A structure that confines and guides light by surrounding a high-index core with a lower-index cladding. Silicon photonics commonly uses silicon about 0.5 µm × 0.22 µm in cross section surrounded by oxide, allowing bend radii of just a few µm.
Japanese name: 導波路
Waveguide appears in 17 practice questions across 1 topic, including Silicon photonics.
Field: Silicon photonics
Answer: C. About 0.8 eV. It is smaller than silicon's band gap, so it propagates with almost no absorption
1.24 ÷ 1.55 ≈ 0.80 eV, which is smaller than silicon's band gap of about 1.12 eV, so it cannot lift valence-band electrons into the conduction band and no band-to-band absorption occurs. Silicon is therefore nearly transparent at telecom wavelengths and can serve as a waveguide material. Conversely, silicon alone cannot make a photodetector for this wavelength. Silicon absorbs light with wavelengths shorter than about 1.1 µm (energies above 1.12 eV). About 1.9 eV is the result of multiplying 1.24 by 1.55, and corresponds to the energy of red light at a wavelength of about 650 nm.
Answer: B. The large index contrast confines light tightly, so it can be bent at small radii of a few µm and devices can be packed densely
Light is confined by total internal reflection at the boundary between the high-index core and the low-index surroundings (cladding), and the larger the index contrast, the tighter the confinement. The difference between silicon and oxide is about 2, orders of magnitude larger than the core–cladding difference in optical fiber (less than 1%), allowing thin waveguides with cross-sections of about 0.5 µm × 0.22 µm and bend radii down to a few µm. On the other hand, the larger the index contrast, the more sidewall roughness scatters light, so propagation loss—though condition-dependent—is about 1–3 dB/cm for a typical strip waveguide (lower for rib waveguides or low-loss processes), far greater than fiber's (about 0.2 dB/km).
Silicon is therefore nearly transparent at telecom wavelengths and can serve as a waveguide material.
Which correctly pairs the photon energy of 1.55 µm light wi…On the other hand, the larger the index contrast, the more sidewall roughness scatters light, so propagation loss—though condition-dependent—is about 1–3 dB/cm for a typical strip waveguide (lower for rib waveguides or low-loss processes), far greater than fiber's (about 0.2 dB/km).
Which correctly describes a silicon waveguide (refractive i…The mode diameter of standard single-mode fiber is about 9–10 µm, while a silicon waveguide's mode is very small, 1 µm or less; butting them together directly causes a large loss from mode mismatch.
Why is an inverse taper, in which the silicon waveguide nar…If the BOX is too thin, light extending outside the waveguide (the evanescent field) leaks into the high-index silicon substrate, so a thick BOX of about 2–3 µm is commonly used.
What is the main role of the buried oxide (BOX) layer in th…In a rib waveguide, the slabs left on both sides are doped to connect the electrodes to the pn junction at the center of the waveguide.
What is the main reason rib waveguides—shallowly etched so …As an Amazon Associate I earn from qualifying purchases.
Propagation loss Band gap Refractive index Silicon photonics Single-mode fiber Grating coupler Dicing Edge coupler C-band Ring resonator