Session P28: Optical Applications: Nonlinear Optics, Waveguides, and Novel Structures

An optical antenna for high-count-rate single-photon-sensitive superconducting transition edge sensors

There are number of promising applications for a GHz count-rate, energy-resolving single-photon detector in the near-infrared. However, such a detector has not yet been perfected. For thermal detectors, this is partly due to the difficulty of coupling relatively large ($\sim $1 micron) photons into the necessarily small ($\sim $100 nm) thermal sensor element. We report on the simulation, fabrication, and preliminary measurements of an antenna-coupled superconducting transition edge sensor. The optical antenna is designed to directly couple incident near-infrared photons into much shorter wavelength surface plasmons, which are then delivered to a nanoscale superconducting niobium detector element at the antenna feed. This detector is inherently energy resolving, unlike the superconducting nanowire single-photon detector (SNSPD) or the single-photon avalanche photodiode (SPAD), and it operates at the relatively convenient temperature of 4 K.   

Nanocrystal-based Optoelectronic Devices

Optoelectronic devices capable of detecting and emitting light on a scale well below its wavelength could have a profound impact on basic and applied experimental research in light-based electronics, on-demand photon generation, and for studying poorly understood quantum phenomena such as blinking and spectral wandering. We present a fabrication procedure for ultrasmall, nanocrystal optoelectronic devices based on self-assembled layers of quantum dots in plasmonically-active gold nanogaps. We provide preliminary experimental results which examine the possibility for surfaced-enhanced fluorescence, subwavelength detection and emission of light as well as plasmon-based optical trapping in these systems.   

Frequency and Intensity Stabilization of Planar Waveguide-External Cavity Lasers

Planar Waveguide External Cavity Lasers (PW-ECL) show an immense potential for use in precision measurement tasks and space missions because of its compactness and simple design. We show the techniques used to frequency and intensity stabilize a PW-ECL 1550nm laser system with the goal of achieving a frequency stability of 30~Hz/sqrt(Hz) and a RIN of less than 10$^{-6}$. These PW-ECL systems are a potential replacement for Non-Planar Ring Oscillator (NPRO) laser systems, which have become a standard for low-noise interferometric applications, if the PW-ECL can meet the required stability. We present the initial experimental results of the intensity and frequency stabilization setup and we show a comparison between PW-ECL lasers and NPRO lasers with respect to measurements and applications requiring a high frequency and intensity stability.   

Experimental setup to demonstrate low-frequency high-precision frequency stabilization of 1550 nm ECL Lasers

Advances in fiber and waveguide technologies have brought about a new type of laser: the Planar Waveguide External Cavity Laser (PW-ECL) that shows a great potential for precision interferometric measurements. We show an experimental setup based on a 1550nm PW-ECL which was designed to achieve a frequency stabilization of 30 Hz/sqrt(Hz) or less at 10 mHz. The presented design makes use of thermal shielding to suppress temperature fluctuations at low frequencies as well as a vacuum system, high finesse cavity and low-noise electronics to reduce the frequency noise. A description of the components used in the design is given and initial results are presented.   

Experimental demonstration waveguide with arbitrary bending angles in hyperuniform disordered photonics materials

Contradicting to the long standing intuition that long-range translational order is required in photonic band gap formation, recently a new class of disordered hyperuniform materials was predicted to possess sizeable photonic band gaps. We report the first experimental demonstration of complete and isotropic photonic band gap for all polarizations in such disordered hyperuniform structures made of alumina with a dielectric constant of 8.7. In periodic structures there are only a limited number of allowed rotational symmetries; hence bending angles of waveguiding channels are greatly limited. In isotropic hyperuniform disordered structures there are no preferential symmetry directions and waveguiding channels can be constructed with arbitrary bending angles. In our study, near 100 percent transmission of electromagnetic waves around sharp corners of arbitrary angles with bending radii smaller than one wavelength are observed experimentally. The hyperuniform disordered structures also enable the realization of isotropic confinement of radiation in cavities and can be used as flexible optical insulator platforms.   

Kerr Nonlinear Modes in Photonic Crystal Waveguide with Off-channel Features

A theoretical method using nonlinear difference equation approach has been developed for investigating guided modes of photonic crystal waveguide for cases in which the guided modes interact with multiple bound electromagnetic modes localized on off-channel impurity features of Kerr nonlinear media. The interest is on the properties of resonant scattering of the modes exhibited by the system formed of both linear and nonlinear media sites in the photonic crystal lattice. The scattering is treated and compared with results of the scattering of the modes in the linear limit of the Kerr media, i.e. in the absence of intensity $|E|^{2}$ term in the Kerr dielectrics derived in recursive difference equation formulation. The equations of the system are simple and can be quickly solved to demonstrate the wide and interesting varieties of behavior present in the system, including among others, optical bistability and induced transparency. Additionally, the method is applied for a case in which the field dependence of Kerr dielectric properties allows two different frequency waveguide modes to interact with one another by a modulation of the off-channel site dielectric properties. In this interaction, the one mode is used to model numerically the transmission characteristics of the other.   

The Phase Effect in perturbative nonlinear optics

Waveform control is essential for ultrafast nonlinear optical processes such as high-order harmonic generation (HHG). For example, a sawtooth-like waveform can enhance the kinetic energies of the electrons such that the cutoff of HHG is extended. In this work, we show that relative phase of the two-color driving laser can affect the outcome of perturbative nonlinear optical processes such as lower-order harmonic generation. Consider the third-harmonic signal generated in argon by the fundamental and second-harmonics of a pump laser with frequencies of $\omega _{1}$, and $\omega _{2}$. A cross-term emerges due to interference of four-wave mixing signals of ($\omega _{1}+\omega _{1}+\omega _{1})$ and ($\omega _{2 + }\omega _{2}-\omega _{1})$. When the intensities of two-color pump at $\omega _{1}$ and $\omega _{2}$ are equal, the modulation in the third-harmonic signal by the cross-term is about 30{\%} of the DC term. As the relative phase between $\omega _{1}$ and $\omega _{2}$ varies, a sinusoidal modulation in output intensity at 3$\omega _{1 }$ is expected. We have also calculated the phase effects for fifth, seventh and ninth harmonic generation, which show more complicated behavior.   

Micro-Photoluminescence for Optoelectronic Material Characterization

A hardware environment and software bundle have been developed for measuring the absolute value of and the variance in photoluminescence (PL) intensity across samples of optoelectrical materials. The fully automated assembly uses a dual-axis translation stage to allow for ``micro-PL'' measurements of the sample surface with a resolution of 10 microns on either axis. The user is given the option to digitally adjust the boundaries of the area being mapped, and set the measurement resolution to produce coarse or fine detailed PL maps of the sample surface. By using a monochromator, the system can perform preliminary measurements of PL at wavelengths ranging from 400nm to 1.7um, and determine the optimal spectral operation settings for detailed mapping. Since the system is a modular design, components can be switched to operate in other spectra ranges as well. As all components are digitally controlled by a PC, a universal user interface and integration module has been created to allow for simultaneous operation of all components with minimal user interaction, and intuitive representations of final data for material quality assessment. Various materials are characterized and discussed to demonstrate the utility.   

Rapid adiabatic passage in nonlinear optics for complete power transfer between ultrabroadband optical pulses

Rapid adiabatic passage is a central tool for full transfer of level populations in an atomic system. Recent work showed the equation of motions describing three-optical-wave mixing in a dielectric medium through a nonlinear electric susceptibility are isomorphic to the optical Bloch equations for a two-level atom (neglecting radiative losses) when the middle frequency wave is strong. We have exploited this analogy for the first time to prove the principle of complete Landau-Zener adiabatic transfer in nonlinear wave mixing. Using intense laser pulses and a specially designed poled potassium titanyl phosphate nonlinear crystal with an adiabatic longitudinal variation of the poling period, we demonstrate complete energy transfer of a near-IR pulse to the mid-IR. Moreover, we find the principle is upheld for huge laser bandwidths. In our experiment the power transfer covers two-thirds of an octave of bandwidth with preservation of the power spectral density profile. Control of optical power transfer through rapid adiabatic passage thus can serve to optimize sources for coherent control and strong-field physics.   

Nano-Gap Embedded Plasmonic Gratings for Surface Plasmon Enhanced Fluorescence

Plasmonic nanostructures have been extensively used in the past few decades for applications in sub-wavelength optics, data storage, optoelectronic circuits, microscopy and bio-photonics. The enhanced electromagnetic field produced at the metal/dielectric interface by the excitation of surface plasmons via incident radiation can be used for signal enhancement in fluorescence and surface enhanced Raman scattering studies. Novel plasmonic structures on the sub wavelength scale have been shown to provide very efficient and extreme light concentration at the nano-scale. The enhanced electric field produced within a few hundred nanometers of these structures can be used to excite fluorophores in the surrounding environment. Fluorescence based bio-detection and bio-imaging are two of the most important tools in the life sciences. Improving the qualities and capabilities of fluorescence based detectors and imaging equipment has been a big challenge to the industry manufacturers. We report the novel fabrication of nano-gap embedded periodic grating substrates on the nanoscale using micro-contact printing and polymethylsilsesquioxane (PMSSQ) polymer. Fluorescence enhancement of up to 118 times was observed with these silver nanostructures in conjugation with Rhodamine-590 fluorescent dye. These substrates are ideal candidates for low-level fluorescence detection and single molecule imaging.   

Micro-manufacturing with Three-dimensional Intensity Patterns: Practical Limits and Considerations

It is possible to generate 3D intensity patterns for micro-manufacturing using a phase hologram displayed on a liquid-crystal spatial light modulator (SLM). Knowledge of the phase and amplitude of a field in a single plane (the SLM plane) allows for calculation of the phase and amplitude in any set of subsequent planes. Iterative phase retrieval algorithms can take a 3D target intensity pattern and generate a hologram for display on the SLM; however, arbitrary 3D intensity patterns are not necessarily achievable because the light field must obey the wave equation. Furthermore, these algorithms have not been discussed from the point of view of lithographic micro-manufacturing. This paper presents one method for making a 3D intensity pattern that can be used to cure resist in a single-shot, and discusses the limits to patterning due to power, resolution, and SLM-related issues. The relationship between the resolution in the patterning volume and physical specifications of the SLM is more restrictive than if the patterning were being done in a single plane, but with sufficient laser power, this algorithm could be used in high-throughput 3D micro-manufacturing.   

High Finesse Microcavity for Gas Sensing

We report our progress in using optical Fabry-Perot microcavities for multiatomic gas sensing. The microcavities consist of one micromirror at a fiber tip and another micromirror on a planar silica substrate, each with a diameter near 50 microns. The micromirrors were fabricated by an improved CO2 laser ablation process that uses feedback from the light emitted during ablation to control the mirror dimensions. A cavity finesse in excess of 50 000 was obtained in the near-infrared. Our goal is to make use of the Purcell effect of cavity quantum electrodynamics to obtain an enhancement of Raman scattering when a double resonance condition is achieved.   

Control of transverse optical patterns in semiconductor quantum well microcavities

Recently, a low intensity all optical switching scheme exploiting directional optical instabilities in a semiconductor quantum well microcavity was proposed. It was demonstrated numerically that a sufficiently strong laser (pump) beam normally incident on the microcavity can suffer directional instabilities, generating new beams in oblique directions. These off-axis beams form a pattern when projected onto a plane in the far field placed transverse to the pump. Furthermore, the numerical results showed that the azimuthal orientation of the transverse optical pattern can be reversibly switched by applying a control beam much weaker than the pattern intensity. These phenomena are mediated by the nonlinear interactions among elementary excitations of the microcavity --- polaritons formed from strong coupling between the quantum well excitons and photons in a cavity mode. In this Contribution, we provide an overview of the rich parametric dependencies of pattern selection, the time scale of pattern formation, and the switching process. We also present an analysis of system's dynamics based on the contributing polariton wave-mixing processes.   

MEMS Fabricated MM-Wave Slow Wave Structure

We report on the fabrication and test of a MEMS slow wave structure designed for a $>$ 40 GHz bandwidth centered on 220 GHz operation, that slows radiation down to group velocity of 8.16 x 10$^{7}$ ms$^{-1}$ where the velocity matches the speed of electrons from a 20 keV source. The slow wave device uses a 40 mm long staggered interdigitated vane structure within a waveguide [1]. Ultimately, such a device will be integrated with an electron beam to become part of a sheet beam travelling wave tube (SBTWT) amplifier. A gold coated deep reactive ion etched (DRIE) silicon test structure was fabricated to test the RF properties of the design. This MEMS structure was coupled to WR-4 waveguide in a metal fixture and the S-parameters measured using a vector network analyzer, allowing extraction of the insertion loss and signal delay as a function of frequency. A further MEMS structure with just 10 cells of the vane structure within a cavity were fabricated which allows points on the dispersion curve to be directly measured as resonances of the structure. Extraction of the dispersion curve verifies the group velocity measurement of the device. \\[4pt] [1] Y-M. Shin {\&} L.R. Barnett, \textit{Appl.Phys. Lett. 2008,} 92 pp. 091501.