scholarly journals Third-Order Nonlinear Spectrum of GaN under Femtosecond-Pulse Excitation from the Visible to the Near Infrared

Photonics ◽  
2019 ◽  
Vol 6 (2) ◽  
pp. 69 ◽  
Author(s):  
Gustavo F. B. Almeida ◽  
Sabrina N. C. Santos ◽  
Jonathas P. Siqueira ◽  
Jessica Dipold ◽  
Tobias Voss ◽  
...  
Keyword(s):  
Optical Switching ◽  
Near Infrared ◽  
Laser Pulses ◽  
Photonic Devices ◽  
Femtosecond Laser Pulses ◽  
Index Of Refraction ◽  
Photon Absorption ◽  
Pulse Excitation ◽  
Two Photon Absorption ◽  
Two Photon Absorption Coefficient

Gallium nitride (GaN) has been established as a promising candidate for integrated electro-optic and photonic devices, aiming at applications from optical switching to signal processing. Studies of its optical nonlinearities, however, lack spectral coverage, especially in the telecommunications range. In this study, we measured the two-photon absorption coefficient (β) and the nonlinear index of refraction (n2) of GaN from the visible to the near-infrared by using femtosecond laser pulses. We observed an increase of β from (1.0 ± 0.2) to (2.9 ± 0.6) ×10−11 m/W as the photon energy approached the band gap from 1.77 up to 2.25 eV (700–550 nm), while n2 varied from (90 ± 30) ×10−20 up to (265 ± 80) ×10−20 m2/W within a broad spectral range, from 0.80 up to 2.25 eV (1550–550 nm). The results were modeled by applying a theory based on the second-order perturbation theory and the Kramers-Kronig relationship for direct-gap semiconductors, which are important for the development of GaN-based nonlinear photonic devices.

scholarly journals Laser ablation of silicon with THz bursts of femtosecond pulses: an experimental and theoretical investigation

2021 ◽  
Author(s):  
Caterina Gaudiuso ◽  
Pavel N. Terekhin ◽  
Annalisa Volpe ◽  
Stefan Nolte ◽  
Bärbel Rethfeld ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Thermal Load ◽  
Laser Pulses ◽  
Ablation Rate ◽  
Pulse Mode ◽  
Femtosecond Laser Pulses ◽  
Photon Absorption ◽  
Burst Frequency ◽  
Two Photon Absorption ◽  
Theoretical Investigations

Abstract In this work, we performed an experimental investigation supported by a theoretical analysis, to improve knowledge on the laser ablation of silicon with THz bursts of femtosecond laser pulses. Laser ablated craters have been created using 200 fs pulses at a wavelength of 1030 nm on silicon samples systematically varying the burst features and comparing to the Normal Pulse Mode (NPM). Using bursts in general allowed reducing the thermal load to the material, however, at the expense of the ablation rate. The higher the number of pulses in the bursts and the lower the intra-burst frequency, the lower is the specific ablation rate. However, bursts at 2 THz led to a higher specific ablation rate compared to NPM, in a narrow window of parameters. Theoretical investigations based on the numerical solution of the density-dependent two temperature model revealed that lower lattice temperatures are reached with more pulses and lower intra-burst frequencies, thus supporting the experimental evidence of the lower thermal load in Burst Mode (BM). This is ascribed to the weaker transient drop of reflectivity, which suggests that with bursts less energy is transferred from the laser to the material. This also explains the trends of the specific ablation rates. Moreover, we found that two-photon absorption plays a fundamental role during BM processing in the THz frequency range.

Nondegenerate and degenerate two-photon absorption in cuprous oxide thin film

2019 ◽  
Vol 28 (02) ◽  
pp. 1950015 ◽  
Author(s):  
Huijun Liang ◽  
Qunchao Ma ◽  
Jian Liu ◽  
Xinwei Shi ◽  
Gongjin Yang ◽  
...  
Keyword(s):  
Thin Film ◽  
Cuprous Oxide ◽  
Near Infrared ◽  
Rf Magnetron Sputtering ◽  
Photonic Devices ◽  
Photon Absorption ◽  
Oxide Thin Film ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nir Absorption

A cuprous oxide (Cu2O) thin film was prepared by radio-frequency (RF) magnetron sputtering. The crystal structure, linear transmission spectrum and film thickness were characterized by X-ray diffraction (XRD), ultraviolet–visible–near infrared (UV–Vis–NIR) absorption spectroscopy and ellipsometry. By performing the pump-probe and [Formula: see text]-scan technique, respectively, nondegenerate and degenerate two-photon absorption (D-TPA) coefficients of the Cu2O thin film at several different excitation wavelengths were experimentally determined. The nondegenerate two-photon absorption (ND-TPA) coefficient always exhibits larger magnitude than the corresponding D-TPA coefficient. In particular, the ND-TPA coefficient shows a maximum value of [Formula: see text][Formula: see text]cm/GW. This study indicates that the cuprous oxide could be a potential material for ultrafast nonlinear photonic devices based on two-photon absorption due to its large ND-TPA coefficient.

scholarly journals Ultrafast sub–30-fs all-optical switching based on gallium phosphide

2019 ◽  
Vol 5 (6) ◽  
pp. eaaw3262 ◽  
Author(s):  
Gustavo Grinblat ◽  
Michael P. Nielsen ◽  
Paul Dichtl ◽  
Yi Li ◽  
Rupert F. Oulton ◽  
...  
Keyword(s):  
Gallium Phosphide ◽  
Optical Switching ◽  
Near Infrared ◽  
Optical Nonlinearity ◽  
Photon Absorption ◽  
Linear Absorption ◽  
Two Photon Absorption ◽  
Two Photon ◽  
All Optical ◽  
All Optical Switching

Gallium phosphide (GaP) is one of the few available materials with strong optical nonlinearity and negligible losses in the visible (λ > 450 nm) and near-infrared regime. In this work, we demonstrate that a GaP film can generate sub–30-fs (full width at half maximum) transmission modulation of up to ~70% in the 600- to 1000-nm wavelength range. Nonlinear simulations using parameters measured by theZ-scan approach indicate that the transmission modulation arises from the optical Kerr effect and two-photon absorption. Because of the absence of linear absorption, no slower free-carrier contribution is detected. These findings place GaP as a promising ultrafast material for all-optical switching at modulation speeds of up to 20 THz.

Plasmon-Enhanced Two-Photon Absorption of Infrared Femtosecond Laser Pulses in Thin Gold Films

JETP Letters ◽  
2019 ◽  
Vol 109 (6) ◽  
pp. 382-386 ◽  
Author(s):  
S. I. Kudryashov ◽  
P. A. Danilov ◽  
S. G. Bezhanov ◽  
A. A. Rudenko ◽  
A. A. Ionin ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Photon Absorption ◽  
Gold Films ◽  
Two Photon Absorption ◽  
Two Photon

scholarly journals Efficient ultrafast all-optical modulation in a nonlinear crystalline gallium phosphide nanodisk at the anapole excitation

2020 ◽  
Vol 6 (34) ◽  
pp. eabb3123 ◽  
Author(s):  
Gustavo Grinblat ◽  
Haizhong Zhang ◽  
Michael P. Nielsen ◽  
Leonid Krivitsky ◽  
Rodrigo Berté ◽  
...  
Keyword(s):  
Gallium Phosphide ◽  
Optical Switching ◽  
Near Infrared ◽  
High Refractive Index ◽  
Photon Absorption ◽  
Optical Modulation ◽  
Infrared Range ◽  
Two Photon Absorption ◽  
All Optical ◽  
Differential Reflectivity

High–refractive index nanostructured dielectrics have the ability to locally enhance electromagnetic fields with low losses while presenting high third-order nonlinearities. In this work, we exploit these characteristics to achieve efficient ultrafast all-optical modulation in a crystalline gallium phosphide (GaP) nanoantenna through the optical Kerr effect (OKE) and two-photon absorption (TPA) in the visible/near-infrared range. We show that an individual GaP nanodisk can yield differential reflectivity modulations of up to ~40%, with characteristic modulation times between 14 and 66 fs, when probed at the anapole excitation (AE). Numerical simulations reveal that the AE represents a unique condition where both the OKE and TPA contribute with the same modulation sign, maximizing the response. These findings highly outperform previous reports on sub–100-fs all-optical switching from resonant nanoscale dielectrics, which have demonstrated modulation depths no larger than 0.5%, placing GaP nanoantennas as a promising choice for ultrafast all-optical modulation at the nanometer scale.

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