Resonant intersubband polariton-LO phonon scattering in an optically pumped polaritonic device

Abstract

We report experimental evidence of longitudinal optical (LO) phonon-intersubband polariton scattering processes under resonant injection of light. The scattering process is resonant with both the initial (upper polariton) and final (lower polariton) states and is induced by the interaction of confined electrons with longitudinal optical phonons. The system is optically pumped with a mid-IR laser tuned between 1094 cm -1 and 1134 cm -1 (=9.14 m and =8.82 m). The demonstration is provided for both GaAs/AlGaAs and InGaAs/AlInAs doped quantum well systems whose intersubband plasmon lies at 10 m wavelength. In addition to elucidating the microscopic mechanism of the polariton-phonon scattering, that is found to differ substantially from the standard single particle electron-LO phonon scattering mechanism, this work constitutes the first step towards the hopefully forthcoming demonstration of an intersubband polariton laser.

Evidence of Intersubband Linewidth Narrowing Using Growth Interruption Technique

“…The MQW structures used in this study were initially designed for the demonstration of intersubband polaritons in metal-insulator-metal (MIM) cavities [10,16]. They have been grown by molecular beam epitaxy on Semi-insulating GaAs.…”

“…Such polaritonic coherent emitter is based on final state stimulation, and it was proposed to exploit longitudinal optical (LO) phonon-polariton interaction as the main spontaneous scattering mechanism. The first study of phonon-polariton scattering was reported several years ago with electrically injected devices [9], and more recently phonon-polariton scattering mediated polaritonic emission was demonstrated under an optical pumping scheme [10]. The threshold intensity for final state stimulation can be estimated using the following expression:…”

“…N QW is the number of quantum wells, α i,f are the matter-part Hopfield coefficients of the initial and final polaritonic states, ω LO is the LO phonon frequency, f is a numerical factor summarizing the intrasubband nature of the scattering process, and L QW is the QW widths. A key aspect towards the demonstration of an intersubband (ISB) polaritonic laser is to reduce the lasing threshold intensity which is around 1 MW/cm 2 for a 36 QWs structure [10]. From the above expression, it appears that both polariton lifetime (upper and lower state) are a lever towards this goal.…”

III-V on CaF2: a possible waveguiding platform for mid-IR photonic devices

“…However, they are low enough to be tolerated for longer mid-IR [13]and THz wavelengths [14]. This confinement strategy, that is typically based on Au-Au thermocompression waferbonding, is amply used for active devices such THz lasers [15][16][17] and detectors [17][18][19], but also for mid-IR devices operating in the strong light-matter coupling regime [20][21][22].…”

Infrared intersubband detection and plasmonics with (Zn,Mg)O and (Cd,Zn)O compounds

“…Other phenomena that can be studied in the multiple quantum wells is the coupling of the intersubband transitions with light-matter excitations, such as LO phonons. This has been already studied in systems such as GaAs/AlGaAs and InGaAs/AlInAs, 178 where the interaction of LO phonons with the ISBTs in the ultra-strong coupling regime, shows optimistic values for the polariton lasing threshold intensity, revealed to be in the order of 70 kW cm -2 .…”