Biophotonics_Concepts_to_Applications

their optical radiation. The characteristics include the spectrum over which the
source emits, the emitted power levels as a function of wavelength, the optical
power per unit solid angle emitted in a given direction, the polarization of the light,
and the coherence properties of the emission. In addition, depending on the physical
operating principles of the light source, it can emit light in either a continuous mode
or a pulsed mode.

4.1 Radiometry

Before examining the physical and functional characteristics of various optical
sources, it will be helpful to define some radiometric terminology. Radiometry
deals with measuring the power and the geometric nature of optical radiation [ 1 – 3 ].

Table 4.1 Characteristics of representative light sources used in biophotonics; YAG
yttrium-aluminum-garnet

Lasing material Laser type Wavelength

Argonfluoride (ArF) Excimer 193 nm

Krypton chloride (KrCl) Excimer 222 nm

Kryptonfluoride (KrF) Excimer 248 nm

Xenon chloride (XeCl) Excimer 308 nm

Xenonfluoride (XeFl) Excimer 351 nm

Argon (Ar) Gas 488.0 and 514.5 nm

Krypton (Kr) Gas 530.9 and 568.2 nm

KTP/Nd:YAG Solid state 532.0 nm

Helium–neon (He–Ne) Gas 632.8 nm

Pulsed dyes Liquid 400 – 500, 550–700 nm

Ruby Solid state 694.3 nm

Alexandrite Solid state 700 – 830 nm

GaAlAs or InGaAsP alloys Semiconductor 760 – 2400 nm

Ti:sapphire Solid state 700 – 1000 nm

Neodynium:YAG (Nd:YAG) Solid state 1064 nm

Holium:YAG (Ho:YAG) Solid state 2.10μm

Ytterbium-dopedfiber Opticalfiber 1030 – 1080 nm

Erbium-dopedfiber Opticalfiber 1530 – 1620 nm

Thulium-dopedfiber Opticalfiber 1750 – 2100 nm

Erbium:YAG (Er:YAG) Solid state 2.94μm

Free-electron laser (FEL) Electromagnetic 5.4, 6.1, 6.45, 7.7μm

Carbon-dioxide (CO 2 ) Gas 10.6μm

4 Fundamentals of Light Sources 93