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Enabled by atomically thickness control (0.26 nm/min) and loss engineering (0.28 dB/cm/min) of graphene oxide (GO) integrated silicon waveguide via ozone treatment, a low-loss (∼5dB/cm) and narrowband (1.1-nm) GO/silicon hybrid waveguide Bragg reflector is demonstrated.

In this work we introduce a tunable GMR filter based on continuously period-chirped (ΔP = 130 nm) gratings using a Ta2O5 waveguide layer with graded thickness (ΔT = 36 nm). The structure of the gradient-period grating is defined using a modified Lloyd’s mirror interferometer with a convex mirror, and Ta2O5 film used for the gradient is deposited using masked e-beam evaporation. The as-realized chirped GMR filter provides sharp transmission dips at resonant wavelengths with a filter bandwidth of approximately 4.2 nm and 0.78 nm when respectively applied to TE and TM polarized light under normal incidence. Gradually sweeping the chirped GMR filter makes it possible to monotonically sweep through resonant wavelengths from 500 to 700 nm, while maintaining stable filter bandwidth and transmission intensity. The optical spectrum of the incoming light can then be loyally reconstructed accordingly. We successfully demonstrate the spectrum reconstruction of a white light emitting diode and a dual-peak laser beam using the proposed chirped GMR filter as a dispersive device.

In this work, we proposed a full-color reflector using three stacked red (R), green (G), and blue (B) reflection gratings which are combined with the tunable 90° twisted nematic liquid crystals (TNLCs). The color reflector based on guided-mode resonance (GMR) gratings reflects strongly at the resonance wavelength. The optical reflectivity of GMR gratings can then be controlled by using 90° TNLCs to change the polarization of incident light. The optical characteristics and the chromaticity of the designed reflectors were evaluated by simulation. An individual RGB chip with/without LC was demonstrated experimentally. The fabricated GMR reflector for red exhibits a high TE/TM polarization ratio of >10:1 and 80% optical reflectivity at resonant wavelength, while the GMR reflector for blue only allows 60% optical reflectivity and a degraded polarization ratio of 3:1 mainly due to high optical absorption of silicon. Nevertheless, the silicon-based GMR reflector enables a wide reflection bandwidth, so a full-color reflector can be realized by vertically stacking RGB tunable reflectors. The proposed full-color reflector therefore exhibits a wide-gamut color space with low driving voltage of

Uniform periodic structure formation over a large sample area has been challenging in laser interference lithography (LIL) mainly due to the Gaussian intensity distribution inherent to a laser beam. In this work, refractive beam shaping devices are applied in a Lloyd's interferometer to create a flat-top light field (2.8% intensity variation over an area of 20 × 20 cm2) for wafer-scale nanopatterning. Around 10−2 variation in fill factors are obtained for all the reported one dimensional and two dimensional periodic structures across a 2-in. wafer, which is 1 order of magnitude lower than the values obtained for the samples exposed to a Gaussian light field. The proposed LIL system also allows gradual light field transitions from the Gaussian, super-Gaussian, and flat-top to the inverse-Gaussian by simply adjusting the spot size of the laser incident to the beam shaper. The authors believe that the proposed LIL system can be applied for a variety of applications that benefit from the nature of periodic na...

This paper presents a novel mirror-tunable laser interference system for the wafer-scale patterning (>4-in.) of submicron grating structures with a flexible periodicity (200–1000 nm) in a compact and cost-effective manner. The proposed system guides and splits the laser beam into two expanded light beams propagating in a downward direction to be reflected by rotatable ultraviolet mirrors to produce interference patterns. The incident angle of two light beams can be controlled by rotating the mirrors until they match the targeted periodicity of the grating, without the need to reconfigure the optical paths. The fact that light polarization changes with the rotation angle of the mirrors necessitates the use of a half-wave plate along each optical path to adjust the direction of polarization perpendicular to the plane of incident light. The proposed system enables large-area fabrication and wide-range grating tunability, making it highly useful for applications that require wafer-scale patterning of submicro...