Optical switch and display unit
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 Δn be a difference between a refractive index n o of the optical waveguide and a refractive index n 1 of the arbitrary layer of the liquid crystal device, “d” be a thickness of the arbitrary layer, and λ be a wavelength of the incident light, the values of Δn, “d”, and λ satisfy a condition of 2.20×10 −3 ≦|Δn·d·λ −1 |≦3.03×10 −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.
1. A display unit comprising:
an optical waveguide for receiving light containing a specific polarized light component as incident light;
a light emergence portions crossing said optical waveguide; and
an optical switch, disposed between said waveguide and said light emergence portion, for making at least a portion of said incident light selectively emergent from said optical waveguide to said light emergence portion;
wherein said optical switch has a light transmissive stacked structure including a function layer for selective emergence of said incident light; and
letting Δn be a difference between a refractive index n o of said optical waveguide and a refractive index n l of an arbitrary layer forming part of said stacked structure, “d” be a thickness of said arbitrary layer, and λ be a wavelength of said incident light, the values of Δn, “d”, and λ satisfy a condition of 2.20×10 −3 ≦|Δn·d·λ −1 |≦3.03×10 −3 ; and
the functional layer of said optical switch has a length, L, in the longitudinal direction of the optical waveguide and said optical waveguide has a thickness in a range of 0.05·L μm to 0.2·L μm.
2. A display unit according to claim 1 , wherein the length, L, of said function layer is 1,000±300 μm.