US 12,265,253 B2
Low loss fiber-to-chip interfaces for lithium niobate photonic integrated circuits
Lingyan He, Cambridge, MA (US); Mian Zhang, Cambridge, MA (US); Amirhassan Shams-Ansari, Cambridge, MA (US); and Marko Loncar, Belmont, MA (US)
Assigned to PRESIDENT AND FELLOWS OF HARVARD COLLEGE, Cambridge, MA (US)
Filed by President and Fellows of Harvard College, Cambridge, MA (US)
Filed on Aug. 20, 2021, as Appl. No. 17/407,856.
Application 17/407,856 is a continuation of application No. PCT/US2020/019306, filed on Feb. 21, 2020.
Claims priority of provisional application 62/809,386, filed on Feb. 22, 2019.
Prior Publication US 2021/0382232 A1, Dec. 9, 2021
Int. Cl. G02B 6/122 (2006.01); G02B 6/12 (2006.01); G02B 6/14 (2006.01); G02B 6/30 (2006.01)
CPC G02B 6/1228 (2013.01) [G02B 6/12004 (2013.01); G02B 6/14 (2013.01); G02B 6/305 (2013.01); G02B 2006/1204 (2013.01); G02B 2006/12061 (2013.01); G02B 2006/12097 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An optical circuit, comprising:
a waveguide comprising an electro-optical material,
the waveguide including an elevated ridge and a slab underlying the elevated ridge, the elevated ridge and the slab extending along a central axis toward an optical interface;
the elevated ridge and the slab each having a plurality of cross-sections along the central axis, each cross-section having a width measured perpendicular to the central axis, wherein the width of elevated ridge is smaller than the width of the slab for every cross-section along the central axis, wherein the elevated ridge is trapezoidal in cross-section,
the elevated ridge including a tapered portion having a first taper, wherein the cross-section of the elevated portion decreases along the central axis toward the optical interface;
the slab including a tapered portion having a second taper, wherein the cross-section of the slab decreases along the central axis toward the optical interface, wherein:
the slab extends beyond the elevated ridge along the central axis to the optical interface; and
an optical fiber optically coupled to said waveguide,
wherein an optical coupling loss associated with the optical coupling between the optical fiber and the waveguide is equal to or less than 1.7 dB/facet at an operating wavelength of 1570 nm, 1680 nm, or any wavelength therebetween.