Investigation of terahertz pulse generation in semiconductors pumped at long infrared wavelengths

Polónyi, Gyula; Mbithi, Nelson M.; Tóth, György; Tibai, Zoltán; Benabdelghani, Imene; Nasi, Luis; Krizsán, Gergő; Hebling, J.

doi:10.1364/josab.469552

Cited by 8 publications

(3 citation statements)

References 28 publications

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“…Pump pulses with longer wavelengths than this can be generated using an optical parametric amplifier (OPA), but their efficiency decreases with wavelength. Model calculations that examine the joint efficiency of the THz and pump sources and take into account the effect of the nonlinear refractive index of NM show that it is not worthwhile to use OPA with wavelengths longer than 2.0 or 3.0 μm for GaP and GaAs, respectively 90 .…”

Section: High-energy Semiconductor-based Terahertz Sourcesmentioning

confidence: 99%

Tilted pulse front pumping techniques for efficient terahertz pulse generation

Tóth,

Polónyi,

Hebling

2023

Light Sci Appl

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Optical rectification of femtosecond laser pulses has emerged as the dominant technique for generating single- and few-cycle terahertz (THz) pulses. The advent of the tilted pulse front pumping (TPFP) velocity matching technique, proposed and implemented two decades ago, has ushered in significant advancements of these THz sources, which are pivotal in the realm of THz pump-probe and material control experiments, which need THz pulses with microjoule energies and several hundred kV/cm electric field strengths. Furthermore, these THz sources are poised to play a crucial role in the realization of THz-driven particle accelerators, necessitating millijoule-level pulses with tens of MV/cm electric field strengths. TPFP has enabled the efficient velocity matching in lithium niobate crystals renowned for their extraordinary high nonlinear coefficient. Moreover, its adaptation to semiconductor THz sources has resulted in a two-hundred-times enhancement in conversion efficiency. In this comprehensive review, we present the seminal achievements of the past two decades. We expound on the conventional TPFP setup, delineate its scaling limits, and elucidate the novel generation TPFP configurations proposed to surmount these constraints, accompanied by their preliminary outcomes. Additionally, we provide an in-depth analysis of the THz absorption, refractive index, and nonlinear coefficient spectra of lithium niobate and widely used semiconductors employed as THz generators, which dictate their suitability as THz sources. We underscore the far-reaching advantages of tilted pulse front pumping, not only for LN and semiconductor-based THz sources but also for selected organic crystal-based sources and Yb-laser-pumped GaP sources, previously regarded as velocity-matched in the literature.

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Section: High-energy Semiconductor-based Terahertz Sourcesmentioning

confidence: 99%

Tilted pulse front pumping techniques for efficient terahertz pulse generation

Tóth,

Polónyi,

Hebling

2023

Light Sci Appl

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“…[26]. According to our recent investigations, GaP pumped at 2.06 µm and GaAs pumped at 3.0 µm are promising, highly efficient THz sources [27].…”

Section: Introductionmentioning

confidence: 98%

Design of Semiconductor Contact Grating Terahertz Source with Enhanced Diffraction Efficiency

et al. 2022

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We report a semiconductor contact grating terahertz source design based on a rectangular profile for phase-matched terahertz generation in the long infrared pump wavelength range. The calculations show that the best diffraction efficiency can be achieved by a filling factor significantly smaller than 50%. Furthermore, the possibility of diffraction efficiency enhancement was investigated by applying three different antireflective coating structures. Numerical simulations have indicated that at 2.06 μm and 3.0 μm pump wavelength, diffraction efficiencies greater than 91% and 89% can be achieved by adding an appropriate antireflective coating to the GaP and GaAs contact grating structure, respectively. In addition, numerical simulations were performed to investigate the influence of wall angles on diffraction efficiency. The results reveal that the wall angle does not significantly affect the diffraction efficiency: while keeping the wall angle deviation from the vertical below 25 degrees, the efficiency drop remains below 5% for otherwise optimal grating parameters.

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“…The longer pumping wavelength and smaller (< 30°) needed tilt angle make it easier to adopt the new techniques, and by that, we can get a well-scaling THz source that operates with excellent efficiency 20 . However, generating the typically needed 1.7–4.0 μm wavelength 21 pump pulses is usually done in an optical parametric amplifier (OPA), which has a decreasing efficiency for long wavelengths, resulting in low system efficiency. An efficient pump laser with the desired wavelength without wavelength conversion would be a solution.…”

Section: Introductionmentioning

confidence: 99%

Possibility of CO2 laser-pumped multi-millijoule-level ultrafast pulse terahertz sources

Tóth,

Illés,

Nazymbekov

et al. 2024

Sci Rep

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In the last decade, intense research has been witnessed on developing compact, terahertz (THz) driven electron accelerators, producing electrons with a sub-MeV—few tens of MeV energy. Such economical devices could be used in scientific and material research and medical treatments. However, until now, the extremely high-energy THz pulses needed by the THz counterparts of the microwave accelerators were generated by optical rectification (OR) of ultrafast Ti:sapphire or Yb laser pulses. These lasers, however, are not very effective. Because of this, we use numerical simulations to investigate the possibility of generating high-energy THz pulses by the OR of pulses produced by CO2 lasers, which can have high plug-in efficiency. The results obtained supposing optical rectification (OR) in GaAs demonstrate that consideration of the self-phase-modulation (SPM) and the second-harmonic-generation (SHG) processes is indispensable in the design of CO2 laser-based THz sources. More interestingly, although these two processes hinder achieving high laser-to-THz conversion efficiency, they can still surpass the 1.5% value, ensuring high system efficiency and making the CO2 laser OR system a promising THz source. Our finding also has important implications for other middle-infrared laser-pumped OR-based THz sources.

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Investigation of terahertz pulse generation in semiconductors pumped at long infrared wavelengths

Cited by 8 publications

References 28 publications

Tilted pulse front pumping techniques for efficient terahertz pulse generation

Tilted pulse front pumping techniques for efficient terahertz pulse generation

Design of Semiconductor Contact Grating Terahertz Source with Enhanced Diffraction Efficiency

Possibility of CO2 laser-pumped multi-millijoule-level ultrafast pulse terahertz sources

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