The present invention provides an optical switch for making part of incident
light, which has been made incident on an optical waveguide, selectively emergent
to a light emergence portion provided outside the optical waveguide. The optical
switch includes a liquid crystal device for selective emergence of the incident
light. An arbitrary layer of the liquid crystal device is set such that letting
n be a difference between a refractive index n0 of the optical
waveguide and a refractive index n1 of the arbitrary layer of the liquid
crystal device, "d" be a thickness of the arbitrary layer, and be a wavelength
of the incident light, the values of n, "d", and satisfy a condition
of 2.2010-3|nd-1|3.0310-3.
With this optical switch, the uniformity of a light emergence efficiency can be
easily realized by making use of a small change region in which the light emergence
efficiency is not largely varied. The present invention also provides a display
unit using the optical switches.
