It is well-known that conservation of phase-space volume or optical etendue leads to strict limits to concentration. Less well- known is the connection between entropy and etendue. Entropy has a logarithmic dependence on etendue in addition to the familiar linear dependence on heat. This trade-off permits, in principle, an exponential boost in concentration. Optical systems that make use of this possibility will be discussed.
© 2009 The Optical SocietyPDF Article