Generation and characterization of tunable multiwavelength continuous-wave and picosecond-pulsed outputs from a semiconductor laser

A novel free-space external-cavity configuration for an anti-reflection coated laser to generate widely tunable dual-wavelength continuous-wave output has been developed. The Fabry-Perot Grating-Lens External Cavity (F-PGLEC) simply consists of a Fabry-Perot filter, a diffraction grating, a converging lens, and a totally reflecting mirror. This scheme is shown to have high reliability and can generate stable output over a 60.8 nm wavelength range. The dual-wavelength output has a spectral separation of 0.9 nm, and a side-mode-suppression ratio (SMSR) of over 25 dB. Dual-wavelength operating condition for the configuration has also been derived.;According to the spectral characteristics of the laser output, a configuration for generation of 120 GHz optical millimeter-wave signal has been developed. This signal is produced by optical heterodyne of two wavelengths from the collinear and linearly polarized output. Optical carrier of the millimeter-wave signal can be tuned over a wavelength range of 61 nm. The signal has been successfully transmitted over a 25 km fiber link.;Pulsed operation of the F-PGLEC laser has also been realized. Widely tunable dual-wavelength picosecond pulses have been generated by harmonic and rational harmonic mode-locking of the 1.5 mum laser. Active mode-locking has been achieved simultaneously at two different wavelengths in the semiconductor laser over a range of 65 nm. The pulse width is about 30 ps. Frequency multiplication of the pulse train has also been achieved using rational harmonic mode-locking. To our knowledge, it is the first report on multiple wavelength rational harmonic mode-locking of a semiconductor laser.;Alternatively, an all fiber-optic configuration to generate the multiwavelength picosecond pulses from a semiconductor laser has been proposed. This novel scheme employs a 600 m highly dispersive fiber and an optical-loop-mirror multiplexer to construct the external laser cavity. Using the self-seeding technique, programmable multiwavelength picosecond pulses can be achieved from the 1.53 mum gain-switched laser. Four-wavelength optical pulses with a spectral separation of 2.6 nm, a SMSR of 16 to 20 dB, and a pulse width of 75 ps have been generated. With the optical bit patterns generated from the multiplexer, output pulses with one, two, or four wavelengths at different combinations can be obtained.