What can you do with light on a chip?
Learn photonic integrated circuits by building them.
Foundations
- 1LightLight as an electromagnetic wave, how this answer was found, what a field is, and where the light used on chips sits in the electromagnetic spectrum.
- 2Maxwell's equationsThe four laws that govern electric and magnetic fields, why they allow a wave that travels at the speed of light, and how a material slows light down by its refractive index.
- 3Describing a waveHow a light wave is described by its wavelength, frequency and amplitude, written as a cosine or as a complex exponential, and measured by its power.
- 4PhaseThe position of a wave in its cycle, how it grows along a path and in a material, and why only differences in phase can be observed.
- 5InterferenceWhen two waves of light meet, their fields add, and the power of the sum depends on their phase difference.
- 6Photonic integrated circuitsChips that guide light along paths of their own, what they are used for today, what they cannot do, and what the rest of this series builds.
- 7WaveguidesHow a strip of silicon holds light and guides it along a chip, first as rays that are totally reflected, then as modes that fit the waveguide.
- 8Phase shiftersHow a circuit sets the phase of light after fabrication, by heating a waveguide or by moving electrical charges in it, and what each method costs.
- 9Splitters and combinersHow light is divided between two waveguides and joined again, and why the result of joining depends on the phases of the incoming light.
- 10The Mach-Zehnder interferometerA circuit that splits light into two paths and recombines it, so that the phase difference between the paths sets how the power divides between two outputs.
- 11Circuits as matricesHow any circuit of waveguides, couplers and phase shifters is described by a matrix of complex numbers, and how connecting circuits multiplies their matrices.
- 12The MZI in practiceWhat Mach-Zehnder interferometers are used for on real chips, and what limits them: imperfect couplers, loss, wavelength, heat and size.