US 12,265,257 B2
Optical modulator
Kenji Nagase, Hong Kong (CN); Hiroshi Take, Hong Kong (CN); Anthony Reymund Melad Binarao, Hong Kong (CN); and Cheng Bu Heng, Hong Kong (CN)
Assigned to TDK CORPORATION, Tokyo (JP)
Filed by TDK CORPORATION, Tokyo (JP)
Filed on Apr. 8, 2022, as Appl. No. 17/716,440.
Claims priority of application No. 202210296417.1 (CN), filed on Mar. 24, 2022.
Prior Publication US 2023/0036811 A1, Feb. 2, 2023
Int. Cl. G02B 6/125 (2006.01); G02B 6/12 (2006.01); G02F 1/035 (2006.01); G02F 1/21 (2006.01); G02F 1/225 (2006.01)
CPC G02B 6/125 (2013.01) [G02F 1/0356 (2013.01); G02F 1/212 (2021.01); G02F 1/2255 (2013.01); G02B 2006/1204 (2013.01); G02B 2006/12097 (2013.01); G02F 2202/20 (2013.01)] 5 Claims
OG exemplary drawing
 
1. An optical modulator comprising:
a substrate;
an electro-optical material layer formed on a predetermined region of the substrate, the electro-optical material layer including an optical waveguide formed in a plane that is parallel to the substrate, the optical waveguide folding back three times in the plane;
a buffer layer formed on the substrate which is provided so as to cover the electro-optical material layer; and
an electrode layer formed on the buffer layer, wherein
the optical guide includes a RF portion optical waveguide which is applied with a modulation signal and is patterned, and a DC portion optical waveguide which is applied with a DC voltage and is patterned,
the electrode layer has a RF portion electrode formed on the buffer layer where the RF portion optical waveguide is located and a DC portion electrode formed on the buffer layer where the DC portion optical waveguide is located,
a film thickness of the DC portion electrode is smaller than a film thickness of the RF portion electrode,
the RF portion optical waveguide includes, in the plane, three linear portions parallel to each other, including a first linear portion, a second linear portion, and a third linear portion, and three curved portions, including a first curved portion, a second curved portion, and a third curved portion,
the DC portion optical waveguide includes, in the plane, a fourth linear portion parallel to the third linear portion,
at the first curved portion, the second linear portion is connected to and folds back from the first linear portion,
at the second curved portion, the third linear portion is connected to and folds back from the second linear portion,
at the third curved portion, the fourth linear portion is connected to and folds back from the third linear portion,
the RF portion electrode includes a first RF portion that overlaps with the first linear portion in a thickness direction of the substrate, a second RF portion that overlaps with the second linear portion in the thickness direction of the substrate and a third RF portion that overlaps with the third linear portion in the thickness direction of the substrate,
the DC portion electrode overlaps with the fourth linear portion in the thickness direction of the substrate,
the overlap between the first RF portion electrode and the first linear portion forms a first overlapping area that elongates in a direction in which the first linear portion extends,
the overlap between the second RF portion electrode and the second linear portion forms a second overlapping area that elongates in a direction in which the second linear portion extends,
the overlap between the third RF portion electrode and the third linear portion forms a third overlapping area that elongates in a direction in which the third linear portion extends,
the overlap between the DC portion electrode and the fourth linear portion forms a fourth overlapping area that elongates in a direction in which the fourth linear portion extends, and
the buffer layer is configured to only overlap the optical waveguide in the thickness direction of the substrate without overlapping other areas of the substrate.