Continuously-tunable single-frequency semiconductor lasers

The design of "ideal" tunable laser sources that are capable of being continuously tuned over the entire gain bandwidth with maximum mode suppression are considered. It is shown that certain extended-cavity three-section configurations satisfy the necessary conditions for such electronic tunability, but that phase shifters with advanced capabilities are necessary. It is also shown that it is not possible to achieve this goal in a two-section configuration, although continuous tuning up to about one longitudinal mode spacing should be possible with some compromise in spurious mode suppression.