Lasing from a single-quantum wire

Abstract

A laser with an active volume consisting of only a single quantum wire in the 1-dimensional (1-D) ground state is demonstrated. The single wire is formed quantum-mechanically at the T-intersection of a 14 nm Al0.07Ga0.93As quantum well and a 6 nm GaAs quantum well, and is embedded in a 1-D single-mode optical waveguide. We observe single-mode lasing from the quantum wire ground state by optical pumping. The laser operates from 5 to 60 K, and has a low threshold pumping power of 5 mW at 5 K. PACS numbers: (78.67.Lt, 78.45.+h, 73.21.Hb, 42.55.Px.) A quantum wire laser is a novel semiconductor laser based on a 1-dimensional (1-D) active region such that the electron and hole carriers are allowed to move only in that one direction. In contrast, more familiar semiconductor lasers are 3-D double-hetero-structure lasers and 2-D quantum well lasers. Because the 1-D density of states (DOS) becomes more enhanced at the bottom of its band edge than the 2-D or 3-D DOS, a quantum wire laser is expected to show improvement in lasing performance [1, 2, 3, 4].However, fabrication of a single quantum wire that lases from the lowest quantum state of the wire is difficult. Indeed all quantum wire lasers so far reported are either multiple-wire lasers [5,6,7,8,9,10], which have many quantum wires in the active region, or they are wide single-wire lasers which lase only in their excitedsubband states [11,12,13]. The excited-state lasing is typically characterized by a lasing energy above the energy of ground-state spontaneous emission at low pump levels. Since excited subbands allow motion of carriers in directions perpendicular to the axis of the wire, such excited-state wire lasing is not expected to have 1-D characteristics.In this paper, we demonstrate a single quantum wire laser with only one 1-D subband, and observe stable single-mode lasing from this ground state subband of our quantum wire.The single quantum wire laser is fabricated by an advanced crystal growth method called cleaved-edge overgrowth with molecular beam epitaxy (MBE) [14], in which two MBE growth steps are separated by an in situ wafer cleave. In the first MBE growth, we successively grew at 600 o C on a non-doped (001) GaAs substrate, a 500 nm GaAs buffer layer, a 1.5 µm Al 0.5 Ga 0.5 As a) Electronic mail: haya@issp.u-tokyo.ac.jp cladding layer, a 250 nm Al 0.35 Ga 0.65 As barrier, a 14 nm Al 0.07 Ga 0.93 As quantum well (stem well), a 250 nm Al 0.35 Ga 0.65 As barrier, 1.5 µm Al 0.5 Ga 0.5 As cladding layer, and a 6.5 µm GaAs cap layer. Then, we cleaved the wafer in the MBE chamber, and grew at 490 o C on the newly exposed (110) edge, a 6 nm GaAs quantum well (arm well), a 10 nm Al 0.5 Ga 0.5 As barrier, a 111 nm Al 0.1 Ga 0.1 As core layer, a 960 nm Al 0.5 Ga 0.5 As cladding layer, and a 10 nm GaAs cap layer. After the growth of the arm well, we interrupted growth and annealed the GaAs surface for 10 minutes at 600 o C [15]. Figure 1 shows a schematic cross-sectional view of the single quantum wire laser structure. At a T-shaped inter-

Self-Organized GaN Quantum Wire UV Lasers

“…Almost all quantum wire lasers reported thus far have been made through molecular beam epitaxy, microfabrication, and lithographical techniques on the GaAs/InP system for visible light emission. 1,3,4 Significant technical hurdles exist for the direct fabrication of GaN-based quantum wire lasers, despite their obvious potential in short-wavelength photonic devices and hightemperature/high-power optoelectronics. [5][6][7][8] Herein, we report the first realization of self-organized, monolithically singlecrystalline GaN/Al x Ga 1-x N (x ) 0.75) core-sheath onedimensional (1D) nanostructures.…”

Nanostructures in GaAs fabricated by molecular beam epitaxy

“…The solid line is the resistance expected for the various wires based on a calculation of the wire area and the measured 2D resistivities of AuPd films code-posited with the wires. The generally good agreement between the two establishes that we are repeatedly able to make metal wires with uniform cross sections as small as 15 nm 2 , which corresponds to the designed wire width of 3 nm. The inset of Figure 7 demonstrates that at the smallest wire diameters achieved with this technique, we already see significant quantum corrections to the wire conductivity at 4.2 K. Shown here is magnetoresistance data for AuPd metal wires 88 nm (top), 20 nm (center), and 5 nm (lower) in diameter.…”

Thermoelectric power in carbon nanotubes and quantum wires of nonlinear optical, optoelectronic, and related materials under strong magnetic field: Simplified theory and relative comparison

“…An enormous range of important applications in the quantum regime, together with a rapid increase in computing power, have generated much interest in the analysis of nanostructured devices for investigating their properties. [26][27][28][29] Examples of such new applications include various quantum wires, [30][31][32][33][34] quantum resistors, 35 resonant tunneling diodes and band filters, 36,37 quantum switches, 38 quantum sensors, [39][40][41] quantum logic gates, 42,43 quantum transistors and subtuners, [44][45][46] heterojunction field-effect transistors ͑FETs͒, 47 high-speed digital networks, 48 high-frequency microwave circuits, 49 optical modulators, 50 optical switching systems, 51 and other devices. Though extensive work has already been done for both the CNTs and QWs, it appears from the literature that the TPM for both the CNTs and the QWs has yet to be investigated in detail.…”