Femtosecond-Laser-Induced Nanoscale Blisters in Polyimide Thin Films through Nonlinear Absorption
Bibliographic record
Abstract
Nonlinear absorption of femtosecond laser pulses provides a unique opportunity to confine energy deposition in any medium to a region that is below the focal diameter of a pulse. Illumination of a polymer film through a transparent high-band-gap material such as glass, followed by nonlinear absorption of 800-nm light in polymers, allows us to further restrict absorption to a very thin layer along the propagation direction. We demonstrate this confinement by simulating femtosecond-laser-induced polymer modification by linear, two-photon, and three-photon absorption, and discuss the control over energy absorption in polymers that multiphoton processes offer. Energy deposited in a thin polymer film induces a protruding blister. We present experimental results for blister diameter and height scaling with variation of pulse energy. Using pulse energies of 20--200 nJ and 0.4-NA focusing, we fabricate blisters with diameters of $1--5.5\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ and heights of $75\phantom{\rule{0.2em}{0ex}}\mathrm{nm}$ to $2\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$. Using 0.95-NA focusing, we obtain laser-induced blisters with diameters as small as 700 nm, suggesting blister-based laser-induced forward transfer is possible on and below the 1-$\ensuremath{\mu}\mathrm{m}$ scale. Submicrometer blister formation with use of femtosecond lasers also offers a method of direct, precise laser writing of microstructures on films with single laser pulses. This method is a possible alternative to lithography, laser milling, and laser-based additive machining.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".