T-shaped waveguides for quantum-wire intersubband lasers

Role of excited states for the material gain and threshold current density in quantum wire intersubband laser structures

“…Also Ref. 9 gives a comparison of their results to the waveguide properties of a quantum well system and also finds results in good agreement with Ref. 11.…”

“…[3][4][5] To this end quantum cascade structures with active regions consisting of quantum wires and quantum dots are studied theoretically as well as experimentally. [5][6][7][8][9] In this work we calculate the material gain and the threshold current density for quantum wire intersubband structures. The obtained results are applied to the quantum wire intersubband structure proposed in Ref.…”

T-shaped single-photon router

“…In this paper, we propose a single-photon routing scheme using a two-level system (TLS). Different from the studies in [20,21], where two infinite one-dimensional (1D) coupled-resonator waveguides (CRWs) form a X-shaped waveguide, we consider a slight structural variation of the two 1D CRWs, i.e., one 1D CRW is infinite and the other is semi-infinite, which form a T-shaped waveguide [22][23][24][25]. The systems studies here, could be implemented using, e.g., artificial atoms [26][27][28] coupled to superconducting circuits [29][30][31].…”

Interlevel Cascade Transition in Electrically Confined Quantum Wire Arrays

“…Quantum structures such as quantum dots (QDs) or wires (QWRs) have unique electronic and optical properties because of their multidimensional quantum confinement . For example, strongly nonlinear transport characteristics, such as Coulomb blockade and resonant tunneling, have been demonstrated in the low-dimensional structures. − A decrease of the nonradiative losses due to the reduced electron-longitudinal-optical-phonon (LO-phonon) scattering has also been shown in the quantum structures. , Because of their unique properties, quantum structures are very attractive for optoelectronic device applications. − The transport and photonic phenomena studies of quantum structures have resulted in the development of tunneling injection quantum dot lasers and quantum wire intersubband emitters and photodetectors. − Recently, the interlevel/intersublevel cascade transitions of carriers have also been studied and developed for terahertz quantum cascade laser applications. ,, Most experimental realizations of the quantum structures rely on physical material removal (etching), which produces inevitable structural damage and device performance degradation. , Other methods, such as self-assembled growth, have addressed this issue but result in limited size uniformity over large areas. , Electrical confinement methods, such as using multiple top metal gates to deplete the two-dimensional electron gas in a heterostructure, have been widely used to form low-dimensional structures. − However, the geometry of these ultrathin devices renders extremely small overlap to optical modes within the visible/infrared bands, and hence they have been mainly used for lateral transport studies and electronic devices. Forming vertical stacks of uniform quantum structures is an attractive method to increase the interaction between photons and electrons .…”