Photolithography is the prevalent microfabrication technology. It needs to meet resolution and yield demands at a cost that makes it economically viable. However, conventional farfield photolithography has reached the diffraction limit, which imposes complex optics and short-wavelength beam source to achieve high resolution at the expense of cost efficiency. Here, we present a cost-effective near-field optical printing approach that uses metal patterns embedded in a flexible elastomer photomask with mechanical robustness. This technique generates sub-diffraction patterns that are smaller than 1/10 th of the wavelength of the incoming light. It can be integrated into existing hardware and standard mercury lamp, and used for a variety of surfaces, such as curved, rough and defect surfaces. This method offers a higher resolution than common light-based printing systems, while enabling parallel-writing. We anticipate that it will be widely used in academic and industrial productions.
In this paper, we propose a polarization-selective color filter that can generate two different color informations simultaneously depending on the polarization direction. The proposed color filter is mainly composed of the etalon structure to generate the color by the structural resonance properties while the upper layer of the etalon is made of plasmonic nanogratings to promote polarization-dependent color properties. When the duty ratio of the silver nanogratings is fixed, the proposed color filter can maintain identical optical properties for orthogonal polarization, while the etalon structure of the proposed color filter can manipulate different color information depending on the cavity height for the horizontal polarization. Finally, we experimentally confirm that polarization-dependent security images can be generated using the proposed color filters with a fixed duty ratio of various nanograting arrays.
van der Waals (vdW) heterostructures provide a powerful method to control the alignment of energy bands of atomically thin 2D materials. Under light illumination, the optical responses are dominated by Coulomb-bound electron−hole quasiparticles, for example, excitons, trions, and biexcitons, whose contributions accordingly depend on the types of heterostructures. For type-II heterostructures, it has been well established that light excitation results in electrons and holes that are separated in different layers, and the radiative recombination is dominated by the interlayer excitons. On the contrary, little is known about the corresponding optical responses of type-I cases. Understanding the optical characteristics of type-I heterostructures is important to the full exploration of the quasiparticle physics of the 2D heterostacks. In this study, we performed optical spectroscopy on type-I vdW heterostacks composed of monolayer MoTe 2 and WSe 2 . Photoluminescence and reflection contrast spectroscopy show that the light absorption and emission are dominated by the Coulomb-bound trions. Importantly, we observed that the MoTe 2 trion emission gets stronger compared with the exciton emission under resonant light excitation to the WSe 2 trion absorption state, especially in the WSe 2 /MoTe 2 /WSe 2 heterotrilayer. A detailed study of photoluminescence excitation further reveals that the chargetransfer mechanism is likely responsible for our observation, which differs from the exciton-dominated dipole−dipole energy transfer in type-II structures. Our demonstration implies that the type-I vdW heterostack provides new opportunities to engineer the light− matter interactions through many-body Coulomb-bound states.
We report a deterministic creation of color centers in diamond by employing single-shot laser writing. After thermal annealing treatment, we have confirmed that the optical emission and spin coherence consist with the conventional single NV.
We create single photon emitters in hexagonal boron nitride using a femtosecond laser and subsequent thermal annealing. Photoluminescence and photon anti-bunching measurements of generated bright spots clearly show that these are the single photon emitters.
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