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Heterogeneous integration of dissimilar materials are essential in achieving advanced functionalities in integrated photonics and electronics integrated chips. Over the years, transfer printing technique has emerged to be a viable and practical process for heterogeneous integration of functional nanomembranes of different crystalline semiconductor materials. Here we report the development of transfer printing automation tools and processes based on commercial Ficontec optical characterization and assemble tool. Custom-made polydimethylsiloxane (PDMS) stamp printing head was developed along with the automatic pick and printing processes. A wide range of materials were also investigated including thin film silicon and monolayer 2D materials. Improved yield and device performance were achieved based on the characterizations of optical and light-matter interactions.

Photonic-crystal surface emitting lasers (PCSELs) exhibit several unique features compared to conventional vertical cavity surface-emitting lasers (VCSEL) including scalability, high power, and high beam quality. They are promising candidates in power-demanding applications such as free-space sensing. Motivated by the experimental advances, there have been significant efforts in developing the simulation tools for PCSELs. In particular, a coupled mode theory (CWT) model for PCSEL was developed, which provides important insights into the operating mechanisms. However, CWT makes several uncontrolled approximations such as a small number of waveguide modes as the basis, which is difficult to justify since the index contrast in PCSELs can be quite large. Here we show that PCSELs, especially its lasing threshold, can be simulated from first-principles by using rigorous coupled-wave analysis (RCWA). Traditionally, RCWA has been widely used to simulate the transmission or reflection of such structures, where the frequency is real. Here, we use RCWA to calculate the scattering matrix (S-matrix) of PCSELs on the complex frequency plane. This approach builds upon the concepts from steady-state ab initio laser theory (SALT). On the complex frequency plane, the poles of the S-matrix correspond to various resonances of the structure, including Fabry-Perot resonances and the guided resonances. We gradually increase the material gain in the PCSEL, and the threshold is retrieved as the gain value for which the first pole crosses the real axis. Other important characteristics such as the quality factor of each mode and the power efficiency of the laser can be computed as well.

We report here experimental result of refractive index (RI) sensing using the singly degenerate high quality (Q) factor mode in photonic crystal slab (PCS) with the incident beam close to normal incidence. Q = 3.2×10 4 was measured with high extinction ratio (ER > 10 dB) for the PCS in air. Q = 1.8×10 4 and spectral sensitivity ( S ) of 94.5 nm/RIU were measured in liquid for the PCS. A detection limit ( DL ) of 10 -5 RIU has been achieved with our device. The high- Q for the singly degenerate mode close to normal incidence with relatively high S is very promising to achieve a lower DL for RI sensing.

We report a novel bi-layer photonic crystal slab (PCS) Fano modulator via a coupled double-layer Si nanomembrane (SiNM) capacitor like structure. Surface normal incident light intensity modulation near 1500nm was achieved by carrier accumulation induced resonance spectral shifting. Device performance simulation suggests the opportunity for high speed modulation exceeding GHz with 20μm × 20μm device size.

Here we report the demonstration of a Si/InAlGaAs/InP PIN cavity enhanced LED around 1.5 um by using membrane transfer method. The silicon layer is acting not only as the optical guiding layer but also the hole injection layer. The new hybrid integrated LED could be further developed as laser source for silicon photonics.

We report the demonstration of bendable inductors, capacitors and switches fabricated on a polyethylene terephthalate (PET) substrate that can operate at high microwave frequencies. By employing bendable dielectric and single crystalline semiconductor materials, spiral inductors and metal-insulator-metal (MIM) capacitors with high quality factors and high resonance frequencies and single-pole, single-throw (SPST) switches were archived. The effects of mechanical bending on the performance of inductors, capacitors and switches were also measured and analyzed. We further investigated the highest possible resonance frequencies and quality factors of inductors and capacitors and, high frequency responses and insertion loss. These demonstrations will lead to flexible radio-frequency and microwave systems in the future.

Based on Fano resonance principles in photonic crystals, high performance broadband reflectors can be realized with 100% reflection. Applying an innovative magnetic field guided metal-assisted chemical etching (MacEtch) process, we report here high performance membrane reflectors on SOI with controlled sidewall etching and high reflection around 1550 nm. This work represents the first demonstration of magnetically guided MacEtch ( h-MacEtch) of periodic arrays of discrete nanoholes of sub-micron dimensions. Such an innovative process can lead to facile formation of large area 2D and 3D nanoscale-structures, for high performance photonic crystal membrane reflectors, filters, and metamaterials. Keywords: Photonic crystals, Fano resonances, membrane reflectors, nano-manufacturing, metal-assisted chemical-etching 1. INTRODUCTION Known from atomic physics, Fano resonances have been employed for a wide variety of nanophotonic structures, such as quantum dots, plasmonics, metamaterials and photonic crystals (PhCs) [1-4]. It can provide an efficient way to channel light from the external environment into the slab , and vice versa. Broadband membrane reflectors (MRs) based on Fano resonance [5], or guided mode resonance [1, 2], have attracted great attention [4, 6-14] in the past few years, where high reflections can be obtained with a single-layer one-dimensional (1-D) grating, or a two-dimensional photonic crystal slab (2D PCS) structure. High performance MRs have been demonstrated on various semiconductors, fabricated using dry etching techniques, along with the demonstrations of innovative lasers on Si, GaAs, and InP substrates. On the other hand, high aspect ratio nano-columns and air-holes have also been realized, through a completely wet metal-assisted chemical etching (MacEtc h) process [15-17]. MacEtch is a wet but directional etching technique which involves a thin layer of noble metal (e.g. Au, Pt, etc.) acting as a catalyst to guide the etch process in a solution that usually consists of an oxidant and an acid. Details of the MacEtch mechanism can be found elsewhere [16, 17]. Such wet processes can lead to the formation of large area, scalable, high quality nanoscale structures, with direct or arbitral shaped topologies, which are critical for the formation of large area 2D and 3D nanoscale-structures [16, 18-23], for high performance photonic crystal membrane reflectors, filters, and metamaterials. Applying an innovative magnetic field guided MacEtch process, we report here high performance membrane reflectors on SOI with controlled vertical etching profile and high reflection around 1550 nm. This work represents the first success on performing MacEtch on SOI wafers.

We investigated numerically an all-dielectric semiconductor-based circular polarizer consisting of silicon helix on glass substrate. Only three turns of the dielectric helix structure provides extremely high polarization suppression ratio above 2,300:1 with almost 100% transmission. Transmission efficiency greater than 85% for one circularly polarized light is maintained for incident angles as high as 30 0 . The influence of the various helix lattice parameters on the polarization gap and the circular dichroism is also presented.

We present here the design of a robust broadband high efficiency surface-normal vertical to in-plane optical coupler using fourth-order gratings. The fourth-order gratings can be designed such that the zero-order diffraction is suppressed while the diffraction efficiencies of the higher orders are enhanced for the in-plane coupling. We numerically demonstrated the surface normal incidence light coupling efficiency of 88.5% at 1,535 nm with a 3 dB bandwidth of 42 nm and 1dB bandwidth of 28 nm. Large fabrication tolerance of the fourth-order grating is also assessed.

Since the zeroth-order Bessel and Airy function are invariant propagation modes in free space, they can be potentially used not only in time but also in space. Different from nonlinear solitary wave, Airy-Bessel configuration wave packets with particle-like nature are a kind of stable linear wave packets without spatio-temporal spread during propagation in free space because it combine spatial Bessel beams with temporal Airy pulses. In the paper, by studying spatially induced group velocity dispersion effect during propagation of ultrashort pulsed Bessel beams, we find that Gaussian- Bessel wave packets can evolve as Airy-Bessel in given propagation conditions. The research results are expected to open up one new channel to generate stable linear localized wave packets.

On-chip laser beam tracking finds innumerable applications. Popularly adopted quadrant photodiodes can only detect laser beam's angle variation up to 0.2° reliably. In this paper, a novel angle detector is designed based on grating coupling. It consists of a grating layer on top of a silicon-on-insulator slab waveguide. The incident light is coupled into guided modes within the waveguide via the grating layer, and then, the incident light's angle can be determined by reading the outputs of light detectors within the waveguide. Performance of the laser angle detector in this paper is demonstrated by full-wave finite-difference-time-domain simulations. Numerical results show that, the detectable angle range can be adjusted by several design parameters and can reach [-4°, 4°]. The device structure in this paper can be straightforwardly extended to two-dimensional photonic crystal configurations.

Graded index polymer films enable novel optics using rigid or flexible substrates, such as waveguides or anti-reflection coatings. Previously, such films have been fabricated by nanoimprint lithography or the decomposition of a single component in polymer blends. Yet, it is desirable to have precise control over the polymer film composition in order to have the most flexibility in designing refractive index profiles. Resonant-infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a polymer thin film deposition technique that enables multi-layer structures on a wide variety of substrate materials, regardless of the solubilities of constituent polymers. In this work, the feasibility of tuning the refractive index of blended polymer films of polystyrene and poly(methyl methacrylate) deposited by RIR-MAPLE is demonstrated. Different polymer blend film compositions are deposited using RIR-MAPLE by varying the polymer target ratio. Transmission electron microscopy and atomic force microscopy are used to characterize the film morphology.

We report here modified absorption property of InGaAs nano-membrane on a Fano filter made of patterned single crystalline silicon nano-membrane transferred onto glass substrate. Placement of an ultra-thin InGaAs film on Si Fano resonant membrane enhances the absorption with simulated enhancement factor ~35 and measured enhancement factor of ~26. Leaky modes in the photonic crystal (PC) consist of high field standing waves that can be coupled to the out of plane radiation mode provided by lattice matching of the PC. We will present simulation, device fabrication and experimental characterization of stacked ultra-thin InGaAs/Si Fano resonance membrane in the IR regime.

Feature extraction plays a vital role in iris recognition, affecting the performance of iris recognition algorithm strongly. In this paper, we present an individual recognition algorithm using fractal dimension based on fractional Brownian random field and lacunarity in feature extraction. Making use of the fractal feature of iris, such as self-similarity and random patterns, fractal dimension can extract texture information effectively. Lacunarity overcomes the limitation of fractal dimension that fractal sets with different textures may share the same fractal dimension value. The combination of fractal dimension and lacunarity makes the feature extraction more comprehensive and distinguishable. The experimental results show that this recognition algorithm can obtain great performance on CASIA 1.0 iris database

With the combination of neuro-genetic approach and laser-induced breakdown spectroscopy (LIBS), an improved method is proposed to predict the concentrations of Ni, Zr and Ba in soil samples. In this method, an artificial neural network (ANN) based on gradient descent with momentum and adaptive learning rate back propagation (GDMABP) algorithm is used. Simultaneously, an optimization strategy based on genetic algorithm (GA) is employed for selecting number of neurons in hidden layer and momentum coefficient in GDMABP ANN and to obtain an optimized network. Subsequently, the network is used to predict concentration of Ni, Zr and Ba from the tested LIBS data. The approach of neuro-genetic for LIBS analysis is described in detail. The predicted results are compared with those obtained from conventional calibration curve method. Overall, the method of combining neuro-genetic approach with LIBS is capable of predicting elemental concentration.

We report the design and optimization of plasmonic thin film photovoltaics (TFPV) based on single crystalline Si nanomembranes, transferred onto ITO/plastic solar cells. Due to the presence of Fabry-Perot (FP) interferences, both near and far field plasmonic field enhancements are modulated by thin film thicknesses. The placement of absorption region (junction location and/or quantum well location) is critical in TFPV efficiency improvement. For TFPV thin film thickness between 200-500 nm, we obtained field enhancement up to 100%, and cell efficiency improvement up to 35%, assuming the standard test one sun AM1.5 radiation conditions. The efficiency enhancement for 200 nm silver particles decreases rapidly with the increase of thin film thicknesses, while we observed less change in cell efficiency enhancement for smaller 100 nm silver particles. Additionally, we observed a relatively large process tolerance window for the size, shape, and placement of Ag nanoparticles, formed by the annealing of ultra-thin Ag thin films.

We report the detailed analysis on the phase discontinuity, field distribution, penetration depth and photon lifetime in 1D and 2D PC mirrors. Compared to classical distributed Bragg reflectors (DBRs), these new types of PC mirrors exhibit different phase discontinuties and slower phase changes over the high reflection bands for surface-normal incident beams. Fabry-Perot (FP) cavity designs were carried out based on these three types of dielectric reflectors. In PC mirror based FP cavities, we observed penetration depth of 2~4μm, which is related to the large phase discontinuity. On the other hand, due to the tight field confinement, the energy penetration depths were ~ 0.1μm in PC mirror based FP cavities, much lower than that in DBR based FP cavities. We will also report on the distinctively different field distribution behaviors in these cavities, which are critical in the design of various active optoelectronic devices.

We report direct measurement of spectrally selective absorption properties of PbSe and PbS colloidal quantum dots (CQDs) in Si nanomembrane photonic crystal cavities on flexible polyethylene terephthalate (PET) substrates. Enhanced optical absorption was obtained when CQD absorption overlaps with photonic crystal Fano resonances. On the other hand, no absorption was observed when the Fano resonance has no spectral overlap with the CQD absorption bands. The measurement results agree well with the simulation results obtained based on 3D FDTD and RCWA simulation techniques. Measured angular and polarization properties also agree well with Fano resonance transmission properties, which were obtained experimentally and, theoretically based on simulated dispersion properties and transmission properties. Bending induced spectral shifts were characterized for potentially flexible photonic device applications.

Crystalline semiconductor nanomembranes (NMs), which are transferable, stackable, bondable and manufacturable, offer unprecedented opportunities for unique and novel device applications. We report here nanophotonic devices based on stacked semiconductor NMs on Si, glass and flexible PET substrates. Photonic crystal Fano resonance-based surface-normal optical filters and broadband reflectors have been demonstrated with unique angle and polarization properties. Flexible photodetectors and solar cells have also been developed based on the NM stacking processes. Such NM stacking process can lead to a paradigm shift on silicon photonic integration and inorganic flexible photonics.

Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) is a promising approach for quantitative analysis without using certified samples and calibration curves. It can overcome the matrix effects. However this method is based on the hypothesis that in the actual temporal observation window the plasma is in local thermal equilibrium (LTE). In this paper, the plasma is generated using a Q-switched Nd:YAG laser hits on certified soil samples in air at atmospheric pressure. The local values of the parameters that characterize laser induced plasma (temperature, electron density) have been derived from the recorded spectra with different observation window. The electron density in the plasma at different time delay after laser firing has been investigated in detail, which can be served as a criterion of the existence of the LTE. As a result, an appropriate time delay is obtained. By comparing the temperatures deduced from the spectroscopy line intensity of neutral atom and ion emissions at different gate width, the optimized time duration which satisfies the LTE is obtained. Finally, we analyze the importance of observation window and its effect on the accuracy and precision of this method.

We report theoretical and experimental investigations of infrared absorption characteristics for PbSe colloidal quantum dots in defect-free photonic crystal (PC) cavities, via Fano resonances. Angle and polarization independent transmission and absorption are feasible for surface normal incident beams with dispersion engineered modal design. Experimental demonstration was done on patterned single crystalline silicon nanomembranes (SiNMs) transferred on glass and on flexible PET substrates, with PbSe QDs backfilled into the air holes of the patterned SiNMs. These findings enable the design of spectrally selective photodetectors at near infrared regime with the desired angle and polarization properties.

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ environmental analysis. The potential of this technique for accurate quantitative analysis of heavy metals in soil could be greatly improved by optimized the time delay, laser energy, working distance, et. and by analyzing the results with a procedure which overcomes the problem related to the physical character of soil sample. A LIBS system for soil analysis is reported here. The optimum experimental conditions for quantitatively measurement of Sr and other heavy metals in soil are presented. A new data acquisition and statistical method has been used to analyze the recorded spectra. The precision of this method, in terms of relative standard deviation (RSD), is of 7 % for Sr I 460.73 nm. The calibration curve for quantitative measurement of Sr has been built. From the calibration curves, the detection limits of Sr in soil were determined to be 15.0 µg/g, and are better than the data reported in literature.

In this paper, a new process for the formation of hemispherical structures as an omni-directional anti-reflection (omni-AR) coating in solar cell is reported. We also demonstrated the simulation results of the angular and spectral dependences of the total reflectivity on various micro-structured surfaces. Close to zero reflection can be achieved in some micro-structured surfaces over an extended spectral region for large ranges of incident light angles. Daily generated current in such hemispherical solar cells hence enhanced to 1.5 times of bulk silicon solar cells. The impact of feature size, density, shape and refractive index has all been investigated. The experimental results agree reasonably well with the theoretical work. Such an omni-AR structure offers an attractive solution to current bulk crystalline silicon solar cells, as well as thin film, organic and future quantum based solar cells.

We here proposed a new kind of ultra-compact filters based on Fano resonances on patterned single crystalline silicon nanomembranes (SiNM), which were fabricated and transferred onto transparent substrates like PET plastic and glass substrates, using a wet transfer process. The angular and polarization dependent transmission characteristics of the filter are experimentally investigated. The filter transmission characteristics are insensitive to the incident angle and polarization for surface-normal incidence. For other incident angle conditions, the transmission peaks/dips shift, according to the modal dispersion properties, as verified with the simulated modal dispersion curves. Both surface-normal and angle-dependent filter transmission measurement results agree well with the numerical simulations.

Infrared photodetectors with spectrally selective response are highly desirable for applications such as hyper-spectral imaging and gas sensing. Owing to the ability of photonic density of states modification and dispersion engineering, photonic crystals appear to be one of the most promising platforms for infrared photodetectors with spectrally-selective absorption enhancement. We report here the latest advances on 1D and 2D dielectric photonic crystal structures for infrared photodetectors, based on defect mode, bandedge effect and the guided mode resonance/Fano effects. High spectral selectivity and tunability is feasible with defect mode engineering, making photonic crystal defect cavities a promising nanophotonic platform for the spectrally selective infrared sensing and hyper-spectral imaging, with the incorporation of quantum well or quantum dot infrared photodetector heterostructures.

We report spectrally selective IR absorption enhancement in the defect-free photonic crystal cavities, via Fano resonances. For a symmetric slab structure (air-slab-air membrane) with an absorptive layer in the center of the slab, enhanced absorption can be observed with enhancement factor ~180 for certain range of r/a values at wavelength of 4 µm. Similar results can also be achieved in an asymmetric slab structure (air-slab-semiconductor substrate), where higher index substrate is feasible for the proposed IR detectors, with optimized design. This important feature ensures flexible design for infrared photodetectors incorporating photonic crystal cavities. Detailed simulations were carried out to understand the design trade-offs on the key parameters, such as the substrate index, the absorption layer thickness, and the air hole radius.

Ultra-small silicon-based photonic-crystal ring resonators (PCRRs), both passive and active, will be key contributors to the emerging low-power nanophotonic technology. We have modeled and simulated the diameter-dependent loss, Q, and FSR of such PCRRs and find a 0.02 dB "intrinsic" loss that is independent of diameter, unlike the ~1/D loss of micro-strip resonators. Close to 100% drop efficiency at the drop channel of 1557.5nm was obtained by design with a high spectral selectivity of Q greater than 1319 in the single-ring PCRR-based add-drop filters with ring radius of 1.2 μm. Ultra-compact polymer modulators were proposed and simulated, based on the hybrid integration of functional polymer materials with Si based PCRRs, which can lead to high speed modulators, suitable for photonic integration and RF photonics.

We proposed an effective index perturbation method to investigate the intrinsic characteristics of three-dimensional photonic-crystal-slab based microcavity with two-dimensional numerical simulation tools such as two-dimensional finite-difference time-domain (2D-FDTD) and plane-wave expansion (2D-PWE) techniques, for reduced computational requirements and fast design feedback. Less than 2% computational error in predicting cavity spectral locations was obtained for two widely used single defect and line defect air hole photonic crystal cavities, by adjusting the effective index to match the dielectric band edge for donor-like defect mode. The correlation between the modified effective index and the cavity (lasing) mode with the highest quality factor Q offers an efficient tool in the design of defect mode based photonic crystal microcavities.

In this paper, we present the simulation results on the absorption modification in a two-dimensional photonic crystal slab (2D PCS) structure, based on three-dimensional finite-difference time-domain technique (3D FDTD). Significantly enhanced absorption at defect level was obtained at surface normal direction in a single defect photonic crystal cavity, for both in-plane and vertical sources. An absorption enhancement factor in the range of 100-6,000 was obtained under different operation conditions, based on the normalized absorption power spectral density with respect to the reference slab without photonic crystals. Complete absorption suppression within the photonic bandgap region was also observed in defect-free cavities. High spectral selectivity and tunability was feasible with defect mode engineering.

We propose here a new class of nano-cavity surface-emitting light source on silicon, based on the integration of colloidal nanocrystal quantum dots (NCQDs) and air-hole two-dimensional photonic crystal (2D PC) slab waveguide cavities. A phenomenological dimensional reduction approach (PDRA) has been developed to investigate the characteristics of this class of NCQD-PC lasers. Over one order of magnitude in gain threshold reduction was obtained in single defect PC cavities owing to the spontaneous emission control. Ultra-compact high efficient light source is feasible based on the relative low gain NCQDs, as compared to conventional epitaxial III-V material systems, owing to the relaxed gain threshold requirement in PC cavities. It is also expected such single defect PC cavity based laser to have an optical output power more than 20 μW with cavity size less than 2 μm, making it an attractive source for optical interconnect and sensing applications.

In this paper, we present the simulation results on the absorption modification in photonic crystal (PC) structures. For one-dimensional (ID) PC, using transfer matrix method (TMM), we obtained enhanced absorption in both defect-free and defect based PC structures. High absorption (>60%) and small bandwidth (< 0.1 λ 0 ) at defect level were observed with optimal absorption layers of 10-15 for structures with single defect. We also present the modified infrared absorption in two-dimensional photonic crystal slabs (2D PCS), based on the three-dimensional finite-difference time-domain method (3D FDTD). The normalized absorption power spectral density in single defect based 2D PCS structures increased by a factor of 18 at the PC defect mode level. This enhancement factor is largely dependent upon the spectral overlap between the absorption material and the defect mode cavity. Complete absorption suppression within the photonic bandgap region was also observed in defect-free cavities, and in single defect cavities when the absorption spectral band has no overlap with the photonic bandgap.

A detailed study was carried out to understand the photonic crystal design rules with very high dielectric constant (e>13), based on plane wave expansion and finite difference time-domain (FDTD) techniques. It is found that the optimal dielectric constant contrast is indeed the one between conventional semiconductors (e=12-14) and air. Either too high or too low contrast can lead to the reduction of complete photonic bandgap. With very high bulk dielectric constant (e=20-25), PbSe nanocrystal quantum dots (NQDs) are suitable for air hole based PC structure with large TE gap. On the other hand, NQD backfilled photonic crystals with tunable bandgap is proposed based on the control of packing density of NQDs inside the air holes of photonic crystal structures. Both theoretical and experimental results on the integration process are reported.

We propose and report a novel photonic crystal (PhC) encapsulation concept, where the originally exposed air holes are sealed off on top of the surface to create an enclosed air column structure in two dimensional (2D) PhC based devices and systems. The impact of encapsulation on the photonic bandgap will be discussed for different encapsulation conditions. Experimental results on encapsulation process will also be reported, with focus on the nanoparticle based self assembly encapsulation. Finally a novel photonic crystal surface emitting laser based on this encapsulation concept will be proposed and discussed. The surface state induced non-radiative recombination and different electrical injection schemes will be discussion with the benefit of encapsulation being discussed in the end.

InP-based 1.6 micrometer microcavity light emitting diodes (MCLEDs) have been designed, fabricated and characterized. Oxide-confined MCLEDs with lateral aperture size down to 1 micrometer have been realized with enhanced output slope efficiency and excellent spectral and spatial properties. Both mirror-free cylindrical MCLEDs with oxide-aperture and 3D MCLEDs have been fabricated and a maximum output power of 0.03 mW at 30 mA for a 30 micrometer device has been realized. The effect of the aperture size on the slope efficiency and spatial properties have been systematically investigated, which shows an enhanced slope efficiency and narrower emission angle for small aperture size devices. The temperature dependent cavity properties have also been carefully examined for both the active region emission peak and cavity resonance peak.

A relatively simple technique for fabrication of GaAs-based quasi-3D photonic crystals has been investigated. Selective impurity-induced layer disordering and wet oxidation techniques are utilized. The feasibility of this technique is successfully demonstrated and a photonic bandgap material with its bandgap around 1.18 micrometers has been fabricated. The electro-optic coefficients have been measured for the first time in such a medium. The process is reproducible an lends itself to integration with other optoelectronic and electronic devices on the same substrate, which might be required for pumping, electrical injection or other functions.