Abstract: An integrated circuit includes optical waveguides defined in a semiconductor layer, and uses removable optical taps to allow for in-process characterization and trimming. These optical waveguides may be trimmed during fabrication of the integrated circuit to improve performance. Note that the trimming may modify indexes of refraction of portions of the optical waveguides or may involve a more invasive process. Moreover, the trimming may exclude or may not involve the use of a polymer and/or the carrier wavelengths at a given temperature may be stable as a function of time. The trimming process may use removable optical taps for external feedback to determine the amount of change required. These optical taps may be formed either in the semiconductor layer or the cladding layer, and they may be disabled with negligible impact to device performance via alterations to the cladding layer after the completion of trimming.

Abstract: The disclosed embodiments relate to a system that implements a hybrid laser. This system includes a reflective gain medium (RGM) comprising an optical gain material coupled to a mirror. This RGM is coupled to a spot-size converter (SSC), which optically couples the RGM to an optical reflector through a silicon waveguide. The SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide. During operation, the RGM, the spot-size converter, the silicon waveguide and the silicon mirror collectively form a lasing cavity, wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon. Finally, a laser output is optically coupled out of the lasing cavity.

Abstract: A reflectivity test circuit is described. The reflectivity test circuit includes a symmetric structure that cancels errors in the reflectivity measurements. In particular, the reflectivity test circuit includes an optical waveguide that is optically coupled to two optical ports and two optical couplers. The optical couplers are optically coupled to adjacent optical waveguides, at least one of which is optically coupled to a third optical port and the mirror. Moreover, a length of the optical waveguide is chosen to match the round-trip optical path length in at least the one of the adjacent optical waveguides. During operation, control logic determines the reflectivity of the mirror based at least on a ratio of an optical power measured on one of the two optical ports to an input optical power on the third optical port.

Abstract: A hybrid optical source comprises an optical gain chip containing an optical gain material that provides an optical signal, and an optical reflector chip including an optical reflector. It also includes a semiconductor-on-insulator (SOI) chip, which comprises a semiconductor layer having a planarized surface facing the semiconductor reflector. The semiconductor layer includes: an optical coupler to redirect the optical signal to and from the planarized surface; and an optical waveguide to convey the optical signal from the optical coupler. While assembling these chips, a height of the optical gain material is referenced against the planarized surface of the semiconductor layer, a height of the optical reflector is referenced against the planarized surface of the semiconductor layer, and the optical reflector is aligned with the optical coupler, so that the optical signal emanating from the optical gain material is reflected by the optical reflector and into the optical coupler.

Abstract: A hybrid optical source comprises an optical gain chip containing an optical gain material that provides an optical signal, and an optical reflector chip including an optical reflector. It also includes a semiconductor-on-insulator (SOI) chip, which comprises a semiconductor layer having a planarized surface facing the semiconductor reflector. The semiconductor layer includes: an optical coupler to redirect the optical signal to and from the planarized surface; and an optical waveguide to convey the optical signal from the optical coupler. While assembling these chips, a height of the optical gain material is referenced against the planarized surface of the semiconductor layer, a height of the optical reflector is referenced against the planarized surface of the semiconductor layer, and the optical reflector is aligned with the optical coupler, so that the optical signal emanating from the optical gain material is reflected by the optical reflector and into the optical coupler.

Abstract: A dual-ring-modulated laser includes a gain medium having a reflective end coupled to an associated gain-medium reflector and an output end, which is coupled to a reflector circuit through an input waveguide to form a lasing cavity. The reflector circuit comprises: a first ring modulator; a second ring modulator; and a shared waveguide that optically couples the first and second ring modulators together. The first and second ring modulators have resonance peaks that are tuned to be offset in alignment from each other to provide an effective reflectance having a flat-top response, which is aligned with an associated lasing cavity mode. The first and second ring modulators are driven in tandem based on the same electrical input signal, whereby the resonance peaks of the first and second ring modulators shift wavelengths in the same direction during modulation, and an effective reflectance stays within the flat-top wavelength range.

Abstract: A reflectivity test circuit is described. The reflectivity test circuit includes a symmetric structure that cancels errors in the reflectivity measurements. In particular, the reflectivity test circuit includes an optical waveguide that is optically coupled to two optical ports and two optical couplers. The optical couplers are optically coupled to adjacent optical waveguides, at least one of which is optically coupled to a third optical port and the mirror. Moreover, a length of the optical waveguide is chosen to match the round-trip optical path length in at least the one of the adjacent optical waveguides. During operation, control logic determines the reflectivity of the mirror based at least on a ratio of an optical power measured on one of the two optical ports to an input optical power on the third optical port.

Abstract: A dual-ring-modulated laser includes a gain medium having a reflective end coupled to a gain-medium reflector and an output end coupled to a reflector circuit to form a lasing cavity. This reflector circuit comprises: a first ring modulator; a second ring modulator; and a shared waveguide that optically couples the first and second ring modulators. The first and second ring modulators have resonance peaks, which are tuned to have an alignment separation from each other. During operation, the first and second ring modulators are driven in opposing directions based on the same electrical input signal, so the resonance peaks of the first and second ring modulators shift wavelengths in the opposing directions during modulation. The modulation shift for each of the resonance peaks equals the alignment separation, so the resonance peaks interchange positions during modulation to cancel out reflectivity changes in the lasing cavity caused by the modulation.

Abstract: An optical source is described. This optical source includes a semiconductor optical amplifier, with a semiconductor other than silicon, which provides an optical gain medium. In addition, a photonic chip, optically coupled to the semiconductor optical amplifier, includes: a first optical waveguide that conveys at least a portion of the optical signal, and a second optical waveguide that conveys at least another portion of the optical signal. Moreover, the photonic chip includes a distributed-Bragg-reflector (DBR) ring resonator that is optically coupled to the first optical waveguide and the second optical waveguide, and that reflects a tunable wavelength in the optical signal. Furthermore, a monitor on the photonic chip measures at least the other portion of the optical signal, and control logic on the photonic chip thermally tunes the tunable wavelength of the DBR ring resonator based on the measurement of at least the other portion of the optical signal.