Combining planar optics such as metalenses or metacorrectors with conventional lenses can drastically improve the optical performance of imaging systems with additional benefits such as cost, size and weight improvements. However, incorporating metacorrectors into conventional lens design requires multiscale simulations to account for the different length scale interactions. Namely, full wave scattering and geometric optics analysis is needed for the metacorrector and hybrid lens design, respectively. Multiscale inverse optimization using Sandia National Laboratories’ MIRaGE along with different wave propagation techniques and commercial-off-the-shelf GO tools are considered to accurately predict hybrid design optical performance.
Incorporating planar optics such as metalenses or metacorrectors into optical designs can drastically improve the performance of imaging systems with additional benefits such as cost, size and weight improvements. However, modeling of such hybrid lenses is challenging because of the multi-scale nature of the simulation. We demonstrate that one can combine ray optic simulations with full wave electromagnetic simulations and Fourier optics approaches to model a whole compound/hybrid lens considering all metasurface unit cell interactions and to study the effect of possible fabrication errors.
KEYWORDS: Modulation transfer functions, Point spread functions, Near infrared, Long wavelength infrared, Lenses, Infrared radiation, Infrared imaging, Diffraction, Visible radiation
In conventional imaging, the information transfer from the object to the image plane is accomplished either with the help of a traditional lens that performs a one-to-one mapping or an unconventional lens that performs a one-to-many mapping. In the first case, the image is formed directly, whereas in the second case, the image is formed after a computation. The conventional lens approach is preferred in most cases due to the high signal-to-noise ratio achievable at each image pixel. By appealing to the fact that for most of the imaging applications, it is only the intensity, which is measured by the detector, the phase of the field in the image or focal plane is a free parameter, something that comes from the inverse diffraction transform. Therefore, it is easy to visualize that this phase of the plane wave after it transmits the lens can have multiple forms. Hence, the final choice can be made based upon specific application tailored requirements like achromaticity, depth-of-focus, wide-angle imaging, etc. This concept was exploited to design an achromatic MDL via inverse design across almost the entire electromagnetic spectrum (λ = 450 nm to 15 μm). Furthermore, a MDL with a Field Of View (FOV) up to 50° for wide-angle imaging as well as a MDL to enable an extreme Depth of Focus (EDOF) imaging of up to 6 m in the NIR were also designed.
We consider the design of nanostructured materials for thermal homeostasis, or the ability to maintain a temperature within a fixed range despite externally varying heat input. Our design uses nano- and microstructured phase-change materials to achieve a sharp change in thermal emission at a particular phase-transition temperature. We use electromagnetic simulations to calculate the thermal infrared absorption spectra for metal and insulator phases of the phase-change material. The results indicate a large increase in thermal emission at the phase transition. We then use numerical simulations of the heat equation to show that the sharp change in emission results in thermal homeostasis. For a varying external heat source, the material experiences much smaller temperature fluctuations than an unstructured or bulk material.
Vertical-external-cavity surface-emitting lasers (VECSELs) have been successfully used in the visible and near-infrared to achieve high output power with excellent Gaussian beam quality. However, the concept of VECSEL has been impossible to implement for quantum-cascade (QC) lasers due to the "intersubband selection rule". We have recently demonstrated the first VECSEL in the terahertz range. The enabling component for the QC-VECSEL is an amplifying metasurface reflector composed of a sparse array of metallic sub-cavities, which allows the normally incident radiation to interact with the electrically pumped QC gain medium. In this work, we presented multiple design variations based on the first demonstrated THz QC-VECSEL, regarding the lasing frequencies, the output coupler and the intra-cavity aperture. Our work on THz QC-VECSEL initiates a new approach towards achieving scalable output power in combination with a diffraction-limited beam pattern for THz QC-lasers. The design variations presented in this work further demonstrate the practicality and potential of VECSEL approach to make ideal terahertz QC-laser sources.
Terahertz quantum cascade (QC) lasers are well suited for the exploration of active metamaterial concepts in the
terahertz frequency range. Terahertz composite right/left handed (CRLH) transmission line metamaterials can be
integrated with quantum cascade laser gainmaterial in order to compensate for losses, and enable laser waveguides
with new functionality. In particular, we consider the use of metamaterial transmission lines as travelling
wave antennas. After presenting the characteristics of a 2.5 THz quantum-cascade laser, calculated radiation
characteristics and beam patterns for a leaky-wave antenna based upon a balanced 1D CRLH transmission line
waveguide are shown.
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