ULTRA BROADBAND MIRROR USING SUBWAVELENGTH GRATING

摘要

A sub-wavelength grating structure that has a very broad reflection spectrum and very high reflectivity comprising segments made of high refractive index material disposed on a layer of low refractive index material and a low refractive index material disposed above and between the segments. The index differential between the high and low index materials determines the bandwidth and modulation depth. The larger difference in refractive indices gives rise to wider reflection bands. The reflection is sensitive to parameters such as the grating period, the grating thickness, the duty cycle of the grating, the refractive index and the thickness of the low index layer underneath the grating. The design is scalable for different wavelengths, and facilitates monolithic integration of optoelectronic devices at a wide range of wavelengths from visible to far infrared. The sub-wavelength grating reflectors may be used in a variety of settings such as tunable etalon filters and as a replacement for conventional distributed Bragg reflectors.