Nanoelectronics, and Nano-optics

Sensor Test System

Nanotechnology is one of the most powerful technologies in modern science. At Samurai Scientists, we have made quantum dot devices (creating artificial atoms with special capabilities), quantum well systems (adjusting the parameters of semiconductors by making sets of layers that are thinner than the charge carriers' de Broglie wavelengths), and few-atoms-thick layers for special coating properties. When materials are made in this way, their physical, electrical, and optical properties can be adjusted based on the size of the particles (or the thickness of the layers), not just the inherent material characteristics. By optimized design, it is even possible to make printed materials act like holograms.

Artists have used nanotechnology and nano-optics for centuries, often without realizing it. In the Middle Ages, artists would grind gold into a paste so it could be used to color glass for stained-glass windows. They discovered that, if they kept grinding the paste, its color would change; the nano-optical properties of the gold were affecting its optical spectrum. Oyster shells also have nano-optical effects; their pearlescence is a nano-optical iridescent effect, which was recently added to some car paints.

Our scientists, on the other hand, worked mostly in two areas: adding nanoparticles of one detector material to a photodector made from a different detector material to artifically enhance the performance of the detector, and applying a protective monolayer to metals, redirecting corrosion charges along the surface rather than allowing them to corrode the protected metal. Our publications in this area include:

  1. Gulses, A.A.; Rai, S.; Padiyar, J., et al. “Laser Beam Shaping with Computer-Generated Holograms for Fiducial Markings.” In: Dudley, A.; Laskin, A.V., editors. Laser Beam Shaping XIX. San Diego, California: SPIE; 11107, 2019. p. 1110716.
         The laser marking method has obvious advantages over other available marking methods in speed, accuracy, and flexibility. Mask marking and beam deflection marking are typical methods, each having advantages and disadvantages. In the former, an opaque mask is directly imaged to create the desired mark. This method is practical and relatively fast, but most of the marking energy is blocked, losing efficiency. Additionally, this method requires a precise and bulky lens system. In the latter method, the focused beam is steered onto the sample, writing point by point. This technique has higher flexibility between marks, but it is slow, requires micro-movements, and accurate micro-motion parts are very expensive.
          We propose an innovative, holographic approach in laser marking. In the new system, a holographic projection system based on a digitally designed computer-generated hologram (CGH) is employed. This specially designed, fully transparent, phase only CGH modulates the high-power writing beam to create any desired image in the far field, where the beam etches a permanent mark of that image onto the designated silicon wafer substrate. Holographic marking combines the advantages of mask and beam deflection marking methods, such as high speed and stationary operation with minimal power loss, in a relatively simple and inexpensive setup. Also, since the holographic projection maintains its image quality after a certain distance, the setup is less prone to spatial alignment errors. We believe that the proposed technique will make significant contributions in the field of laser marking.
  2. Gulses, A.A.; Kurtz, R.M.; Islas, G.; Anisimov, I. “Lasers with Intra-Cavity Phase Elements.” In: Glebov, A.L.; Leisher, P.O., editors. High Power/Energy Laser Components and Packaging IV. San Francisco, California: SPIE; 10513, 2018. p. 1051342.
         Conventional laser resonators yield multimodal output, especially at high powers and short-cavity lengths. Since high order modes exhibit large divergence, it is desirable to suppress those to improve laser quality. Traditionally, such modal discriminations can be achieved by simple apertures providing absorptive loss for large diameter modes, while allowing the lower orders, such as the fundamental Gaussian, to pass through. However, modal discrimination may not be sufficient for short-cavity lasers in many cases, in addition to the power loss and overheating caused by absorption.
          To improve laser mode control with minimal energy loss, a set of systematic experiments have been executed using phase-only elements; composed of an intra-cavity step function and a diffractive out-coupler made of a computer-generated hologram. The platform was a 15 cm long solid-state laser that employs a neodymium-doped yttrium orthovanadate crystal rod, giving out 1064 nm multimodal output. Finally, it was shown that those intra-cavity phase elements are highly effective in obtaining beams with reduced M-squared values and at relatively higher powers, yielding improved brightness figures. The utilization of more sophisticated diffractive elements can be promising for more difficult laser systems.
  3. Kurtz, R.M.; Pradhan, R.D.; Parfenov, A.V., et al. “High Speed Nanotechnology-Based Photodetector.” In: Gaburro, Z.; Cabrini, S., editors. Nanophotonic Materials and Systems II. San Diego, California: SPIE; 5925, 2005. p. 111-120.
          An inexpensive, easily integrated, 40 Gbps photoreceiver operating in the communications band would revolutionize the telecommunications industry.  While generation of 40 Gbps data is not difficult, its reception and decoding require specific technologies.  We present a 40 Gbps photoreceiver that exceeds the capabilities of current devices.  This photoreceiver is based on a technology we call “nanodust.” This new technology enables nanoscale photodetectors to be embedded in matrices made from a different semiconductor, or directly integrated into a CMOS amplification circuit.  Photoreceivers based on quantum dust technology can be designed to operate in any spectral region, including the telecommunications bands near 1.31 and 1.55 micrometers.  This technology also lends itself to normal-incidence detection, enabling a large detector size with its associated increase in sensitivity, even at high speeds and reception wavelengths beyond the capability of silicon.
  4. Calizo, I.; Alim, K.A.; Fonoberov, V.A., et al. “Micro-Raman Spectroscopic Characterization of ZnO Quantum Dots, Nanocrystals and Nanowires.” In: Eyink, K.G.; Huffaker, D.L.; Szmulowicz, F., editors. Quantum Dots, Particles, and Nanoclusters IV: SPIE; 6481, 2007. p. 64810N.
          Nanostructures, such as quantum dots, nanocrystals and nanowires, made of wurtzite ZnO have recently attracted attention due to their proposed applications in optoelectronic devices. Raman spectroscopy has been widely used to study the optical phonon spectrum modification in ZnO nanostructures as compared to bulk crystals. Understanding the phonon spectrum change in wurtzite nanostructures is important because the optical phonons affect the light emission and absorption. The interpretation of the phonon peaks in the Raman spectrum from ZnO nanostructures continues to be the subject of debates. Here we present a comparative study of micro-Raman spectra from ZnO quantum dots, nanocrystals and nanowires. Several possible mechanisms for the peak position shifts, i.e., optical phonon confinement, phonon localization on defects and laser-induced heating, are discussed in details. We show that the shifts of ~2 cm-1 in non-Resonant spectra are likely due to the optical phonon confinement in ZnO quantum dots with the average diameter of 4 nm. The small shifts in the non-Resonant spectra from ZnO nanowires with the diameter ~20 nm – 50 nm can be attributed to either defects or large size dispersion, which results in a substantial contribution from nanowires with smaller diameters. The large red-shifts of ~10 cm-1 in the resonant Raman spectrum from nanocrystals were proved to be due to local laser heating.
  5. Kurtz, R.M.; Alim, K.A.; Pradhan, R.D., et al. “High Speed Nano-Optical Photodetector for Free Space Communication.” In: George, T.; Cheng, Z., editors. Micro (MEMS) and Nanotechnologies for Space Applications II. Orlando, FL: SPIE; 6556, 2007. p. 65560H.
          An inexpensive, easily integrated, sensitive photoreceiver operating in the communications band with a 50-GHz bandwidth would revolutionize the free-space communication industry. While generation of 50-GHz carrier AM or FM signals is not difficult, its reception and heterodyning require specific, known technologies, generally based on silicon semiconductors. We present a 50 GHz photoreceiver that exceeds the capabilities of current devices. The proposed photoreceiver is based on a technology we call Nanodust. This new technology enables nano-optical photodetectors to be directly embedded in silicon matrices, or into CMOS reception/heterodyning circuits. Photoreceivers based on Nanodust technology can be designed to operate in any spectral region, the most important to date being the telecommunications band near 1.55 micrometers. Unlike current photodetectors that operate in this spectral region, Nanodust photodetectors can be directly integrated with standard CMOS and silicon-based circuitry. Nanodust technology lends itself well to normal-incidence signal reception, significantly increasing the reception area without compromising the bandwidth. Preliminary experiments have demonstrated a free-space responsivity of 50 A/(W/cm2), nearly an order of magnitude greater than that offered by current 50-GHz detectors. We expect to increase the Nanodust responsivity significantly in upcoming experiments
  6. Kurtz, R.; Bennahmias, M., inventors; Luminit, LLC assignee. Graphene Anti-Corrosion Coating and Method of Application Thereof. Patent US009920447B2. 2018 March 20. 8 p.
          A graphene composite coating on a metal surface with excellent corrosion resistance by electrophoretic or electrolytic deposition has been obtained. The composite coating was shown to significantly increase the resistance of the metal surface to electrochemical degradation. The graphene coating significantly reduces cathodic current, which is an indicator of the rate of corrosion at the interface between the cathodic material and the anodic material.