A gain medium is pumped by a source. An optical wave passes through a photonic integrated circuit (PIC) that comprises: a substrate comprising Silicon, a plurality of photonic structures, an input port coupling an optical wave into a waveguide formed in the PIC, and an output port coupling an optical wave out of a waveguide formed in the PIC. Propagation of an optical wave circulating around a closed path of a laser ring cavity is limited using an optical isolator such that, when the pump source exceeds a lasing threshold, the optical wave propagates in a single direction through the gain medium and the PIC. From output coupler, an output that is provided that comprises a fraction of the power of an optical wave that is incident upon the output coupler, and remaining power of the optical wave is redirected around the closed path of the laser ring cavity. The fraction can be greater than 0.5.

An optical device has a first photonic waveguide provided on a substrate, a second photonic waveguide provided on the substrate and extending side by side with the first photonic waveguide, and a looped waveguide continuously connecting the first photonic waveguide and the second photonic waveguide on the substrate, wherein a width of at least one of the first photonic waveguide or the second photonic waveguide varies continuously along an optical axis, between a first position located at a side opposite to the looped waveguide and a second position connected to the looped waveguide, and wherein cross sections of the first photonic waveguide and the second photonic waveguide are congruent at the second position, and are incongruent at the first position.

The present disclosure discloses an optical module including a circuit board and a light-emitting assembly. In the light-emitting assembly, a wavelength tuning mechanism is formed of a semiconductor optical amplification chip, a silicon optical chip and a semiconductor refrigerator. The semiconductor optical amplification chip may provide a plurality of wavelengths, and a wavelength selection is carried out by an optical filter in the silicon optical chip; a temperature adjustment for the optical filter is achieved by the semiconductor refrigerator, so as to further adjust a performance of the filter for wavelength selection. The above device is provided in a housing to facilitate packaging of the devices.

Provided is a semiconductor laser element including: a resonator structure; and a first reflection film and a second reflection film provided on a non-emission end surface of the resonator structure and an emission end surface of the resonator structure, respectively. Reflectance R of the second reflection film at a gain wavelength satisfies the following relational expression: R1≤R≤R(Oc)×C where R1 is reflectance of the second reflection film when the resonator structure performs laser oscillation with power 1.4 times a minimum value of threshold power which is minimum power for the resonator structure to perform the laser oscillation, R(Oc) is reflectance of the external resonance mirror, and C is a ratio of light, which is reflected by the external resonance mirror and is incident in the resonator structure, to light which is reflected by the external resonance mirror.

A tunable laser assembly uses a fundamental wavelength between 1 μm and 1.1 μm to alternately generate laser output light at two or more output wavelengths within the range of 184 nm to 200 nm by directing the fundamental light through different regions of a fan-out periodically poled nonlinear crystal to generate corresponding different down-converted signals, and using different nonlinear summing crystals to mix the different down-converted signals with a fifth harmonic of the fundamental wavelength. Each nonlinear summing crystal has a crystal axis aligned at an angle relative to the light propagation direction to facilitate the efficient transmission and summing of the fifth harmonic with an associated down-converted signal. In response to a user-selected output wavelength, a frequency control system positions the fan-out periodically poled nonlinear crystal to generate a corresponding down-converted signal frequency and positions an associated nonlinear summing crystal to receive the fifth harmonic and the corresponding down-converted signal.

A synthesizer includes a first resonator mirror, a second resonator mirror, and a gain medium disposed within a laser resonator cavity defined by the first resonator mirror and the second resonator mirror. The synthesizer includes a saturable absorber operationally coupled to the gain medium and having active control such that the saturable absorber is configured to generate a waveform via an injection locking signal to create a mode locking effect, the waveform having a frequency comb defined by dimensions of the gain medium. The synthesizer also includes a crystal electro-optical modulator disposed within the laser resonator cavity. The waveform passes through the modulator to impinge on a photodiode to output an emission RF waveform. Changing the voltage applied to the modulator changes the index of refraction of the modulator, altering an optical path length of the laser resonator cavity to adjust a frequency of the emission RF waveform.

A tunable laser includes a reflective semiconductor optical amplifier (SOA), a grating codirectional coupler, and a reflective microring resonator. The grating codirectional coupler and the reflective microring resonator are both formed on a silicon base. An anti-reflection film is disposed on a first end surface of the reflective SOA, and the first end surface is an end surface, coupled to a first waveguide of the grating codirectional coupler, of the reflective SOA. A second waveguide of the grating codirectional coupler is coupled to the first waveguide, a first grating is disposed on the first waveguide, a second grating disposed opposite to the first grating is disposed on the second waveguide, and the first grating and the second grating constitute a narrow-band pass filter. The second waveguide is connected to the reflective microring resonator.

A semiconductor ring laser including a closed loop laser cavity and an optical gain device that is optically interconnected with the closed loop laser cavity. The optical gain device includes a first optical gain segment and a second optical gain segment. The first optical gain segment and the second optical gain segment being non-identical, optically interconnected with each other, and electrically isolated from each other. A PIC including a semiconductor ring laser and to an opto-electronic system that includes a PIC. The opto-electronic system can be one of a transmitter, a receiver, a transceiver, a coherent transmitter, a coherent receiver and a coherent transceiver. The opto-electronic system can for example, but not exclusively, be used for telecommunication applications, LIDAR or sensor applications.

A laser. In some embodiments, the laser includes an optical amplifier, and an output reflector. The output reflector may be configured to receive light from the optical amplifier and to reflect light at a first wavelength back toward the optical amplifier. The output reflector may include a wavelength-selective element, and a coupler configured to receive the light from the optical amplifier and to couple a portion of the light to the wavelength-selective element.

Systems and methods here may include improved tunable lasers having a tunable filter and a tunable channel selector that can control precisely the wavelength and the bandwidth of the light emitted by the laser, while suppressing light that may otherwise be emitted by the laser outside the desired wavelength and bandwidth with unidirectional ring lasers having a resonator of which forms a ring and where light propagates only in one of the two possible directions.