R. Anis
Applied Research & Photonics, Inc.,
United States
Keywords: terahertz, dendrimer-dipole-excitation, Overcoming Abbe diffraction limit, lattice-scale imaging, semiconductor yield improvement
Summary:
Scientific imaging is the key for just about any field of modern science and technology. However, high resolution imaging is restricted by a physical barrier known as Abbe diffraction limit. The diffraction limit dictates that no features less than half the wavelength of light can be resolved by a microscope. Hence, up until now, only electron microscope could be used to image the atomic lattice because electron wavelength is in the picometers. Therefore, a new approach of new approach of high-resolution imaging independent of wavelength is of paramount importance for scientific progress. Cameraless imaging details have been described elsewhere [1]. A brief description is given here. The main objective for avoiding the camera route is twofold. First, overcoming the Abbe diffraction limit, and second, achieving Angstrom scale resolution with bigger wavelengths. Since the camera route depends on a charged coupled device (CCD) or a similar focal plane array, the resolution of a camera is entirely dependent on the resolution of such device. The same is true for any image recording instrument. The Abbe diffraction limit [2] established an upper boundary of resolution achievable by any electromagnetic (EM) energy; the smallest object that can be resolved is half the wavelength of the light (EM energy) being deployed for imaging. Since the electron wavelength is in picometers, an electron microscope can resolve the atomic lattice. Therefore, any technique deploying the wavelength-based image formation must obey the Abbe diffraction limit; hence, visible light and/or UV light cannot see the atomic lattice. Scientists had thought that if one could overcome this physical barrier of Abbe diffraction limit, then imaging the lattice with bigger wavelength could have been possible. However, this connotation is wrong because as long as wavelength dependent imaging is utilized, the diffraction limit is unavoidable. Therefore, decoupling of wavelength dependence on image formation is the key for achieving higher image resolution with bigger wavelengths. The Terahertz Scanning Spectrometer and 3D Imaging system (TNs3DI) embodies the following key factors. (1) A new terahertz generation mechanism, dendrimer dipole excitation (DDE), for high power, up to 30 THz, continuous wave, stable terahertz generation. (2) Overcoming the Abbe diffraction limit for lattice resolution imaging with bigger (T-ray) wavelength. A succession from photographic film to CCD (current) to camera-less imaging (next gen.). (3) Replacing and complementing many functionalities of an atomic force microscope (AFM), scanning electron microscope (SEM), and transmission electron microscope (TEM) by T-ray technique, it uniquely identifies location, depth, and type of defects, where it exists. (4) Interfaces of epitaxial semiconductor via nondestructive route for sub-surfaces analysis with layer-by-layer imaging and spectral characterization. The decoupling of wavelength from the image formation physics has been achieved by (1) scanning an object to be imaged by a nanoscanner, (2) storing the reflected intensity in a matrix termed as the Beer-Lambert reflection matrix (BLR matrix), and (3) utilizing an algorithm to generate the volume image from the BLR matrix. Once the image is generated, it can be rendered as a surface image or a volume image.