Interaction of Strong Single-Cycle Terahertz Pulses with Semiconductor Quantum Wells

Danielson, J.R.; Lee, Yun Shik; Prineas, J. P.; Steiner, J. T.; Kira, M.; Koch, S. W.

doi:10.1103/physrevlett.99.237401

Cited by 118 publications

(52 citation statements)

References 30 publications

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“…The advent of sources of intense terahertz electromagnetic radiation enables the study of semiconductors in a regime where time-dependent perturbation theory fails completely. Exciting new quantum coherent phenomena emerge, including the dynamical Franz-Keldysh effect [6,7], non-linear excitonic effects [8][9][10][11], and highorder sideband generation [12][13][14]. High-order sideband generation is a cousin of high-order harmonic generation from atoms in intense laser fields [15][16][17].…”

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confidence: 99%

Terahertz Electron-Hole Recollisions inGaAs/AlGaAsQuantum Wells: Robustness to Scattering by Optical Phonons and Thermal Fluctuations

et al. 2013

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Electron-hole recollisions are induced by resonantly injecting excitons with a near-IR laser at frequency fNIR into quantum wells driven by a 10 kV/cm field oscillating at fTHz = 0.57 THz. At T = 12 K, up to 18 sidebands are observed at frequencies f sideband = fNIR + 2nfTHz, with −8 ≤ 2n ≤ 28. Electrons and holes recollide with total kinetic energies up to 57 meV, well above the ELO = 36 meV threshold for longitudinal optical (LO) phonon emission. Sidebands with order up to 2n = 22 persist up to room temperature. A simple model shows that LO phonon scattering suppresses but does not eliminate sidebands associated with kinetic energies above ELO.The interaction of electrons and holes in semiconductors has long been a rich area of study in physics. In most cases, the electron and hole are treated as point particles within the effective mass approximation [1]. In this approximation, the effects of the lattice are parametrized by the dielectric constant of the semiconductor and the effective masses of the electrons and holes. Calculations based on the effective mass approximation successfully predict, for example, the binding energies and the frequencies of internal transitions of impurity-bound electrons and excitons in GaAs [2] and in GaAs/AlGaAs quantum wells [3][4][5]. The effective mass approximation, however, belies the rich complexity of the microscopic physics. In GaAs, for example, ground-state excitons are collective excitations of more than 10 5 atoms in the crystal. The advent of sources of intense terahertz electromagnetic radiation enables the study of semiconductors in a regime where time-dependent perturbation theory fails completely. Exciting new quantum coherent phenomena emerge, including the dynamical Franz-Keldysh effect [6,7], non-linear excitonic effects [8][9][10][11], and highorder sideband generation [12][13][14]. High-order sideband generation is a cousin of high-order harmonic generation from atoms in intense laser fields [15][16][17]. Excitons are created by a near-infrared laser in a semiconductor driven by an intense terahertz field. The terahertz field ionizes the exciton into an electron and a hole that it then pulls apart and smashes back together. Upon recollision, the electron and hole can recombine across the band gap with the acquired kinetic energy carried off by light with frequency above that of the near-IR laser.In this Letter, we report that the electron-hole recollision process-which, in its theoretical descriptions to date has been treated as a purely ballistic process-is surprisingly robust against scattering. We report electronhole recollisions both with kinetic energy well above the threshold for emission of a longitudinal optical (LO) phonon and at room temperature. We model our results by treating the electron-hole pair as a single particle with the appropriate reduced mass subject to dephasing and LO phonon scattering.Two quantum well (QW) samples with 20 QW repetitions were studied. Both samples were grown on semiinsulating GaAs substrates by molecular beam epitax...

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Terahertz Electron-Hole Recollisions inGaAs/AlGaAsQuantum Wells: Robustness to Scattering by Optical Phonons and Thermal Fluctuations

et al. 2013

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“…[4][5][6][7] While laser-based THz radiation at frequencies 20-100 THz has been generated by difference frequency mixing in nonlinear inorganic crystals, 8 the generation of highpower THz single-cycle pulses above 1 MV/cm in the range of 0.1-10 THz, the so-called THz gap, is still challenging due to the limited availability of appropriate THz emitters. 9 Only recently, single-cycle pulses at 0.8 THz central frequency of 1 MV/cm have been demonstrated by optical rectification (OR) in LiNbO 3 (Ref.…”

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Strong-field single-cycle THz pulses generated in an organic crystal

Hauri

Ruchert

Vicario

et al. 2011

Applied Physics Letters

199

133

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We present high-power single-cycle carrier-envelope phase locked THz pulses at a central frequency of 2.1 THz with MV/cm electric field strengths and magnetic field strengths beyond 0.3 T. The THz radiation is generated by optical rectification in an organic salt crystal 4-N,N-dimethylamino-4′-N′-methyl stilbazolium tosylate called DAST pumped with the signal wavelength of a powerful optical parametric amplifier. Conversion efficiencies of more than 2% are reported.

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“…Strong-field terahertz (THz) sources hold promise for enabling myriads of novel applications. They possess intense electric and magnetic fields at frequencies which are particularly amenable to studies of condensed matter dynamics [1][2][3], manipulation of molecules [4], highharmonic generation (HHG) [5], and compact chargedparticle acceleration [6][7], among others. Therefore, there is a great need for the development of robust and efficient strong-field THz sources.…”

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Terahertz generation in lithium niobate driven by Ti:sapphire laser pulses and its limitations

Carbajo

Ravi

et al. 2014

Opt. Lett.

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We experimentally investigate the limits to 800 nm-to-terahertz (THz) energy conversion in lithium niobate at room temperature driven by amplified Ti:Sapphire laser pulses with tilted-pulse-front. The influence of the pump central wavelength, pulse duration, and fluence on THz generation is studied. We achieved a high peak efficiency of 0.12% using transform limited 150 fs pulses and observed saturation of the optical to THz conversion efficiency at a fluence of 15 mJ/cm 2 . We experimentally identify two main limitations for the scaling of optical-to-THz conversion efficiencies: (i) the large spectral broadening of the optical pump spectrum in combination with large angular dispersion of the tilted-pulse-front and (ii) free-carrier absorption of THz radiation due to multi-photon absorption of the 800 nm radiation. Strong-field terahertz (THz) sources hold promise for enabling myriads of novel applications. They possess intense electric and magnetic fields at frequencies which are particularly amenable to studies of condensed matter dynamics [1][2][3], manipulation of molecules [4], highharmonic generation (HHG) [5], and compact chargedparticle acceleration [6][7], among others. Therefore, there is a great need for the development of robust and efficient strong-field THz sources.These sources are predominantly accelerator-based facilities (delivering up to 100 µJ THz energy) [8,9] or ultrafast laser-based table-top systems [10]. Laboratory scale systems are of particular interest due to accessibility and relatively low cost. In this category, laser-induced air/gas plasmas (delivering up to 5 µJ THz energy) [11] and optical rectification (OR) of infrared (IR) pulses in nonlinear optical crystals (delivering up to 0.4 mJ THz energy) [12] have emerged as the most common methods of all THz generation modalities. The highest optical-toTHz conversion efficiencies (henceforth referred to as conversion efficiency) in excess of 1% at room temperature have been achieved by OR employing angularly dispersed femtosecond IR pump pulses in lithium niobate [13,14]. As a result, these systems are especially relevant to generating mJ-level THz pulses [12]. In this approach, angular dispersion is introduced to compensate for the large difference in refractive indices between IR and THz frequencies by forming a tilted-pulse-front. The generated THz then propagates perpendicular to this tilted-pulsefront and phase matching is achieved in a non-collinear configuration. OR systems based on lithium niobate are powered predominantly by sources in the 1 µm and 800 nm wavelength regions. While the former yields much higher conversion efficiencies, today, 800 nm sources based on Ti:Sapphire systems prevail in ultrafast laser technology as the most accessible and widely employed sources. Consequently, exploring the limits to achievable conversion efficiency is a great value in the pursuit of accessible high-energy THz sources.In this paper we extensively investigate the limits of conversion efficiency with 800 nm systems through a systemati...

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Interaction of Strong Single-Cycle Terahertz Pulses with Semiconductor Quantum Wells

Cited by 118 publications

References 30 publications

Terahertz Electron-Hole Recollisions inGaAs/AlGaAsQuantum Wells: Robustness to Scattering by Optical Phonons and Thermal Fluctuations

Terahertz Electron-Hole Recollisions inGaAs/AlGaAsQuantum Wells: Robustness to Scattering by Optical Phonons and Thermal Fluctuations

Strong-field single-cycle THz pulses generated in an organic crystal

Terahertz generation in lithium niobate driven by Ti:sapphire laser pulses and its limitations

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