Microwave Signal Generation Using Self-heterodyning of a Fast Wavelength Switching SG-DBR Laser

July 21, 2008

Microwave signal generation using single-chip fast wavelength-tunable SG-DBR lasers is demonstrated. Microwave signals are established by a self-heterodyne technique. The laser frequency is square-wave modulated back and forth between two closely spaced wavelengths. These two wavelengths are made time coincident using a fiber Mach-Zehnder interferometer. The difference frequency is detected and amplified. Microwave signals up to 12 GHz have been measured by frequency modulating the phase section of the SG-DBR laser. Millimeter wave difference frequencies are easily available from the SG-DBR laser. Microwave signal spectral widths as narrow as 10 MHz have been achieved for low back mirror current inputs. Spectral width results as a function of device DC bias condition are presented. A high-speed wavelength switching SG-DBR package has been built for this application. Time resolved frequency step measurements have shown inherent thermal transients of approximately 200 ns upon wavelength switching. From the square wave switching profile, switching times of approximately 40 ns were achieved.