ABSTRACT
The referenced article [Opt. Express30, 36489 (2022)10.1364/OE.470330] has been retracted by the authors.
ABSTRACT
The integration of metasurfaces and optical waveguides is gradually attracting the attention of researchers because it allows for more efficient manipulation and guidance of light. However, most of the existing studies focus on passive devices, which lack dynamic modulation. This work utilizes the meta-waveguides with liquid crystal(LC) to modulate the on-chip spectrum, which is the first experimentally verified, to the authors' knowledge. By applying a voltage, the refractive index of the liquid crystal surrounding the meta-waveguides can be tuned, resulting in a blue shift of the spectrum. The simulation shows that the 18.4 dB switching ratio can be achieved at 1550 nm. The meta-waveguides are prepared using electron beam lithography (EBL), and the improved transmittance of the spectrum in the short wavelength is experimentally verified, which is consistent with the simulation trend. At 1551.64 nm wavelength, the device achieves a switching ratio of ≈16 dB with an active area of 8 µm × 0.4 µm. Based on this device, an optoelectronic computing architecture for the Hadamard matrix product and a novel wavelength selection switch are proposed. This work offers a promising avenue for on-chip dynamic modulation in integrated photonics, which has the advantage of a compact active area, fast response time, and low energy consumption compared to conventional thermal-light modulation.
ABSTRACT
Metasurface with metal-insulator-metal (MIM) structure has absorption properties for incident light at specific wavelengths. In this paper, we propose an infrared metasurface absorber based on silicon-based complementary metal oxide semiconductor (CMOS) process. By adding the prepared infrared metasurface absorber to the liquid crystal on silicon (LCoS) chip, it is used as the absorbing layer of LCoS configured between the pixel unit and the CMOS driver circuit. The effect of zero-order light caused by the gap between pixels in LCoS spatial light modulator (LCoS-SLM) on the light modulation function of the device is effectively reduced. Experiments show that the LCoS-SLM with infrared metasurface absorption structure can eliminate the zero-order light interference between the pixel gaps to a great extent and improve the modulation efficiency of the device. The proposed LCoS-SLM integrating infrared metasurface absorber structure based on silicon-based CMOS process has the advantages of low-cost and high modulation efficiency, which has high application value in the fields of holographic display, optical computing and optical communication.
ABSTRACT
Multispectral optoacoustic tomography (MSOT) has become the dominant technical solution for photoacoustic imaging (PAI). However, the laser source of fiber output in the current MSOT method is typically a TEM00 Gaussian beam, which is prone to artifacts and incomplete due to the uneven distribution of the irradiated light intensity. Here, we propose a novel method to improve the quality of photoacoustic image reconstruction by modulating the wavefront shaping of the incident laser beam based on the designed scattering structure. In the experiment, we add the designed scattering structure to the current hemispherical photoacoustic transducer array device. Through experiments and simulations, we investigate and compare the effects of different scattering structures on laser intensity modulation. The results show that an ED1-C20 diffusion structure with a scattering angle of 20 degrees has the most effective modulation of the beam intensity distribution. And we choose gold nanoparticles of 50-100 nanometers (nm) diameters and index finger capillary vessels respectively as the medium of PAI. We obtain the highest ratio of PAI area increases of gold nanoparticles and index finger to devices compare without scattering structure is 29.69% and 634.94%, respectively. Experimental results demonstrate that our method is significantly higher quality than traditional methods, which has great potential for theoretical application in medical PAI.
ABSTRACT
Polarization splitter-rotators (PSRs) are an essential component in on-chip polarization-sensitive and polarization-division multiplexing systems. In this work, we propose an ultracompact and high-performance silicon-based polarization splitter-rotator utilizing anisotropic metasurfaces, which is the first to combine the two, to our knowledge. The tilted periodic metasurface structure has different modulation effects on different polarized light fields, such as the transverse-electric (TE) mode and the transverse-magnetic (TM) mode, which are beneficial for designing polarization management devices. According to the results, the entire length of the silicon PSR was ~13.5 µm. The TE-to-TM conversion loss and polarization conversion ratio ere -0.154 dB and 96.5% at 1.55 µm, respectively. In the meanwhile, the cross talk and reflection loss were -27.0 dB and -37.3 dB, when the fundamental TE mode was input. The insertion loss and cross talk were -0.19 dB and -25.01 dB at the central wavelength when the fundamental TM mode was input. In addition, the bandwidth reached up to ~112 nm with polarization conversion loss and insertion loss higher than -0.46 dB and -0.36 dB. The simulations also show that the designed devices had good fabrication tolerance.
