A Dense Wavelength Division Multiplexing (DWDM) photonic integration circuit (PIC) that implements a DWDM system, such as a transceiver, is described. The DWDM PIC architecture includes photonic devices fully integrating on a single manufacturing platform. The DWDM PIC has a multi-wavelength optical laser, a quantum dot (QD) laser with integrated heterogeneous metal oxide semiconductor (H-MOS) capacitor, integrated on-chip. The multi-wavelength optical laser can be a symmetric comb laser that generates two equal outputs of multi-wavelength light. Alternatively, the DWDM PIC can be designed to interface with a stand-alone multi-wavelength optical laser that is off-chip. In some implementations, the DWDM PIC integrates multiple optimally designed photonic devices, such as a silicon geranium (SiGe) avalanche photodetector (APD), an athermal H-MOS wavelength splitter, a QD photodetector, and a heterogenous grating coupler. Accordingly, fabricating the DWDM PIC includes a unique III-V to silicon bonding process, which is adapted for its use of SiGe APDs.

A system and methods are drawn to a self-injection locked tunable laser using an InGaN/GaN gain chip to produce precise laser output at visible wavelengths. An external cavity length is adjusted by motorized stage to tune a resonance frequency of the external cavity to match the resonance frequency of the laser and self-injection lock the mode of the wavelength. Fine tuning is provided by adjusting the tilt angle of the partially reflective mirror. The laser diode may be operated at a range of injection currents and temperatures and provides precise control of output laser wavelengths and linewidths.

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.

A sensor system includes an optical aperture, a light source configured to generate a light pulse along a first optical path, a reflective surface configured to reflect the light pulse from the first optical path to a second optical path for passing through the optical aperture, a beam steering device positioned in the optical aperture and configured to steer the light pulse along different directions to one or more objects in an angle of view of the sensor system, a detector configured to receive a reflected light pulse and convert the reflected light pulse into an electrical signal, the reflected light pulse being reflected back from the one or more objects and passed through the beam steer device, and a spatial filtering device positioned between the beam steering device and the detector to block undesirable light in both the light pulse and the reflected light pulse.

A wireless communication device includes a quantum cascade laser (QCL) configured to generate a terahertz (THz) or microwave carrier signal. The QCL includes a laser waveguide, a laser optical gain medium incorporated in the laser waveguide, and at least one electrode. An antenna may be integrated with the electrode. The device may be a transmitter, the electrode configured to receive an input baseband signal, the QCL configured to couple the THz or microwave carrier signal and the input baseband signal into a THz or microwave communication signal, and the antenna configured to transmit the THz or microwave communication signal. The device may be a receiver, the antenna configured to receive a THz or microwave communication signal, and the QCL configured to de-couple the THz or microwave communication signal from the THz or microwave carrier signal into an output baseband signal.

Examples disclosed herein relate to multi-wavelength semiconductor lasers. In some examples disclosed herein, a multi-wavelength semiconductor laser may include a silicon-on-insulator (SOI) substrate and a quantum dot (QD) layer above the SOI substrate. The QD layer may include and active gain region and may have at least one angled junction at one end of the QD layer. The SOI substrate may include a waveguide in an upper silicon layer and a mode converter to facilitate optical coupling of a lasing mode to the waveguide.

Provided are a laser device and a method of transforming laser spectrum, which provide a laser frequency stabilization and significant narrowing a laser spectrum. A laser device includes at least one multiple longitudinal mode laser (L) for generating a laser light having a spectrum of multiple longitudinal modes; at least one high quality factor (high-Q) microresonator (M) optically feedback coupled to the at least one multiple longitudinal mode laser (L); and a tuner (TU) for tuning the spectrum of multiple longitudinal modes of the laser light. The laser device is configured to output an output laser light having an output spectrum with at least one dominant longitudinal laser mode each at a reduced linewidth of the dominant longitudinal laser mode. The laser device allows increasing an emission power of a narrow linewidth lasing without an additional amplification while keeping a compact size of a device with a limited number of optical elements.

A system and methods are drawn to a self-injection locked tunable laser using an InGaN/GaN gain chip to produce precise laser output at visible wavelengths. An external cavity length is adjusted by motorized stage to tune a resonance frequency of the external cavity to match the resonance frequency of the laser and self-injection lock the mode of the wavelength. Fine tuning is provided by adjusting the tilt angle of the partially reflective mirror. The laser diode may be operated at a range of injection currents and temperatures and provides precise control of output laser wavelengths and linewidths.

The present invention relates to a coherent optical transistor device including: first and second coherent optical laser beams from a laser source; wherein the first beam has a relatively higher power/energy than the second beam of at least 2:1; and a permanent sub-wavelength structure in a unitary section into which the first and second beams enter, which permanently modifies a refractive index in both transverse and longitudinal directions; wherein every transverse spatial grating Fourier component in the sub-wavelength structure is phase-shifted by 90 degrees (pi/2) from each of corresponding Fourier components of a spatial interference of the first and second optical beams; and a refractive index profile in the unitary structure in the longitudinal direction is permanently modified, leading to a complete transfer of energy from the first to the second optical beam, resulting in a gain mechanism that results in an amplified signal beam and an inverted signal beam.

A frequency chirp correction method for the photonic time-stretch system comprises acquiring the stretching signal, i.e. acquiring the time-domain data after the time-domain stretching. First, the time-domain data of the stretching signal is Fourier transformed to obtain the spectral distribution. The spectral distribution is then convoluted with the first frequency-domain correction factor, and then multiplied with the second frequency-domain correction factor to obtain the modified frequency spectrum. Finally, the modified frequency spectrum is performed by the inverse Fourier transform to obtain the time-domain signal after the frequency chirp correction.