Optical element, laser module, retinal projection device, and near-eye wearable device

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 configured to convert a polarization mode of visible light from a TM0 mode to a TE0 mode,
• wherein the mode converter comprises:
• a first waveguide extending in a first direction along the main surface;
• and
• a second waveguide extending in the first direction,
• wherein the first waveguide comprises:
• a taper section including a first incident end on which the visible light is incident and a first emission end from which the visible light is emitted, the taper section having a length in a second direction along the main surface and intersecting the first direction that increases from a first length at the first incident end to a second length toward the first emission end;
• and
• a first line section through which the visible light emitted from the first emission end propagates,
• wherein the second waveguide comprises a second line section arranged side by side with the first line section in the second direction,
• wherein the first length is a length at which a first effective refractive index, which is an effective refractive index of the TM0 mode, is higher than a second effective refractive index, which is an effective refractive index of a TE1 mode,
• wherein the second length is a length at which the first effective refractive index is lower than the second effective refractive index,
• wherein the first line section and the second line section constitute an asymmetrical directional coupler,
• wherein the asymmetrical directional coupler includes a second incident end and a second emission end which are both ends in the first direction, and
• wherein a length of the first line section in the second direction and a length of the second line section in the second direction are set such that a magnitude relationship between the second effective refractive index in the first line section and a third effective refractive index, which is an effective refractive index of the TE0 mode, in the second line section at a position different from the second incident end of the asymmetrical directional coupler is inverted to a magnitude relationship between the second effective refractive index in the first line section and the third effective refractive index in the second line section at the second incident end.