The undesirable optical proximity effect (OPE) that appeared in the digital micro-mirrors device (DMD) based maskless lithography directly influences the final exposure pattern and decreases the lithography quality. In this manuscript, a convenient method of intensity modulation applied for the maskless lithography is proposed to optimize such an effect. According to the pulse width modulation based image recognition of DMD, we replaced the digital binary mask with a special digital grayscale mask to modulate the UV intensity distribution to be closer to the expectation in a way of point-by-point modification. The exposure result applying the grayscale mask has a better consistency with the design pattern than that for the case in which the original binary mask is used. The effectiveness of this method was analyzed by the image subtraction technique. Experimental data revealed that the matching rate between the exposure pattern and the mask pattern has been improved from 78% to 91%. Besides, more experiments have been conducted to verify the validity of this method for the optical proximity optimization and its potential in the high-fidelity DMD based maskless lithography.

We demonstrate a tilt-modulated phase imaging method to adjust the gap inconsistency for wafer-mask leveling in proximity lithography. Two gratings with close periods are etched on the mask and used as leveling marks. At the illumination of a monochromatic planar wave, the diffracted image of one grating is projected back onto the other one beside it through reflection at the wafer surface. Any wafer-mask tilts in two orthogonal sections are directly modulated into the phase distribution of the interference field and can be directly remedied according to the frequency and angle deviation of the two sets of fringes. Finally, wafer-mask leveling can be achieved at only one spot with preserved accuracy. Computational and experimental results confirm that tilts at the magnitude of ${10}^{-3}\mathrm{rad}$ can be readily resolved by this method.

Plasmonic metasurfaces act as appealing platforms for flexible and accurate wave regulation, but their functionalities in wavefront or spectral tuning are settled upon manufactured. So the ability to dynamically tailor the amplitude, phase or polarization is highly desirable for many scenarios of micro & nano photonics and the integrated optoelectronics. Here, one type of plasmonic metasurface devices for active wavefront control is demonstrated in the mid-infrared regime. Fundamentally, the switchable and tunable lensing is exemplified by phase change of refractive index and the generalized Snell’s law as well as the Pancharatnam-Berry phase. As a proof of concept, the metal-insulator (MI) and metal-insulator-metal (MIM) architectures are employed with the phase change medium and an optimized energy conversion efficiency of cross polarization. In a wide spectral range between 2.8 μ m and 3.8 μ m, the reflective beam focuses with a cross-polarization efficiency of 80% in the amorphous state, but defocuses in the crystalline state with zero cross-polarization, i.e. the ‘on’ and ‘off’ states of the metalens. Further, both device architectures show tunable focal length from 4.4 µ m to 4.8 µ m (MI) and 3.4 µ m and 3.6 µ m (MIM) respectively upon switching between the two states. As a result, our scheme potentially paves a way to flexibly construct the active photonic devices for the reconfigurable wavefront engineering in integrated optoelectronics, i.e. beam switch, tunable steering and lensing, etc.

Metasurfaces have emerged as a unique group of two-dimensional ultra-compact subwavelength devices for perfect wave absorption due to their exceptional capabilities of light modulation. Nonetheless, achieving high absorption, particularly with multi-band broadband scalability for specialized scenarios, remains a challenge. As an example, the presence of atmospheric windows, as dictated by special gas molecules in different infrared regions, highly demands such scalable modulation abilities for multi-band absorption and filtration. Herein, by leveraging the hybrid effect of Fabry–Perot resonance, magnetic dipole resonance and electric dipole resonance, we achieved multi-broadband absorptivity in three prominent infrared atmospheric windows concurrently, with an average absorptivity of 87.6% in the short-wave infrared region (1.4–1.7 μm), 92.7% in the mid-wave infrared region (3.2–5 μm) and 92.4% in the long-wave infrared region (8–13 μm), respectively. The well-confirmed absorption spectra along with its adaptation to varied incident angles and polarization angles of radiations reveal great potential for fields like infrared imaging, photodetection and communication.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

Since accurate alignment is essential for projection lithography, an extended dual-grating based alignment scheme is proposed. This method is an extension of the basic dual-grating alignment model, the mechanism of which is explained to make it clear how the extended scheme performs in projection lithog raphy. The framework of the extended alignment scheme for projection lithography is constructed, and the process of key parameter determination is then detailed. In both cases, a tiny shift of the wafer during the alignment process can be resolved by a conspicuous displacement or phase variation of corresponding fringes. Analytical results indicate that alignment is independent of the gap between wafer and mask, disturbance from the fluctuation in illumination can be neglected, and alignment resolution in sub nanometers can be realized with this scheme.