An apparatus includes an optical splitter configured to receive an optical signal and to split the input optical signal to provide a first and a second optical signal. The apparatus further includes an interferometer comprising a first arm and a second arm, with the first arm being configured to receive the first optical signal, and the second arm being configured to receive the second optical signal. Notably a portion of the first arm is exposed to a reference gas that attenuates light of a characteristic wavelength. The apparatus further includes an optical coupler configured to receive an output optical signal from the first arm, and an output optical signal from the second arm and to provide a third optical signal; and a photodetector configured to receive the third optical signal, and to provide a photocurrent. The photocurrent increases when the difference between the characteristic wavelength and the wavelength of the optical signals increases. The apparatus also comprises a feedback control circuit configured to change the properties of the laser to be locked until an error signal indicative of the difference between the characteristic wavelength and the wavelength of the laser is substantially zero.

A device for measuring optical spectra at high speed and with high resolution using tunable optical laser comb sources. In one embodiment there is provided a first tunable comb laser source and a second tunable comb laser source whereby the wavelength of each comb laser source is chosen such that the combination of the two sources provides a continuous spectral coverage over a band in an optical spectrum under a selected wavelength tuning condition. By overlapping the two comb sources in the manner described the deadzone issue is overcome in the most spectrally efficient way possible.

A device for measuring optical spectra at high speed and with high resolution using tunable optical laser comb sources. In one embodiment there is provided a first tunable comb laser source and a second tunable comb laser source whereby the wavelength of each comb laser source is chosen such that the combination of the two sources provides a continuous spectral coverage over a band in an optical spectrum under a selected wavelength tuning condition. By overlapping the two comb sources in the manner described the deadzone issue is overcome in the most spectrally efficient way possible.

Provided here are: a semiconductor laser section formed on a surface of a semiconductor substrate; a spot-size converter section in which an optical waveguide having a core layer for propagating laser light emitted from the semiconductor laser section is provided; and a monitor PD section which is provided on the spot-size converter section laterally with respect to a propagation direction of the laser light; wherein, the regions of a PD anode electrode and a PD cathode electrode in the monitor PD section are partially opposed to each other through an insulating film, so that the surge breakdown voltage of the monitor PD section is increased.

In the present disclosure, in an EADFB laser in which an SOA has been integrated, a new configuration in which deterioration of optical waveform quality is solved or mitigated while keeping characteristics that a manufacturing process can be simplified by using the same layer structure is indicated. In the optical transmitter of the present disclosure, a waveguide structure having a tapered structure in at least a part of the SOA waveguide is adopted. A width of the waveguide is changed to be reduced in an SOA region, and an amount of carrier consumption is made uniform in an optical waveguide direction. A waveguide width is continuously reduced in an optical waveguide direction in the SOA so that the optical confinement coefficient is reduced, and light power distributed in an active layer region is made constant.

In the present disclosure, in an EADFB laser in which an SOA has been integrated, a new configuration in which deterioration of optical waveform quality is solved or mitigated while keeping characteristics that a manufacturing process can be simplified by using the same layer structure is indicated. In the optical transmitter of the present disclosure, a waveguide structure having a tapered structure in at least a part of the SOA waveguide is adopted. A width of the waveguide is changed to be reduced in an SOA region, and an amount of carrier consumption is made uniform in an optical waveguide direction. A waveguide width is continuously reduced in an optical waveguide direction in the SOA so that the optical confinement coefficient is reduced, and light power distributed in an active layer region is made constant.

An exposure system according to an aspect of the present disclosure includes a laser apparatus that outputs pulsed laser light, an illuminating optical system that guides the pulsed laser light to a reticle, a reticle stage, and a processor that controls the output of the pulsed laser light from the laser apparatus and the movement of the reticle performed by the reticle stage. The reticle has a first region where a first pattern is disposed and a second region where a second pattern is disposed, and the first and second regions are each a region continuous in a scan width direction perpendicular to a scan direction of the pulsed laser light, with the first and second regions arranged side by side in the scan direction. The processor controls the laser apparatus to output the pulsed laser light according to each of the first and second regions by changing the values of control parameters of the pulsed laser light in accordance with each of the first and second regions.

An exposure system according to an aspect of the present disclosure includes a laser apparatus that outputs pulsed laser light, an illuminating optical system that guides the pulsed laser light to a reticle, a reticle stage, and a processor that controls the output of the pulsed laser light from the laser apparatus and the movement of the reticle performed by the reticle stage. The reticle has a first region where a first pattern is disposed and a second region where a second pattern is disposed, and the first and second regions are each a region continuous in a scan width direction perpendicular to a scan direction of the pulsed laser light, with the first and second regions arranged side by side in the scan direction. The processor controls the laser apparatus to output the pulsed laser light according to each of the first and second regions by changing the values of control parameters of the pulsed laser light in accordance with each of the first and second regions.

A QCL may include a substrate, an emitting facet, and semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the emitting facet of the substrate. The QCL may include an optical grating being adjacent the active region and configured to emit one of a CW laser output or a pulsed laser output through the emitting facet of substrate.

The present disclosure is generally directed to an EML with a filter layer disposed between an active region of the EML and a substrate of the EML to absorb a portion of unmodulated light energy, and preferably the unmodulated light energy caused by transverse electric (TE) substrate mode. The filter layer preferably comprises a material with an energy band gap (Eg) that is less than the energy band gap of the predetermined channel wavelength to absorb unmodulated laser light.