A spot-size converter includes first and second waveguide structures. The first waveguide structure extends longitudinally along a waveguide axis from a first end to a second end and is configured to support a first optical mode at the first end. The second waveguide structure is formed within the first waveguide structure. The second waveguide structure extends longitudinally between the first end and the second end. The second waveguide structure is configured to support a second optical mode at the second end. The second optical mode has a different diameter than the first optical mode. The second waveguide structure includes a waveguide core that has a first cross-sectional area in a first plane normal to the waveguide axis at the first end and a second cross-sectional area in a second plane normal to the waveguide axis at the second end. The second cross-sectional area is larger than the first cross-sectional area.

A wavelength tunable laser includes: a heating layer, a dielectric layer, reflectors, a transport layer, a support layer, and a substrate layer. The heating layer is located above the transport layer; the transport layer is located above the support layer, and the transport layer includes an upper cladding layer, a waveguide layer, and a lower cladding layer from top to bottom; the reflector is located in the transport layer; the support layer has a protection structure, where the protection structure forms a hollow structure together with the transport layer and the substrate layer, and the hollow structure has a support structure; and the substrate layer is located below the support layer. The heating layer, the reflector, and a part of the transport layer form a suspended structure to prevent heat dissipation. Thus thermal tuning efficiency can be improved, and power consumption can be lowered.

Provided is an optical semiconductor element including: a stacked structure body 20 formed of a first compound semiconductor layer 21, a third compound semiconductor layer (active layer) 23, and a second compound semiconductor layer 22. A fundamental mode waveguide region 40 with a waveguide width W.sub.1, a free propagation region 50 with a width larger than W.sub.1, and a light emitting region 60 having a tapered shape (flared shape) with a width increasing toward a light emitting end surface 25 are arranged in sequence.

A laser diode includes a ridge portion, channel portions located adjacent to the ridge portion such that the ridge portion is sandwiched, the channel portions being shorter in height than the ridge portion, terrace portions adjacent to opposite sides of the respective channel portions from the ridge portion and longer in height than the channel portions, supporting portions provided over the respective channel portions, separated from side surfaces of the ridge portion or side surfaces of terrace portions or both, and made of resin, a ceiling portion including first portions provided over the supporting portions and second portions continuous with the first portions and located over the respective channel portions with hollow portions interposed therebetween, the ceiling portion being made of resin, and a metal layer provided over the ceiling portion and connected to an upper surface of the ridge portion.

A laser diode includes a ridge portion, channel portions located adjacent to the ridge portion such that the ridge portion is sandwiched, the channel portions being shorter in height than the ridge portion, terrace portions adjacent to opposite sides of the respective channel portions from the ridge portion and longer in height than the channel portions, supporting portions provided over the respective channel portions, separated from side surfaces of the ridge portion or side surfaces of terrace portions or both, and made of resin, a ceiling portion including first portions provided over the supporting portions and second portions continuous with the first portions and located over the respective channel portions with hollow portions interposed therebetween, the ceiling portion being made of resin, and a metal layer provided over the ceiling portion and connected to an upper surface of the ridge portion.

In some implementations, a thermally-controlled photonic structure may include a suspended region that is suspended over a substrate; a plurality of bridge elements connected to the suspended region and configured to suspend the suspended region over the substrate, where a plurality of openings are defined between the plurality of bridge elements; and at least one heater element having a modulated width disposed on the suspended region. The at least one heater element having the modulated width may include at least one section of a greater width and at least one section of a lesser width. The at least one section of the greater width may be in alignment with an opening of the plurality of openings and the at least one section of the lesser width may be in alignment with a bridge element of the plurality of bridge elements.

A laser diode includes a ridge portion, channel portions located adjacent to the ridge portion such that the ridge portion is sandwiched, the channel portions being shorter in height than the ridge portion, terrace portions adjacent to opposite sides of the respective channel portions from the ridge portion and longer in height than the channel portions, supporting portions provided over the respective channel portions, separated from side surfaces of the ridge portion or side surfaces of terrace portions or both, and made of resin, a ceiling portion including first portions provided over the supporting portions and second portions continuous with the first portions and located over the respective channel portions with hollow portions interposed therebetween, the ceiling portion being made of resin, and a metal layer provided over the ceiling portion and connected to an upper surface of the ridge portion.

A semiconductor laser includes a main body, a strip having a narrower width provided on the main body, and an active zone that generates light radiation, wherein surfaces of the main body laterally with respect to the strip and side surfaces of the strip are covered with an electrically insulating protective layer, an electrically conductive layer as a contact is provided on a top side of the strip, a cavity is provided between a side surface of the strip and the protective layer at least in a delimited section.

A method for manufacturing a semiconductor laser of the present invention includes a step of forming an insulating film on a surface of a grooved semiconductor substrate, a step of pasting an insulating sheet to a top surface of the insulating film so as to cover an opening of the groove and forming an insulating layer on the semiconductor substrate, a step of forming an opening of providing a first opening in the insulating layer so that a part corresponding to an electrode of the semiconductor substrate is exposed and a step of forming the electrode on a top surface of the insulating layer so as to fill the first opening.

A method for manufacturing a semiconductor laser of the present invention includes a step of forming an insulating film on a surface of a grooved semiconductor substrate, a step of pasting an insulating sheet to a top surface of the insulating film so as to cover an opening of the groove and forming an insulating layer on the semiconductor substrate, a step of forming an opening of providing a first opening in the insulating layer so that a part corresponding to an electrode of the semiconductor substrate is exposed and a step of forming the electrode on a top surface of the insulating layer so as to fill the first opening.