Bulletin of the American Physical Society
2017 Annual Meeting of the APS Mid-Atlantic Section
Volume 62, Number 19
Friday–Sunday, November 3–5, 2017; Newark, New Jersey
Session E4: Optics-I |
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Chair: Dan Bubb, Rutgers University, Camden Room: 225, Campus Center, NJIT |
Saturday, November 4, 2017 10:00AM - 10:36AM |
E4.00001: Enhanced laser processing through plasmonic interactions Invited Speaker: Daniel Bubb The strong interaction between laser light and plasmonic materials can be used to enhance traditional laser processing techniques. In this talk, I will review some aspects of the extinction of laser light by nanoparticles and how that may be utilized to form nanoalloys, porate soft material surfaces, and to study nano-particle interactions on surfaces. This processing technique is broadly applicable to diverse areas such as drug delivery, nonlinear optics, and micro-machining. [Preview Abstract] |
Saturday, November 4, 2017 10:36AM - 10:48AM |
E4.00002: Laser Power Beaming Hazard Analysis for Unmanned Ground and Aerial Vehicles Louis Rizzo, Kate Duncan, James Zunino, John Federici Laser power beaming (LPB) is the wireless transmission of electrical power with the use of a laser source and a receiving device in the form of photovoltaic arrays. There is a recent increase in the desire for systems utilizing LPB to power unmanned aerial and ground vehicles limited by short operational time due to battery life. The required lasers for this application present serious dangers to the operators of LPB systems. This can be a limiting factor for LBP, allowing its application to limited areas of laser hazard zones and requiring drone operators wear personal protection equipment. This paper discusses topics in hazard analysis for 125 watt infrared lasers with continuous wavelengths ranging from 800nm to greater than 1400nm under the guidelines of the American Standard for the Safe Use of Lasers. The intention is to find an optimum wavelength range and corresponding enlarged beam diameters that reduce laser hazards and meet the application requirements to power small drones while operational. The analysis concludes that an eye safe minimum expanded beam diameter of 43 cm occurs for a wavelength of 1297nm and a skin safe minimum beam diameter of 28 cm occurs for wavelengths between 1100-1400nm. [Preview Abstract] |
Saturday, November 4, 2017 10:48AM - 11:00AM |
E4.00003: Charging Dynamics of Single InGaAs Quantum Dots under Resonant Excitation Samantha Isaac, Gary Lander, Disheng Chen, Samet Demircan, Glenn Solomon, Edward Flagg Quantum dots (QDs) have potential to generate single indistinguishable photons, thus are prime candidates to be sources of photonic quantum bits, or qubits, necessary for quantum computation protocols. In theory, photon emission requires only resonant excitation. But resonant excitation can cause a QD to transition to a different charge state, eliminating the resonance fluorescence and reduces the QD's suitability to act as an efficient photon source. A counter to this effect is implementation of a low-power above-band laser that supplies the local environment with charge carriers. Ultimately, the carriers can relax into the quantum dot, returning it to the initial charge state. If QDs are to be used to generate photonic qubits, the charge relaxation processes must be characterized. To probe the charging dynamics, we modulate the above-band excitation while measuring the time-resolved resonance fluorescence. We phenomenologically fit the time-resolved fluorescence and extract the corresponding charging and neutralization rates as functions of both laser powers. The power dependence of the rates suggest there exists an external reservoir that supplies charge carriers to the QD, and that neutralization is dominated mostly by Auger processes. [Preview Abstract] |
Saturday, November 4, 2017 11:00AM - 11:12AM |
E4.00004: Phosphor-free InGaN/AlGaN white-light- emitting diodes on flexible substrates. Moab Rajan Philip, Thang Ha Quoc Bui, Mehrdad Djavid, Hieu Nguyen We report high-performance III-nitride nanowire light-emitting diodes (LEDs) on copper (Cu) substrates via the substrate-transfer approach. The nanowire (NW) LEDs were initially grown on silicon-on-insulator (SOI) substrate by molecular beam epitaxy. SOI substrate was then removed by dry and wet-etching methods. In contrast to conventional NW LEDs on Si, the NW LEDs on Cu offer advantages including better efficient thermal management and enhanced light-extraction efficiency (LEE), made feasible due to the use of highly thermally conductive metal substrates and metal reflectors. Moreover, LEDs on Cu have better current$-$voltage characteristics and stronger electroluminescence, photoluminescence intensities, in comparison to NW LEDs on Si. Finite difference time domain (FDTD) simulations revealed that the LEE of NW LED on Cu is 9 times higher than that of the LED on Si for the same nanowire radius of 60 nm and spacing of 130 nm. Moreover, by tuning the device-active region by varying In/Ga flux ratios, we achieved phosphor-free high-brightness LEDs on Cu with highly stable white-light emission and high color-rendering index of $\sim $95. III-nitride on metal substrates are thus expected to revolutionize the future era of flexible displays, wearable and general lighting devices. [Preview Abstract] |
Saturday, November 4, 2017 11:12AM - 11:48AM |
E4.00005: Imaging single nanoparticles using laser terahertz emission microscopy Invited Speaker: Daniel Mittleman Laser Terahertz Emission Microscopy (LTEM) is a terahertz imaging method providing an improved imaging resolution, limited by the spot size of the incident laser beam i.e. typically a few \textmu m. Inspired by recent results in terahertz nano-spectroscopy, we have improved the resolution of the LTEM technique by three orders of magnitude, by exploiting plasmonic coupling to a metallic Atomic Force Microscope (AFM) tip with a diameter on the order of 20 nm. Our setup is based on a commercial AFM which is coupled to a femtosecond laser (100 fs, 80 MHz repetition rate, 820 nm). The AFM uses an 80 \textmu m-long metal probe tip, tapping at 18 kHz with an amplitude of 110 nm. The back-scattered laser light is detected with a photodiode while the forward-scattered terahertz signal is detected with electro-optic sampling in ZnTe. By performing lock-in detection to the tapping frequency of the AFM probe, we can simultaneously record a near-field image at 820 nm, an LTEM image, and an AFM topography image. By locking to a higher harmonic of the tip oscillation the background of scattered light can be suppressed for both the optical and terahertz signals. Our sample is prepared by drop-casting an aqueous solution of surfactant-stabilized gold nanorods onto a wafer of lightly p-doped InAs (N$_{\mathrm{c}}$\textasciitilde 10$^{\mathrm{16}})$ which is known to work well as a THz emitter. We measure a region of this wafer in the vicinity of a single nanorod. We observe that the LTEM image of the nanorod, formed using emission from the underlying substrate, is in excellent agreement with the other more conventional measurements, with an image resolution of \textasciitilde 20 nm, limited by the size of the AFM tip. We note that the LTEM signal is highest from the bare InAs wafer and drops when the tip is on top of the gold particle, suggesting that the gold nanoparticle partially screens the emission from the InAs surface. Our measurements clarify the emission mechanism, and the role of the extended metal tip in transducing the THz signal into the far field. [Preview Abstract] |
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