The term biophotonics denotes a combination of biology and photonics, with photonics being the science and technology of generation, manipulation, and detection of photons, quantum units of light. Photonics is related to electronics and photons. Photons play a central role in information technologies such as fiber optics the way electrons do in electronics.
Biophotonics can also be described as the "development and application of optical techniques, particularly imaging, to the study of biological molecules, cells and tissue". One of the main benefits of using optical techniques which make up biophotonics is that they preserve the integrity of the biological cells being examined.
Biophotonics has therefore become the established general term for all techniques that deal with the interaction between biological items and photons. This refers to emission, detection, absorption, reflection, modification, and creation of radiation from biomolecular, cells, tissues, organisms and biomaterials. Areas of application are life science, medicine, agriculture, and environmental science. Similar to the differentiation between "electric" and "electronics" a difference can be made between applications, which use light mainly to transfer energy via light (like Therapy or surgery) and applications which excite matter via light and transfer information back to the operator (like diagnostics). In most cases the term biophotonics is only referred to the second case.
Biophotonics can be used to study biological materials or materials with properties similar to biological material, i.e., scattering material, on a microscopic or macroscopic scale. On the microscopic scale common applications include microscopy and optical coherence tomography. On the macroscopic scale, the light is diffuse and applications commonly deal with diffuse optical imaging and tomography (DOI and DOT).
In microscopy, the development and refinement of the confocal microscope, the fluorescence microscope, and the total internal reflection fluorescence microscope all belong to the field of biophotonics.
DOT is a method used to reconstruct an internal anomaly inside a scattering material. The method is noninvasive and only requires the data collected at the boundaries. The typical procedure involves scanning a sample with a light source while collecting light that exits the boundaries. The collected light is then matched with a model, for example, the diffusion model, giving an optimization problem.
Fluorescence Resonance Energy Transfer, also known as Foerster Resonance Energy Transfer (FRET in both cases) is the term given to the process where two excited "fluorophores" pass energy one to the other non-radiatively (i.e., without exchanging a photon). By carefully selecting the excitation of these flurophores and detecting the emission, FRET has become one of the most widely used techniques in the field of Biophotonics, giving scientists the chance to investigate sub-cellular environments. See the full article on FRET