A tunable laser, including: a gain section configured to provide an optical gain for lasing; a multi-channel splitter section configured to split an input signal into multiple outputs; and a multi-channel reflection section, the multi-channel reflection section including multiple arms of unequal lengths and configured to provide an optical feedback and a mode selection function for the laser to work. The gain section, the multi-channel splitter section, and the multi-channel reflection section are sequentially connected in that order. The facet of the gain section away from the multi-channel splitter section is an optical output facet of the laser. When arranging the multiple arms of the multi-channel reflection section in an order according to their lengths, length difference between adjacent arms are unequal. Facets of the multiple arms away from the multi-channel splitter section are coated with reflection films.

An optical source is described. This optical source includes a semiconductor optical amplifier (with a semiconductor other than silicon) that provides an optical gain medium and that includes a reflector. Moreover the hybrid external cavity laser includes a photonic chip with: an optical waveguide that conveys an optical signal output by the semiconductor optical amplifier; and a ring resonator, having a resonance wavelength, which reflects at least a resonance wavelength in the optical signal, where the reflector and the ring resonator define an optical cavity. Furthermore, the photonic chip includes: a thermal-tuning mechanism that adjusts the resonance wavelength; a photo-detector that measures an optical power output by the ring resonator; and control logic that adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength.

A tunable laser, including: a gain section configured to provide an optical gain for lasing; a multi-channel splitter section configured to split an input signal into multiple outputs; and a multi-channel reflection section, the multi-channel reflection section including multiple arms of unequal lengths and configured to provide an optical feedback and a mode selection function for the laser to work. The gain section, the multi-channel splitter section, and the multi-channel reflection section are sequentially connected in that order. The facet of the gain section away from the multi-channel splitter section is an optical output facet of the laser. When arranging the multiple arms of the multi-channel reflection section in an order according to their lengths, length difference between adjacent arms are unequal. Facets of the multiple arms away from the multi-channel splitter section are coated with reflection films.

According to another aspect of the present disclosed technology, a diode laser assembly, includes an optical fiber having a cladding and a large mode area (LMA) core, wherein the LMA core comprises a fiber Bragg grating disposed within the LMA core, a plurality of diode lasers configured to emit light, optics configured to receive the light and to couple the light into the LMA core, and one or more features in the optical fiber to couple higher order modes of the light leaving substantially single mode light to propagate in the LMA core wherein a portion of the single mode light propagating in the LMA core is reflected by the fiber Bragg grating and is coupled back through the optics into the plurality of diode lasers to lock the wavelength of light emitted from each diode laser of the plurality.

A semiconductor laser resonator configured to generate a laser beam includes a gain medium layer including a semiconductor material and comprising at least one protrusion formed by at least one trench to protrude in an upper portion of the gain medium layer. In the semiconductor laser resonator, the at least one protrusion is configured to confine the laser beam as a standing wave in the at least one protrusion.

A multimode laser includes a semiconductor amplifier, a laser resonator constituted between a loop mirror including a waveguide formed on a semiconductor substrate and the semiconductor amplifier, in which a characteristic shape of reflectance of the loop mirror is a convex shape in an oscillation wavelength range.

A light-emission device includes: a first light emitting element chip; a second light emitting element chip having a light output higher than a light output of the first light emitting element chip, the second light emitting element chip being configured to be driven independently from the first light emitting element chip and arranged side by side with the first light emitting element chip; and a light diffusion member including a first region provided on an emission path of the first light emitting element chip and a second region provided on an emission path of the second light emitting element chip, and having a diffusion angle at the second region larger than a diffusion angle at the first region.

A laser apparatus may include: a master oscillator configured to output a pulsed laser beam at a repetition rate, the master oscillator including at least one semiconductor laser apparatus; at least one amplifier configured to amplify the pulsed laser beam from the master oscillator, the at least one amplifier being configured to include at least one gain bandwidth; and a controller for controlling a parameter affecting an output wavelength of the pulsed laser beam from the master oscillator such that a wavelength chirping range of the pulsed laser beam from the master oscillator overlaps at least a part of the at least one gain bandwidth.

An optical source is described. This optical source may include a semiconductor laser chip and a silicon-photonics chip that provide an optical cavity. The semiconductor laser chip may provide gain at multiple lasing wavelengths in a band of wavelengths. Moreover, the silicon-photonics chip may adjust a size of an optical signal proximate to an interface between the semiconductor laser chip and the silicon-photonics chip. Furthermore, by adjusting a phase of a phase shifter and resonance frequencies of a micro-ring resonator in the silicon-photonics chip, a center frequency of a passband of the micro-ring resonator may be matched to a non-zero integer multiple of a cavity-mode spacing. This may allow the optical source to mode-lock the lasing wavelengths of the optical source by suppressing unwanted lasing wavelengths and re-enforcing the lasing wavelengths. In some embodiments, a free-spectral range of the optical source may be between 100 GHz and 800 GHz.

A gain medium (14) includes a substrate (34) and an active region (38) coupled to the substrate (34). The active region (38) includes a central section (28), a first end section (24), and a first tapered section (26). The central section (28) has a central width (28b) that is substantially constant along the central section (28). The first end section (24) has a first end width (24b) that is substantially constant along the first end section (24). Further, the first end dimension (24b) is smaller than the central dimension (28b). The first tapered section (26) connects the first end section (24) to the central section (28). The first tapered section (26) has a first tapered width (26b) that tapers from the central section (28) to the first end section (24).