An adjustable extremely short external cavity (ESEC; cavity length 0...50 microns) can be used to tune the wavelength of an edge emitting Fabry-Perot semiconductor laser up to two percents. This means about 30 nm tuning range for the 1550-nm lasers and about 15 nm tuning range for the 800-nm lasers. In addition to the use in WDM and other tunable laser applications, this phenomenon can be directly used in realizing wavelength tuning sensitive near field sensors. In this paper, we discuss the ESEC laser tuning mechanism by using various numerical models and experimentation. We show simulations and experimental results for two different wavelength tuning schemes: a single mirror tuning, and tuning by using a micromachined Fabry Perot interferometer. In addition, we discuss and show results on wavelength tuning enhanced readout in near field optical data storage, and on near field surface profilometry via laser wavelength tuning.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.