Diffractive optical devices are essential in developing compact and thin augmented reality (AR) devices. Surface-reliefgratings (SRG) and volume-holographic gratings (VHG) are typical gratings with periodic material changes. VHG is relatively easy to manufacture, making it a popular choice for R&D teams developing AR exit pupil expander (EPE) applications. In the past, the Kogelnik algorithm was combined with the Ansys Zemax OpticStudio ray tracing engine to simulate VHG for AR applications. However, due to its more approximate calculations, the accuracy of this method is lower than that of the rigorous coupled wave analysis (RCWA) method. This study aims to investigate the theoretical differences between the Kogelnik and RCWA methods, implement their algorithms in practice, and compare the accuracy of the two methods for AR EPE applications using the Zemax OpticStudio ray tracing engine.
Diffractive optical elements such as surface-relief gratings (SRGs) have become popular in modern applications, such as head-up displays (HUD), augmented reality (AR) and virtual reality (VR) head-mounted displays (HMD). Their ability to diffract rays in any desired angle and their wavelength and angular selectivity allows the creation of optical systems that are more compact and lighter than exclusively refractive and reflective optical designs. Traditionally, optical raytracing and diffraction efficiency were calculated separately, and the optical design was done iteratively. OpticStudio now supports the simulation of gratings with the diffraction efficiency by utilizing RCWA calculations. A demonstration of an optical system with the diffraction efficiency implemented will be presented as well.
In recent years, there is a growing need for lighting equipment that creates complex, specific illumination and light intensity distributions, such as road surface drawing lamps, aesthetic design lighting, and direct backlighting. When designing such lighting equipment, we may often have to use a cut-off method, which is a method of projecting a partially shaded image. This method is inefficient for many reasons, as we are purposefully cutting off the light source for illumination. The development of manufacturing capabilities has made feasible the fabrication of more complex optical components, with the freeform shape as its highest candidate. This has opened up the possibility of new design approaches. We propose a design solution that meets the high demand for illumination performance in a more straightforward configuration, using complex free-form surfaces and a ray mapping approach as opposed to flooding the detector with millions of non-sequential rays. A conventional optical surface utilizes a parametric equation for the illumination lens, which can be challenging to control for higher orders of the polynomial function. The optical lens designed with conventional methods require complex parts and, in the end, has a low light efficiency due to the shading of the light source. The proposed illumination method takes advantage of a lighter computational approach via ray mapping and leverages the spatially selective surface sag over a grid of points in the OpticStudio TrueFreeForm surface.
We have developed thermal emitters of linearly polarized and narrow-band mid-infrared light based on highly
controlled plasmon resonance in narrow and deep rectangular Au gratings. This optical source is a series of one-dimensional
metal-insulator-metal optical cavities with a closed end. This characteristic results in the control of the
thermal radiation, emitting a narrow infrared spectrum at a specific wavelength of 2.5-5.5 micro-meters. The wavelength
is specified 100nm wide, 1000nm deep dimensions of the cavity were accurately manufactured. The maximum emittance
reaches 0.90, and the FWHM/wavelength of the peak is as narrow as 0.13-0.23. Furthermore, we have demonstrated
simple chemical analysis based on orthogonally polarized two-color infrared waves emitted from an integrated grating.
This simple emitter is expected to play a key role in the infrared sensing technologies for analyzing our environment.
This paper presents the development of a nanofabricated mid-infrared optical source, thermally emitting linearly
polarized light. The optical source in the current study is a heated series of one-dimensional metal-insulator-metal
cavities with a closed end on a Au surface. This closed cavity exhibits the so-called organ pipe resonance resulting in
specific frequencies being selectively emitted from the blackbody heat source. This characteristic results in the control of
the thermal radiation, thereby emitting a narrow infrared spectrum at a specific wavelength of 2.5-5.35 micro-meters.
The wavelength is specified by a theoretical model and 100nm wide, 1000nm deep dimensions of the cavity were
accurately manufactured. The maximum emittance reaches 0.90, and the peak width Δλ/λ is as narrow as 0.13-0.23. As
a demonstration, the Cyclohexane concentration in Benzene is determined with a simple optical system. This simple
emitter is expected to play a key role in the infrared sensing technologies for analyzing our environment.
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