[19p-C309-1~16] 13.6 ナノ構造・量子現象・ナノ量子デバイス

▲ [19p-C309-1] [INVITED] Resonantly Excited Excitons for Second-Order Optical Non-Linearity and Realisation of a Broadly Tuneable THz Source and Absorption Spectrometer

〇Richard Hogg¹、Avan Majeed²、Pavlo Ivanov¹、Benjamin Stevens²、Edmund Clarke³、Iain Butler¹、David Childs¹、Osamu Kojima⁴ (1.James Watt School of Engineering, University of Glasgow, UK、2.EEE Department, University of Sheffield, UK、3.EPSRC National Epitaxy Facility, University of Sheffield, UK、4.Graduate School of Engineering, Kobe University, Japan)

キーワード：Resonant Excitonic, THz source, Tuneable

A broadly tunable THz source is realized via difference frequency generation utilising resonant excitation of GaAs/AlAs quantum well excitons at room temperature. Resonant excitation results in an enhancement to χ⁽³⁾. Symmetry breaking of the electronic wavefunctions is made by utilizing a built-in electric-field across a p–i–n junction, resulting in effective χ⁽²⁾ processes derived from χ⁽³⁾.
Nonlinear processes occur at ~4 W cm⁻² enabling area and power scaling of the THz emitter. Phase matching is realized laterally through normal incidence excitation, akin to two colour interference.
Collimated 130 mW continuous wave (CW) semiconductor lasers with ~1mm beam diameters are used, with one resonant with the heavy-hole exciton, whilst the other is tuned through the excitonic absorption bands.
A THz signal is generated from 0.2–6 THz and efficiencies of ~3 × 10^–5, realising ~9 μW of THz power.
We show transmission spectroscopy of atmospheric features, indicating ~20GHz linewidths.