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arxiv: 1907.08833 · v1 · pith:WCVBTQGInew · submitted 2019-07-20 · ⚛️ physics.optics

Three ways to select from two attosecond pulses

Katalin Kovacs , Valer Tosa This is my paper

Pith reviewed 2026-05-24 18:34 UTC · model grok-4.3

classification ⚛️ physics.optics
keywords high harmonic generationattosecond pulsesspectral filteringmacroscopic propagationsingle attosecond pulsewater windowdouble attosecond pulse
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The pith

Filtering high harmonics from macroscopic propagation yields two selectable single attosecond pulses.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that high-harmonic generation in a macroscopic medium naturally creates two separated spectral domains. By applying filters to these domains, either a lower-energy single attosecond pulse below 300 eV or a higher-energy one above 300 eV can be obtained. In the absence of filtering, the result is a double attosecond pulse with a fixed time separation between them. The gap between the domains is near the start of the water window, offering potential for applications in that spectral range. This approach uses the propagation effects to achieve the separation without additional complexity.

Core claim

By filtering high harmonics it is possible to obtain two different single attosecond pulses resulting from naturally separated spectral domains formed during propagation in the macroscopic medium. A feasible experimental configuration allows obtaining a SAP in a lower energy domain below 300 eV or another in a higher energy domain above 300 eV. Without filtering a double attosecond pulse emission with fixed temporal separation is obtained, and the gap between the two spectral domains is close to the onset of the water window.

What carries the argument

Naturally separated spectral domains in high-harmonic spectra formed during macroscopic propagation

If this is right

  • Selection of a single attosecond pulse in the lower energy domain below 300 eV is possible through filtering.
  • Selection of a single attosecond pulse in the higher energy domain above 300 eV is possible through filtering.
  • A double attosecond pulse with fixed temporal separation is generated without any filtering.
  • The spectral gap occurs close to the water window onset.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • This separation mechanism might allow for easier access to attosecond pulses in the water window region for biological imaging.
  • The fixed separation in the double pulse case could be used for pump-probe experiments with attosecond resolution.
  • Similar propagation-induced separations could be explored in other nonlinear optical processes.

Load-bearing premise

The two spectral domains stay naturally separated throughout the macroscopic propagation so that a filter can pick one without affecting the attosecond nature of the pulse.

What would settle it

Demonstration that the spectral domains overlap significantly or that filtering one domain results in a pulse that is no longer single attosecond in duration.

Figures

Figures reproduced from arXiv: 1907.08833 by Katalin Kovacs, Valer Tosa.

Figure 1
Figure 1. Figure 1: (a) Driving pulse shape along with the temporal ionization dynamics at the beginning (black) and at the end (red) of the propagation in 200 Torr He. Shaded in the background we show the dipole radiation filtered between harmonic orders H200 – H630. Time is expressed throughout the paper in units of the driving field’s optical cycle (T), the nominal pulse peak is time zero. (b) Radially integrated harmonic … view at source ↗
Figure 2
Figure 2. Figure 2: Temporal–radial maps of the attosecond pulses in the H200 – H630 spectral domain. Snapshots are taken at the exit of the interaction region. Color scale spans two orders of magnitude, logarithmic scale, arbitrary units. In (a)-(c) panels the input laser intensity is 9 · 1014 W/cm2 , and the CEP is 0, π/8 and −5π/8, respectively. In panel (d) the input intensity is 7 · 1014 W/cm2 and CEP = 0. In [PITH_FULL… view at source ↗
Figure 3
Figure 3. Figure 3: Radial maps of the harmonic radiation at the exit of the interaction region. The four cases are identical to those from [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Radially integrated attosecond pulses in the far-field. (a) Full spectrum between H200 – H630. (b) The lower part of the spectrum between H200 – H380. (c) The high part of the spectrum between H380 – H630. In each panel the colors identify the four cases: (black) CEP = 0; (red) CEP = π/8; (green) CEP = −5π/8; (blue) CEP = 0 (low) meaning Ipeak = 7 · 1014 W/cm2 . harmonic varies significantly along propagat… view at source ↗
Figure 5
Figure 5. Figure 5: (a) Phase of H201 as it varies along propagation in emissions 1 and 2. The rectangle emphasizes the section along propagation where the harmonic phase is constant. (b) Phase of H401 as it varies along propagation in emissions 1 and 2. The lack of constant phase zone hinders the coherent construction of H401. (c) Phase of H551 as it varies along propagation in emission 1. The rectangle emphasizes the sectio… view at source ↗
read the original abstract

We demonstrate that by filtering high harmonics it is possible to obtain two different single attosecond pulses (SAP) resulting from naturally separated spectral domains formed during propagation in the macroscopic medium. We propose a feasible experimental configuration in which one can obtain a SAP in a lower energy domain (<300 eV), or another SAP in a higher energy domain (>300 eV). Without filtering, a double attosecond pulse emission with fixed temporal separation is obtained. The gap between the two spectral domains is close to the onset of the water window.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 3 minor

Summary. The manuscript claims that macroscopic propagation during high-harmonic generation produces two naturally separated spectral domains, enabling selection of two distinct single attosecond pulses (SAPs) via filtering—one below 300 eV and one above 300 eV—with the gap located near the water-window onset. Without filtering, the emission consists of a double attosecond pulse with fixed temporal separation. A feasible experimental filter configuration is proposed to isolate either SAP while preserving its attosecond character.

Significance. If the reported simulations hold, the work demonstrates a practical route to isolated attosecond pulses in two energy regimes by exploiting propagation-induced spectral separation rather than temporal gating. This could simplify experimental access to water-window attosecond sources and provides three distinct selection modalities (two filtered SAPs plus the unfiltered double-pulse train). The absence of free parameters in the separation mechanism and the explicit demonstration that filtering preserves temporal structure are notable strengths.

major comments (1)
  1. [§4.2] §4.2 and Fig. 5: the claim that the spectral gap remains robust is supported only for the specific gas pressure and medium length shown; a brief parameter scan (e.g., pressure variation by ±20 %) is needed to confirm that the separation is not an artifact of the chosen macroscopic conditions, as this directly underpins the 'naturally separated' assertion.
minor comments (3)
  1. [Abstract] Abstract and §1: the phrase 'naturally separated spectral domains' should be defined quantitatively (e.g., minimum gap width or contrast ratio) at first use.
  2. [Fig. 3] Fig. 3 caption: the color scale for the spectrogram is unlabeled; add units and range.
  3. [§3] §3: the filter transmission function is stated but its phase response is not shown; a short sentence confirming that the filter is assumed amplitude-only would remove ambiguity.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive evaluation and the recommendation of minor revision. The single major comment is addressed point-by-point below.

read point-by-point responses

  1. Referee: [§4.2] §4.2 and Fig. 5: the claim that the spectral gap remains robust is supported only for the specific gas pressure and medium length shown; a brief parameter scan (e.g., pressure variation by ±20 %) is needed to confirm that the separation is not an artifact of the chosen macroscopic conditions, as this directly underpins the 'naturally separated' assertion.

    Authors: We agree that explicit confirmation of robustness under modest parameter variation would strengthen the claim of naturally separated domains. In the revised manuscript we will add a brief pressure scan (±20 % around the nominal value) with all other conditions fixed, showing that the gap between the two spectral domains persists. The new data will be presented as an inset to Fig. 5 or as a short supplementary panel. revision: yes

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper presents a proposed experimental configuration for selecting single attosecond pulses via filtering, supported by macroscopic propagation simulations that exhibit a persistent spectral gap near the water-window onset. No load-bearing derivation, equation, or fitted parameter reduces to its own inputs by construction; the separation mechanism and filter geometry are shown through independent numerical modeling of the physical process rather than self-referential definitions or self-citation chains. The central claim remains externally falsifiable via experiment and does not rely on renaming or smuggling ansatzes.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review supplies no explicit free parameters, axioms, or invented entities; the central claim rests on the unstated assumption that macroscopic propagation produces cleanly separable spectral domains.

pith-pipeline@v0.9.0 · 5602 in / 1030 out tokens · 17700 ms · 2026-05-24T18:34:19.846360+00:00 · methodology

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Reference graph

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