A laser apparatus is provided, comprising a semiconductor substrate, an active layer disposed on the semiconductor substrate, a folded waveguide disposed on the active layer and forming a resonant structure, the folded waveguide comprising at least two substantially straight waveguide portions coupled by a connecting waveguide structure, with the folded waveguide having a first end and a second end located at one or more edges of the semiconductor substrate, wherein at least one of the ends includes a mirror, and an electrode coupled to the folded waveguide and configured to create photons in the folded waveguide when receiving electrical power. The waveguide emits laser light comprising the photons, with the laser light emitted at an edge of the semiconductor substrate.

A apparatus includes a tunable laser configured to include a tunable filter and a mirror; a first optical splitter provided between the tunable filter and the mirror, the first optical splitter including a first port and a second port on a tunable filter side and a third port and a fourth port on a mirror side, in which the tunable filter is coupled to the first port and the mirror is coupled to the third port, respectively; a first optical waveguide coupled to the second port; a second optical waveguide coupled to the fourth port; and an optical coupler with which the first optical waveguide and the second optical waveguide are combined.

An optical transmission apparatus includes a first multilevel optical phase modulator and a first semiconductor optical amplifier. The first semiconductor optical amplifier includes a first active region having a first multiple quantum well structure. Assuming that a first number of layers of a plurality of first well layers is defined as n.sub.1 and a first length of the first active region is defined as L.sub.1 (?m): (a) n.sub.1=5 and 400?L.sub.1?563; (b) n.sub.1=6 and 336?L.sub.1?470; (c) n.sub.1=7 and 280?L.sub.1?432; (d) n.sub.1=8 and 252?L.sub.1?397; (e) n.sub.1=9 and 224?L.sub.1?351; or (f) n.sub.1=10 and 200?L.sub.1?297.

An artificial saturable absorber uses additive pulse mode-locking to enable pulse operation of an on-chip laser operation. Four different artificial saturable absorbers are disclosed. The first includes an integrated coupler, two arms each containing some implementation of the end-reflector, and a phase bias element in one arm. The second includes an integrated directional coupler, two integrated waveguide arms, and another integrated coupler as an output. The third includes an integrated birefringent element, integrated birefringent-free waveguide, and integrated polarizer. And the fourth includes a multimode waveguide that allows for different modes to propagate in such a way that the difference in the spatial distribution of intensity causes a nonlinear phase difference between the modes. These are just some examples of an on-chip fully integrated artificial saturable absorber with instantaneous recovery time that allow for generation of sub-femtosecond optical pulses at high repetition rates using passive mode-locking.

A semiconductor laser device is disclosed that includes a laser resonator situated to produce a laser beam, with the laser resonator including an angled distributed Bragg reflector (a-DBR) region including first and second ends defining an a-DBR region length corresponding to a Bragg resonance condition with the first end being uncleaved and including a first mode hop region having a first end optically coupled to the a-DBR region first end and extending a first mode hop region length associated with the a-DBR region length to a second end so as to provide a variable longitudinal mode selection for the laser beam.

The teachings herein disclose a laser assembly (20) that implements a composite cavity formed in part in a III/V die (22), in part in a silicon die (26), and in part in a glass member (24) having a waveguide (44) coupling the cavity portion in the III/V die with the cavity portion in the silicon die. This arrangement capitalizes on the lasing efficiency of the III/V die, which is used as the gain medium while advantageously using the glass member to extend the lasing cavity into the silicon die. Laser-scribing the cavity waveguide in place after mounting the III/V die, the silicon die or dies, and the glass member, greatly relaxes the mounting alignment precision needed for the constituent parts of the overall assembly. Moreover, in one or more embodiments, glass member includes one or more laser-scribed waveguides operative as optical interconnects going between two or more silicon dies.

A laser device comprises a gain chip that emits light, and a photonics chip optically coupled to the gain chip. The photonics chip comprises a waveguide platform including an input waveguide optically coupled to the gain chip. The input waveguide optical communicates with a cascaded arrangement of waveguide grating structures on the waveguide platform. The grating structures comprise a first grating structure that produces a single resonance frequency within a stopband, and a second grating structure in optical communication with the first grating structure. The second grating structure diffracts a narrowband resonance, overlapping with the stopband of the first grating structure, back toward the gain chip, while passing any light outside of the stopband of the first grating structure out of the waveguide platform. The grating structures cooperate to yield a single resonance frequency that feeds back into the gain chip to produce a self-injection lock for the laser device.

A mode-locked semiconductor laser capable of changing the spacing between the carrier frequencies of its output comb. In an example embodiment, the mode-locked semiconductor laser is implemented as a hybrid solid-state device comprising a III-V semiconductor chip and a silicon chip attached to one another to form a laser cavity. The III-V semiconductor chip includes a gain medium configured to generate light in response to being electrically and/or optically pumped. The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity. Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity and, as a result, the output-comb frequency spacing. In some embodiments, the output-comb frequency spacing can be changeable at least by a factor of 1.5.

An optical transmitter includes a reflective semiconductor optical amplifier (RSOA) coupled to an input end of a first optical waveguide. An end of the first optical waveguide provides a transmitter output for the optical transmitter. Moreover, a section of the first optical waveguide between the input end and the output end is optically coupled to a ring modulator that modulates an optical signal based on an electrical input signal. A passive ring filter (or a 1N silicon-photonic switch and a bank of band reflectors) is connected to provide a mirror that reflects light received from the second optical waveguide back toward the RSOA to form a lasing cavity. Moreover, the ring modulator and the passive ring filter have different sizes, which causes a Vernier effect that provides a large wavelength tuning range for the lasing cavity in response to tuning the ring modulator and the passive ring filter.

An optical functional device includes: first and second optical couplers each including a multi-mode interferometer waveguide portion having a first end portion and a second end portion, two units of first input/output ports and two units of second input/output ports; and first and second arc-shaped waveguides each optically connecting one of the first and second input/output ports of the first and second optical coupler and one of the first and second input/output ports of the second optical coupler, respectively. Further, the first optical coupler, the second optical coupler, the first arc-shaped waveguide, and the second arc-shaped waveguide constitute a ring resonator, and each of the multi-mode waveguide portions of the first optical coupler and the second optical coupler have a narrow portion, an average width of the narrow portion in a longitudinal direction being narrower than widths at the first end portion and the second end portion.