"Let there be light." With these words, proclaims the book of Genesis, the sacred process of creation was begun. Greek mythology, similarly, depicts the conquest over Chaos by ordered illumination, while the cosmologist cites a dazzling explosion of brightness as the birth of the universe. At all levels, the emergence of light has been intimately intertwined with the mergence of life--dawn represents the resurrection of day; Lazarus stumbled into sunlight from gm blackness of his tomb; the infant completes a journey from the unlit womb to the bright world. It is therefore understandable that humankind has always considered light an essential