Photonic Crystal Circular Nanobeam Cavity Laser with Type-II GaSb/GaAs Quantum Rings as Gain Material

Abstract

The optical emission from type-II semiconductor nanostructures is influenced by the long carrier lifetime and can exhibit remarkable thermal stability. in this study, utilizing a high quality photonic crystal circular nanobeam cavity with a high quality factor and a sub-micrometer mode volume, we demonstrated an ultra-compact semiconductor laser with type-ii gallium antimonide/gallium arsenide quantum rings (GaSb/GaAs QRs) as the gain medium. the lasing mode localized around the defect region of the nanobeam had a small modal volume and significant coupling with the photons emitted by QRs. it leads the remarkable shortening of carrier lifetime observed from the time-resolved photoluminescence (tRpL) and a high purcell factor. furthermore, a high characteristic temperature of 114 K was observed from the device. The lasing performances indicated the type-II QRs laser is suitable for applications of photonic integrated circuit and bio-detection applications.Semiconductor nanostructures based on gallium antimonide (GaSb) and gallium arsenide (GaAs) have aroused considerable research interest because of their type-II band alignments and distinct material properties from those of the known InAs/GaAs based systems 1,2 . The staggered type-II band alignment leads to spatially indirect transitions of carriers and several unique optical properties such as the long carrier lifetime, wide coverage of emission wavelengths in the infrared (IR) regime, and stable emission less sensitive to the thermal effect. The optical characteristics and carrier dynamics of GaSb/GaAs quantum dots (QDs) systems have been investigated 3-8 and utilized in various applications including lasers 9-13 , optical memories 14-18 , bioimages 19 , and light emitting diodes 20,21 . However, the spatially indirect transition of carriers in type-II band structures also lowers the radiative recombination probability and hence limits the corresponding emission efficiency 22 . Recently, with the optimized source flux ratio during molecular beam epitaxy (MBE) 23-27 , the growth of GaSb/GaAs quantum rings (QRs) has been demonstrated, and these nanostructures exhibit the more intense photoluminescence (PL) than GaSb/GaAs QDs do 28,29 . The QRs have the less abrupt GaSb/GaAs interfaces but larger surface area than QDs do, which improve the wave function overlap between electrons and holes and therefore boost up the radiative recombination significantly 30 . The luminescence from coupled GaSb/GaAs QRs at room temperature can be even comparable to that of type-I InAs QDs 29 , indicating that GaSb QRs might play a role in the applications of laser diodes and light-emitting diodes 28,31 .Recently the novel low-dimensional gain materials such as QW 32,33 , QD 12,13,[34][35][36][37][38] , and two-dimensional materials 39,40 were integrated with compact optical cavities for lasing devices under continuous-wave 32,35,36,40 and electrical injection pumping 34,37,38 conditions. In this study, we demonstrated a photonic crystal (PhC) circular nanobeam defect cavity 41 laser...

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“…Therefore, we obtained an experimental Purcell factor, F=11.36 by using Eq. 5, which is comparable to previously reported values 59 .…”

“…The Purcell factor (F) is a measure of the enhancement of the spontaneous emission rate of a quantum emitter in the presence of a cavity, and it is de ned as the ratio of the emission rate (or radiative decay rate) in the cavity ( ) to the emission rate in free space ( ) 58, 59 . Mathematically, the Purcell factor is given by: 3…”