7 results on '"Altwaijry, Najd"'
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2. Sensitivity Enhancement in Photoconductive Light Field Sampling.
- Author
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Altwaijry, Najd, Qasim, Muhammad, Zimin, Dmitry, Karpowicz, Nicholas, and Kling, Matthias F.
- Subjects
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BULK solids , *ELECTRIC currents , *LIGHT sources , *ELECTRIC lighting , *INFORMATION processing - Abstract
The emerging field of lightwave electronics is driving optoelectronic information processing beyond current classical limitations and has the potential to eventually reach petahertz frequencies. One of the major obstacles in reaching not only higher switching frequencies but also higher repetition rates with low‐power light sources is the efficiency of related devices. A device is presented based on a multilayered material that shows a 13‐fold enhancement in terms of converting light to electric current compared to bulk solids. Furthermore, the device exhibits an almost flat intensity response within its working range. The outstanding properties of engineered multilayered devices promise to push technology for lightwave electronics applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
3. Pushing the boundaries of photoconductive sampling in solids
- Author
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Altwaijry, Najd Abdulaziz S.
- Abstract
The advent of laser-based optical tools featuring few-cycle pulses with durations of less than a hundred femtoseconds in the late 1980s enabled scientists to initiate and observe the evolution of chemical reactions. This powerful approach combined the interactions of light and matter and unleashed an unprecedented metrology concept that tracks the interactions of atoms and molecules in their natural timescales. Electron wavepacket dynamics take place in the attosecond range, a thousand times faster than molecules. In optical terms, such durations typically last less than the half-cycle duration of optical fields. Consequently, the investigation of such electronic processes necessitates measurement techniques capable of resolving the oscillations of the electric field of light. The primary objective of this thesis is to develop and advance novel field characterisation techniques based on photoconductive sampling. The first portion of this thesis addresses broadband field characterisation based on nonlinear photoconductive sampling. A theoretical analysis of current formation and localisation in solids is presented, prompting the fabrication of a heterostructured sample with the aim of enhancing the magnitude of the signal obtained from the measurement technique. A thorough proof-of-principle experiment is performed, whereby a significant enhancement in signal magnitude is established. As a consequence of signal improvement, the heterostructured sample reaches the desired stability regime earlier than its traditional bulk counterparts. Moreover, the performance of the heterostructured sample for field characterisation is compared to fused silica and benchmarked against the well-established technique of electro-optic sampling. These results pave the way towards field sampling in low pulse energy systems. The following section details broadband field characterisation based on linear photoconductive sampling by employing tailored pulses from a waveform synthesiser. Visible-ultraviolet pulses are utilised to inject carriers in a common semiconductive material (gallium phosphide), enabling the complete characterisation of a mid-infrared test field. Furthermore, the technique is validated against electrooptic sampling. When compared to electro-optic sampling, the response function of linear photoconductive sampling is concerned with the intensity envelope of the gating field, relaxing the strict requisites on the temporal phase of the gate. The demonstrated results represent a significant achievement in extending field sampling techniques beyond 100 THz and towards the visible range. Finally, a machine learning-based algorithm for denoising waveforms obtained from a laboratory setting is developed and implemented. The algorithm is based on a one-dimensional convolutional neural network, ideal for processing data presented on an evenly spaced grid. The model is compared with well-established methodologies, namely denoising via the fast Fourier transform and wavelet analysis and exhibits excellent performance, extending the repertoire of tools typically used for combating noise. The field characterisation methodologies presented in this thesis pave the way towards accessible and cost-effective field sampling techniques, enabling researchers to study field-induced electron dynamics in matter and usher in ultrafast optoelectronic signal processing towards the PHz range. In general, the field characterisation techniques presented occupy a small footprint, and the measurements take place in ambient air conditions, facilitating their integration in existing experimental infrastructures. With the aid of AI-accelerator chips, the machine learning tool developed in this thesis can be implemented during laboratory measurements as a concurrent denoising technique.
- Published
- 2023
- Full Text
- View/download PDF
4. Broadband Photoconductive Sampling in Gallium Phosphide.
- Author
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Altwaijry, Najd, Qasim, Muhammad, Mamaikin, Mikhail, Schötz, Johannes, Golyari, Keyhan, Heynck, Michael, Ridente, Enrico, Yakovlev, Vladislav S., Karpowicz, Nicholas, and Kling, Matthias F.
- Subjects
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GALLIUM phosphide , *PHOSPHIDES , *ELECTRIC field strength , *ELECTRIC lighting - Abstract
Direct measurements of the electric field of light enable new observations of light–matter interactions. In the near‐infrared and visible spectral ranges, this typically relies on techniques that exploit nonlinearities in gases or solids, which limits their sensitivity. Here, a method for the detection of broadband near‐infrared fields spanning more than one octave from 110 to 220 THz based on linear absorption in a semiconductor is demonstrated. This technique, which avoids complex vacuum setups and works under ambient conditions, employs linear photoconductive sampling (LPS) in gallium phosphide. Simulations reveal that the response function of LPS is concerned with the intensity envelope of the gate field, in contrast to electro‐optic sampling, relaxing the stringent temporal requirements on the gate pulse. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
5. Multi-octave, CEP-stable source for high-energy field synthesis.
- Author
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Alismail, Ayman, Haochuan Wang, Barbiero, Gaia, Altwaijry, Najd, Hussain, Syed Ali, Pervak, Volodymyr, Schweinberger, Wolfgang, Azzeer, Abdallah M., Krausz, Ferenc, and Fattahi, Hanieh
- Subjects
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OPTICAL frequency conversion , *OPTICAL parametric amplifiers , *QUANTUM optics , *ELECTRIC field strength , *LASER pumping - Abstract
The article presents a report on the research related to multi-octave, carrier-envelope phase (CEP)-stable source for high-energy field synthesis. Topics discussed include extension to petahertz frequencies has enhanced the depth of our insight into microscopic ultrafast dynamics; capture the four-dimensional microscopic dynamics of electrons outside the atomic core; and wavelength is markedly reduced due to the higher quantum diffusion and lower recombination probability.
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- 2020
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6. Contrast enhancement in near-infrared electro-optic imaging.
- Author
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Mamaikin M, Ridente E, Altwaijry N, Weidman M, and Karpowicz N
- Abstract
Access to subtle ultrafast effects of light-matter interaction often requires highly sensitive field detection schemes. Electro-optic sampling, being an exemplary technique in this regard, lacks high sensitivity in an imaging geometry. We demonstrate a straightforward method to significantly improve the contrast of electric field images in spatially resolved electro-optic sampling. A thin-film polarizer is shown to be an effective tool in enhancing the sensitivity of the electro-optic imaging system, enabling an adjustment of the spectral response. We show a further increase of the signal-to-noise ratio through the direct control of the carrier envelope phase of the imaged field.
- Published
- 2022
- Full Text
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7. Carrier-envelope phase stable, 5.4 μJ, broadband, mid-infrared pulse generation from a 1-ps, Yb:YAG thin-disk laser.
- Author
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Alismail A, Wang H, Altwaijry N, and Fattahi H
- Abstract
We report on a simple scheme to generate broadband, μJ pulses centered at 2.1 μm with an intrinsic carrier-envelope phase (CEP) stability from the output of a Yb:YAG regenerative amplifier delivering 1-ps pulses with randomly varying CEP. To the best of our knowledge, the reported system has the highest optical-to-optical efficiency for converting 1-ps, 1 μm pulses to CEP stable, broadband, 2.1 μm pulses. The generated coherent light carries an energy of 5.4 μJ, at 5 kHz repetition rate, that can be scaled to higher energy or power by using a suitable front end, if required. The system is ideally suited for seeding broadband parametric amplifiers and multichannel synthesizers pumped by picosecond Yb-doped amplifiers, obviating the need for active timing synchronization. Alternatively, this scheme can be combined with high-power oscillators with tens of μJ energy to generate CEP stable, multioctave supercontinua, suitable for field-resolved and time-resolved spectroscopy.
- Published
- 2017
- Full Text
- View/download PDF
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