Low-loss photonic crystal waveguide having large core radius

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising alternating layers of at least two dielectric materials having different refractive indices, the alternating layers surrounding the core about the waveguide axis, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ, wherein the refractive indices and thicknesses of at least some of the alternating dielectric layers substantially satisfy the following equality:
• d hi d lo = n lo 2 - 1 n hi 2 - 1
• where dhi and dlo are the thicknesses of adjacent higher-index and lower-index layers, respectively, and nhi and nlo are the refractive indices of the adjacent higher-index and lower-index layers, respectively.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising a photonic crystal structure having a photonic band gap, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate alone the wave guide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ, wherein at least a first end of the waveguide includes a coupling segment over which the refractive index cross-section is continuously varied with respect to the waveguide axis.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising a photonic crystal structure having a photonic band gap, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ,
• further comprising a second waveguide coupled to the first mentioned waveguide, wherein the cross-section of the second waveguide adjacent the first waveguide comprises regions of doped silicon located to improve coupling of the working mode into the second waveguide.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising a photonic crystal structure having a photonic band gap, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ.
• further comprising a second waveguide coupled to the first mentioned waveguide, wherein the cross-section of the second waveguide adjacent the first waveguide comprises a hollow ring contacting the first waveguide to thereby improve coupling of a working mode into the second waveguide.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region comprising alternating layers of at least two different dielectric materials surrounding the core about the waveguide axis, the confinement region having an average index greater than that of the core, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising alternating layers of at least two dielectric two materials surrounding the core about the waveguide axis, the two dielectric materials having refractive indices that differ by at least 10%, wherein during operation the confinement region guides EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the core has an average refractive index smaller than about 1.3 for a frequency in the first range of frequencies,
• wherein the core has a diameter in a range between about 4 λ and 80 λ, wherein λ is a wavelength corresponding to a central frequency in the first frequency range, and
• wherein the dielectric confinement region extends transversely from the core for at least a distance of about 6 λ.

An optical waveguide comprising:

• a dielectric core region extending along a waveguide axis;
• and
• a dielectric confinement region surrounding the core about the waveguide axis, the confinement region comprising at least 12 pairs of alternating layers of dielectric material having different refractive indices, the layers sufficient to guide EM radiation in at least a first range of frequencies to propagate along the waveguide axis,
• wherein the refractive indices of the alternating layers differ by at least 10% for a frequency in the first range of frequencies,
• wherein the pairs of alternating layers each have a thickness equal to about a, and
• wherein the core has a diameter in a range between about 10 a and 100 a.