statusrunning_shifted_ldospersistent GPU worker
iteration10projection β=1
morphologyη=0.500.45 / 0.50 / 0.55 cycle
target-line LDOS1.228anthracene-normalized shifted Q/V
best target LDOS1.441best accepted morphology evaluation
peak LDOS1.332on the tracked pole
tracked Q809.5minimum of field and energy fits
calibrated pole768.693 nmpublished target 768.555 nm
mode volume3.449 µm³energy / molecule-plane |Ey|²
gray fraction22.04%slow β=1→64 continuation
## Reconstruction target and forward qualification
The source is the published [Device 23 full-boundary campaign](https://www.christianmlange.com/cavitygrad/optimization/device23-full-boundary-q/#outcome-so-far).
Its final physical checkpoint has **λ=768.555 nm,
Q=1183.52**. The unavailable numeric 4 nm level set was
reconstructed from the lossless matched-axis geometry PNG. The PNG hash,
coordinate calibration, 40 fitted hole contours, and ~5.1 nm raster uncertainty
are stored in `device23_geometry.json`.
FDTDX finds one clean corresponding pole at **757.888 nm,
Q=1662.36**, with fit error 2.10e-05. The 20 and
25 nm area-averaged grids agree in wavelength to 0.02 nm. The remaining 1.39%
frequency offset is retained visibly as a fixed reconstruction/discretization
calibration; it is not retuned during optimization. The raw FDTDX Q is
1.405× the Tidy3D value, so Q is tracked
as useful solver telemetry rather than claimed as cross-engine parity.
The red star is the **Ey-oriented emitter at the centre of the 200 nm
anthracene film**. Holes and later topology changes etch only Si₃N₄; the plane
of the cavity is air wherever nitride is absent.
## Initial and evolving single-etch mask
Only the positive x/y quadrant is simulated, using the exact `(1, -1, 0)`
parity of a centred Ey dipole. The displayed mask is unfolded for inspection.
A 50 nm conic filter, η=0.45/0.50/0.55 morphology cycle, pinned terminal
waveguide, and 50 nm outer-air rail prevent the optimizer from exploiting the
edge of the 1 µm-wide design region.
## Fields at the molecule, cavity, and complete vertical domain
Every field panel is a literal FDTDX phasor and is normalized independently so
that the molecular-plane evanescent field remains visible beside the stronger
Si₃N₄ field. The x-z panel includes the complete z extent through both PML
interfaces.
## Objective and history
The differentiated objective is
$$
\log\!\left[\frac{(Q/V)_\mathrm{anth}}
{1 + \left(2Q\,\Delta\omega/\omega_0\right)^2}\right].
$$
Adjacent iterations intentionally evaluate different robust projections.
The history therefore draws η=0.45, 0.50, and 0.55 as separate colored tracks;
only points with the same η should be compared as a trajectory. Dotted LDOS
curves show the corresponding on-pole value before target-line detuning.
A short pulse fits the field and stored-energy decay independently; the lower
Q is used. The pole is recentered between coherent fits with stopped gradients,
which is the Shaker-style shift that avoids differentiating the pole-motion
Hessian. Steps fail closed if either residual exceeds 18%, the two Q estimates
differ by more than 2×, or the calibrated pole leaves the declared tracking
window. Full binarization is deliberately slow and reaches β=64 after roughly
600 accepted iterations.