Wavelength detection using narrowband reflectance filters

We have developed a novel system to detect the wavelength of an optical beam that is compact, inexpensive, yet capable of extremely high wavelength resolution. The system is comprised of a one- dimensional photonic crystal slab (PCS) narrowband reflectance filter operating as a position sensitive sensor and a linear charge-coupled device (CCD) sensor array. Depending on the wavelength of the incident light, the PCS provides a transmission minimum at different locations along its length, as shown in Fig. 1. The position of the transmission minimum is recorded by the CCD sensor array and is used to determine the incident wavelength. Using this technique, we show that wavelength changes as small as 0.011 nm can be resolved. Such a system could be utilized for a wide variety of applications including spectroscopic identification of compounds and rapid testing of light emitters such as light emitting diodes (LEDs) and Organic LEDs, in a compact and economical fashion.