Phase shifter
Photonic chips are an experimental feature. Switch them on under Help › Experimental features.
A phase shifter is a section of waveguide with a phase you set, as a heater or an electro-optic section gives. It tunes a Mach–Zehnder between its outputs, or a ring's resonance, and its drive input lets the electronics modulate it, sweep it or lock it.
Ports
Ports 1 and 2, one each side, and an electrical input, drive.
The model
The section is a waveguide of its length \(\ell\), with the phase \(\phi\) set and \(\pi\) more for each \(V_\pi\) volts on its drive \(v\) added:
\[S_{12} = S_{21} = 10^{-\alpha\ell/20}\,\exp\!\left(-\frac{i 2\pi\, n_\text{eff}(\lambda)\,\ell}{\lambda}\right) e^{-i\left(\phi + \pi v/V_\pi\right)},\]with the waveguide’s loss \(\alpha\) (dB/cm) and its effective index to first order in wavelength (see Photonic chips: waveguides). The phase is the same at every wavelength. Give it a sweep to swing a Mach–Zehnder through its fringes.
A drive
Wired to the electronics, the drive sets the phase through time, worked out quasi-statically: the chip is solved again across the drive’s swing (see Electronics: drives). A sine about quadrature on a Mach–Zehnder’s heater makes its output follow the drive; with the on-chip photodiode wired back through a lock-in, it reads out a ring’s or an interferometer’s phase. \(V_\pi\) is 5 V to begin with.
Settings
| Field | Default | Meaning |
|---|---|---|
phase | 0 | Phase (°) |
len | 100 | Length (µm) |
neff | 2.44 | n_eff at 1550 nm |
ng | 4.2 | Group index |
loss | 2 | Loss (dB/cm) |
From the tool's own tables, file format version 1: the names are those in a .jekray file.
Also wg: si, sin or custom, the waveguide preset; and vpi (V), the drive’s half-wave voltage.
Readouts
Its ports and what they join, and the powers where the fibre network reaches them.
Assumptions
- The phase is set directly: no heater power, no thermal crosstalk to its neighbours, and no loss that comes with a carrier-based shifter.
- The drive acts at once: no thermal time constant, as a heater has.
Related
- Fibre stretcher, its fibre counterpart.
- 2×2 MMI and directional coupler.