WebBeamPROP

Waveguide

Preset

Cladding material

Background index (n₀)

Core material

Core index (n)

Core κ (imag. index; + loss, − gain)

Core width

Core height

Core center X

Core center Y

Bend radius R (0 = straight)

Device

Device type

Taper end width

Branch separation

Coupler gap

MMI width

S-bend offset

MZI arm Δn

Grating period Λ

Index modulation Δn

Apodization (0–1)

Grating length (0 = whole)

Split/combine fraction

Launch offset X

Launch offset Y

Custom z-profile n(x,y,z)

Define an arbitrary refractive-index profile that varies along z. Enter a JS expression returning the TOTAL index at coordinates (x,y,z) in µm. Variables: x, y, z, p (z = propagation distance 0…L, p.nClad/p.nCore/p.coreW…). When non-empty it overrides the device geometry and rebuilds every step. Examples: p.nClad + (p.nCore-p.nClad)*Math.exp(-(x*x)/(w*z/100+1)**2) (z-widening guide) or a step-index rectangle. Leave empty to use the Device selector above.

n(x,y,z) expression

Analysis

Number of modes (1–6)

View mode

Launch→mode coupling η: —

S-parameters (4-port)

Full S-matrix over all ports (inputs first, then outputs). Forward BPM gives the transmission block; a first-Born bidirectional BPM adds the diagonal reflections S11/S22/… from back-scatter off ∂n/∂z. |S|² = fractional power, IL = −10·log₁₀|S|², ∠ = phase. Straight guides reflect ≈0; tapers / y-branches / MMIs show real Fresnel reflection.

Output coupling & radiation

After a 2D BPM run the output near-field at z=L is Fourier-transformed to the angular far-field (NFFF), then overlapped with a Gaussian SMF mode to give fiber coupling efficiency η and insertion loss IL.

Fiber MFD (1/e², µm)

Coupling η: — Insertion loss: — dB Half-angle: — Peak angle: —

Substrate leakage: —

Tier-1/2 advanced optics

RSoft BeamPROP gap features: modal BPM (MEM), 2D grating diffraction, polarization analysis, multi-wavelength S sweep, Touchstone export.

MEM mode count

Grating Λx (µm)

Grating Λy (µm)

Sweep λ from (µm)

to (µm)

Points

Multimode coupled BPM

Coupled-mode BPM: each of N guided modes carries its own β_m, and a linear coupling matrix κ sloshes power between modes (directional coupler / mode converter).

Mode count N (2–6)

Coupling κ (1/mm)

Launch

Parameter sweep

Sweep parameter

From

Points

Animate output field

Optimizer (auto-tune)

Scans the parameter and refines to the value that maximizes/minimizes the chosen figure of merit.

Figure of merit

Goal

Coarse points

Dispersion analyzer

Sweep the effective index across a wavelength band to extract waveguide dispersion: n_eff, group index n_g, GVD β₂, dispersion parameter D, and third-order β₃. Use it to design anomalous-dispersion waveguides (solitons / modulation instability) or normal dispersion for compression.

λ from (µm)

to (µm)

Points

Mode

Simulation

Wavelength λ

Window width

Window height

Grid Nx

Grid Ny

Propagation distance

Step size Δz

Suggest a grid that resolves the guided field (Nyquist + evanescent tail) and keeps the paraxial step accurate. Fills the fields below and refreshes the live grid-quality readout.

Propagation scheme

Propagation solver

Vectorial BPM (Ex, Ey)

Anisotropy (birefringence)

Δn (n_y − n_x)

Scalar polarization

n_xx (ordinary axis)

n_yy (extraordinary axis)

Δn_x (n_xx − n_core)

n_xy (off-diagonal)

Boundary condition

Input field

Beam width

Advanced physics

Nonlinear material

Kerr n₂ (normalized)

Launch power ×

Tuning Δn (direct)

Thermal ΔT [K]

EO drive V

Gain g₀ [1/µm]

Saturation Iₛₐₜ (norm.)

Linear loss α [1/µm]

Kerr: Δn = n₂·|E|² (n₂ normalized). Pick a nonlinear material to load a physically-ordered n₂. Launch power scales intensity (and the Kerr effect) so you can reach the modulation-instability / soliton regime. Active medium: amplitude × exp((g₀/(1+I/Iₛₐₜ) − α)·Δz). Tuning adds Δn = Δn(direct) + dn/dT·ΔT + dn/V·V; for MZI it shifts only the upper arm.

Active tuning (EO/TO)

Electro-optic / thermo-optic phase shift. The induced Δn = dnTune + (dn/dT)·ΔT + (dn/V)·V is applied to the active region; the readout reports the effective-index shift Δn_eff and the accumulated phase Δφ = k₀·Δn_eff·L (and Vπ for an MZI).

Δn_eff (induced): — Phase shift Δφ: — Vπ (MZI): — Switch state: —

Linear EO/TO model (Δn_eff ∝ Δn). For MZI the arm phase shift sets the bar/cross state.

Pulse / Nonlinear Dynamics

Time-domain generalized NLSE (split-step Fourier) for the guided-mode temporal envelope: solitons, modulation instability, dispersion walk-off. β₂<0 = anomalous (soliton / MI); β₂>0 = normal (broadening). γ = n₂ω₀/(c·A_eff).

Envelope model

Material preset

Pulse shape

Pulse width τ [ps]

Peak power P₀ [W]

GVD β₂ [ps²/km]

Walk-off β₁ [ps/km]

TOD β₃ [ps³/km]

Loss α [dB/km]

Eff. area A_eff [µm²]

Kerr n₂ [×1e-20 m²/W]

Length L [m]

Time window [ps]

Time samples

Raman fraction f_R

Self-steepening

Noise seed [%]

Launch pol. angle [°]

Birefringence Δβ₁ [ps/m]

Number of modes

Mode coupling κ [1/mm]

Transverse samples

Transverse window [µm]

Beam waist w₀ [µm]

Core index n

ANo reference case held.

Soliton order N: — MI offset Ω: — Energy split: —

Top: pulse evolution |u(t,z)|² (t horizontal, z vertical). Bottom: output spectrum |û(ω)|².

Physics diagnostics

Characteristic lengths and regime classification, updated live from the pulse parameters above.

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Analysis & tools

Cross-section inspector, parameter sweeps, 3D evolution surface, saved-case library and enhanced export.

Cross-section inspector

Click the evolution map above to pick a propagation distance z; the full |u(t)|² and |û(ν)|² profiles at that z are drawn here.

z = —

Parameter sweep heatmap

Peak output power over a (P₀, β₂) grid centred on the current values. Colour = peak |u|² (W) at z=L.

Metric

3D evolution surface

|u(t,z)|² rendered as a rotatable 3D surface. Drag to rotate.

Auto-rotate

Saved-case library

Name and store multiple runs (beyond A/B), restore or delete them. Stored locally in this browser.

Enhanced export

Templates

Load device template

Local presets

Save the current setup under a name and restore it later. Stored locally in this browser (separate from the JSON file export).

max

Show index profile

z = 0.0 µm

Colormap Contrast

Field intensity |E|² Relative power: 1.000 Step: 0 Effective index n_eff: — live

Ready

Adjust parameters and press Run. Drag the slider to scrub along z; press Play to animate. Use Mode Solver to compute the guided-mode n_eff.

Note: paraxial (Fresnel) BPM is default. Enable Wide-angle for high index contrast. Large bend radius R bends the guide via conformal mapping.

Transverse intensity vs propagation (x–z)

Longitudinal slice (|E|² vs z at fixed x)

Pick a transverse position — drag the slider or click the field map above — to plot intensity along propagation at that cut. The red dashed line marks the cut on the field view.

Mode analysis

Compute the guided modes of the current geometry and decompose the launch field onto them.

Modes to show

3D field volume (x–y–z)

Auto-rotate