm−2 and 100 A cm−2, respectively. The diodes with the engineered TJs show a record-low differential resistivity of 1.6 × 10−4 Ω cm2 at 5 kA cm−2.

A sidewall activation process was optimized for buried magnesium-doped p-GaN layers yielding a significant reduction in tunnel junction-enabled light emitting diode (LED) forward voltage. This buried activation enabled the realization of cascaded blue LEDs with fully transparent GaN homojunction tunnel junctions. The initial optimization of buried p-GaN activation was performed on PN junctions grown by metal organic chemical vapor deposition (MOCVD) buried under hybrid tunnel junctions grown by MOCVD and molecular beam epitaxy. Next the activation process was implemented in cascaded blue LEDs emitting at 450 nm, which were enabled by fully transparent GaN homojunction tunnel junctions. The tunnel junction-enabled multi-active region blue LEDs were grown monolithically by MOCVD. This work demonstrates a state-of-the-art tunnel junction-enabled cascaded LED utilizing homojunction tunnel junctions which do not contain any heterojunction interface.

This feature issue contains a series of papers that report the most recent advances in the field of mid-infrared light sources used for medical applications, including tissue imaging, reconstruction, excision, and ablation. Many biomolecular compounds have strong resonances in the mid-infrared region and medicine is ideally suited to exploit this. The precision, sterility, and versatility of light in mid-infrared is opening more opportunities and this feature issue captures some of the most exciting.

An indium phosphide photonic integrated circuit transmitter with integrated linewidth narrowing capability is demonstrated. Frequency discrimination is achieved with an asymmetric Mach-Zehnder interferometer.

While social platform and news portal play a big role in Internet today, it also becomes the valuable medium for public opinions. We want to perform sentiment analysis in these public opinions. Many works have been done on sentiment analysis in different sectors for English language. But works in Bengali language are limited to only Bengali corpus and micro-blogging. So we have targeted a special sector which is Bangladesh Cricket where people express their opinions in their native Bengali languages on social medias in every moment. So we have prepared a dataset of three sentiment classes about Bangladesh Cricket from real people sentiments. We have processed our dataset by removing unnecessary words from the Bengali texts. Then we have used TF-IDF Vectorizer for vectorization and the classifier Support Vector Machine to classify our data.