“…The value of 0.094 (94 × 10 –3 ) means that 94 photons out of 10 3 spontaneously emitted photons are coupled to a lasing mode and serve as a ‘seed’ for oscillation [ 63 ]. That is to say, a large β indicates that more spontaneous photons can be incorporated into the lasing mode, thus reducing the threshold current [ 64 ]. Fig.…”
Room temperature low threshold lasing of green GaN-based vertical cavity surface emitting laser (VCSEL) was demonstrated under continuous wave (CW) operation. By using self-formed InGaN quantum dots (QDs) as the active region, the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm−2, the lowest ever reported. The QD epitaxial wafer featured with a high IQE of 69.94% and the δ-function-like density of states plays an important role in achieving low threshold current. Besides, a short cavity of the device (~ 4.0 λ) is vital to enhance the spontaneous emission coupling factor to 0.094, increase the gain coefficient factor, and decrease the optical loss. To improve heat dissipation, AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding. The results provide important guidance to achieving high performance GaN-based VCSELs.
“…The value of 0.094 (94 × 10 –3 ) means that 94 photons out of 10 3 spontaneously emitted photons are coupled to a lasing mode and serve as a ‘seed’ for oscillation [ 63 ]. That is to say, a large β indicates that more spontaneous photons can be incorporated into the lasing mode, thus reducing the threshold current [ 64 ]. Fig.…”
Room temperature low threshold lasing of green GaN-based vertical cavity surface emitting laser (VCSEL) was demonstrated under continuous wave (CW) operation. By using self-formed InGaN quantum dots (QDs) as the active region, the VCSEL emitting at 524.0 nm has a threshold current density of 51.97 A cm−2, the lowest ever reported. The QD epitaxial wafer featured with a high IQE of 69.94% and the δ-function-like density of states plays an important role in achieving low threshold current. Besides, a short cavity of the device (~ 4.0 λ) is vital to enhance the spontaneous emission coupling factor to 0.094, increase the gain coefficient factor, and decrease the optical loss. To improve heat dissipation, AlN layer was used as the current confinement layer and electroplated copper plate was used to replace metal bonding. The results provide important guidance to achieving high performance GaN-based VCSELs.
“…The distinct spatial capability in the spatial graph grammar makes the SGG an ideal specifying formalism to interpret abstract painting styles and graphic designs. SGG has been applied to mobile interface adaptation [31], UML diagram interpretation [32], reverse engineering [33] and Web interface interpretation [34].…”
Section: Toward More Systematic and Creative Approachesmentioning
Ma ny argue that with the rapid advances of modern technology, particularly digital display and computer graphics, digital art is more expressive than traditional visual art. This increased expressive power, compounded with highly advanced artifi cial intelligence, has created tremendous opportunities for the realization of computational aesthetics and even simulated creativity [1]. If the potential of computational aesthetics is achieved, we would see a profound impact on various application domains where computer technology has traditionally played only an assistive role, such as graphic and industrial design. This is not to advocate the possibility of replacing human creativity with computational creativity; rather, the advancement of computational aesthetics would further extend human creativity by providing inspiration to artists and graphic/industrial designers.
I. emergIng new dIsCIplInes In Arts And ComputIngWhen combining visual art with digital technology, two lines of questioning tend to emerge. On the one hand are questions such as: "How can the computer automatically generate various forms of visually aesthetic expressions?" On the other hand, some ask: "How can the theory and techniques of traditional visual art help beautify modern technology outputs and products and enhance their usability?" Addressing such questions, two interdisciplinary areas have emerged in recent years: computational aesthetics and aesthetic computing [2]. Both computational aesthetics and aesthetic computing aim at bridging computer science, philosophy, cognitive science and the fi ne arts through analytic and synthetic investigation. Figure 1 illustrates a conceptual map of the relationships between various computer science areas (in rectangular nodes) and arts (in oval nodes), moving from theories to applications. The dotted arrows in Fig. 1 help to conceptualize that computational aesthetics aims at answering the fi rst question above, that is, "How can the computer automatically generate various forms of visually aesthetic expressions?" In other words, computational aesthetics investigates how modern technology helps the arts. This technology in fact serves to create tools that can enhance the expressive power of visual art and heighten human understanding of aesthetic evaluation, perception and meaning. In the reverse direction, illustrated by the dashed arrows in Fig. 1, aesthetic computing addresses the second question-"How can the theory and techniques in the traditional visual arts help beautify modern technology outputs and products and enhance their usability?" This issue includes the aesthetic design of computer algorithms, simulation, visualization, human-machine interfaces and high-tech products, so that users are highly engaged and thus usability is enhanced. An interesting example of aesthetic computing is the application of Kandinsky's aesthetics to Java programming [3]. In 2006, Malina [4] highlighted the aesthetic computing activities published in Leonardo over the previous 40 years.We have previously ex...
The control of spontaneous emission is one of important characteristics of a planar microcavity. The integrals in the spherical coordinate for TE and TM modes spontaneous emission spectra of a quantum well (QW) embedded in a planar microcavity are derived with new variables dependent on wavelength and Taylor series including the two polarizations of the vacuum field. The approximate expressions of spontaneous emission in QW planar microcavities are obtained. The approximate results show that spontaneous emission spectra agree well with that in the numerical integral for planar semiconductor microcavities, in which Fermi-Dirac distribution functions of electrons and holes are considered. The main contribution to the spontaneous emission, radiated into all direction, has been found.
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