Bachelor of Science, Peking University, Physics (2014)
Doctor of Philosophy, Princeton University, Electrical Engineering (2019)
Shanhui Fan, Postdoctoral Faculty Sponsor
- Inverse Design of Lightweight Broadband Reflector for Relativistic Lightsail Propulsion ACS PHOTONICS 2020; 7 (9): 2350–55
Maximal nighttime electrical power generation via optimal radiative cooling
2020; 28 (17): 25460–70
We present a systematic optimization of nighttime thermoelectric power generation system utilizing radiative cooling. We show that an electrical power density >2 W/m2, two orders of magnitude higher than the previously reported experimental result, is achievable using existing technologies. This system combines radiative cooling and thermoelectric power generation and operates at night when solar energy harvesting is unavailable. The thermoelectric power generator (TEG) itself covers less than 1 percent of the system footprint area when achieving this optimal power generation, showing economic feasibility. We study the influence of emissivity spectra, thermal convection, thermoelectric figure of merit and the area ratio between the TEG and the radiative cooler on the power generation performance. We optimize the thermal radiation emitter attached to the cold side and propose practical material implementation. The importance of the optimal emitter is elucidated by the gain of 153% in power density compared to regular blackbody emitters.
View details for DOI 10.1364/OE.397714
View details for Web of Science ID 000560936200091
View details for PubMedID 32907066
- Global T operator bounds on electromagnetic scattering: Upper bounds on far-field cross sections PHYSICAL REVIEW RESEARCH 2020; 2 (3)
- Active Control of Multiple, Simultaneous Nonlinear Optical Processes in Plasmonic Nanogap Cavities ACS PHOTONICS 2020; 7 (4): 901–7
- Fundamental limits to radiative heat transfer: Theory PHYSICAL REVIEW B 2020; 101 (3)
- Fundamental Limits to Radiative Heat Transfer: The Limited Role of Nanostructuring in the Near-Field PHYSICAL REVIEW LETTERS 2020; 124 (1)
Fundamental Limits to Radiative Heat Transfer: The Limited Role of Nanostructuring in the Near-Field.
Physical review letters
2020; 124 (1): 013904
In a previous Letter, we derived fundamental limits to radiative heat transfer applicable in near- through far-field regimes, based on the choice of material susceptibilities and bounding surfaces enclosing arbitrarily shaped objects; the limits exploit algebraic properties of Maxwell's equations and fundamental principles such as electromagnetic reciprocity and passivity. In this Letter, we apply these bounds to two different geometric configurations of interest, namely dipolar particles or extended structures of infinite area in the near field of one another. We find that while near-field radiative heat transfer between dipolar particles can saturate purely geometric "Landauer" limits, bounds on extended structures cannot, instead growing very slowly with respect to a material response figure of merit (an "inverse resistivity" for metals) due to the deleterious effects of multiple scattering between bodies. While nanostructuring can produce infrared resonances, it is generally unable to further enhance the resonant energy transfer spectrum beyond what is practically achieved by planar media at the surface polariton condition.
View details for DOI 10.1103/PhysRevLett.124.013904
View details for PubMedID 31976696
T-Operator Bounds on Absorption, Scattering and Thermal Emission for Arbitrary Objects
View details for Web of Science ID 000612090002321
- T Operator Bounds on Angle-Integrated Absorption and Thermal Radiation for Arbitrary Objects PHYSICAL REVIEW LETTERS 2019; 123 (25)
- Inverse-designed photonic fibers and metasurfaces for nonlinear frequency conversion (vol 6, pg B82, 2018) PHOTONICS RESEARCH 2019; 7 (4): 493
- Material scaling and frequency-selective enhancement of near-field radiative heat transfer for lossy metals in two dimensions via inverse design PHYSICAL REVIEW B 2019; 99 (4)
T Operator Bounds on Angle-Integrated Absorption and Thermal Radiation for Arbitrary Objects.
Physical review letters
2019; 123 (25): 257401
We derive fundamental per-channel bounds on angle-integrated absorption and thermal radiation for arbitrarily structured bodies-for any given material susceptibility and bounding region-that simultaneously encode both the per-volume limit on polarization set by passivity and geometric constraints on radiative efficiencies set by finite object sizes through the scattering T operator. We then analyze these bounds in two practical settings, comparing against prior limits as well as near optimal structures discovered through topology optimization. Principally, we show that the bounds properly capture the physically observed transition from the volume scaling of absorptivity seen in deeply subwavelength objects (nanoparticle radius or thin film thickness) to the area scaling of absorptivity seen in ray optics (blackbody limits).
View details for DOI 10.1103/PhysRevLett.123.257401
View details for PubMedID 31922767
High Efficiency Second Harmonic Generation in Gallium Phosphide Ring Resonators on Oxide
View details for Web of Science ID 000482226302424
400%/W second harmonic conversion efficiency in 14 mu m-diameter gallium phosphide-on-oxide resonators
2018; 26 (26): 33687–99
Second harmonic conversion from 1550 nm to 775 nm with an efficiency of 400% W-1 is demonstrated in a gallium phosphide (GaP) on oxide integrated photonic platform. The platform consists of doubly-resonant, phase-matched ring resonators with quality factors Q ∼ 104, low mode volumes V ∼ 30(λ/n)3, and high nonlinear mode overlaps. Measurements and simulations indicate that conversion efficiencies can be increased by a factor of 20 by improving the waveguide-cavity coupling to achieve critical coupling in current devices.
View details for DOI 10.1364/OE.26.033687
View details for Web of Science ID 000454149000018
View details for PubMedID 30650802
- Inverse design in nanophotonics NATURE PHOTONICS 2018; 12 (11): 659–70
Inverse design of compact multimode cavity couplers
2018; 26 (20): 26713–21
Efficient coupling between on-chip sources and cavities plays a key role in silicon photonics. However, despite the importance of this basic functionality, there are few systematic design tools to simultaneously control coupling between multiple modes in a compact resonator and a single waveguide. Here, we propose a large-scale adjoint optimization approach to produce wavelength-scale waveguide-cavity couplers operating over tunable and broad frequency bands. We numerically demonstrate couplers discovered by this method that can achieve critical, or nearly critical, coupling between multi-ring cavities and a single waveguide at up to six widely separated wavelengths spanning the 560-1500 nm range of interest for on-chip nonlinear optical devices.
View details for DOI 10.1364/OE.26.026713
View details for Web of Science ID 000446055500101
View details for PubMedID 30469752
- Inverse-designed photonic fibers and metasurfaces for nonlinear frequency conversion [Invited] PHOTONICS RESEARCH 2018; 6 (5): B82–B89
- Enhanced nonlinear frequency conversion and Purcell enhancement at exceptional points PHYSICAL REVIEW B 2017; 96 (22)
Overcoming limits to near-field radiative heat transfer in uniform planar media through multilayer optimization
2017; 25 (13): 14746–59
Radiative heat transfer between uniform plates is bounded by the narrow range and limited contribution of surface waves. Using a combination of analytical calculations and numerical gradient-based optimization, we show that such a limitation can be overcome in complicated multilayer geometries, allowing the scattering and coupling rates of slab resonances to be altered over a broad range of evanescent wavevectors. We conclude that while the radiative flux between two inhomogeneous slabs can only be weakly enhanced, the flux between a dipolar particle and an inhomogeneous slab-proportional to the local density of states-can be orders of magnitude larger, albeit at the expense of increased frequency selectivity. A brief discussion of hyperbolic metamaterials shows that they provide far less enhancement than optimized inhomogeneous slabs.
View details for DOI 10.1364/OE.25.014746
View details for Web of Science ID 000404189800077
View details for PubMedID 28789058
- General formulation of coupled radiative and conductive heat transfer between compact bodies PHYSICAL REVIEW B 2017; 95 (16)
- Near-Field Radiative Heat Transfer under Temperature Gradients and Conductive Transfer ZEITSCHRIFT FUR NATURFORSCHUNG SECTION A-A JOURNAL OF PHYSICAL SCIENCES 2017; 72 (2): 141–49
Topology optimization in nonlinear nanophotonics: from frequency conversion to exceptional points
View details for Web of Science ID 000427296202168
- Exact formulas for radiative heat transfer between planar bodies under arbitrary temperature profiles: Modified asymptotics and sign-flip transitions PHYSICAL REVIEW B 2016; 94 (20)
- Measuring the Charge of a Single Dielectric Nanoparticle Using a High-Q Optical Microresonator PHYSICAL REVIEW APPLIED 2016; 6 (4)
- Strongly coupled near-field radiative and conductive heat transfer between planar bodies PHYSICAL REVIEW B 2016; 94 (12)
- Giant frequency-selective near-field energy transfer in active-passive structures PHYSICAL REVIEW B 2016; 94 (11)
- Temperature control of thermal radiation from composite bodies PHYSICAL REVIEW B 2016; 93 (12)
- Amplified and directional spontaneous emission from arbitrary composite bodies: A self-consistent treatment of Purcell effect below threshold PHYSICAL REVIEW B 2016; 93 (12)
- Fluctuating volume-current formulation of electromagnetic fluctuations in inhomogeneous media: Incandescence and luminescence in arbitrary geometries PHYSICAL REVIEW B 2015; 92 (13)
- Enhanced Raman scattering of single nanoparticles in a high- Q whispering-gallery microresonator PHYSICAL REVIEW A 2015; 91 (4)
Optimizing detection limits in whispering gallery mode biosensing
2014; 22 (5): 5491–5511
A theoretical analysis of detection limits in swept-frequency whispering gallery mode biosensing modalities is presented based on application of the Cramér-Rao lower bound. Measurement acuity factors are derived assuming the presence of uncoloured and 1/ f Gaussian technical noise. Frequency fluctuations, for example arising from laser jitter or thermorefractive noise, are also considered. Determination of acuity factors for arbitrary coloured noise by means of the asymptotic Fisher information matrix is highlighted. Quantification and comparison of detection sensitivity for both resonance shift and broadening sensing modalities are subsequently given. Optimal cavity and coupling geometries are furthermore identified, whereby it is found that slightly under-coupled cavities outperform critically and over coupled ones.
View details for DOI 10.1364/OE.22.005491
View details for Web of Science ID 000333579200106
View details for PubMedID 24663890
- Dissipative optomechanical coupling between a single-wall carbon nanotube and a high-Q microcavity PHYSICAL REVIEW A 2013; 88 (2)
Temperature-insensitive detection of low-concentration nanoparticles using a functionalized high-Q microcavity
2013; 52 (2): 155–61
The ability to detect nanoparticles in extremely dilute solutions in the presence of environmental noise is crucial for biosensing applications. In this paper we propose a scheme for detecting target nanoparticles through their scattering effects in a high-Q whispering gallery microcavity. The detection signal, defined as the total linewidth broadening of the two new split modes that appear upon nanoparticle adsorption, is highly sensitive and proportional to the nanoparticle concentration. Furthermore, this new method of detection eliminates the requirement for strict temperature control and is capable of distinguishing the signal from the biorecognitions (e.g., antibodies) initially attached to the resonator and that from the target nanoparticles (e.g., antigens).
View details for DOI 10.1364/AO.52.000155
View details for Web of Science ID 000313746100006
View details for PubMedID 23314630
- Coupling of diamond nanocrystals to a high-Q whispering-gallery microresonator PHYSICAL REVIEW A 2012; 86 (4)