Experimental and theoretical studies on the characteristics and applications of GaAlAs/GaAs self-pulsing laser diodes center on two main topics : 1) optical spectra of self-pulsing laser diodes with wavelength-selective optical feedback, and 2) simple amplitude shift keying(ASK) transmitter using a 790nm compact-disk self-pulsing laser diode.
With a wavelength-selective optical feedback, single mode operation of self-pulsing laser diode is first demonstrated and the optical spectral characteristics of self-pulsing laser diodes are clarified numerically and experimentally. The results show that the optical spectra obtained with feedback are not always narrower than those obtained without feedback. Single longitudinal mode spectra can be obtained only in the regions where the self-pulsing frequencies of the laser diode with a grating reflector are greater than those of the solitary self-pulsing laser diode. We analyse these phenomena by multimode rate equations with an optical feedback term and describe their physical mechanism.
As application of self-pulsing laser diodes, a simple amplitude shift keying (ASK) optical link is demonstrated by using a low-cost self-pulsing laser diode and an envelope detector for a low-cost broadband local area network. A link sensitivity of -22dBm was achieved at 200Mb/s. Because the self-pulsing frequency can be tuned by the bias current, frequency division multiplexing can be simply implemented for multiuser applications.