Optical sources having a strongly scattering gain medium providing laser-like action

A method for detecting the presence of a structure within an object, comprising the steps of:

• providing a surface region of the object with a gain medium comprised of an electromagnetic radiation emitting and amplifying first phase and an electromagnetic radiation scattering second phase, the gain medium being responsive to electromagnetic radiation having a first wavelength for emitting electromagnetic radiation with wavelengths within a band of wavelengths having a second wavelength that differs from the first wavelength;
• irradiating the gain medium with a first pulse of radiation having the first wavelength;
• propagating the emitted radiation having the second wavelength into the object;
• in response to the propagating radiation encountering a change in an index of refraction that is associated with the structure, reflecting a portion of the propagating radiation back toward the surface of the object;
• in response to the reflected radiation entering the gain medium coincidentally with a second pulse, enhancing the emission of the electromagnetic radiation with wavelengths within the band of wavelengths having the second wavelength;
• detecting the enhanced emission;
• and
• correlating the detected enhanced emission with a time between the occurrence of the first and the second pulses for determining at least a distance from the structure to the surface of the object.