Optical element and laser module

An optical element comprising:

• a substrate including a main surface;
• and
• a core layer provided on the main surface and made of a material having an electro-optic effect,
• wherein the core layer comprises a mode converter extending in a first direction along the main surface, the mode converter configured to convert a polarization mode of visible light between a TM0 mode and a TE0 mode,
• wherein the mode converter comprises:
• an incident portion positioned at one end of the mode converter in the first direction and on which the visible light in a first polarization mode which is one polarization mode among the TM0 mode and the TE0 mode is incident;
• an emission portion positioned at another end of the mode converter in the first direction, the emission portion configured to emit the visible light in a second polarization mode which is another polarization mode among the TM0 mode and the TE0 mode;
• a first conversion portion provided between the incident portion and the emission portion, the first conversion portion configured to convert the polarization mode of the visible light between the TM0 mode and a TE1 mode;
• and
• a second conversion portion provided between the incident portion and the emission portion, the second conversion portion configured to convert the polarization mode of the visible light between the TE0 mode and the TE1 mode,
• wherein the first conversion portion comprises a first end and a second end which are both ends in the first direction, and an upper tapered portion and a lower tapered portion which are stacked in a second direction intersecting the main surface,
• wherein in a first region of the first conversion portion from the first end to an intermediate position between the first end and the second end, a length of the upper tapered portion in a third direction intersecting the first direction and the second direction continuously increases from a first length at the first end to a second length, which is longer than the first length, toward the intermediate position,
• wherein in the first region, a length of the lower tapered portion in the third direction continuously increases from the first length at the first end to a third length, which is longer than the second length, toward the intermediate position,
• wherein in a second region of the first conversion portion from the intermediate position to the second end, a length of the upper tapered portion in the third direction continuously increases from the second length at the intermediate position to a fourth length, which is longer than the second length and shorter than the third length, toward the second end, and
• wherein in the second region, a length of the lower tapered portion in the third direction continuously decreases from the third length at the intermediate position to the fourth length toward the second end.