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1. Controlling Ultrafast Photoemission via Simultaneous Laser Mixing and Shaping

   https://doi.org/10.1364/UFO.2023.F4.5  

   Lemons, Randy; Hirschman, Jack; Neveu, Nicole; Duris, Joseph; Marinell, Agostino; Durfee, Charles; Carbajo, Sergio (March 2023, Optica Publishing Group)

   We present a novel, versatile framework to generate W-level temporally shaped, near transform-limited, UV picosecond pulses via non-colinear sum frequency generation and demonstrate it producing temporally flattop, high-power UV pulses capable of enhancing femtosecond- and attosecond-level electron and Xray free electron lasers brightness. 

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2. Implementation of Broadband near-UV Pump Pulses for Ultrafast 2D Electronic-Vibrational Spectroscopy

   https://doi.org/10.1364/UP.2020.Tu2A.2  

   Sandwisch, Jason W.; Gaynor, James D.; Khalil, Munira (January 2020, Optica Publishing Group)

   We present the generation of efficient, tunable sub-20 fs broadband near UV pulses. The tunable pulses are used in two-dimensional electronic-vibrational spectroscopy and reveal additional vibronic states in an excited state intramolecular proton transfer process. 

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3. Measuring Simultaneously Spatially and Temporally Focused Ultrafast Laser Pulses Using the Dispersion Scan Technique

   https://doi.org/10.1364/CLEO_SI.2020.SM3H.6  

   Wilhelm, Alex M.; Schmidt, David D.; Adams, Daniel E.; Durfee, Charles G. (May 2020, Conference on Lasers and Electro-optics (CLEO))

   null (Ed.)

   We demonstrate a novel dispersion scan algorithm using grating dispersion. We also propose using the intrinsic dispersion of temporally focused laser pulses to characterize the pulse structure by scanning a nonlinear crystal through focus. 

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4. Experimentation with Prolate Spheroidal Wave Function Pulses for Physical-Layer Security

   https://doi.org/10.1109/TELSIKS46999.2019.9002015  

   Wang, Tyan-Lin; Djordjevic, Ivan B. (October 2019, 2019 14th International Conference on Advanced Technologies, Systems and Services in Telecommunications (TELSIKS))

   Prolate spheroidal wave functions (PSWF) are a temporally orthogonal set of waveforms in which energy is concentrated in a finite time window and finite bandwidth. In wireless communications, where binary information is encoded onto a sequence of pulses, individual symbols can conceivably be represented by different orders of PSWF pulse shapes for transmission. Because these pulses have approximately constant bandwidth and pulsewidth across all orders, they are an interesting alternative to conventional modulation formats. Although they are certainly capable of improving spectral efficiency and data capacity, in this study we investigate their feasibility in achieving physical-layer security in wireless RF transmissions. 

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5. Spatiotemporal coupling of attosecond pulses

   https://doi.org/10.1073/pnas.1817626116  

   Wikmark, Hampus; Guo, Chen; Vogelsang, Jan; Smorenburg, Peter W.; Coudert-Alteirac, Hélène; Lahl, Jan; Peschel, Jasper; Rudawski, Piotr; Dacasa, Hugo; Carlström, Stefanos; et al (March 2019, Proceedings of the National Academy of Sciences)

   The shortest light pulses produced to date are of the order of a few tens of attoseconds, with central frequencies in the extreme UV range and bandwidths exceeding tens of electronvolts. They are often produced as a train of pulses separated by half the driving laser period, leading in the frequency domain to a spectrum of high, odd-order harmonics. As light pulses become shorter and more spectrally wide, the widely used approximation consisting of writing the optical waveform as a product of temporal and spatial amplitudes does not apply anymore. Here, we investigate the interplay of temporal and spatial properties of attosecond pulses. We show that the divergence and focus position of the generated harmonics often strongly depend on their frequency, leading to strong chromatic aberrations of the broadband attosecond pulses. Our argument uses a simple analytical model based on Gaussian optics, numerical propagation calculations, and experimental harmonic divergence measurements. This effect needs to be considered for future applications requiring high-quality focusing while retaining the broadband/ultrashort characteristics of the radiation. 

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