A laser diode chip is described, comprising: an n-type semiconductor region (3), a p-type semiconductor region (5), and an active layer (4) arranged between the n-type semiconductor region (3) and the p-type semiconductor region (5), an n-type contact (9) and a p-type contact (8), at least one heating element (14) arranged on a side of the laser diode chip facing the p-type semiconductor region (5), the heating element (14) functioning as a resistance heater, and at least one metallic seed layer (7, 11), wherein the heating element comprises a part (11) of the seed layer, and wherein the p-type contact (8) is arranged on a further part (7) of the seed layer (7, 11).

The upper surface of the semiconductor substrate has a slope descending from the projection in the second direction at an angle of 0-12° to a horizontal plane. The mesa stripe structure has an inclined surface with a slope ascending from the upper surface of the semiconductor substrate at an angle of 45-55° to the horizontal plane, the mesa stripe structure having an upright surface rising from the inclined surface at an angle of 85-95° to the horizontal plane. The buried layer is made from semiconductor with ruthenium doped therein and is in contact with the inclined surface and the upright surface. The inclined surface is as high as 80% or less of height from the upper surface of the semiconductor substrate to a lower surface of the quantum well layer and is as high as 0.3 μm or more.

A laser system according to one aspect of the present disclosure includes a first solid-state laser device, a wavelength conversion system, an excimer amplifier, and a control unit. The first solid-state laser device includes a first multiple semiconductor laser system, a first semiconductor optical amplifier, and a first fiber amplifier. The first multiple semiconductor laser system includes a plurality of first semiconductor lasers configured to perform continuous wave oscillation in a single longitudinal mode with different wavelengths, a first spectrum monitor, and a first beam combiner. The control unit controls an oscillation wavelength and light intensity of each line of a first multiline spectrum generated by the first semiconductor lasers to obtain an excimer laser beam having at least a target center wavelength or a target spectral line width instructed by an external device.

A multi-channel laser source, including: a bus waveguide coupled, at an output end of the bus waveguide, to an output of the multi-channel laser source; a first semiconductor optical amplifier; a first back mirror; a first wavelength-dependent coupler, having a first resonant wavelength, on the bus waveguide; a second semiconductor optical amplifier; a second back mirror; and a second wavelength-dependent coupler, on the bus waveguide, having a second resonant wavelength, different from the first resonant wavelength. In some embodiments the first semiconductor optical amplifier is coupled to the bus waveguide by the first wavelength-dependent coupler, which is nearer to the output end of the bus waveguide than the second wavelength-dependent coupler, the second semiconductor optical amplifier is coupled to the bus waveguide by the second wavelength-dependent coupler, and the first wavelength-dependent coupler is configured to transmit light, at the second resonant wavelength, along the bus waveguide.

An optical detection device and method for detecting temperature changes and/or wavelength changes of an optical probe signal includes transmitting an optical probe signal having a predetermined wavelength to an optical input port of an optical waveguide; detecting first and second optical detection signal at first and second optical output ports via first and second opto-electrical converters which create corresponding first and second electrical signals; measuring values of the first and second electrical signal and determining an absolute temperature or a temperature change of the optical waveguide and/or an absolute wavelength value or a wavelength change of the optical probe signal via values measured of the first and second electrical signals and first and second previously determined wavelengths and temperature dependencies of both first and second power transfer functions.

A multi-channel laser source, including: a bus waveguide coupled, at an output end of the bus waveguide, to an output of the multi-channel laser source; a first semiconductor optical amplifier; a first back mirror; a first wavelength-dependent coupler, having a first resonant wavelength, on the bus waveguide; a second semiconductor optical amplifier; a second back mirror; and a second wavelength-dependent coupler, on the bus waveguide, having a second resonant wavelength, different from the first resonant wavelength. In some embodiments the first semiconductor optical amplifier is coupled to the bus waveguide by the first wavelength-dependent coupler, which is nearer to the output end of the bus waveguide than the second wavelength-dependent coupler, the second semiconductor optical amplifier is coupled to the bus waveguide by the second wavelength-dependent coupler, and the first wavelength-dependent coupler is configured to transmit light, at the second resonant wavelength, along the bus waveguide.

A laser wavelength control device, includes a memory; and a processor coupled to the memory and configured to: measure a wavelength of a laser beam emitted by a light source, when the measured wavelength is not in a target wavelength band, adjust a voltage to be applied to the light source such that a wavelength of the laser beam falls within the target wavelength band, and when a wavelength measured after the adjustment of the voltage is not in the target wavelength band, adjust a temperature of the light source such that the wavelength of the laser beam falls within the target wavelength band.

Techniques and circuitry for a semiconductor laser with enhanced lasing wavelengths stabilization are described. A semiconductor laser can generate an optical signal (e.g., single or multi-wavelength), for use in a Dense Wavelength Division Multiplexing (DWDM) interconnect system. The stabilization circuitry can include temperature sensor circuitry that measures an operational temperature of the semiconductor laser, and a feedback controller that can determine a temperature-induced wavelength shift that may be experienced by the multi-wavelength optical signal based on the laser's temperature. The feedback controller is also configured to generate a compensation signal that is determined to cause a complimentary shift in the multi-wavelength optical signal, where the complimentary shift can compensate for the temperature-induced wavelength shift. An integrated MOS capacitor of the laser can be charged by the signal in a manner that effectuates the complimentary shift and tunes the multi-wavelength optical signal to compensate for temperature-induced shift, thereby enhancing stabilization.

A laser apparatus includes: a laser unit including a light source unit configured to change a frequency of laser light to be output; and a monitor unit configured to acquire a monitor value corresponding to a frequency equivalent amount corresponding to the frequency of the laser light; and a control unit configured to control the frequency of the laser light by supplying a control amount to the laser unit. The monitor unit at least includes: a first frequency filter and a second frequency filter; a first detection unit; and a second detection unit. The control unit is configured to acquire a target frequency, acquire a first ratio and a second ratio, set, as a monitor value corresponding to the frequency of the laser light, one of the first ratio, the second ratio, a third ratio, acquire a target value, and control the control amount.

Provided is a semiconductor laser including: a core layer having an active layer and a diffraction grating layer optically coupled to the active layer; and paired clad layers arranged sandwiching the core layer, and formed with a waveguide along the core layer, and the semiconductor laser includes: a flat layer provided continuously with the diffraction grating layer along the waveguide; and a temperature control mechanism for controlling the temperature of the flat layer to a temperature different from that of the diffraction grating layer.