Ultracompact nonimaging devices for optical wireless communications

Advanced optical design methods using the tools of nonimaging optics (inste ad of conventional imaging tools) produce ultracompact devices that combine high collection efficiency with a concentration (or collimating) capabilit y close to the thermodynamic limit. After a general overview covering the m ost important design methods and devices in nonimaging optics, two of these designs, the so-called RX and RXI, are presented. Even though it is design ed within the nonimaging framework, the RX device nevertheless has imaging properties that complement its valuable performance as a nonimaging device. The RXI is extremely compact: its aspect ratio (thickness/aperture diamete r) is less than 1/3. When working as a receiver, that is, by placing a phot odiode in the correct position, it attains an increase in irradiance that l akes it beyond 95% of the theoretical thermodynamic limit (i.e., a concentr ation of 1600 times with an acceptance angle of +/-2.14 deg). As an emitter , similar intensity gains can be obtained within an angle almost as large a s 95% of the thermodynamic limit. The combination of high concentration fac tors, relatively wide acceptance angles, simplicity, and compactness makes these devices almost unique. The measurements carried out with several RXI prototypes, all of them made by PMMA injection, are also presented. (C) 200 0 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)01610- X].