candidate drug compounds have become effective pharmaceutical research and
development tools.- Point of care (POC) tests and analyses:Point of care (POC) testing or
diagnostics is a broad term that refers to the delivery of healthcare evaluations,
products, and services by clinicians to patients at the time of care.
Photonics-based devices include ophthalmological instruments, optical oxime-
ters, compact portable microscopes, microscopes running on smartphones,
fluorescent imagingflow cytometers on a smartphone, and webcam-based
biosensors. - Environmental monitoring: Biophotonics spectroscopic techniques and tools
(including the use of spectrometric add-ons to smartphones) are being used to
measure and monitor concentrations of airborne particles in the atmosphere
(e.g.,fine dust, pollens, and chemical pollutants) and to detect pathogens (e.g.,
bacteria, viruses, and protozoa) in bodies of water. - Food safety: Concerns about food safety (e.g., the presence of contaminants and
natural pathogens, food fraud, and food adulteration) are being addressed
through biophotonics techniques and tools such as high-performance chro-
matography, Fourier transform infrared spectroscopy, surface-enhanced Raman
spectroscopy, and biosensors. - Manufacturing process control: Spectroscopic techniques are being used and
developed further for the non-contact, non-destructive compositional analyses
and quality control of complex biological material used in the manufacturing of
pharmaceutical, nutritional, and cosmetic products.
1.3 Biophotonics Spectral Windows.
As described in Sect.2.1, light propagates in the form of electromagnetic waves
[ 25 – 28 ]. In free space, light travels at a constant speed c = 299,792,458 m/s (or
approximately 3× 108 m/s). In biophotonics the free-space speed of light could be
expressed in units such as 30 cm/ns, 0.3 mm/ps, or 0.3μm/fs. The speed of light in
free space is related to the wavelengthλand the wave frequencyνthrough the
equation c =νλ. Upon entering a transparent or translucent dielectric medium or a
biological tissue the lightwave will travel at a slower speed s. The ratio between
cand the speed s at which light travels in a material is called therefractive index(or
index of refraction) n of the material (with n≥1), so that
s¼c=n ð 1 : 1 ÞTable1.4lists the indices of refraction for a variety of substances. Note that in
many cases the refractive index changes with wavelength.
8 1 Overview of Biophotonics