Improved wavelength stability of GaAs laser diodes under amplitude modulation

Spectral properties of commercially available Fabry-Perot and distributed Bragg reflector (DBR) GaAlAs and InGaAs laser diodes operating under deep current modulation are presented. At kHz modulation frequencies spectral widths of commercial diodes are 2.5 nm 15 dB down from the maximum intensity. Structural modifications can narrow this value to 0.4 nm. Prototype DBR devices with maximum output power of 110 mW exhibit extremely narrow CW linewidths of 4 MHz, and are suitable for coherent communication as well as direct detection communication formats.