Tunable distributed-feedback laser gratings for telecom applications, manufactured by electron-beam lithography

A wide-range tunable laser component has been developed, based on a closely spaced array of 12 distributed feedback (DFB) grating lasers, 3 nm apart in wavelength, fabricated by electron-beam lithography. Coarse wavelength selection is achieved by selecting the appropriate laser stripe with a microelectromechanical system tilt mirror. We describe the application of direct-wire e-beam lithography to array DFB grating manufacture, with accurate multiple wavelengths and phase shifts required to optimize the spectral characteristics of the laser. The grating pitch is approximately 0.24 μm, but must be controlled to better than 0.01 nm. We have used an averaging technique with relatively coarse address unit and pixel size to fabricate multiple-pitch gratings without rescaling. This allows the use of a conventional thermal-field-emission Gaussian-beam system, at high throughput appropriate for manufacturing.