Calculation of the nonlinear free-carrier absorption of terahertz radiation in semiconductor heterostructures

Zhang, Chaofeng; Cao, Jiafeng

doi:10.1103/physrevb.70.193311

Cited by 6 publications

(2 citation statements)

References 17 publications

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“…Free carrier absorption (FCA), this mechanism mainly occurs in semiconductor nonlinear materials. [47,48] After the electrons in the valence band absorb incident photons and transition to the conduction band to generate carriers, these electrons (holes) are excited by the additionally absorbed photons to a higher state in the conduction band. This mechanism is similar to the mechanism of RSA, with the increase of light intensity, the nonlinear absorption increases.…”

Section: Free Carrier Absorptionmentioning

confidence: 99%

Third-order nonlinear optical properties of graphene composites: A review*

Shang¹,

Li²,

Wang³

et al. 2021

Chinese Phys. B

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Graphene has excellent thirdorder nonlinear optical (NLO) properties due to its unique electronic band structure and wideband gap tunability. This paper focuses on the research progress of graphene and its composite materials in nonlinear optics in recent years. In this review, recent results on graphene (or graphene oxide)–metal nanoparticles (G-MNPs), graphene–metal–oxide nanoparticles (G-MONPs), graphene–metal sulfide nanoparticles (G-MSNPs), and graphene–organic molecular composites (G-OM) have been discussed. In addition, the enhancement mechanism of nonlinear absorption (NLA) and optical limiting (OL) have also been covered.

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Section: Free Carrier Absorptionmentioning

confidence: 99%

Third-order nonlinear optical properties of graphene composites: A review*

Shang¹,

Li²,

Wang³

et al. 2021

Chinese Phys. B

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“…Alternatively, if a strong terahertz ͑THz͒ field is applied, the dynamical Franz-Keldysh effect, ac Stark effect, replica of dark excitonic state, THz sidebands, as well as nonlinear absorption of THz waves show up in the absorption spectrum. [15][16][17][18][19] The mixing of optical and THz frequencies has potential applications in wavelength division multiplexing. [20][21][22] In addition, the optical absorption spectrum of semiconductor structures in the presence of both a dc and a THz field were investigated by some researchers.…”

Section: Intersubband Optical Absorption In a Step Asymmetric Semiconmentioning

confidence: 99%

Intersubband optical absorption in a step asymmetric semiconductor quantum well driven by a terahertz field

Zhu

Zhang

Zhao

2009

Journal of Applied Physics

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Influence of polarization-induced electric field on the wavelength and the absorption coefficient of the intersubband transitions in Al x Ga 1 − x N ∕ Ga N double quantum wellsThe nonlinear optical absorption in a three-subband step asymmetric semiconductor quantum well driven by a strong terahertz ͑THz͒ field is investigated theoretically by employing the intersubband semiconductor-Bloch equations. We show that the optical absorption spectrum strongly depends on the intensity, frequency, and phase of the pump THz wave. The strong THz field induces THz sidebands and Autler-Townes splitting in the probe absorption spectrum. Varying the pump frequency can bring not only the new absorption peaks but also the changing of the energy separation of the two higher-energy levels. The dependence of the absorption spectrum on the phase of the pump THz wave is also very remarkable.

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Competition between Free Carriers and Excitons Mediated by Defects Observed in Layered WSe₂ Crystal with Time‐Resolved Terahertz Spectroscopy

Zhu

Zhao

et al. 2018

Advanced Optical Materials

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are new types of semiconductors in which adjacent layers are held by van der Waals force. [1] TMDs have many rich physical properties such as extremely weak phonon-assisted photoluminescence (PL) in bulk structures, relatively strong PL yield in monolayer structures, [2][3][4][5] strong valley-dependent absorption in visible range, [6][7][8] and strong nonlinear optical response. [9][10][11][12] By taking advantage of these properties, significant progresses have been made in the development of electronic and optoelectronic technologies by these materials, [13,14] such as photodetectors, [15] field-effect transistors, [16][17][18] solar cells, [19,20] light-emitting diodes, [21,22] valleytronics, [8,23] integrated circuits, [24] and so on.The exciton binding energy in the monolayer TMDs has been observed in the range of 0.1-1.1 eV, [25][26][27][28] which is larger than that in traditional bulk semiconductors and traditional quantum well. [29,30] This rich excitonic state makes it possible to observe the complex exciton dynamics at room temperature, [31] such as charged and neutral phase of carriers, [32] trions, [33] and biexciton. [34] Meanwhile, bounded exciton could not only dominate the optical response but also play an important role in the optoelectronic processes, such as photocurrent generation and photoconduction in TMD semiconductors. [33,35,36] As a typical TMD material, the bulk WSe 2 has an indirect bandgap of 1.2 eV, and it would transform to the ≈1.65 eV direct bandgap as decreasing to monolayer. [37,38] WSe 2 has been widely used in optoelectronic devices due to its high absorption coefficients in the visible range. Field-effect transistors based on single crystal WSe 2 have been achieved and a carrier mobility comparable to silicon at room temperature was demonstrated. [39] Besides, WSe 2 can also play an important role in the development of van der Waals heterostructures, [40][41][42] in which long-lived interlayer excitons have been observed.Recently, ultrafast time-resolved photoexcited carrier dynamics has been studied in layered TMDs by the most widely used tools, such as optical-pump optical-probe spectroscopy, [43] PL spectroscopy, [38] photocurrent spectroscopy, [36] and electroluminescence. [35,44] The prevalentThe dynamics of photoexcited species is quite important for the development of next-generation ultrafast optoelectronic devices based on transition metal dichalcogenides (TMDs). Herein, time-resolved optical pump terahertz (THz) probe spectroscopy, which is sensitive to both bounded excitons and free electrons/holes, is employed to study the dynamics of photo-induced carriers in the typical layered TMDs crystal tungsten diselenide (WSe 2 ). Initial photoexcitation could generate both free carriers and excitons. The free carriers decay followed by phonon-assistance (≈30 ps) and defect-assistance (≈200-280 ps). The excitons decay followed by the phonon-assisted recombination (≈100 ps) and the defect-induced exciton separation (≈40-200 ps). With the increasing of pump fluence, more f...

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Calculation of the nonlinear free-carrier absorption of terahertz radiation in semiconductor heterostructures

Cited by 6 publications

References 17 publications

Third-order nonlinear optical properties of graphene composites: A review*

Third-order nonlinear optical properties of graphene composites: A review*

Intersubband optical absorption in a step asymmetric semiconductor quantum well driven by a terahertz field

Competition between Free Carriers and Excitons Mediated by Defects Observed in Layered WSe₂ Crystal with Time‐Resolved Terahertz Spectroscopy

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Calculation of the nonlinear free-carrier absorption of terahertz radiation in semiconductor heterostructures

Cited by 6 publications

References 17 publications

Third-order nonlinear optical properties of graphene composites: A review*

Third-order nonlinear optical properties of graphene composites: A review*

Intersubband optical absorption in a step asymmetric semiconductor quantum well driven by a terahertz field

Competition between Free Carriers and Excitons Mediated by Defects Observed in Layered WSe2 Crystal with Time‐Resolved Terahertz Spectroscopy

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Competition between Free Carriers and Excitons Mediated by Defects Observed in Layered WSe₂ Crystal with Time‐Resolved Terahertz Spectroscopy