Extremely large nondegenerate nonlinear index and phase shift in epsilon-near-zero materials [Invited]

Benis, Sepehr; Munera, Natalia; Faryadras, Sanaz; Stryland, Eric Van; Hagan, David J.

doi:10.1364/ome.464846

Cited by 10 publications

(9 citation statements)

References 60 publications

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“…Blue and red patterns indicate organic and inorganic ENZ materials, respectively. Data source: AZO, ITO, , FTO, and HTJsq …”

Section: Discussionmentioning

confidence: 99%

Tunable Organic ENZ Materials with Large Optical Nonlinearity

Hu,

Yu,

Liu

et al. 2023

ACS Photonics

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Epsilon-near-zero (ENZ) materials have shown significant potential for nonlinear optical applications due to their extraordinary enhancement of optical nonlinearity. Our experiments show that poly(3,4-ethylenedioxythiophene) (PEDOT) films can be modified to boost their conductivity and exhibit ENZ wavelengths from mid-infrared to visible regimes. Degenerate optical nonlinearity coefficients of EG-modified PEDOT films with an ENZ wavelength of 1587 nm are enhanced at 1550 nm to be larger than those of most of the inorganic ENZ materials. The small linear index and the large nonlinear index cause a 210% change in transmittance between low and high power intensities. We attribute the ENZ enhancement to the increased absorptance of bipolarons in PEDOT films. The pump−probe technique reveals the transient process of the bipolaron transition. The highly tunable carrier concentration and mobility enable PEDOT to be an extraordinary nonlinear optical material, which leads to new possibilities of PEDOT:PSS in plasmonics, nonlinear optics, and on-chip nanophotonic devices.

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“…Blue and red patterns indicate organic and inorganic ENZ materials, respectively. Data source: AZO, ITO, , FTO, and HTJsq …”

Section: Discussionmentioning

confidence: 99%

Tunable Organic ENZ Materials with Large Optical Nonlinearity

Hu,

Yu,

Liu

et al. 2023

ACS Photonics

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“…It is important to view GZO in context with other popular ENZ materials such as ITO [35], AZO [6], and CdO [56]. As noted before, all the nonlinear measurements are highly dependent on external parameters such as probe and excitation wavelengths, intensity, and angle as well as material parameters such as thickness and doping concentrations making comparison difficult.…”

Section: Nonlinear Coefficients and Comparisons To Other Enz Materialsmentioning

confidence: 99%

“…The probe branch was focused through a 5 mm thick sapphire crystal to generate a supercontinuum white light, which was filtered for the near-infrared (λ probe = 1000-1600 nm) and polarized for cross-polarization with respect to the pump beam to avoid two-beam coupling. [53,54] This does not affect the nonlinearity because free carrier effects are isotropic [35]. The pump and probe were spatially overlapped at the sample position with an average pump sample spot size of 700 µm diameter (defined as 1/e of the peak intensity).…”

Section: Linear Gzo Properties and Experimental Setupmentioning

confidence: 99%

“…Materials such as indium tin oxide (ITO) [15][16][17] and aluminum-doped zinc oxide (AZO) [18][19][20] have been popular in the last few years with various enhanced nonlinear properties reported, [21]. For example, ENZ materials show adiabatic frequency shifting (∆f ∼ THz) [22][23][24][25][26][27][28][29], large amplitude modulation (∆T > 50%) [30][31][32], and extreme changes in refractive index (∆n ∼ 1) [33][34][35]. In addition, when coupled with metastructures, these ENZ films can further enhance the nonlinear properties achieved [26,[35][36][37][38][39][40][41].…”

Section: Introductionmentioning

confidence: 99%

“…For example, ENZ materials show adiabatic frequency shifting (∆f ∼ THz) [22][23][24][25][26][27][28][29], large amplitude modulation (∆T > 50%) [30][31][32], and extreme changes in refractive index (∆n ∼ 1) [33][34][35]. In addition, when coupled with metastructures, these ENZ films can further enhance the nonlinear properties achieved [26,[35][36][37][38][39][40][41]. Gallium-doped zinc oxide (GZO) is proposed to show similar nonlinear optical performance to AZO films but has not been thoroughly studied experimentally.…”

Section: Introductionmentioning

confidence: 99%

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Gallium-doped zinc oxide: nonlinear reflection and transmission measurements and modeling in the ENZ region

et al. 2023

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Strong nonlinear materials have been sought after for decades for applications in telecommunications, sensing, and quantum optics. Gallium-doped zinc oxide is a II-VI transparent conducting oxide that shows promising nonlinearities similar to indium tin oxide and aluminum-doped zinc oxide for the telecommunications band. Here we explore its nonlinearities in the epsilon near zero (ENZ) region and show n2,eff values on the order of 4.5×10-3 cm2GW-1 for IR pumping on 200-300 nm thin films. Measuring nonlinear changes in transmission and reflection with a white light source probe in the near-IR while exciting in the near-IR provides data in both time and wavelength. Three films varying in thickness, optical loss, and ENZ crossover wavelength are numerically modeled and compared to experimental data showing agreement for both dispersion and temporal relaxation. In addition, we discuss optimal excitation and probing wavelengths occur around ENZ for thick films but are red-shifted for thin films where our model provides an additional degree of freedom to explore. Obtaining accurate nonlinear measurements is a difficult and time-consuming task where our method in this paper provides experimental and modeled data to the community for an ENZ material of interest.

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Nonlinear Loss Engineering in Near‐Zero‐Index Bulk Materials

Jaffray,

Clerici,

Heijnen

et al. 2023

Advanced Optical Materials

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Transparent conducting oxides (TCOs) show unprecedented optical nonlinearities in the near infrared wavelength range, where the real part of their linear refractive index approaches zero. More specifically, the Kerr nonlinearities of these materials have sparked widespread attention due to their magnitude and speed. However, due to the absorptive nature of these nonlinear processes, it is of fundamental interest to further investigate the imaginary component of the nonlinear index. The present work studies the nonlinear optical absorption properties of aluminium‐doped zinc oxide (AZO) thin films in their near‐zero‐index (NZI) spectral window. It is found that the imaginary part of the refractive index is reduced under optical excitation such that the field penetration depth more than doubles. An optically induced shift of the NZI bandwidth of ≈120 nm for a pump intensity of 1.3 TW cm−2 is also demonstrated. Looking into the optically induced spectral redistribution of the probe signal, local net gain is recorded, which is ascribed to a nonlinear adiabatic energy transfer. The present study adds key information about the fundamental interplay between real and imaginary nonlinear indices in NZI media, while advancing parametric amplification as viable direction for loss compensation.

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Extremely large nondegenerate nonlinear index and phase shift in epsilon-near-zero materials [Invited]

Cited by 10 publications

References 60 publications

Tunable Organic ENZ Materials with Large Optical Nonlinearity

Tunable Organic ENZ Materials with Large Optical Nonlinearity

Gallium-doped zinc oxide: nonlinear reflection and transmission measurements and modeling in the ENZ region

Nonlinear Loss Engineering in Near‐Zero‐Index Bulk Materials

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