According to one embodiment, a semiconductor optical device including a substrate, a filter layer arranged on the substrate, and a semiconductor light receiving element arranged on the filter layer, wherein the filter layer includes a periodic structure through which a light of a desired wavelength range in incident light is transmitted, and which is constituted of different refractive index materials.

A battery protection device includes a first transistor, a switch control circuit, a controller, and a photocoupler. The first transistor is connected between one of the pack terminals of a battery pack and a battery module and controls a current flow between the pack terminals and the battery module. The switch control circuit outputs a first control signal for turning on or turning off the first transistor. The controller outputs a second control signal. The photocoupler is connected to a control terminal of the first transistor, is turned on or turned off according to the second control signal, and turns off the first transistor if turned on.

The present disclosure provides an optical module comprising: a photoelectric conversion unit, a first demodulation circuit, and a second demodulation circuit; the first demodulation circuit and the second demodulation circuit are respectively connected to the photoelectric conversion unit; the photoelectric conversion unit is configured to convert the received optical signal into an electrical signal; the first demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a high-frequency electrical signal; the second demodulation circuit is configured to demodulate an electrical signal converted by the photoelectric conversion unit and generate a low-frequency electrical signal.

A semiconductor device includes a light emitting element comprising a substrate having a first and a second surface and an outer edge connecting the first and second surfaces. A light emitting layer is on a central portion of the first surface but not on a peripheral portion between the central portion and the outer edge of the substrate. A first insulating layer is disposed on the peripheral portion of the first surface, a side surface of the light emitting layer, and a third surface of the light emitting layer that is spaced from the first surface of the substrate. A first electrode is electrically contacting the third surface of the light emitting layer. A light receiving element is provided in a propagation path of light emitted from the light emitting element.