This paper presents a novel metamaterial micro-fluidic sensor with two pairs of symmetrical double split-ring resonators (DSRR) compared to state of the art, which exhibits unique high-Q (~653) resonance and a 34% higher S21 magnitude than a single DSRR and allow, for the first time, real-time dual-channel biochemical testing through the design of two micro channels underneath the metamaterial DSRR. Polyimide was chosen as the substrate material and it shows good temperature stability at -200~300 °C, which makes the sensor enabling to work in harsh environment.

This paper presents a chemical sensor using a metamaterial absorber, which consisted of an Au Bottom layer, a FR4 substrate and a double-split-square-resonator (DSSR).The resonance generated by DSSR, which is extraordinarily sensitive to changes of the effective dielectric constant around the capacitive gap. The proposed sensor shows a great sensitivity and a high value of Q by a creative periodic DSSR structure and the Au Bottom layer. In addition, the relationship between the absorption frequency and chemical concentration is demonstrated by simulation.

We review our previous efforts on exploring decision-aided maximum likelihood (DA-ML) phase estimation scheme for carrier phase recovery in coherent optical communication systems in view of its high linear computational efficiency. With the fundamental assumption of constant phase noise within each observation block, the block length effect (BLE) is expected to degrade system performance adversely. To counteract or even eliminate the effect, we recently proposed a flexible DA-ML phase estimation method by taking consideration of time-varying laser phase noise and weighted coefficients based on ML criterion. Numerical verifications show such a flexible DA-ML scheme is very robust against time-varying phase noise. It can reduce phase estimation variance and improve the laser linewidth tolerance, which result in BER performance improvement significantly. In practice, by adopting the flexible DA-ML method with a relatively longer block length, BLE can be completely eliminated. BER performance can thus be easily improved without careful search for optimum block length or forgotten factors.

In this talk, I will focus on our recent work on particle guidance and optomechanics in optofluidic hollow-core photonic crystal fibers (HC-PCFs). In the first part I will introduce a flying particle irradiation sensor realized in liquid-filled HC-PCF, where we applied a dual-beam optical trapping scheme to tweezer a fluorescent particle inside the HC and to propel the particle along the HC-PCF via balancing the radiation pressure forces. When the fluorescent particle is flying through irradiated regions, its emitted fluorescence is captured by guided modes of the fiber core and so can be monitored at the fiber end. The system works as a remote irradiation sensor for visible and ultraviolet wavelengths (determined by the absorption properties of the fluorescent particle) with a measured spatial resolution of ~10 μm.

In the second part, I will talk about a new method to efficiently couple broadband light into optofluidic hollow waveguides, based on the optomechanically trapping of a silica nanospike inside the core of the HC-PCF. The nanospike, fabricated by thermally tapering a piece of standard single mode fiber (SMF), guarantees the adiabatic evolution of the fundamental mode from SMF to HC-PCF. Meanwhile it can be optically trapped in the center of the HC due to its strong optomechanical interaction and back-action with the HC. We demonstrate that using a silica nanospike, a trapping beam (at 1064 nm wavelength) with relatively high power can optically align the coupling of another weak broadband supercontinuum signal (~575 – 1064 nm) into the HC-PCF, with the unique advantages of self-stabilization and reflection-free. This method is of potential relevance for any application where the efficient delivery of broadband light into liquid-core waveguides is desired.

References:

[1] R. Zeltner, D. S. Bykov, S. Xie, T. G. Euser, and P. St.J. Russell, "Fluorescence-based remote irradiation sensor in liquid-filled hollow-core photonic crystal fiber", Appl. Phys. Lett. 108, 231107, 2016.

[2] S. Xie, R. Pennetta, and P. St.J. Russell, “Self-alignment of glass fiber nanospike by optomechanical back-action in hollow-core photonic crystal fiber”, Optica 3(3), 277-282, 2016.

[3] R. Zeltner, S. Xie, R. Pennetta, and P. St.J. Russell, "Broadband, Lensless, and Optomechanically Stabilized Coupling into Microfluidic Hollow-Core Photonic Crystal Fiber Using Glass Nanospike", ACS Photonics 4(2), 378–383, 2017.

We design and fabricate a simple micro-system to collect analyte molecules in fluids for surface-enhanced Raman scattering (SERS) detection. The system is based on catalytic Au/SiO/Ti/Ag layered microengines by employing roll-up nanotechnology [1] and the Raman spectrum. Finite-difference time-domain method is employed to illustrate the excitation of localized surface plasmon modes by calculating the electromagnetic field on the rough microengine surface. The bubble-propelled microengines [2] adsorb analyte molecules in fluids, acting as molecule carriers. Pronounced SERS signals are observed on microengines with more carrier molecules compared with the same structure without automatic motions, which indicates outstanding molecule collection performance. Furthermore, optimized collection efficiency of the system is obtained by controlling the fuel concentration. This facile system for molecule collection and detection could spur expanding applications in bioanalysis and lab-on-a-chip research. [3]

There is no doubt that the optical fiber has had a transformative impact on technology and photonics. The standard optical fiber, the lasing optical fiber, and the microstructured optical fiber have all spawned major industries and enabled new scientific and technological breakthroughs. There has been a drive to increase the functionality of the optical fiber and this talk will outline some of the key results in the development of the functionalized optical fiber. This will include the integration of semiconductors and low dimensional materials into the fiber geometry and how these can be exploited to produce optical fibers with new abilities.

The talk covers the enabling power of hollow-core photonic crystal fibers (HC-PCF) and their functionalized form Photonic Microcells (PMC) by showing how the association of glass, gas and light has created several paradigms in fields as different as photonics, nonlinear and high field optics, cold atom and laser metrology, and plasma physics. I start by reviewing the principle of optical guidance in Inhibited-Coupling HC-PCF which led to ultra-low loss hollow fibres, and highlights its enabling power in handling light and gas in extreme situations such as ultra-high energy laser handling, multi-octave optical comb generation, single-cycle pulse compression, in-fibre plasma generation, and cold atom harboring in micro-structure photonic components. I will then finish with an intriguing yet powerful way of nano-structuring molecular gas using a recently developed Lamb-Dicke regime of stimulated-Raman-scattering. Here, hydrogen molecules inside a photonic bandgap hollow core fibre are deeply-trapped in self-nanostructured optical lattice to emit watt-level CW Stokes-radiation with sub-Doppler resolved spectral sidebands and with a sub-recoil linewidth as low as ~3 kHz, which is ~6 orders-of-magnitude narrower than what conventional stimulated Raman scattering predicts. This new route of trapping molecules could open new paths in several fields such as trapping and cooling molecules, or manufacturing of gas nanostructures such as micro-mirrors and micro-cavities as we do with solid-state materials.

Diffraction phase microscopy(DPM) [1-2], which combines the benefits of high temporal sensitivity of common path interferometry and single-shot feature , has been used for quantitative phase imaging at the individual cell level. In this paper, a laser DPM system is designed and built up, and the spatial noise standard deviation of the system is measured as 5.3 nm. A standard polystyrene sphere is used as the calibration sample, and the measured phase shift shows good agreement with the expected one. The unwrapped phase image of  an G.lamblia cyst is reconstructed, thereby an elliptical shape with  is deduced, and the dry mass is calculated to be 54 pg. The results demonstrate that DPM can be a useful and versatile tool for the morphological and biochemical  characterization of single protozoan parasite.

Schematic of experimental setup for DPM is shown in Fig.1. A He-Ne laser instead of traditional halogen lamp is used as a light source. The beam from the laser is spatially filtered, collimated and aligned to the input port of the microscope, which produces magnified image of the sample at the output port. An amplitude diffraction grating is placed at the output port, which creates multiple copies of the image at different angles. Under the 4f configuration, a spatial filter placing at the fourier plane of lens L5 allows full 0th order passing as a imaging field, and filters down 1st order as a reference field while blocking other orders. After Lens L6, the two beams from the fourier plane interfere to produce a spatially modulated interferogram at the camera plane. Before measuring the sample, the spatial noise standard deviation is characterized as 5.3 nm.  

To demonstrate the accuracy of the system, individual microspheres  were used as the calibration sample. Fig.2 illustrate the interferogram of a sphere and phase reconstruction steps, in which a Hilbert transform method in combination with Goldstein’s algorithm is used [3]. The phase shift induced by a polystyrene bead is written as

Where n(x,y) and n₀ are refractive index of the sample and that of the surrounding media, respectively. h(x,y) is the local thickness of the sample. As a result, the measured phase shift agrees well with the expected one [4].

The interferogram and unwrapped phase image of a Giardia cyst are shown in Fig.3(a) and (b), respectively. The proteins of Giardia labmlia constitute the greatest proportion of the cell solids, and the refractive index can be expressed as:

Where α  and C are the refractive index increment and concentration of protein or DNA in the Giardia labmlia, respectively. Using this relationship, the dry mass of the Giardia labmlia can be calculated by integrating phase shift over the entire area of the isolated Giardia labmlia, as follows[5]:

where α≈0.2ml/g. In this way, the dry mass of this individual Giardia labmlia cyst is approximated as 54 pg.

Optical single side-band (SSB) signal modulation combined with direct-detection (DD) is favorable for data center interconnections and short-reach metro networks, because it alleviates the power fading and improves the spectrum efficiency (SE). However, in addition to the transmitted baseband signal, both its Hilbert transform and the signal-signal beat interference (SSBI) can be generated and hence introduce the interference. We analyze the generation of the linear and nonlinear interference in theory and experimentally demonstrate the interference mitigation schemes in an optical single side-band Nyquist-pulse shaping PAM-4 (NPAM-4) system.

With rapid development of cloud services, real-time video, and online social networks, there occurs an urgent requirement of transmission capacity for optical metro and access networks. The network operating at 100 Gb/s or 400 Gb/s has drawn significant research efforts as well as standardization activities, such as the IEEE 802.3bs 400G Ethernet Task. Compared with other modulation formats, PAM-4 has advantages of low cost, free of digital to analog converter (DAC), and easy implementation. In this work, we propose nonlinear digital signal processing in metro and access networks. We experimentally demonstrated 4x28Gb/s C-band directed modulated laser (DML)-based metro network over 160-km fiber transmission. We also experimentally demonstrate, for the first time, 2 × 64 Gb/s O-band PAM-4 signal transmission over 70 km SMF using DMLs with a bandwidth of 18 GHz. The sparse Volterra filter (SVF) is also proposed to compensate the transmission impairments with substantial computational complexity reduction.