A photodetector having a small form factor and having high detection efficiency with respect to both visible light and infrared rays may include a first electrode, a collector layer on the first electrode, a tunnel barrier layer on the collector layer, a graphene layer on the tunnel barrier layer, an emitter layer on the graphene layer, and a second electrode on the emitter layer. The photodetector may be included in an image sensor. An image sensor may include a substrate, an insulating layer on the substrate, and a plurality of photodetectors on the insulating layer. The photodetectors may be aligned with each other in a direction extending parallel or perpendicular to a top surface of the insulating layer. The photodetector may be included in a LiDAR system.

An optic-microwave frequency discriminator includes: a fiber coupler receives and combines a first laser and a second laser, than the fiber coupler respectively generates and outputs a first light signal and a second light signal; a photodiode module respectively receives the first light signal and the second light signal, and converts the first light signal into a first microwave signal and converts the second light signal into a second microwave signal; a microwave phase shifter generates a shifted microwave signal by introducing a phase shift to the second microwave signal; a 90° microwave bridge combines the first microwave signal and the shifted microwave signal for generating a first bridge signal and a second bridge signal; a normalized balanced detection module generates an error signal; and a control module generates a controlling voltage signal according to the error signal for tuning a frequency of the second laser.

An optic-microwave frequency discriminator includes: a fiber coupler receives and combines a first laser and a second laser, than the fiber coupler respectively generates and outputs a first light signal and a second light signal; a photodiode module respectively receives the first light signal and the second light signal, and converts the first light signal into a first microwave signal and converts the second light signal into a second microwave signal; a microwave phase shifter generates a shifted microwave signal by introducing a phase shift to the second microwave signal; a 90° microwave bridge combines the first microwave signal and the shifted microwave signal for generating a first bridge signal and a second bridge signal; a normalized balanced detection module generates an error signal; and a control module generates a controlling voltage signal according to the error signal for tuning a frequency of the second laser.

A compact, wavelength-stabilized laser source is provided by utilizing a specialty gain element (i.e., formed to include a curved waveguide topology), where a separate wavelength stabilization component (for example, a fiber Bragg grating (FBG)) is used one of the mirrors for the laser cavity. That is, the FBG takes the place of the physical “front facet” of the gain element, and functions to define the laser cavity in the first instance, while also utilizing the grating structure to impart the desired wavelength stability to the output from the packaged laser source. As a result, the FBG is disposed within the same package used to house the gain element and provides a wavelength-stabilized laser source in a compact form.

A compact, wavelength-stabilized laser source is provided by utilizing a specialty gain element (i.e., formed to include a curved waveguide topology), where a separate wavelength stabilization component (for example, a fiber Bragg grating (FBG)) is used one of the mirrors for the laser cavity. That is, the FBG takes the place of the physical “front facet” of the gain element, and functions to define the laser cavity in the first instance, while also utilizing the grating structure to impart the desired wavelength stability to the output from the packaged laser source. As a result, the FBG is disposed within the same package used to house the gain element and provides a wavelength-stabilized laser source in a compact form.

The optical module includes: a housing having first and second end walls and a pair of side walls; a semiconductor laser element; a first TEC; a wavelength locker unit including an optical splitting component and an etalon filter; and a second TEC. The second end wall is provided with a feedthrough. The pair of side walls is not provided with an external connection terminal. The second TEC is disposed between the first TEC and the second end wall and has: a first substrate thermally coupled to a bottom surface of the housing; a second substrate thermally coupled to the etalon filter; and a heat transfer part that transfers heat. The optical module further includes a wiring pattern that is arranged side by side with the heat transfer part and that supplies electric power to the first TEC from the feedthrough.

An optical transmitter includes: a set of reflective semiconductor optical amplifiers (RSOAs) or other reflective gain media, a set of ring filters, a set of intermediate waveguides, a shared waveguide, a shared loop mirror, and an output waveguide. Each intermediate waveguide channels light from an RSOA in proximity to an associated ring filter to cause optically coupled light to circulate in the associated ring filter. The shared waveguide is coupled to the shared loop mirror, and is located in proximity to the set of ring filters, so that light circulating in each ring filter causes optically coupled light to flow in the shared waveguide. Each RSOA forms a lasing cavity with the shared loop reflector, wherein each lasing cavity has a different wavelength associated with a resonance of its associated ring filter. The output waveguide is optically coupled to the shared loop mirror and includes an electro-optical modulator.

According to the present invention, a semiconductor device includes a substrate comprising a front end face, a rear end face and side faces, a plurality of semiconductor lasers provided on the substrate, a forward optical multiplexer to multiplex forward output light of the plurality of semiconductor lasers and output the multiplexed light to the front end face, a backward optical multiplexer to multiplex backward output light of the plurality of semiconductor lasers and output the multiplexed light to the rear end face and a plurality of backward waveguides connected to an output section of the backward optical multiplexer, wherein the plurality of backward waveguides includes a main waveguide disposed at a center of the output section and a plurality of lateral waveguides disposed on both sides of the main waveguide to bend toward the side faces and output light from the side faces diagonally to the side faces.

A technology of effectively interrupting light reflected from a wavelength selective filter so as not to be fed back to a laser diode chip in a semiconductor laser package having a function of adjusting a relative intensity ratio of a signal of “1” and a signal of “0” using an optical filter. Since an optical interruption device may effectively interrupt a light feedback to the laser diode chip by adjusting characteristics of a 45 degree partial reflection mirror in an existing TO-can type laser device having the 45 degree partial reflection mirror and additionally disposing one λ/4 waveplate, unlike previously known optical isolators using an existing Faraday rotator, the signals of “1” and “0” may be effectively adjusted in a TO-can type laser device having a small volume, thereby improving a function of communication.

A technology of effectively interrupting light reflected from a wavelength selective filter so as not to be fed back to a laser diode chip in a semiconductor laser package having a function of adjusting a relative intensity ratio of a signal of “1” and a signal of “0” using an optical filter. Since an optical interruption device may effectively interrupt a light feedback to the laser diode chip by adjusting characteristics of a 45 degree partial reflection mirror in an existing TO-can type laser device having the 45 degree partial reflection mirror and additionally disposing one λ/4 waveplate, unlike previously known optical isolators using an existing Faraday rotator, the signals of “1” and “0” may be effectively adjusted in a TO-can type laser device having a small volume, thereby improving a function of communication.