A mesa (34) includes a resonator and a second conductivity type contact layer (24). Grooves (32) are provided on both sides of the mesa (34). The first conductivity type contact layer (12) and a side face of the mesa (34) including an end face of the resonator construct an L shape (50). The first conductivity type contact layer (12) constructs bottom surfaces of the L shape (50) and the grooves (32). A side face of the groove (32) includes a slope (38) near the bottom surface (46) and a side face (42) above. A side face of the L shape (50) includes a slope (40) near the bottom surface (48) and a side face (44) above. A first electrode (28) is connected to the first conductivity type contact layer (12) at the bottom surface (46) of the groove (32). A second electrode (30) is connected to the second conductivity type contact layer (24) above the mesa (34).

A mesa (34) includes a resonator and a second conductivity type contact layer (24). Grooves (32) are provided on both sides of the mesa (34). The first conductivity type contact layer (12) and a side face of the mesa (34) including an end face of the resonator construct an L shape (50). The first conductivity type contact layer (12) constructs bottom surfaces of the L shape (50) and the grooves (32). A side face of the groove (32) includes a slope (38) near the bottom surface (46) and a side face (42) above. A side face of the L shape (50) includes a slope (40) near the bottom surface (48) and a side face (44) above. A first electrode (28) is connected to the first conductivity type contact layer (12) at the bottom surface (46) of the groove (32). A second electrode (30) is connected to the second conductivity type contact layer (24) above the mesa (34).

Multi-surface emitting mid-IR multiwavelength distributed-feedback quantum cascade ring lasers laid out in a concentric circle are disclosed. The lasers utilize quantum cascade core designs to produce optical gain in the mid-infrared region and may generate several wavelengths simultaneously or sequentially. Methods of making along with methods of using such devices are also disclosed.

A semiconductor integrated optical device includes a waveguide mesa having a first multilayer including a first core layer, a second multilayer including a second core layer, and a butt joint interface between the first core layer and the second core layer; a support having first to third regions; and a buried semiconductor region provided on the support. The first multilayer has a first mesa width on the first region. The second multilayer has a second mesa width on the second region. On the third region, the second multilayer has a waveguide portion having a third mesa width smaller than the first and the second mesa widths. The second core layer has a waveguide core thickness on the second region. In the waveguide portion, the second core layer has a core portion having a thickness different from the waveguide core thickness at a position away from the butt-joint interface.

An optical semiconductor device includes a semiconductor substrate; a plurality of mesa stripes, which are arranged side by side on the semiconductor substrate, and each of which includes an active layer and a diffraction grating, the diffraction grating extending up to a back end surface of each of the plurality of mesa stripes; a plurality of electrodes, each of which is electrically connected to an upper surface of a corresponding one of the plurality of mesa stripes, having a pad portion for wire bonding; a plurality of waveguides, each of which is optically connected to the active layer of a corresponding one of the plurality of mesa stripes; and a reflective film provided at back end surfaces of the plurality of mesa stripes and having a reflectivity of 30% or more, wherein a center-to-center distance at back end surfaces of two mesa stripes at both ends of the plurality of mesa stripes is 150 m or less, and wherein at least two mesa stripes, of the plurality of mesa stripes, are configured to be driven at the same time.

Examples disclosed herein relate to multi-wavelength semiconductor lasers. In some examples disclosed herein, a multi-wavelength semiconductor laser may include a silicon-on-insulator (SOI) substrate and a quantum dot (QD) layer above the SOI substrate. The QD layer may include and active gain region and may have at least one angled junction at one end of the QD layer. The SOI substrate may include a waveguide in an upper silicon layer and a mode converter to facilitate optical coupling of a lasing mode to the waveguide.

A semiconductor laser (2) includes an n-type semiconductor substrate (1), a stack of an n-type cladding layer (4), an active layer (5), and a p-type cladding layer (6) successively stacked on the n-type semiconductor substrate (1). An optical waveguide (3) includes a non-impurity-doped core layer (9) provided on a light output side of the semiconductor laser (2) on the n-type semiconductor substrate (1) and having a larger forbidden band width than the active layer (5), and a cladding layer (10) provided on the core layer (9) and having a lower carrier concentration than the p-type cladding layer (6). The semiconductor laser (2) includes a carrier injection region (X1), and a non-carrier-injection region (X2) provided between the carrier injection region (X1) and the optical waveguide (3).

A process of forming a semiconductor optical device is disclosed. The semiconductor optical device provides a waveguide structure accompanied with a heater for varying a temperature of the waveguide structure. The process includes steps of: (a) forming a striped mask on a semiconductor substrate; (b) selectively growing a dummy layer on the semiconductor substrate; (c) removing the patterned mask; (d) burying the dummy layer by a supplemental layer; (e) exposing a portion of the dummy layer by etching a portion of the supplemental layer; (f) and removing the dummy layer by immersing the dummy layer within a solution that shows an etching rate for the dummy layer enough faster than an etching rate for the supplemental layer and the substrate so as to leave a void in a region the dummy layer had existed.

A quantum cascade laser has a core region including a first injection layer, an active region, and a second injection layer. The active region includes a first well layer, a second well layer, a third well layer, a first barrier layer, and a second barrier layer. The first barrier layer is disposed between the first well layer and the second well layer and separates the first well layer from the second well layer. The second barrier layer is disposed between the second well layer and the third well layer and separates the second well layer from the third well layer. The first barrier layer has a thickness of 1.2 nm or less, and the second barrier layer has a thickness of 1.2 nm or less.

A quantum cascade laser having a laser structure that includes a semiconductor mesa, a first end surface, a second end surface, and a first electrode provided on the semiconductor mesa. The laser structure includes a first region having the first end surface and a second region located between the second end surface and the first region. The semiconductor mesa includes a first mesa portion and a second mesa portion that are respectively included in the first region and the second region. The semiconductor mesa includes a first superlattice layer, a second superlattice layer, and a conductive semiconductor region. The first superlattice layer extends from the first end surface in the second axis direction and is included in the first mesa portion and the second mesa portion, and the second superlattice layer is provided in one of the first mesa portion and the second mesa portion.