Abstract

We have recently proposed [1,2] a 4-section semiconductor laser which is capable of tuning over several tens of nanometers. A schematic of this device is shown in Fig. 1, along with the reflection spectra of the two mirrors which form the backbone of this device. These two mirrors consist of "sampled" gratings with mismatched periodic reflection spectra, as indicated in Fig. 1. Lasing in this structure occurs where two reflection maxima are aligned. By inducing index changes in one mirror relative to the other, adjacent reflectivity maxima can be brought into alignment, resulting in wide-range discontinuous tuning with very small index changes. Wavelength coverage between the maxima can be obtained by inducing identical index changes in the two mirrors, and adjusting the phase-shifter appropriately, much like 3-section lasers [3].

© 1992 Optical Society of America