An injection locking laser source is provided for an optical communications system. The injection locking laser source includes a laser cavity configured to receive an externally injected low linewidth primary light source. The laser cavity includes a cavity length, a cavity facet reflectivity, and a cavity quality factor. The injection locking laser source further includes an emitting region configured to output a secondary light source injection locked to the externally injected low linewidth primary light source at a stable detuning frequency based on a photon number, a steady-state phase, and a carrier number of the primary light source injected into the cavity.

A narrow linewidth mid infrared laser, including a pumping laser diode with a fast-axis compressor and a pumping wavelength λ.sub.o; and an optical resonator arranged to receive the pumping wavelength λ.sub.o, the optical resonator including a laser crystal with a lasing wavelength λ.sub.p, a dichroic mirror, and a nonlinear crystal to generate an idler wavelength λ.sub.i.

A semiconductor light-emitting device includes an active layer including quantum dots, a diffraction grating, a low-reflectance film disposed at a light-emitting end of the active layer, and a high-reflectance film disposed at another end of the active layer and having an optical reflectance higher than an optical reflectance of the low-reflectance film.

A laser source includes an optical resonator including first and second reflectors having first and second reflection spectral bands. A gain medium is disposed in the optical resonator. The gain medium has a gain spectrum. Center wavelengths of at least two of: the first reflection spectral band; the second reflection spectral band; or the gain spectrum are offset relative to each other for reduction of a spectral variance of the laser source. For example, the first and the second reflection spectral bands may be offset relative to one another to form an overlap area above a lasing threshold. The lasing is limited to the overlap area. When the overlap area accommodates a single lasing mode, the output emission of the laser source is monochromatic.

A semiconductor light-emitting device includes an active layer including quantum dots, a diffraction grating, a low-reflectance film disposed at a light-emitting end of the active layer, and a high-reflectance film disposed at another end of the active layer and having an optical reflectance higher than an optical reflectance of the low-reflectance film.

This disclosure describes a multi-junction laser diode with improved wavelength stability. The multi-junction laser diode is found in an edge emitting laser (EEL). The disclosed system and method are suited for improving the wavelength stability of multi-junction EEL without coupling the laser modes of the individual junctions and without using any external elements such as Fiber Bragg Gratings (FBR), Volume Bragg Gratings (VBG) or Thermoelectric Cooling (TEC).

An injection locking laser source is provided for an optical communications system. The injection locking laser source includes a laser cavity configured to receive an externally injected low linewidth primary light source. The laser cavity includes a cavity length, a cavity facet reflectivity, and a cavity quality factor. The injection locking laser source further includes an emitting region configured to output a secondary light source injection locked to the externally injected low linewidth primary light source at a stable detuning frequency based on a photon number, a steady-state phase, and a carrier number of the primary light source injected into the cavity.

Two or more lasers or other temperature sensitive optical devices can be disposed in an operating environment, for example in a common enclosure exposed to the environment. The environment can have a temperature that fluctuates, for example in connection with random events, weather, seasons, etc. Each laser's temperature can track the temperature of the environment in steps, with each laser following a distinct temperature track. The lasers can alternate outputting light into a wavelength division multiplexing channel. For example, during one timeframe, one laser can provide an optical communication signal having a wavelength complying with a wavelength division multiplexing criterion. During another timeframe, the other laser can provide an optical signal having substantially the same wavelength. Operating a laser at an elevated temperature can shorten laser lifetime. To mitigate temperature induced failure, a replacement laser can be engaged when a failure predictor, precursor, or indicator meets a threshold.