We demonstrate the deterministic control of femtosecond dual-comb soliton motion in an Er:fiber laser. Introducing fast intra-cavity modulation, we control individual solitons within two interlaced soliton combs in the harmonically-modelocked state. Upon extra-cavity recombination of both combs, we can obtain reconfigurable pulse pairs at arbitrary delays. Based on realtime spectroscopy, we resolve the transient inter-soliton trajectories.The approach employs laser-intrinsic soliton dynamics and provides all-optically swept pulse pairs for i.e. pump-probe spectroscopy at ⪆kHz scanning frequencies.
The novel field-resolved microscopy scheme of Quantum-probe Field Microscopy (QFIM) utilized fluorescence quanta to images local THz-electric waveforms [1]. In this contribution, we discuss the basis of the ultrafast microscopy scheme and the recovery of multi-Terahertz signals from fluorescence data. We elaborate fundamental aspects of time-domain sampling of electric waveforms and different strategies to recover response functions of systems under investigation.
[1] M.B. Heindl, et al., “Ultrafast imaging of terahertz electric waveforms using quantum dots”, Light: Science & Applications 11, 2022.
We recently discovered a novel ultrafast coupling mechanism of femtosecond solitons via coherent optical phonons inside a solid-state laser cavity, forming stably bound states - “Soliton molecules”[1]. Moreover, preceding the stable binding, the relative motion of two solitons can be harnessed to sample THz phonons using real-time spectroscopy within a single rapid all-optical delay sweep. In this contribution, we discuss the sampling and contrast mechanism for highspeed spectroscopy and compare the scheme to conventional extra-cavity time-domain Raman sampling schemes.
[1] A. Völkel et al., Intracavity Raman Scattering couples Soliton Molecules with Terahertz Phonons, Nature Comms. 13 (1) (2022)
In this contribution, we present a novel type of sub-cycle field-resolved microscopy of Terahertz electric near-fields inside micro- and nanostructures. The “Quantum-probe Field Microscopy” (QFIM) scheme is based on fluorescence microscopy of semiconductor Quantum-dot luminescence and harnesses the Quantum-confined Stark effect for recording stroboscopic “movies” of ultrafast resonant and propagating THz-excitations. The scheme is compatible with strong local driving field strengths, sub-micrometer resolution and sub-cycle sampling of multi-THz waveforms. We discuss experimental implementations, recent results and future prospects of this versatile microscopy scheme.
Stable arrangements of temporal solitons are reported for essentially every implementation of femtosecond fiber lasers. Their formation can be tracked with today’s real-time instrumentation. However, the underlying interaction mechanism frequently remained elusive and predictions of soliton separations in actual sources are often missing. Here, we present the experimental analysis of bound-state trajectories in a femtosecond Er:fiber laser and reveal the underlying universal coupling mechanism. We demonstrate all-electronic switching between two stable soliton molecules and the feasibility of tuning bound-state separations. The results are applicable to various ultrafast sources and may readily be adapted for generating femtosecond pulse pairs in spectroscopy and material processing.
Optical activity spectroscopy such as circular dichroism (CD) and optical rotatory dispersion (ORD) is frequently employed to investigate (bio)-molecular structures and chiroptical responses of materials. Here we present an innovative, simple configuration for the quick and sensitive measurements of broadband optical activity spanning the visible and nearinfrared. A linearly polarized light illuminates a chiral sample to create a chiral free-induction decay field (CFID), along with an orthogonally polarized achiral transmitted field which serves as the phase-locked local oscillator for heterodyne amplifications. A common-path birefringent interferometer varies the relative delay between the chiral and achiral components and a balanced photodetector records their delay-dependent interferogram from which broadband CD and ORD spectra are obtained by the Fourier transform. Using an incoherent thermal light source, we achieve state-of-the-art sensitivity for broadband CD and ORD spectra, with a measurement time of just a few seconds. The setup allows highly sensitive measurements of glucose concentration and real-time monitoring of fast asymmetric chemical reactions. In comparison to standard spectropolarimeters, our setup is considerably faster, more compact, and cost-effective, as it does not require any monochromator, photo-elastic modulator, or lock-in amplifier. The setup also accepts ultrashort pulses, thus paving the way towards broadband transient optical activity spectroscopy and broadband CD imaging.
Bound-states of temporal solitons − termed “Soliton molecules” or “Soliton crystals” – are observed in microcavities and ultrafast resonators. Recently, we introduced high-speed spectroscopy to resolve the formation and control of such states in mode-locked Ti:sapphire oscillators by employing real-time spectral interferometry [1,2].
In this contribution, we resolve a novel mechanism mediating short-range soliton bound-states based on real-time measurements and by introducing a refined analysis of relative soliton phases. We corroborate our findings with a numerical interaction model for the coherent soliton coupling and discuss prospects for future schemes of high-speed intra-cavity spectroscopy.
Shannon's information theory teaches us that the amount of information gained in a measurement is inversely proportional to its predictability. Difficult to capture, flash-like signals contain far more information than repetitive waveforms. The Photonic Time Stretch data acquisition invented two decades ago, has emerged as the most successful solution to single-shot measurements of transient events. This talk will review the fundamentals of photonic time stretch and its numerous applications in science, biomedicine and as mathematical inspiration for a new class of numerical algorithms.
Photoemission from nanostructures offers sub-wavelength field localization and enhancement. Excited by ultrashort pulses, electron emission can be confined and controlled in both time and space. Studies with metallic nanotips have examined the transition to strong-field conditions in photoemission. Reaching deeply into this regime with ultrashort mid-infrared pulses, we generate photoelectrons up to hundreds of electron volts and observe dynamics in which electrons are ejected from the field-enhanced region in less than an optical half cycle. Moreover, single cycle terahertz pulses are shown to yield a novel means of control over the photoemission process.
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