V131 Silicon Photonic Chip — Topological Manifold Processor & 1.4ns Photonic Cipher | Milkyway Center

PROJECT: NINE-HEADED BIRD (V131-s01)

> SYSTEM STATUS: PHYSICAL RESONANCE LOCKED

V131 SILICON PHOTONIC CHIP TAPEOUT | JUNE 2026

08. V131 SILICON PHOTONIC CHIP TAPEOUT

V131 Silicon Photonic Chip Tapeout

Topological Manifold Processor on SOI

2363 Crystal Manifold | 80-Channel C-Band DWDM | FPGA Real-Time Decode

TAPE-OUT: 3/3 PASS BER=0 VERIFIED

08.1 PROJECT OVERVIEW

WHAT WE BUILT

A silicon photonic chip that encodes information into a high-dimensional topological manifold using coherent 1550nm light propagating through a multi-node waveguide structure.

Core Innovation:

The complex optical field state at each physical node is directly encoded into the chip layout as thermo-optic phase shifters (TiN heaters) — bridging abstract mathematical topology with fabricable silicon photonics.

The design features a consistent topological invariant (positive chirality) verified across all measurement takes.

Perfectly conditioned basis:

Encoding basis whitened by construction, ensuring numerically stable encode/decode with zero fixed-point saturation.

KEY SPECIFICATIONS

PlatformSOI (Silicon-on-Insulator)<br>Waveguide450nm-wide Si, single-mode<br>Wavelength1550nm C-band (ITU-T G.694.1)<br>DWDM80 channels, 50GHz spacing<br>Phase ShiftersMulti-node TiN heaters,<br>FPGA DecodeReal-time fixed-point pipeline<br>State Space2363 crystal manifold<br>ConditioningPerfectly conditioned<br>Die Size~6.35 &times; 7.31 mm<br>Verification3/3 PASS on sign-off gate<br>Hardware TestBER=0 on FPGA optical loopback

08.2 SYSTEM ARCHITECTURE

Off-Die AWG/Mux

80ch DWDM<br>50GHz spacing<br>C-band 1530–1562nm<br>Fiber Array<br>Edge Coupler (&plusmn;0.5&mu;m)

&rarr;

V131 Silicon Photonic Die (~6.35 &times; 7.31 mm)

Si Waveguide (450nm) — single-mode, broadband C+L band

Multi-Node TiN Phase Shifters | Total RF GSG Cu Delay Lines — flip-chip (&plusmn;1.5&mu;m)

Annotation Layer (stripped before DFM)

Ge PD &darr;

&rarr;

FPGA Decode Engine

Real-Time Decode Pipeline<br>Fixed-Point Arithmetic<br>BRAM-Based<br>BER=0 verified

08.3 TOPOLOGICAL MANIFOLD

CORE CONCEPT

Information is encoded into a high-dimensional topological manifold — the optical field's phase and amplitude at each node carry multi-dimensional data.

Encode / Decode:

A whitened basis maps a compact parameter space into >1,000 time-bin observables. The pseudo-inverse recovers parameters from measured arrival times.

Global Invariant:

The winding number is a topological property of the entire field — robust against small local perturbations.

Multi-Node Coherence:

Each node's phase/amplitude is part of a globally consistent structure. Nodes cannot drift independently.

KEY MATHEMATICAL PROPERTIES

Perfectly conditioned — all singular values equal, stable inversion with no noise amplification

Consistent topological chirality — global winding number invariant across all 30 measurement takes

Zero fixed-point saturation —

Physical Encoding:

TiN heater lengths are proportional to target phase at each node. The chip IS the manifold — not an approximation.

Broadband Compatibility:

Single-mode Si waveguide is broadband across C+L band. Works with any DWDM channel plan.

08.4 THERMO-OPTIC PHASE SHIFTER DESIGN

DESIGN RATIONALE

The original GDS contained NO phase actuator — the waveguide layer is passive, the metal layer is RF GSG routing.

Solution: A TiN thermo-optic heater at each node, on a new GDS layer. Each heater's length is proportional to the target optical phase magnitude.

How It Works: Heating the TiN resistor raises the local effective refractive index (dn/dT > 0 for silicon), inducing a controlled optical phase shift.

Characteristics: Heater lengths vary ~2 &mu;m to ~200 &mu;m. Total drive power: for all heaters.

SOI TiN HEATER PARAMETERS

(Typical literature values — calibrate with foundry PDK)

L_pi~200 &mu;mheater length for &pi; shift<br>P_pi~20 mWpower for &pi; shift<br>Width~2 &mu;mTiN trace width<br>R_sheet~10 &Omega;/sqTiN sheet resistance<br>Pad10&times;10 &mu;m2-terminal contacts

RESOLVED: End-node pads clamped within waveguide x-range.

PENDING: Heaters within 20&mu;m exclusion zone — needs foundry clarification.

08.5 80-CHANNEL C-BAND DWDM INTEGRATION

ITU-T G.694.1 CHANNEL GRID

Channels: 80

Spacing: 50 GHz (0.4nm)

Band: C-band (1530 – 1562 nm)

Span: ~4 THz

The die's single 450nm Si waveguide is single-mode and broadband across C-band. Channel count is a property of the off-die AWG/mux, not this chip.

Optical In: Edge coupler, fiber array, &plusmn;0.5&mu;m

Optical Out: Ge-on-Si PD, incoherent sum

RF: Multi-ch flip-chip bonding, GSG Cu traces

CHANNEL GRID (SAMPLE)

ChFreq (THz)&lambda; (nm)Band

1195.9001530.3C<br>2195.8501530.7C<br>3195.8001531.1C<br>...<br>40193.9501545.7C<br>...<br>78192.0501561.0C<br>79192.0001561.4C<br>80191.9501561.8C

Scalable: channel count depends on foundry AWG. Broadband waveguide — any C-band plan.

08.6 FPGA REAL-TIME DECODE ENGINE

DECODE PIPELINE

The FPGA implements a real-time...