High efficiency surface-emitting laser with subwavelength antireflection structure

Monolithic graded-refractive-index glass-based antireflective coatings: broadband/omnidirectional light harvesting and self-cleaning characteristics

“…As such, AR coatings can: (i) raise the efficiency and power output of the photovoltaic devices; 1,2 (ii) enhance the light extraction from light emitting diodes; 3 (iii) increase transmissivity and eliminate unwanted ghost images in flat panel displays, architectural windows and lenses; [4][5][6][7] (iv) reduce background noise, thereby increasing the sensor performance in imaging systems and detectors; 8,9 and (v) minimize the reflection induced failure of laser components in high-power laser systems. 10,11 To realize the full potential of AR coatings, it is highly desirable that the coated optical element provide spectrally broadband reduction in reflectance over a wide range of incident angles. However, there exists no single inorganic optical material with a low index of refraction (i.e., close to that of air, n = 1) that can be applied to any glass platform to enable broadband and omnidirectional AR characteristics.…”

All-dielectric unidirectional dual-grating output coupler

“…air sub air e n n (5) To investigate the properties and behavior of the proposed dual grating structure, the properties of each individual grating are rigorously studied by means of the Rigorous Coupled Wave Analysis (RCWA), using both its original form for infinite transverse gratings [9] and its application to finite-sized integrated optical structures [10][11][12]. Finally, the integration of both gratings in a single device is studied using this same finite waveguide eigenmode expansion method.…”

“…al [15]. Chirping the superstrate grating fill factor [5], depth, or period will also provide for the ability to shape the spatial distribution of output power, but will admittedly make the computational design process much more costly in time and memory requirements Fig. 14(b) shows the angular spectrum of this Transverse Poynting vector component calculated using a discrete Fourier transform performed on our non-uniformly spaced longitudinal sampling window.…”

“…1. Attempts to force unidirectional coupling of the diffracted energy have previously involved the addition of either a metallic coating [5] or a thin-film quarter-wave-stack coating to either the grating or the substrate [6]. Metallization of either the grating or the substrate introduces additional absorption and scattering losses which are also problems that should try to be minimized.…”

“…In recent years, the concept of dual-side wafer processing for semiconductor waveguides has been introduced. By integrating a superstrate-side diffraction grating with either a substrate side refractive or diffractive element, numerous applications in spatial and spectral beam control have been introduced [5,7,8]. In this work, we present a novel all-dielectric unidirectional grating coupler that avoids the need for any additional material deposition.…”