IPS Meeting 2020 - Institute of Physics Singapore

Assoc. Prof. QIU Cheng-Wei Electrical and Computer Engineering National University of Singapore	Plenary 1: Optical Micromanipulation with Meta-fluidics and Meta-structures
	21 Dec, 9:00am
	This talk will demonstrate fundamental physics and origin, as well as experimental results, of extraordinary optical force phenomena, including negative pulling force, tunable lateral force, chiral force, negative radiation torque, and force application in biomedical applications. A comprehensive insight will be provided toward how to structure the light beams in meta-fluidics and meta-photonics, and how to tailor light-matter interaction to realize functionalized micromanipulations. The microfluidic chamber serves as a very powerful means to construct a coordinated light lattice, by the judicious interplay between optical force and drag force. Novel materials, like phase-change materials, chiral, and graphene, are also explored as new means. We also extend the previous micromanipulation toward nanomanipulation for sub-1nm particles, and propose novel scheme of synchronized dual barriers to sort out nanoparticles with single-digit nanometer precision. Furthermore, we shed a light to the recent advance in metasurface as a promising technology to structure complex lights so as to provide unexpected manipulation of nanoparticle.

Assoc. Prof. Dawn TAN Engineering Product Development Singapore University of Technology and Design	Plenary 2: Advances in Nonlinear Integrated CMOS Photonics
	21 Dec, 9:45am
	Nonlinear optics processes rely strongly on the nonlinear figure of merit and magnitude of the nonlinearity of the platform. Nonlinear integrated optics further allow high field localization that facilitates high nonlinear phase acquisition at low powers. CMOS-compatible ultra-silicon-rich nitride devices possess large Kerr nonlinearity and absence of two-photon absorption at telecommunications wavelengths. These advantageous properties have enabled the demonstration of high gain amplifiers and soliton-effects in USRN devices. Nonlinear USRN Bragg gratings are further demonstrated to possess three orders of magnitude larger group velocity dispersion compared to photonic waveguides. Time-resolved measurements reveal high-order Bragg soliton dynamics as well as observation of compression and fission triggered by large third-order dispersion. We further discuss device designs enabling close to ten-fold soliton-effect temporal, as well as the implementation of integrated spectro-temporal compression systems.

Asst. Prof. Yvonne GAO Centre for Quantum Technologies and Department of Physics, National University of Singapore	Plenary 3: Quantum Information Processing with Bosonic Modes in Circuit QED
	21 Dec, 11:00am
	Over the past decade, the circuit quantum electrodynamics technology has emerged as one of the leading contenders for practical quantum computation. In particular, bosonic quantum states stored in superconducting microwave cavities provide highly robust and versatile building blocks for hardware-efficient quantum error-correction and information processing. In this talk, I will introduce some of the recent scientific achievements demonstrated in this framework and discuss the strategy for realising universal quantum computation and other related applications using bosonic modes in circuit QED.

Dr. Leonid KRIVITSKY IMRE A*STAR Singapore	Plenary 4: Infrared metrology with visible light: the power of quantum correlations
	21 Dec, 11:45am
	Infrared (IR) optical range is important for material characterization and sensing. Also, imaging in the IR range yields superior image contrast with low scattering losses. IR metrology is widely used in petrochemical, pharma, biomedical, homeland security, and other areas. Even though there are well-developed conventional IR metrology methods, the remaining challenges are associated with the high cost and low efficiency of IR light sources and detectors. To mitigate these issues, we are developing new quantum-enabled techniques that allow us to retrieve the properties of materials in the IR range from measurements of visible range photons. Our approach uses the nonlinear interference of frequency correlated photons produced via spontaneous parametric down-conversion (SPDC) [1, 2]. We generate one photon in the visible range and its correlated counterpart in the IR range. Then we build an interferometric setup around the SPDC source and observe the interference of visible photons. The visibility and phase of the observed interference depend on the properties of the IR photon, which interacts with the sample. Thus, we can infer the properties of the sample in the IR range from measurements of visible range photons. In a series of experiments, we demonstrate applications of this method in IR spectroscopy [1-4], optical coherence tomography (OCT) [5], polarimetry [6], and wide-field microscopy [7, 8]. In all these demonstrations, we infer the IR properties of the samples from the measurements of the interference pattern in the visible range using off-shelve components. We are thus making IR measurements more affordable for practical applications. [1] D. Kalashnikov, et al., Nature Photonics 10, 98 (2016). [2] A. Paterova, et al., Scientific reports 7, 42608 (2017). [3] A. Paterova, et al., New Journal of Physics 20, 043015 (2018). [4] A. Paterova and L. Krivitsky, Light: Science & Applications 9:82 (2020). [5] A. Paterova, et al., Quantum Science & Technology 3, 025008 (2018). [6] A. Paterova, et al., Opt. Express 27, 2589-2603 (2019). [7] A. Paterova, et al., Appl. Phys. Lett. 117, 054004 (2020) – Editor’s Pick. [8] A. Paterova et al., Science Advances 6:eabd0460 (2020).

Asst. Prof. Marco BATTIATO School of Physical and Mathematical Sciences Nanyang Technological University	Plenary 5: From ultrafast spin currents to spintronics THz emitters and subpicosecond giant spin injection in semiconductors
	21 Dec, 2:00pm
	In 2010 I proposed the existence of out-of-equilibrium spin current pulses [1-3] and that they could explain the origin of the ultrafast demagnetisation. [4] A number of experimental works have confirmed such picture [5-8] and realised predictions such as the transfer of magnetisation in the non-magnetic substrate and the ultrafast increase of magnetisation. [5-6] The most interesting application was the development of the now widely known spintronics THz emitters. [8] Spintronics THz emitters have attracted a lot of attention, because of the wide and continuum spectrum as well as their ease of both production and use over alternative technologies. Few years ago I made another prediction: the possibility of injecting these ultrashort spin current pulses from a ferromagnetic metal into a semiconductor. [9] By taking advantage of the strongly out-of-equilibrium electronic distribution, such ultrashort spin currents pulses were predicted to be injected into a semiconductor with a huge intensity and high spin polarisation. We have recently proved this experimentally [11] by producing ultrashort spin current pulses into cobalt, injecting them into monolayer MoS2 and measuring emitted THz radiation. As predicted, we observed a giant spin current, orders of magnitude larger than typical injected spin current densities in modern devices. Such current pulses have the possibility of becoming the carriers of information in future spintronics running at unprecedented frequencies above the THz regime. Acknowledgements As many authors contributed to the presented results, please see the cited references for a comprehensive list. [1] M. Battiato, K. Carva, P.M. Oppeneer, Phys Rev. Lett. 105, 027203 (2010). [2] M. Battiato, K. Carva, P.M. Oppeneer, Phys Rev. B 86, 024404 (2012). [3] M. Battiato, P. Maldonado, P.M. Oppeneer, J. Appl. Phys. 115, 172611 (2012). [4] E. Beaurepaire, J.-C. Merle, A. Daunois, and J.-Y. Bigot, Phys. Rev. Lett. 76, 4250 (1996). [5] A. Melnikov et al., Phys. Rev. Lett. 107, 076601 (2011). [6] D. Rudolf, … M. Battiato, et al., Nature Comm. 3, 1037 (2012). [7] A. Eschenlohr, M. Battiato, et al., Nature Mater. 12, 332 (2013). [8] T. Kampfrath, M. Battiato, et al, Nature Nanotechnol. 8, 256 (2013). [9] M. Battiato and K. Held, Phys Rev. Lett. 116, 196601 (2016). [10] M. Battiato J. Phys. Condens. Matter 29, 174001 (2017). [11] L. Cheng, …, M. Battiato et al., Nature Physics (2019).

Assoc. Prof. EDA Goki Department of Physics National University of Singapore	Plenary 6: Ultrafast dynamics across 2D materials interfaces
	21 Dec, 2:45pm
	One of the most remarkable features of van der Waals heterostructures based on two-dimensional (2D) materials is the ultrafast photo-induced interlayer charge transfer, which is known to occur in sub-picosecond time scales. Such ultrafast dynamics offers promise for the realization of novel hot carrier optoelectronic devices where non-thermalized or “hot” photocarriers are harnessed to achieve unconventional functions. In this talk, I will discuss a few examples of hot carrier optoelectronic phenomena in heterostructures of 2D transition metal dichalcogenides and our approach to probing the ultrafast dynamics of the system through steady-state photocurrent and quantum yield measurements. First, I will discuss near-infrared-to-visible light upconversion in an electrically biased 2D materials heterostack. Second, I will highlight our observation of unexpected photoresponse of these devices arising from exciton-exciton annihilation (EEA). I will show how EEA can result in highly energetic electrons and holes due to significantly uneven distribution of annihilation energies.