Our research team has achieved a significant milestone by generating pulses with sub-20-attosecond (as) timing jitter from a 200-MHz all-Polarization-Maintaining (PM) erbium-doped (Er:) Nonlinear Amplifying Loop Mirror (NALM) fiber laser. Accurate measurement of these temporal fluctuations was conducted using the Balanced Optical cross-Correlation (BOC) technique. Through comprehensive investigation, we identified the critical parameters responsible for timing jitter, including dispersion and pump power, and validated their impact. The fine-tuning of the contributing factors allowed us to demonstrate an exceptionally low integrated timing jitter of only 15.59 attoseconds, integrated from 10 kHz to 10 MHz. This accomplishment stands as the lowest value ever documented for any free-running mode-locked fiber lasers that are erbium-doped.
Semiconductor nanowires (NWs) have shown robust hot carrier effects due to their small dimensions. Here, we study the cooling mechanisms of hot electrons in the time domain via transient absorption spectroscopy. Probe energies below the bandgap are used to determine the evolution of the carrier effective mass while probe energies above the bandgap track the conduction band occupation. From excitation intensity dependent measurements, we confirm that electron-hole interactions are a major cooling channel at large carrier density, given the high ratio of mh/me of InAs. Our experiments indicate that this cooling channel is amplified in passivated core-shell NWs. We associate this effect with spatial carrier separation caused by Fermi-level pinning in unpassivated NWs. In core-shell NWs, bands are considerably more flat which increases radiative recombination and electron-hole scattering with the latter cooling the hot electron population. Our results highlight the advantages of carrier separation if high carrier densities are to be used for hot phonon bottlenecks.
KEYWORDS: Picosecond phenomena, Absorption, Spectroscopy, Ultraviolet radiation, Femtosecond phenomena, Temperature metrology, Signal processing, Molecules, Chemical species, Laser systems engineering
The electron photodetachment of the aqueous halides and hydroxide is studied after excitation in the lowest CTTS state.
The initially excited state is followed by an intermediate assigned to a donor-electron pair that displays a competition of
recombination and separation. The geminate dynamics measured in the various CTTS systems reveal a strong influence
of the parent radical. The electron survival probability decreases significantly from 0.77 to 0.29 going from F- to OH-.
Results for I- show that excitation of a higher-lying CTTS state opens a new relaxation channel, which directly leads to
fully hydrated electron, while the relaxation channel discussed above is not significantly affected. Using pump-repump-probe
spectroscopy the pair species is verified via a secondary excitation with separation of the pairs so that the yield of
released electrons is increased. Three pulse spectroscopy on aqueous hydroxide give evidence for an additional ultrafast
(~700 fs) geminate recombination channel in this system. Comparison of these data with similar experiments on neat
water after two-photon excitation with total energy of 9.2 eV demonstrates the important role of (OH-)* for the indirect
photoionization of water.
The electron photodetachment from 2.5~mM aqueous iodide solution is
studied in the temperature range 25 to 75°C. The dynamics
following excitation of the anion at 242~nm into the lowest CTTS state are studied in the spectral range of 400-1000~nm. A first intermediate is observed that builds up with a time constant of 220 to 180~fs in the investigated temperature interval and is assigned to an iodine:electron pair in a transient solvent configuration. Subsequent solvent reorganization leads to a quasi-equilibrated hydrated atom:electron pair (I:e-)hyd. The latter builds up with a time constant of 700 to 540~fs going from 25°C to 75°C. The following relaxation seems to be governed by partially diffusion-controlled recombination of the electron in the presence of an attraction potential well with depth of about 850~cm-1. The experimental result for the lifetime of the
hydrated I:e- pair is 21 to 16~ps going from 25°C to
75°C.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.