Daniel Petter
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View article: Diffraction of Light from Optical Fourier Surfaces
Diffraction of Light from Optical Fourier Surfaces Open
Diffractive surfaces shape optical wavefronts for applications in spectroscopy, high-speed communication, and imaging. The performance of these structures is primarily determined by how precisely they can be patterned. Fabrication constrai…
View article: Fourier surface grating couplers for integrated photonics
Fourier surface grating couplers for integrated photonics Open
We incorporate Fourier surfaces into silicon waveguides with vertical tapers for next-generation photonic grating couplers. By combining thermal scanning-probe lithography and reactive-ion etching, we generate gratings with smoothly apodiz…
View article: Bragg scattering of an ultracold dipolar gas across the phase transition from Bose-Einstein condensate to supersolid in the free-particle regime
Bragg scattering of an ultracold dipolar gas across the phase transition from Bose-Einstein condensate to supersolid in the free-particle regime Open
We present an experimental and theoretical study of the high-energy\nexcitation spectra of a dipolar supersolid. Using Bragg spectroscopy, we study\nthe scattering response of the system to a high-energy probe, enabling\nmeasurements of th…
View article: Freeform nanostructuring of hexagonal boron nitride
Freeform nanostructuring of hexagonal boron nitride Open
Hexagonal boron nitride (hBN)-long-known as a thermally stable ceramic-is now available as atomically smooth, single-crystalline flakes, revolutionizing its use in optoelectronics. For nanophotonics, these flakes offer strong nonlinearitie…
View article: Observation of a narrow inner-shell orbital transition in atomic erbium at 1299 nm
Observation of a narrow inner-shell orbital transition in atomic erbium at 1299 nm Open
We report on the observation and coherent excitation of atoms on the narrow inner-shell orbital transition, connecting the erbium ground state [Xe]4f12(3H6)6s2 to the excited state [Xe]4f11((4I15/2)0)5d(5D3/2)6s2(15/2,3/2)70. This transiti…
View article: Excitation Spectrum of a Trapped Dipolar Supersolid and Its Experimental Evidence
Excitation Spectrum of a Trapped Dipolar Supersolid and Its Experimental Evidence Open
We study the spectrum of elementary excitations of a dipolar Bose gas in a three-dimensional anisotropic trap across the superfluid-supersolid phase transition. Theoretically, we show that, when entering the supersolid phase, two distinct …
View article: Probing the Roton Excitation Spectrum of a Stable Dipolar Bose Gas
Probing the Roton Excitation Spectrum of a Stable Dipolar Bose Gas Open
We measure the excitation spectrum of a stable dipolar Bose-Einstein condensate over a wide momentum range via Bragg spectroscopy. We precisely control the relative strength ε_{dd} of the dipolar to the contact interactions and observe tha…
View article: Long-Lived and Transient Supersolid Behaviors in Dipolar Quantum Gases
Long-Lived and Transient Supersolid Behaviors in Dipolar Quantum Gases Open
By combining theory and experiments, we demonstrate that dipolar quantum gases of both $^{166}$Er and $^{164}$Dy support a state with supersolid properties, where a spontaneous density modulation and a global phase coherence coexist. This …
View article: Realization of a Strongly Interacting Fermi Gas of Dipolar Atoms
Realization of a Strongly Interacting Fermi Gas of Dipolar Atoms Open
We realize a two-component dipolar Fermi gas with tunable interactions, using erbium atoms. Employing a lattice-protection technique, we selectively prepare deeply degenerate mixtures of the two lowest spin states and perform high-resoluti…
View article: Quantum-Fluctuation-Driven Crossover from a Dilute Bose-Einstein Condensate to a Macrodroplet in a Dipolar Quantum Fluid
Quantum-Fluctuation-Driven Crossover from a Dilute Bose-Einstein Condensate to a Macrodroplet in a Dipolar Quantum Fluid Open
In a joint experimental, theoretical effort, we report on the formation of a macrodroplet state in an ultracold bosonic gas of erbium atoms with strong dipolar interactions. By precise tuning of the s-wave scattering length below the so-ca…