Daquan Yang

High sensitivity and high Q-factor nanoslotted parallel quadrabeam photonic crystal cavity for real-time and label-free sensing

We experimentally demonstrate a label-free sensor based on nanoslotted parallel quadrabeam photonic crystal cavity (NPQC). The NPQC possesses both high sensitivity and high Q-factor. We achieved sensitivity (S) of 451 nm/refractive index unit and Q-factor >7000 in water at telecom wavelength range, featuring a sensor figure of merit >2000, an order of magnitude improvement over the previous photonic crystal sensors. In addition, we measured the streptavidin-biotin binding affinity and detected 10 ag/mL concentrated streptavidin in the phosphate buffered saline solution.

High-Q and high-sensitivity width-modulated photonic crystal single nanobeam air-mode cavity for refractive index sensing

We propose a novel optical sensor based on a one-dimensional (1D) photonic crystal (PhC) single nanobeam air-mode cavity (SNAC). The performance of the device is investigated theoretically. By introducing a quadratically modulated width tapering structure, a waveguide-coupled 1D-PhC SNAC with a calculated high quality factor of 5.16×10(6) and an effective mode volume of V(eff)∼2.18(λ/n(si))(3) can be achieved. For the air mode mentioned above, the light field can be strongly localized inside the air region (low index) and overlaps sufficiently with the analytes. Thus, the suggested PhC SNAC can be used for high-sensitivity refractive index sensing with an estimated high sensitivity of 537.8 nm/RIU. To the best of our knowledge, this is the first PhC single nanobeam geometry that features both high Q-factors and high sensitivity, and is potentially an ideal platform for realizing ultracompact lab-on-a-chip applications with dense arrays of functionalized spots for multiplexed sensing.

Refractive index sensing utilizing parallel tapered nano-slotted photonic crystal nano-beam cavities

We demonstrate refractive index sensing using parallel tapered nano-slotted photonic-crystal nano-beam cavities with three-dimensional (3D) finite-difference time-domain (3D-FDTD) simulation. The electric field of the cavity mode is strongly concentrated in the slot region leading to a large light–matter overlap, which is expected to add a significant contribution to sensitivity, and thus we present high refractive-index sensitivity of more than 600  nm/refractive index units. Additionally, the quality (Q)-factor in the proposed design is theoretically investigated, and through tapering the diameter of the pores outside the Bragg mirrors in nano-beam cavities and the width of the adjacent nano-slots, an optimal Q-factor of 11770 is obtained. A high figure of merit (FOM=4637) of the designed model has been obtained. We anticipate that this geometry is potentially an ideal platform for refractive-index based bio-sensing.

Microdisplacement sensor based on high-Q nanocavity in slot photonic crystal

A microdisplacement sensor formed by a fixed and mobile hole-array based slot photonic crystal (slot-PhC) components is demonstrated. The sensing technique is based on a nanoscale cavity with a high-Q factor in photonic crystals (PhCs). The high-Q nanocavity (H0-cavity) is formed by only laterally shifting two adjacent holes outwards slightly in the opposite direction. The properties of the microdisplacement sensor are analyzed theoretically and simulated using the finite-difference time-domain method. The simulation results indicate that with a proper operating frequency, a quasilinear measurement of microdisplacement is achieved with a sensitivity of 1.0a −1 ( a is the lattice constant) in the sensing range between 0.00a and 0.20a. Although other researchers such as Xu et al. 1 who demonstrated a micro displacement sensor possessing an equivalent sensitivity, the Q factor is only 40. In this paper, combined with harmonic analysis, we show numerically that an intrinsic Q value of up to 6×10 3 is achieved. In addition, it is worth mentioning that when the parameters of the H0-cavity are determined, the resonant frequency of the H0-cavity remains approximately constant as the mobile PhC segment shifts along the common axis. It will be easier and more accurate for measurements in practical applications.

Ultrahigh-

We present a novel optical sensor based on the design of ultrahigh-Q and low-mode-volume 1-D single photonic crystal (PhC) slot nanobeam cavity (SNC) in which the air-hole radius is parabolically tapered. The performance of the device is investigated theoretically. In order to achieve high Q-factor and high sensitivity simultaneously, the slot geometry is exploited to make the optical field strongly localized inside the low index region and overlaps sufficiently with the analytes. With the three-dimensional finite-difference time-domain (3D-FDTD) method, we demonstrate that the proposed single 1-D PhC-SNC sensor device possess an ultrahigh sensitivity (S) up to ~900 nm/RIU (refractive index unit, RIU) and a high Q-factor in air up to > 107 at the telecom wavelength range. The optimized figure of merit is > 107. In addition, an ultrasmall mode volume of Vm ~0.01 (λ/ηair)3 has been achieved, which is more than three orders of magnitude smaller than our previous works [Appl. Phys. Lett. 105, 063118 (2014)] and, thus, is potentially an ideal platform for realizing ultracompact laboratory-on-a-chip applications with dense arrays of functionalized spots for multiplexed gas sensing.

Q

A tunable high-order sideband spectra generation scheme is presented by using a photonic molecule optomechanical system coupled to a waveguide beyond the perturbation regime. The system is coherently driven by a two-tone laser consisting of a continuous-wave control field and a pulsed driving field which propagates through the waveguide. The frequency spectral feature of the output field is analyzed via numerical simulations, and we confirm that under the condition of intense and nanosecond pulse driving, the output spectrum exhibits the properties of high-order sideband frequency spectra. In the experimentally available parameter range, the output spectrum can be efficiently tuned by the system parameters, including the power of the driving pulse and the coupling rate between the cavities. In addition, analysis of the carrier-envelop phase-dependent effect of high-order sideband generation indicates that the system may present dependence upon the phase of the pulse. This may provide a further insight of the properties of cavity optomechanics in the nonlinear and non-perturbative regime, and may have potential applications in optical frequency comb and communication based on the optomechanical platform.

and Low-Mode-Volume Parabolic Radius-Modulated Single Photonic Crystal Slot Nanobeam Cavity for High-Sensitivity Refractive Index Sensing

The relationship between the re∞ection phase curve and the dispersion curve of a H-shaped slot fractal uniplanar compact electromagnetic bandgap (HSF-UC-EBG) structure is investigated in this paper. It is demonstrated numerically and theoretically that the pole (located at phi = 180 degrees) of the re∞ection phase curve is related to the EBG location of the dispersion curve. More speciflcally, the pole is always located in the bandgap and the frequency shift characteristics of the pole and the EBG location are the same. Therefore, locations of the artiflcial magnetic conductor (AMC) and EBG can match with the AMC point and the pole, respectively. By realizing and making appropriate use of this, we can tailor the AMC and EBG locations to coincide in the frequency region only by reducing the spectral distance (d) between the AMC point and the pole. This method can improve the computational e-ciency signiflcantly. Parametric studies have been performed to obtain guidelines for reducing d. Finally, an example to design HSF-UC-EBG structure with simultaneous AMC and EBG properties by using this technique is presented with detail steps.

Tunable high-order sideband spectra generation using a photonic molecule optomechanical system

Detecting and weighing individual nanoparticles is an important approach to studying the behavior and properties of single particles. Here, we illustrate an effective mass sensing scheme using optomechanical resonator system. Based on the optomechanically induced transparency phenomenon, a Stokes’ field reference approach is used to sense the mass of the particle on the microresonator. The field intensity of the transmission field will be changed by the effect of the particle, which avoids the limits of decay-induced spectral width in the resonance shift detection. Exploiting the perturbation method, we theoretically evaluated the dynamical behavior of the system and achieved femtogram-level mass sensing without the need for high cavity

A POLE AND AMC POINT MATCHING METHOD FOR THE SYNTHESIS OF HSF-UC-EBG STRUCTURE WITH SIMULTANEOUS AMC AND EBG PROPERTIES

Q

Effective Mass Sensing Using Optomechanically Induced Transparency in Microresonator System

-value, as well as strong coupling strength in the optomechanical system.