Dual-wavelength semiconductor laser with wavelength separation as large as 203 nm is reported. With the short-wavelength mode located in 1345.4 nm and the long-wavelength mode in 1548.6 nm, the operation region of the laser system covers both the medium-wave band (1300 nm region) and long-wave band (1500 nm region) in optical communication. Random selection of oscillating wavelength position between 1345.4 nm and 1548.6 nm is also possible with fixed wavelength separation. This broadband laser system provides an opportunity for all-optical switching between the medium-wave band and long-wave band in optical communication.
Anti-competition of laser modes is observed in dual-wavelength semiconductor lasers with single gain medium. Under anti-competition, the increase of intensity of one lasing mode could enhance the intensity of another mode, which is opposite to the usual mode competition. In our experiment, anti-competition can be observed for wavelength separation larger than 111 nm, and gradually disappears for wavelength separation less than 100 nm. Besides, anti-competition can also be influenced by the intensity and the wavelength position of both modes. A simple theoretical analysis shows that anti-competition is due to the physics similar to optical pumping.
A very wide tuning range of dual-wavelength semiconductor lasers with properly designed nonidentical InGaAsP quantum wells is reported. By well aligning the external cavity, the dual-wavelength operation can be achieved with a record wavelength separation about 191 nm (27.4 THz) at 22.7°C. The wide separation of two wavelengths is possible due to a proper modification of the external-cavity configuration and reduced gain competition of laser modes.