An optical device and method is disclosed for forming the optical device within the wide-bandgap semiconductor substrate. The optical device is formed by directing a thermal energy beam onto a selected portion of the wide-bandgap semiconductor substrate for changing an optical property of the selected portion to form the optical device in the wide-bandgap semiconductor substrate. The thermal energy beam defines the optical and physical properties of the optical device. The optical device may take the form of an electro-optical device with the addition of electrodes located on the wide-bandgap semiconductor substrate in proximity to the optical device for changing the optical property of the optical device upon a change of a voltage applied to the optional electrodes. The invention is also incorporated into a method of using the optical device for remotely sensing temperature, pressure and/or chemical composition.