{"id":"b6193b2f-7d70-4398-a05d-b0a9d2f26a8c","arxiv_id":"2607.13954","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"ZPAN crystals grown from acetone with 5% water generate terahertz pulses near 1 MV/cm with a smooth 0.5-3.4 THz spectrum and can be grown much larger than typical organic THz crystals.","lead":"The organic crystal ZPAN, grown by slow evaporation from an acetone-water mixture, produces terahertz pulses with peak fields near 1 MV/cm and a smooth spectrum up to 3.4 THz. The material can be grown as large rectangular crystals, which the authors argue makes it attractive for scaling terahertz generation to high-power lasers.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Aperture-scaling claim is not supported by the demonstrated crystal geometry: a 12-mm circular aperture cannot fit on the 1-cm-wide face, and no damage data support the fixed-fluence scaling.","rationale":"The reader's weakest-assumption analysis correctly identifies the aperture-scaling claim as the most load-bearing part of the paper's significance argument. The experimental THz characterization is credible but the headline 'near 1 MV/cm' has no error bars, and the d-tensor calculation relies on approximations; however, these are secondary. The scaling claim is internally inconsistent with the reported crystal geometry: the main face is 7 cm × 1 cm, so a 12-mm circular aperture does not fit. Since ZPAN's generation efficiency is lower than DAST's, the only route to 'better than DAST' is a larger aperture, which the demonstrated crystals cannot provide. The absence of damage-threshold data further weakens the extrapolation to high pulse energies. These are addressable issues, so the CONDITIONAL verdict stands; no change is needed.","tokens_in":11251,"tokens_out":6178,"duration_ms":61655,"concrete_test":"Attempt to fabricate a 12-mm circular aperture from a ZPAN crystal grown by the reported method and measure its damage threshold and THz output at 1450 nm, ~100 fs, ~2 mJ/cm², comparing with a 10-mm DAST aperture under identical conditions. If the 12-mm aperture cannot be prepared or the crystal damages before reaching the scaled pulse energy, the Fig. 8 scaling claim is not physically realizable.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's principal advantage over DAST is the scaling argument in 'Comparison with Other Common NLO Crystals' and Fig. 8. ZPAN's demonstrated crystal face is 7 cm × 1 cm; the 1-cm width is smaller than the 12-mm diameter used in the Fig. 8 example, so a circular 12-mm aperture cannot be cut from the reported crystals. The only way ZPAN outperforms DAST in Fig. 8 is through aperture area, since its efficiency is lower (~1.7% vs ~2.4%). Without a larger usable aperture, the claim that ZPAN enables 'significantly stronger THz pulses than any other organic crystals' is unsupported. The scaling model also assumes THz output grows quadratically with aperture at fixed fluence and that the crystal survives proportionally larger pulse energies; no damage-threshold measurements are provided, and thermal/absorption effects at larger apertures are not addressed. If a rectangular aperture is used instead, the advantage would scale only linearly with length, not quadratically. This concern is addressable by growing wider crystals or by reframing the comparison, but as written the central high-power claim is overstated.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports the synthesis, crystal growth, and structural characterization of the organic crystal ZPAN, which packs noncentrosymmetrically (Pna2_1) when grown by slow evaporation from acetone with 5 vol% water. The crystals grow as large rectangular prisms (up to 7 cm × 1 cm × 0.2 cm) with a (010) main face and a [001] polar axis. The authors measure THz generation by optical rectification at pump wavelengths 1250–1550 nm, for crystal thicknesses 170–730 μm, and report a peak-to-peak THz field near 1 MV/cm with a smooth spectrum from 0.5 to 3.4 THz. They also extract the THz refractive index and absorption coefficient, compare ZPAN with BNA, DAST, and GaP, and present a calculated d-tensor that is compared with azimuthal pump-polarization measurements. The paper's central high-power claim is that ZPAN's large crystal faces allow aperture scaling to exceed the THz output of DAST and other organic crystals.","tokens_in":11527,"tokens_out":4842,"duration_ms":50780,"significance":"If the central claims hold, ZPAN would be a useful addition to organic THz generation materials: it combines a broad 0.5–3.4 THz spectrum with a peak-to-peak field comparable to DAST, and the reported growth of centimeter-scale crystals is genuinely unusual for this class. The structural work is thorough: SC-XRD including Flack parameter analysis, face-indexing of the grown crystals, and comparison of anhydrous, hydrated, and centrosymmetric forms. The wavelength- and thickness-dependent THz measurements and the direct comparison of measured azimuthal data with a calculated d-tensor response are also strengths. However, the absolute 1 MV/cm value is presented as a single waveform without uncertainty or calibration details, and the aperture-scaling advantage that underpins the 'high-power' claim is not supported by the demonstrated crystal dimensions or by damage-threshold data. These issues are addressable but need to be fixed before the paper's headline conclusions can be accepted.","major_comments":[{"comment":"The aperture-scaling argument is not supported by the demonstrated crystal geometry. The largest ZPAN crystals are 7 cm × 1 cm × 0.2 cm, so a 12-mm circular aperture (the example in Fig. 8) exceeds the 1-cm width. At fixed fluence, a rectangular aperture limited by the 1-cm width would scale THz output only linearly with length, not quadratically with diameter. No damage-threshold or saturation measurements are reported to justify the fixed-fluence, constant-efficiency scaling assumed in the figure. This overstates the conclusion that ZPAN can generate 'significantly stronger THz pulses than any other organic crystals.' The authors should either demonstrate a circular aperture >10 mm, present a model for rectangular apertures with realistic dimensions, or reframe the claim as a potential advantage contingent on further growth development.","section":"Comparison with Other Common NLO Crystals, Fig. 8"},{"comment":"The headline near-1 MV/cm peak-to-peak field is a single waveform with no error bars, no stated number of repeat measurements, and no description of how the absolute field was calibrated in the electro-optic sampling detection (e.g., GaP EO coefficient, probe wavelength, focal spot size, and systematic uncertainties). The comparison with DAST and BNA in Fig. 7 also appears to combine data from different setups and references without a common uncertainty budget. The central quantitative claim therefore rests on a single, uncalibrated-looking waveform. Please add calibration details and at least an uncertainty estimate for the peak field.","section":"THz Generation Measurements, Fig. 4"},{"comment":"The d-tensor calculation uses Lorentz local-field factors in which the refractive indices of the two non-polar principal axes are set to DAST's value of 1.6, an ad hoc approximation that is acknowledged in the text. The resulting d values (e.g., d33 = 117.64 pm/V) and the face-dependent polarizations in Table 1 depend directly on this choice. Since the measured THz index of ZPAN is about 2.2, the local-field factors could be substantially different. The authors should provide a sensitivity analysis (e.g., using n = 1.6 and n = 2.2 for the non-polar axes) to show that the conclusions about (100) and (010) face capability and the azimuthal fits in Fig. 10 are robust. Without this, the agreement between model and experiment is a weaker confirmation than implied.","section":"Theoretical and Experimental THz Generation Capabilities, Eq. (1)"}],"minor_comments":[{"comment":"The text refers to 'table 8' when describing the calculated polarizations; this should be Table 1.","section":"Theoretical section, Table 1 caption"},{"comment":"The caption/inset says BNA and DAST efficiencies come from Ref. [9] and Ref. [10], respectively, but Ref. [9] is OH1 and Ref. [10] is BNA. Please check the reference assignments.","section":"Fig. 7 inset"},{"comment":"The expressions P100 = Py2 + Pz2, etc., are written as sums of squares; they should be squared magnitudes or the vector-sum magnitude sqrt(Py^2 + Pz^2) should be explicitly defined.","section":"Eq. (2) and P100/P010/P001 definitions"},{"comment":"Heading capitalization is inconsistent ('Crystal Face testing results'); also 'Paige Petersen' in author list is listed as 'P. Peterson' in the author contributions section.","section":"Crystal Face testing results heading"},{"comment":"The SI contains a placeholder 'Error! Bookmark not defined.' in the Table of Contents; this needs to be fixed.","section":"Supporting Information Table of Contents"}],"recommendation":"major_revision","confidential_remarks":"The paper is a solid materials-characterization study with a clearly disclosed commercial conflict of interest. My main concern is that the market-facing 'high-power aperture scaling' claim goes beyond the demonstrated data: the actual crystals are 1 cm wide, and no damage or scaling experiments are shown. I think a major revision that reframes the scaling argument as a testable future direction, adds uncertainty/calibration for the absolute THz field, and sensitivity-tests the d-tensor local-field approximation would bring the claims in line with the evidence."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a solid materials paper with a real new result—a reproducible growth protocol for centimeter-scale noncentrosymmetric ZPAN crystals and a thorough THz characterization. The 1 MV/cm field and 0.5–3.4 THz spectrum are consistent with the measurements shown. The face indexing and structure determination are careful. The d-tensor calculation is reasonable as a design estimate; it leans on a published hyperpolarizability and an assumed refractive index taken from DAST, which is a legitimate approximation, not a circular fit.\n\nThe soft spot is the aperture-scaling claim. The crystals are 7 cm × 1 cm rectangular plates; a 12-mm circular aperture cannot fit on the 1-cm width. The quadratic scaling in Fig. 8 assumes a circular aperture that the paper does not actually demonstrate. With a rectangular aperture, output at fixed fluence scales linearly with length, not quadratically. And there is no damage-threshold data to support the implied pulse-energy scaling. That is load-bearing for the conclusion that ZPAN can generate 'significantly stronger THz pulses than any other organic crystals,' and as written it is not supported.\n\nEverything else holds up. The wavelength- and thickness-dependent measurements are internally consistent; the 3.4 THz absorption explains the spectral cutoff; the azimuthal dependence fits the model. The comparison with DAST, BNA, and GaP at 1450 nm is useful. I would like error bars on the headline field and raw data in a repository, but those are minor.\n\nWho is this for? Anyone working on high-field THz sources or organic NLO crystal growth. It deserves serious peer review. The authors need to fix the scaling argument—either grow wider crystals or reframe the claim around rectangular apertures with a clear damage-threshold roadmap.","headline":"ZPAN is a credible experimental step forward in organic THz crystals, but the aperture-scaling claim oversells the demonstrated crystal geometry.","tokens_in":12064,"tokens_out":1410,"would_cite":true,"duration_ms":13559,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"The organic crystal ZPAN, grown in large noncentrosymmetric plates, generates near-1 MV/cm terahertz pulses with a smooth 0.5–3.4 THz spectrum and scales with pump aperture.","keywords":["ZPAN","terahertz generation","organic nonlinear optical crystal","optical rectification","crystal growth","Pna2_1","aperture scaling","DAST"],"falsifier":"Measure terahertz pulse energy from a ZPAN crystal as a function of pump aperture diameter at a fixed fluence (about 2 mJ/cm2) and compare to the predicted quadratic scaling; if the output is sub-quadratic or the crystal damages before the aperture reaches 12 mm, the scalability advantage over DAST fails. A second check would be to reproduce the 1 MV/cm peak-to-peak field with an independent measurement at 1450 nm on a ~670-μm crystal.","tokens_in":11130,"feed_emoji":"💎","tokens_out":5468,"duration_ms":50477,"temperature":0.7,"pith_summary":"This paper establishes that ZPAN, an organic nonlinear optical crystal, can be reliably grown in large, noncentrosymmetric plates using a slow-evaporation acetone–water method, and that these crystals generate high-intensity terahertz light via optical rectification. The authors measure a peak-to-peak terahertz field near 1 MV/cm with a smooth spectrum from 0.5 to 3.4 THz, and they show the crystal's large 7 cm × 1 cm face enables a path to higher terahertz output by scaling the pump aperture—something impractical for other organic crystals like DAST. A sympathetic reader would care because high-intensity terahertz sources are needed for imaging, spectroscopy, and nonlinear terahertz science, and ZPAN's size advantage could make it a practical workhorse.","feed_headline":"A 7-cm organic crystal pushes terahertz near 1 MV/cm","feed_subtitle":"Large-crystal growth lets ZPAN scale THz output with pump aperture, outpacing smaller organic crystals.","key_machinery":"The central mechanism is optical rectification in the noncentrosymmetric Pna2_1 lattice, where the molecular hyperpolarizability vectors align constructively along the [001] polar axis. The key enabling capability is the reproducible growth protocol—slow evaporation from acetone with 5% water—that yields large, high-quality (010)-faced plates. Calculated second-order coefficients (largest d333 = 117.64 pm/V) and polarization analysis show that both the (100) and (010) faces are active for THz generation, while the (001) face is inactive, consistent with the molecular packing.","core_discovery":"ZPAN crystals grown by slow evaporation from acetone with 5 vol% water consistently adopt the noncentrosymmetric space group Pna2_1, with the (010) face as the main growth face and the [001] direction as both the polar axis and the elongated growth axis. When the near-infrared pump is polarized along [001], optical rectification produces a peak-to-peak terahertz electric field near 1 MV/cm with a smooth spectrum from 0.5 to 3.4 THz. The large crystal size (up to 7 cm × 1 cm) allows the pump aperture to be scaled, so that total terahertz output can increase quadratically with aperture at fixed fluence, potentially surpassing DAST at high pulse energies.","pith_inferences":["The paper's aperture-scaling comparison normalizes to DAST's maximum 10-mm aperture, but it does not demonstrate that ZPAN can be fabricated into a circular aperture larger than 10 mm; growing and polishing such an aperture on the 7 cm × 1 cm plates is untested. (Editorial inference.)","The d-tensor calculation approximates the refractive indices of the two non-[001] axes using DAST values; if the actual ZPAN indices differ, the magnitudes of d333 and the comparison with DAST could shift. (Editorial inference.)","The paper does not measure the damage threshold at high pulse energies; if ZPAN damages at lower fluence than DAST, the aperture-scaling advantage would be reduced. (Editorial inference.)","The 3.4 THz absorption likely corresponds to a phonon mode; crystal engineering or deuteration might shift it and extend the usable terahertz bandwidth beyond 4 THz. (Editorial inference.)"],"forward_implications":["ZPAN can generate near-1 MV/cm peak-to-peak terahertz fields with a smooth spectrum from 0.5 to 3.4 THz when pumped around 1450 nm.","The large 7 cm × 1 cm crystal faces enable terahertz output scaling with pump aperture, which could allow ZPAN to outperform DAST at high pulse energies.","Pump wavelengths from 1350 to 1550 nm all produce similar terahertz spectra, offering flexibility in laser source choice.","A strong absorption at ~3.4 THz sets the upper spectral limit, so ZPAN is best suited for the 1–3 THz range.","The calculated d tensor indicates the (100) face could also generate terahertz via the off-diagonal d322 coefficient if that face can be grown to useful size."],"fun_headline_variants":["ZPAN crystal achieves near-1 MV/cm THz field","7-cm ZPAN crystal scales THz with pump size","Large organic crystal yields high-intensity THz","Aperture-scalable ZPAN hits 1 MV/cm THz"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The central claim that ZPAN can surpass DAST at high power assumes that terahertz output scales quadratically with pump aperture at fixed fluence and that the crystal survives proportionally larger pulse energies; the largest reported crystal is a 7 cm × 1 cm plate, so a 12-mm circular aperture does not yet fit its 1-cm width, and no high-energy damage data are presented.","fun_headline_variants_meta":{"raw":{"variants":["ZPAN crystal achieves near-1 MV/cm THz field","7-cm ZPAN crystal scales THz with pump size","Large organic crystal yields high-intensity THz","Aperture-scalable ZPAN hits 1 MV/cm THz"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000237,"raw_usage":{"total_tokens":1373,"prompt_tokens":803,"completion_tokens":570,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":547,"completion_tokens_details":{"reasoning_tokens":500}},"tokens_in":547,"tokens_out":570,"duration_ms":6198,"temperature":1.0,"reasoning_tokens":500,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-02T03:12:37.777906+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure terahertz pulse energy from a ZPAN crystal as a function of pump aperture diameter at a fixed fluence (about 2 mJ/cm2) and compare to the predicted quadratic scaling; if the output is sub-quadratic or the crystal damages before the aperture reaches 12 mm, the scalability advantage over DAST fails. A second check would be to reproduce the 1 MV/cm peak-to-peak field with an independent measurement at 1450 nm on a ~670-μm crystal.","supporting_citations":[],"review_version":1}