Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session F23: Laser Science |
Hide Abstracts |
Sponsoring Units: DLS Chair: Richard Averitt, Univ of California - San Diego Room: BCEC 158 |
Tuesday, March 5, 2019 11:15AM - 11:27AM |
F23.00001: High-resolution spectroscopy of whispering gallery mode optical microcavities in the evanescent field of tapered optical fibers. Nathan Jordan, Alex King, Addison Ogonoski, Pranav Sultania, Marshall Ma, Mucheng Li, Yundong Ren, Yuxiang Liu, Kamil Ekinci, Sean Andersson, Oleksiy Svitelski Optical cavities with whispering gallery mode (WGM) resonances are interesting as building blocks for photonic devices, including fiber-integrated couplers and spectrometers, photonic crystals, and lasers. The high Q factors (103-106) along with their sensitivity to the surrounding environmental conditions allow the use of optical cavities as sensors of various physical quantities. We present results on polarized optical spectroscopy of spherical WGM resonant microcavities (D~5-50 micron) made of plastic, and silica and barium titanate glass, performed in air and water. The resonances were excited by evanescent light from optical fibers tapered either by chemical etching or by thermal pulling. The results of our experiments are consistent with theoretical predictions. We will discuss how to use these WGM resonances in order to apply forces to microparticles for microfluidic and biomedical applications. |
Tuesday, March 5, 2019 11:27AM - 11:39AM |
F23.00002: Home-made Spectrometer to Study Whispering Gallery Mode Resonators Marshall Shendu Ma, Addison Ogonoski, Pranav Sultania, Kamil Ekinci, Sean Andersson, Oleksiy Svitelskiy Whispering gallery mode (WGM) resonances are promising phenomena for fiber-based photonic applications such as directional couplers, spectrometers, and light generators. These resonances can also be useful for applying forces to dielectric microbeads and sorting them. We designed and built a simple system to excite and detect the WGM resonances of microbeads in atmosphere and in a liquid environment. The system consists of a tunable laser, an optical fiber with a tapered region where the WGM resonators are placed, and a photo detector to monitor the power transmitted through the fiber. The tunable laser has a wavelength range of approximately 1500-1600 nm and a peak output power of 1.5 mW. The tapered region is produced by chemical etching with hydrofluoric acid of a standard SMF-28 optical fiber. The WGM resonances are excited in plastic or glass microbeads with diameters in the 10 to 45 micron range. The preliminary results were obtained at steps of 1 and 0.1 nm/s in a wavelength sweeping mode. The power transmission was more than 40% which is sufficient to overcome the substantial power loss occurred in a liquid environment. |
Tuesday, March 5, 2019 11:39AM - 11:51AM |
F23.00003: Efficient, phase-resolved polarization-dependent two-dimensional coherent spectroscopy Jared Wahlstrand, Galahad Wernsing, Leon Lu, Alan D Bristow Capturing spectra for multiple polarization configurations in two-dimensional coherent spectroscopy allows access to different quantum pathways in the light-matter interactions probed by the technique. This is typically done by manually rotating waveplates. We demonstrate a liquid crystal variable retarder-based control scheme to efficiently capture common polarization configurations of the rephasing four-wave mixing of a semiconductor microcavity, showing that the presence of biexcitons alters the nonlinear response of the exciton polaritons. We find the proper phase of the complex 2D spectrum for the collinear polarization configuration in the usual way, by comparing the four-wave mixing emission to the spectrally-resolved transient absorption. Importantly, because the phase shift induced by the variable retarders is known, spectra for all other polarization configurations can be correctly phased. |
Tuesday, March 5, 2019 11:51AM - 12:03PM |
F23.00004: Coupling length phase matching scenarios in dual-core silica fibers Jing Su, Ivan Biaggio We analyze optical dual core silica fiber configurations that can be achieved to obtain phase matched third-order nonlinear optical frequency conversion to obtain farther infrared laser sources from near-infrared lasers. The phase matching principle is based on the coupling length phase matching (CLPM) principle, which allows to tune the phase matching condition by tuning the distance between the two cores in the fiber. We describe the corresponding phase matching tuning curves for different choices of pump lasers and discuss the advantages and limitations of the technique. |
Tuesday, March 5, 2019 12:03PM - 12:15PM |
F23.00005: Floquet optical ring resonators Kathleen McGarvey-Lechable, Pablo Bianucci This work discusses Floquet optical ring resonators (FORRs) on the silicon nitride photonics platform. A FORR builds upon the principles of a standard ring resonator with the addition of a small, periodic perturbation to the ring’s dielectric material. Similar to a standard photonic crystal, this perturbation results in the formation of multiple photonic band gaps (PBGs) in the ring’s optical spectrum. The size of the PBGs can be related to the degree of coupling between degenerate propagating and counter-propagating resonances of the ring. Through application of Bloch-Floquet theory, it is seen that the degree of spectral splitting between two degenerate modes can be precisely controlled by varying the strength of the l-th order Fourier coefficient of the ring’s dielectric profile. Additionally, multiple Fourier coefficients may be added to the unperturbed ring’s dielectric profile to split resonances across a broad spectrum of the ring. As a result, FORRs provide a new degree of freedom in manipulating the dispersion relation of a ring resonator, providing control over the spectral frequency and group velocity dispersion of a resonance. Potential applications of FORRs include dispersion engineering of optical frequency combs and integrated single photon sources. |
Tuesday, March 5, 2019 12:15PM - 12:27PM |
F23.00006: Exceptional points in microresonator Brillouin laser systems Yukun Lu, Yu-Hung Lai, Myoung-Gyun Suh, Kerry Vahala We theoretically proposed and experimentally demonstrated the existence of exceptional points (EPs) in an on-chip microresonator Brillouin laser system. The coalescence of the eigenfrequencies as well as the eigenmodes is presented. When the laser system is operating near the EP, the boosted rotational sensitivity is confirmed, which enables on-chip optical gyroscopes with unprecedented sensitivity. Moreover, EPs also emerge below the lasing threshold, and the coherent perfect absorption (CPA) can be realized by tuning the pump power. EPs in on-chip microresonator Brillouin systems have applications in precise sensing and optical information manipulating. |
Tuesday, March 5, 2019 12:27PM - 12:39PM |
F23.00007: Spontaneous symmetry breaking in an optical microcavity Qi-Tao Cao, Yun-Feng Xiao Spontaneous symmetry breaking is a ubiquitous property in diverse fields of modern physics, which is, however, elusive in optical domain. As a prominent photonic platform, the ultrahigh-Q whispering-gallery (WG) microcavity supports clockwise (CW) and counterclockwise (CCW) propagating waves with balanced amplitudes. Such chiral symmetry in a WG microcavity can be explicitly broken by removing the parity or time-reversal symmetry in previous works [1,2]. In this work, we report the experimental demonstration of the spontaneous chiral symmetry breaking in a single WG microcavity. The Kerr nonlinearity gives rise to an intensity-dependent CW-CCW coupling that becomes zero beyond a threshold, causing the original standing-wave mode to be unstable and spontaneously evolve into two chiral states with the unbalanced CW and CCW components [3,4]. Furthermore, we extended such the spontaneous symmetry breaking to the active regime and realized a unidirectional microlaser with the controllable chirality. |
Tuesday, March 5, 2019 12:39PM - 12:51PM |
F23.00008: Spatiotemporal Mode-Locking is Generalized Mode-Locking Logan Wright, Pavel Sidorenko, Zachary M Ziegler, Andrei Isichenko, Bors Malomed, Curtis Robert Menyuk, Demetrios Christodoulides, Frank W Wise In mode-locking, light in a resonator self-organizes into a nonlinear attractor, the dissipative soliton, often with rich dynamics. Mode-locking has enabled a myriad of applications through ultrashort duration pulses, high peak intensity, and broad frequency comb spectra. Virtually all work on the topic has considered light propagating on only one dimension, as in single-mode fiber. We recently demonstrated spatiotemporal mode-locking [1], the self-organized locking of many spatial and longitudinal modes into coherent pulses, i.e., three-dimensional mode-locking. Adding new dimensions to light’s self-organization gives rise to new ways to control the light field. Here, we outline a general theory of spatiotemporal mode-locking, showing it to be a generalization of mode-locking, and present new experimental measurements of qualitatively new mode-locked states, comprising nearly 30 million locked modes. Additionally, we predict numerous other novel forms of mode-locking, and phenomena, such as spatiotemporal dissipative soliton competition. |
Tuesday, March 5, 2019 12:51PM - 1:03PM |
F23.00009: Optically pumped lasing from Er-doped GaN epilayers in the infrared region Yizhou Wang, Ho Vinh, Hongxing Jiang, Jingyu Lin, Vinh Q Nguyen We report the realization of room-temperature, stimulated-emission in Er-doped GaN epilayers prepared by metal-organic chemical vapor deposition in the infrared region at room temperature. The lasing action of the Er doped GaN epilayers under optically pumped using an UV laser for the above bandgap excitation has been characterized. The observation of the amplified spontaneous emission has been presented through characteristic features of threshold behavior of emission intensity as functions of pump intensity, excitation length, and spectral linewidth narrowing by the variable stripe technique. Varying excitation length of the variable stripe setup, we have observed the optical gain of the GaN:Er epilayers is up to 75 cm-1. The generation of coherent radiation at 1.54 μm at room temperature paves the way for extended functionalities and integration capabilities for optoelectronic devices. |
Tuesday, March 5, 2019 1:03PM - 1:15PM |
F23.00010: A new high-efficiency regime for gas-phase terahertz lasers: Experiment and ab-initio theory Fan Wang, Paul Chevalier, Arman Amirzhan, Marco Piccardo, Federico Capasso, Steven G Johnson, Henry O Everitt In this work, we present both a new theoretical description and experimental validations of molecular gas optically pumped far infrared (OPFIR) lasers that have much higher efficiency than traditional OPFIR lasers with much more compact volumes. First, we demonstrate a 13CH3F OPFIR laser that achieves 10× greater efficiency and 1000× smaller volume than comparable commercial lasers. To fully understand this, we developed a new ab-initio theory that matches experiments quantitatively, within experimental uncertainties with no free parameters, by accurately capturing the interplay of millions of degrees of freedom in the laser—unlike previous OPFIR-laser models involving only a few energy levels that failed to even qualitatively match experiments at high pressures. Our model is general enough to capture the lasing behaviors of many other gases. By optically pumping N2O with a QCL instead of a CO2 laser, we predict a new regime of broad frequency-tunability for this traditionally narrow-band THz source. These results offer the possibility of a new generation of compact, frequency-tunable THz sources. |
Tuesday, March 5, 2019 1:15PM - 1:27PM |
F23.00011: A White Random Laser Yun-Tzu Hsu, Shu-Wei Chang, Wei-Cheng Liao, Yu-Ming Liao, Cheng-Fu Hou, Ying-Huan Chen, Chia-Tse Tai, Chen-You Su, Tai-Yuan Lin, Yang-Fang Chen Random laser with intrinsically uncomplicated fabrication processes, high spectral radiance, angle-free emission, and conformal onto freeform surfaces is in principle ideal for a variety of applications, ranging from lighting to identification systems. In this work, a white random laser (White-RL) with high-purity and high-stability is designed, fabricated, and demonstrated via the cost-effective materials (e.g., organic laser dyes) and simple methods (e.g., all-solution process and self-assembled structures). Notably, the wavelength, linewidth, and intensity of White-RL are nearly isotropic, nevertheless hard to be achieved in any conventional laser systems. Dynamically fine-tuning colour over a broad visible range is also feasible by on-chip integration of three free-standing monochromatic laser films with selective pumping scheme and appropriate colour balance. With these schematics, White-RL shows great potential and high application values in high-brightness illumination, full-field imaging, full-colour displays, visible-colour communications, and medical biosensing. |
Tuesday, March 5, 2019 1:27PM - 1:39PM |
F23.00012: High-order harmonic generation from hybrid lead halide perovskites Hideki Hirori, Peiyu Xia, Yasushi Shinohara, Tomohito Otobe, Yasuyuki Sanari, Hirokazu Tahara, Nobuhisa Ishi, Jiro Itatani, Kenichi Ishikawa, Tomoko Aharen, Masashi Ozaki, Atsushi Wakamiya, Yoshihiko Kanemitsu Nonlinear optical current induced by strong laser fields produces coherent radiation in spectral ranges inaccessible by lasers. Such high-harmonic generation (HHG) in solids is different from that in atomic gases; it has been shown that the intraband current caused by ultrafast acceleration of electron wave packets constitutes the nonlinear current [1,2]. However, how the concurrent field-driven population change in valence band contributes the nonlinear current remains unclear. Here, we studied the crystal orientation dependence of HHG intensity for hybrid organic–inorganic halide perovskites, which is well reproduced by the calculations based on an ab-initio approach. Our picture indicates that the virtual population change in the valence band is responsible for the HHG, which is of vital importance for achieving high generation efficiency and taking a full of information on bandstructure. |
Tuesday, March 5, 2019 1:39PM - 1:51PM |
F23.00013: Time- and angle-resolved photoemission spectroscopy using ultrafast XUV source at around 20 eV Yangyang Liu, John Beetar, Md Mofazzel Hosen, Gyanendra Dhakal, Christopher Sims, Firoza Kabir, Klauss Dimitri, Sabin Regmi, Michael Chini, Madhab Neupane Time- and angle-resolved photoemission spectroscopy (trARPES) has several advantages over conventional static ARPES measurements. Using trARPES, one can measure electronic states above the Fermi level, track femtosecond or picosecond dynamics in materials, and study transient laser-dressed band structures. We have developed a trARPES setup using high-order harmonic probe pulses produced using a commercial turn-key Yb:KGW laser. The laser, which emits 1030 nm, 290 fs laser pulses with average power of 20 W and tunable repetition rate between 50-200 kHz, is frequency-doubled using a BBO crystal, and focused into a krypton-filled gas cell to generate high-order harmonics. We eliminate low-order harmonic using an aluminum foil filter and optimize the harmonic cutoff using the laser intensity, thereby isolating the 9th harmonic at 21.7 eV. The 9th harmonic probe will be combined with a portion of the 1030 nm laser with a variable time delay for pump-probe experiments. Here, we will present the full characterization of the harmonic light source, as well as first time-resolved measurements in topological materials. |
Tuesday, March 5, 2019 1:51PM - 2:03PM |
F23.00014: Ultrafast relaxation of laser-excited flat nanoislands and nanoparticles investigated by ultrafast electron diffraction Ahmed Esmail, Hui Xiong, Hani Elsayed-Ali Ultrafast electron diffraction is used to probe the electron-phonon energy relaxation and phonon dynamics in Bi flat nanoislands and nanoparticles. The sample was excited with 110-fs laser pulses. By controlling the temperature and laser fluence during the annealing of thin Bi films, we prepare polycrystalline flat nanoislands and nanoparticles and investigate their relaxation dynamics. The temporal development of the various relaxation pathways is probed with a temporal resolution up to ~1.5 ps. The results show dependence on direction and varies between the nanoislands and nanoparticles. The response of the (110) diffraction peak for the 5-nm thick flat nanoislands is found to be faster than ~16 nm diameter nanoparticles. The response of diffraction for both particle shapes is found to be anisotropic. We also investigate the superheating of flat nanoislands and nanoparticles by monitoring the long-range order with excitation at various levels. |
Tuesday, March 5, 2019 2:03PM - 2:15PM |
F23.00015: Ultra-high speed laser-surgery with ultrafast bursts of pulses Fatih Ilday Ultrafast lasers allow thermal damage-free ablation irrespective of the material type. However, this process is slow and inefficient, with ablation volume having the remarkably poor logarithmic depedence on incident pulse energy. We recently demonstrated (Ilday et al., Nature 2016) ablation-cooled laser-material, whereby ultrafast pulses are sent in bursts, each containing hundreds of pulses separated by merely 100s of picoseconds, such that there is no time for heat to diffuse away from the processing region. The ablation rate increases by orders of magnitude and ablation becomes the dominant heat removal mechanism. Thus, the rest of the target material remains cool and without damage. We also reduced the required laser pulse energies by 1000 times and achieved record speeds in cutting biological tissue, metals and semiconductors (reaching 1 mm3/s). This new regime, where the ablation volume scales linearly with burst energy, has received much industrial interest, but there is also remarkable potential for extremely high-efficient and fast laser surgery. Is it possible to reach 1 mm3/s with biological tissue without thermal damage? As a more basic question, what the limitations to further decreasing the pulse separation time to less than the time it takes for ablation to occur. |
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