- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Enhanced Terahertz Detection Efficiency via Grating-Assisted Noncollinear Electro-Optic Sampling
摘要： Sensitive detection of phase-locked terahertz (THz) pulses is routinely achieved using electro-optic sampling (EOS), a technique that harnesses second-order optical nonlinearities in a crystalline semiconductor. The thickness and electro-optic coefficient of such a crystal set the detection sensitivity in EOS, while its linear optical properties often determine the accessible detection bandwidth through the phase-matching conditions. Here, we demonstrate how a periodically patterned structure on the incident surface of an EOS crystal can be used to overcome bandwidth limitations by enabling noncollinear propagation between the THz waves and a near-infrared (NIR) gating pulse. The concept is demonstrated with phase gratings etched on a 1-mm-thick gallium phosphide (GaP) semiconductor. The use of a diffracted NIR gating pulse to retrieve the THz waveform results in a sensitivity enhancement of a factor of approximately 2 with regard to the spectral maximum at 2 THz and exceeding an order of magnitude at 5 THz. This extends the spectral detection bandwidth up to 5 THz, which is twice as large as that achievable in a similar configuration with collinear THz and NIR pulses, facilitating the broadband detection of weak signals in THz spectroscopy.
关键词： electro-optic sampling,phase grating,gallium phosphide,noncollinear propagation,terahertz
更新于2025-09-12 10:27:22
-
Integrated color photodetectors in 40 nm standard CMOS technology
摘要： For the further integration of receivers in multi-color visible light communication systems, a novel color photodetector (PD) was designed and fabricated by using a 40 nm standard complementary metal oxide semiconductor (CMOS) process without any process modifications. The PD consists of CMOS photodiode and two-dimensional (2D) polysilicon subwavelength grating above the photodiode. The 2D polysilicon grating is controlled in structural parameters to realize color filtering, based on guided-mode resonance, for the first time in a standard CMOS process. Here three kinds of color PDs were designed to respond to the three primary colors. The measured results demonstrate that the color PDs exhibit wavelength selectivity in the visible range (400-700 nm) and the maximum peaks in the spectral response curves of them are at 660 nm (red), 585 nm (green) and 465 nm (blue), respectively. In addition, the added 2D polysilicon grating almost does not reduce the responsivity of the photodiodes.
关键词： two-dimensional polysilicon subwavelength grating,Color photodetector,visible light communication,complementary metal oxide semiconductor (CMOS)
更新于2025-09-12 10:27:22
-
46.2: <i>Invited Paper:</i> The Development of Grating Waveguide Technology for Near‐Eye Display in Augmented Reality
摘要： Augmented Reality (AR) is generally considered as the next generation computing platform after PC and smart phones, with extensive applications and colossal market capacity. As the most essential hardware of AR wearables, the Near-Eye Display (NED) system determines the final pattern of the product. In this paper, the NED solutions of mainstream AR eyewares are discussed, and the advantages and disadvantages of prism, freeform, arrayed waveguide and grating waveguide, the four popular technologies in NED of AR, are compared. Based on above information, the strengths of grating waveguide in AR products are analyzed, the principles and processing technology are introduced, and the prospect of grating waveguide to be the future of NED in AR is proposed.
关键词： grating waveguide,augmented reality,near-eye display
更新于2025-09-12 10:27:22
-
Rectangular and sinusoidal Au-Grating as plasmonic sensor: A comparative study
摘要： Sensitivity of surface plasmon resonance sensor (SPRS) is mainly associated to efficient excitation of surface plasmon polaritons (SPPs) waves. In this work, effect of 50 nm thick Au film designed as rectangular and sinusoidal grating structure on glass substrate has been explored by finite element analysis (FEA) using COMSOL Multiphysics 5.3a. The comparison between the rectangular and sinusoidal gratings for efficient sensing has been presented here. Slit width (SW) for grating device has been optimized by applying far-field and near-field analysis while periodicity of grating structure is kept constant. Far field transmission spectra for both devices have been analyzed by illuminating the grating device through excitation port from the substrate side. Resonance wavelength (RW) dips for plasmonic grating device has been examined in each transmission spectrum for different values of refractive indices (RI). The sensitivity of plasmonic grating device has been calculated by measuring the shift in resonance wavelength by varying refractive index of analyte. The sinusoidal grating supporting fundamental plasmonic mode is found to be more sensitive (717 nm/RIU) as compared to simple rectangular grating (693 nm/RIU). Being highly sensitive to minute change in refractive index, such devices are efficiently applicable in real life.
关键词： Plasmonic sensor,Sinusoidal grating,Finite element analysis,Refractive index sensing,Sensitivity,Rectangular grating
更新于2025-09-11 14:15:04
-
Parasitic-coupled high-gain graphene antenna employed on PBG dielectric grating substrate for THz applications
摘要： In THz frequency region, the high-gain miniaturized patch antenna is essential to overcome the atmospheric losses. A novel dual-band miniaturized graphene antenna array with parasitic-coupled feed and mounted on PBG dielectric grating substrate is proposed in the operating frequency band from 0.85 to 1.04 THz. The analysis of graphene surface conductivity, surface wave polariton (SPP) of photonic band gap (PBG) substrate, and the dielectric grating substrate has been done for the verification of a projected design. Parametric analysis of PBG radius, periodic perturbation of dielectric grating substrate, and mutual coupling distance has been verified to achieve the enhanced radiation characteristics of the antenna. The minimum return loss of ?52.58 dB, VSWR of 1.005, impedance bandwidth of 33.34 GHz, the peak gain of 16.4 dB, and peak directivity of 17 dBi the projected design. The parasitic-coupled method is suitable to reduce the complexity of the antenna array and proposed design is useful in imaging, security using spectroscopy, and wireless communication applications.
关键词： parasitic coupling,PBG,dielectric grating,graphene,THz band
更新于2025-09-11 14:15:04
-
Mode Sensitivity Analysis of Subwavelength Grating Slot Waveguides
摘要： In this paper, we investigate the mode sensitivity (Smode) of subwavelength grating slot (SWGS) waveguides. Smode is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of Smode. The measured Smode value of 79% is consistent with the theoretical prediction of 83%.
关键词： Subwavelength grating,sensor,silicon-on-insulator,integrated optics,slot waveguide
更新于2025-09-11 14:15:04
-
Sub-decibel silicon grating couplers based on L-shaped waveguides and engineered subwavelength metamaterials
摘要： The availability of low-loss optical interfaces to couple light between standard optical fibers and high-index-contrast silicon waveguides is essential for the development of chip-integrated nanophotonics. Input and output couplers based on diffraction gratings are attractive coupling solutions. Advanced grating coupler designs, with Bragg or metal mirror underneath, low- and high-index overlays, and multi-level or multi-layer layouts, have proven less useful due to customized or complex fabrication, however. In this work, we propose a rather simpler in design of efficient off-chip fiber couplers that provide a simulated efficiency up to 95% (?0.25 dB) at a wavelength of 1.55 μm. These grating couplers are formed with an L-shaped waveguide profile and synthesized subwavelength grating metamaterials. This concept jointly provides sufficient degrees of freedom to simultaneously control the grating directionality and out-radiated field profile of the grating mode. The proposed chip-to-fiber couplers promote robust sub-decibel coupling of light, yet contain device dimensions (> 120 nm) compatible with standard lithographic technologies presently available in silicon nanophotonic foundries. Fabrication imperfections are also investigated. Dimensional offsets of ± 15 nm in shallow-etch depth and ± 10 nm in linewidth’s and mask misalignments are tolerated for a 1-dB loss penalty. The proposed concept is meant to be universal, which is an essential prerequisite for developing reliable and low-cost optical couplers. We foresee that the work on L-shaped grating couplers with sub-decibel coupling efficiencies could also be a valuable direction for silicon chip interfacing in integrated nanophotonics.
关键词： grating couplers,silicon photonics,L-shaped waveguides,subwavelength metamaterials,optical interfaces
更新于2025-09-11 14:15:04
-
Demonstration of polarization control GaN-based micro-cavity lasers using a rigid high-contrast grating reflector
摘要： We reported on Gan microcavity (Mc) lasers combined with one rigid tio2 high-contrast grating (HcG) structure as the output mirror. the HcG structure was directly fabricated on the Gan structure without an airgap. The entire MC structure comprised a bottom dielectric distributed Bragg reflector; a GaN cavity; and a top HCG reflector, which was designed to yield high reflectance for transverse magnetic (tM)- or transverse electric (te)-polarized light. the Mc device revealed an operation threshold of approximately 0.79 MW/cm2 when pulsed optical pumping was conducted using the HcG structure at room temperature. The laser emission was TM polarized with a degree of polarization of 99.2% and had a small divergence angle of 14° (full width at half maximum). This laser operation demonstration for the Gan-based Mc structure employing an HcG exhibited the advantages of HcGs in semiconductor lasers at wavelengths from green to ultraviolet.
关键词： Gan microcavity lasers,high-contrast grating reflector,GaN,polarization control,TiO2
更新于2025-09-11 14:15:04
-
Switchable multi-wavelength thulium-doped fiber laser employing a polarization-maintaining sampled fiber Bragg grating
摘要： A continuous wave, switchable multi-wavelength, thulium-doped fiber laser (TDFL) with a polarization-maintaining sampled fiber Bragg grating (PM-SFBG) is proposed and demonstrated for the first time. A length of 150 m highly-nonlinear fiber (HNLF) was used to introduce the four-wave mixing effect for the efficient suppression of the wavelength competition existing in the gain medium of thulium-doped fiber. By adjusting the state of polarization (SOP) of light in the laser cavity, two six-wavelength operations at two orthogonal SOPs and a ten-wavelength operation were obtained. When the TDFL ran at the six-wavelength operation mode with a pump power of 4.11 W, there were at least four lasing wavelengths with an optical signal-to-noise ratio (OSNR) higher than 30 dB, and when it ran at the ten-wavelength operation mode with a pump power of 4.60 W, there were nine lasing wavelengths with an OSNR higher than 30 dB. Regardless of the operation mode, the TDFL exhibited high stability.
关键词： sampled fiber Bragg grating,thulium-doped fiber laser,multi-wavelength
更新于2025-09-11 14:15:04
-
Zero-Birefringence Silicon Waveguides Based on Tilted Subwavelength Metamaterials
摘要： Polarization independent silicon-on-insulator nanowires are highly sought after, due the inherent high birefringence of this material platform. State-of-the-art designs of non-birefringent waveguides include ridge waveguides and square nanowires, which either imply large dimensions, multiple etching steps, low fabrication tolerances or high wavelength dependence. In this work, we overcome all the aforementioned limitations through tilted subwavelength structures which provide anisotropy control of the resulting metamaterial. With a waveguide cross section of only 300 nm x 550 nm (height x width), the zero-birefringence point is obtained for an approximately 48?-tilt of the subwavelength structure. Birefringence of the nominal design deteriorates by only 9.10?3 even in the presence of size deviations of ± 10 nm. Moreover, birefringence is maintained under 6.10?3 in a 100-nm bandwidth around the central wavelength of 1550 nm. This innovative approach is readly adaptable to a wide range of waveguide sizes, while maintaining single-etch-step fabrication.
关键词： polarization independence,silicon-on-insulator (SOI),sub-wavelength grating (SWG),Zero-birefringence waveguides,anisotropy engineering
更新于2025-09-11 14:15:04