This PDF file contains the front matter associated with SPIE Proceedings Volume 9624, including the Title Page, Copyright information, Table of Contents, Introduction, Authors, and Conference Committee listing.

Thermal effect plays a key role and has been utilized for various photonic devices. For silicon photonics, the thermal effect is usually important because of the large thermo-optical coefficient of silicon material. This paper gives a review for the utilization of thermal effects for silicon photonics. First, the thermal effect is very beneficial to realize energy-efficient silicon photonic devices with tunability/switchability (including switches, variable optical attenuators, etc). Traditionally metal micro-heater sitting on a buried silicon-on-insulator (SOI) nanowire is used to introduce a phase shift for thermal tunability by injecting a electrical current. An effective way to improve the energy-efficiency of thermal tuning is reducing the volume of the optical waveguide as well as the micro-heater. Our recent work on silicon nanophotonic waveguides with novel nano-heaters based on metal wires as well as graphene ribbons will be summarized. Second, the thermal resistance effect of the metal strip on a hybrid plasmonic waveguide structure can be utilized to realize an ultra-small on-chip photodetector available for an ultra-broad band of wavelength, which will also be discussed.

A kind of diffractive optical elements (DOE) with star-ring topological structure is proposed and their focusing and imaging properties are studied in detail. The so-called star-ring topological structure denotes that a large number of pinholes distributed in many specific zone orbits. In two dimensional plane, this structure can be constructed by two constrains, one is a mapping function, which yields total potential zone orbits, corresponding to the optical path difference (OPD); the other is a switching sequence based on the given encoded seed elements and recursion relation to operate the valid zone orbits. The focusing and imaging properties of DOE with star-ring topological structure are only determined by the aperiodic sequence, and not relevant to the concrete geometry structure. In this way, we can not only complete the traditional symmetrical DOE, such as circular Dammam grating, Fresnel zone plates, photon sieves, and their derivatives, but also construct asymmetrical elements with anisotropic diffraction pattern. Similarly, free-form surface or three dimensional DOE with star-ring topological structure can be constructed by the same method proposed. In consequence of smaller size, lighter weight, more flexible design, these elements may allow for some new applications in micro and nanphotonics.

Planar metalens composed of V-shaped nano-antennas which can realize subwavelength focusing has been fabricated by Focused Ion Beam etching technology. The metalens was completely flat due to the phase manipulation deriving from the different V-shaped nano-antennas aligned in concentric circles. Comparing to conventional curved lens, the as-made metalens was flat and ultrathin (less than thickness of 100 nm) with light weight. Simulation results demonstrated that the focal length can be accurately controlled by changing the arrangement of the nano-antennas.

The temperature-dependent reflection spectrums of ultrahigh order guided modes of symmetrical metal-cladding waveguide (SMCW) are measured in angular interrogation. The results show that the reflection spectrum is characterized by extremely narrow resonance dip, which agrees well with numerical calculation. Based on the falling or rising edge of resonance dip of ultrahigh order guided modes of SMCW, a temperature sensor with characteristic of high sensitivity is proposed. Meanwhile, by experimentally determine the linear character between the shift of resonance angle and the variation of temperature, a method of angle compensation is put forward to extend the sensing range. Owing to its characteristics of high sensitivity, low cost and easy fabrication, the temperature sensor based on SMCW will be a promising sensor in many fields.

Being one of the appealing MEMS devices for both immersion and air-coupled applications, capacitive micromachined ultrasonic transducers (CMUTs) are often featuring vacuum/sealed cavities. However, the pressure differential across the membrane requires higher drive voltage to start the vibration. Besides, the air film formed in the narrow gap consequently being squeezed provides additional damping as well as stiffening for the membrane. Moreover, the fabrication technologies encounter difficulties in stress control and thin membrane releasing during the hermetical cavity formations. In this paper, we propose using surface micromaching technology to fabricate CMUTs with vented square membrane for air-coupled applications. In order to compare the performance of CMUTs with and without vented holes on the membrane using finite element analysis (FEA), we have developed several 3D finite element models using commercially available FEA software (COMSOL Multiphysics). According to the simulation results, our design remains the similar first resonant frequency and has higher frequency interval, indicating a better signal-to-noise rate (SNR). Eigenfrequency comparison between CMUTs with the same movable area implies that the presence of the vented holes lowers the first order frequency by around 5.7%. We have demonstrated that the idea of fabricating air-coupled CMUTs with vented holes on the square membrane is feasible and our proposal could stay around the designed resonant frequency. Further characterization will be done in the near future.

Structural Long period gratings (LPGs) in photonic crystal fiber (PCF) were successfully fabricated using the femtosecond laser micromachining system by introducing periodic side-holes. High temperature characterizations of the fabricated gratings have been performed. The structural gratings written with the femtosecond laser micromachining technique can suffer a low shift of the resonance wavelengths with sensitivity of 23pm/oC while the temperature is increased from 20°C to 1200°C. The LPGs have been found to have negligible temperature sensitivity whilst exhibiting useful strain (-1.86pm/με)and strong directional bend sensitivity with -4.40nm•m (180°) and -2.79nm•m (0°) at low temperature. The unique sensing characteristics enable many potential sensing applications in high temperature environments, such as space aircraft, nuclear power plants, and the chemical industry.

A low-cost lithography technology is presented in this paper for fabrication of sub-micron order one-dimensional diffraction gratings. A Lloyd’s mirror interferometer which can generate stable interference fringes is used as fabrication tool. The Lloyd’s mirror interferometer is composed of a mirror and a substrate coated by photoresist, which are placed by nighty degrees. A plane wave is projected onto the Lloyd’s mirror and divided into two halves, one of which is directly projected onto the substrate and the other one reaches the substrate after being reflected by the mirror. These two beam interfere with each other and generate interference fringes, which are exposed onto the photoresist. After being developed, the exposed photoresist shows a one-dimensional surface-relief grating structures. In conventional lithography system based on the principle mentioned above, gas lasers, such as He-Cd laser are widely employed. The cost and footprint of such laser sources, however, are always high and bulky. A low-cost system by using cost-efficient 405 nm laser diodes is then proposed for solving these problems. A key parameter, coherence length that determines one-dimensional grating width is systematically studied. A fabrication system based on the interference lithography principle and 405 nm laser diodes is constructed for evaluation of the feasibility of using laser didoes as laser source. Gratings with 570 nm pitch are fabricated and evaluated by an atomic force microscope. Experiments results show that low-cost 405 nm laser diode is an effective laser source for one-dimensional grating fabrication.

The electronic structure of the self-assembled quantum dot is presented in this paper to explore the efficient design of quantum dot solar cell. The electronic states of InAs quantum dot embedded in a GaAs matrix have been studied in this article, in which it is assumed the effective mass is independent of level energy for simplification. The shape effect and the layer effect for single quantum dot are investigated, and a simple one-band model for array quantum dots is studied. In the array quantum dots the wave function interaction will be strong, when the space between quantum dots is very close, which will affect the level energy.

In this paper the single mode condition of silicon-on-insulator (SOI) rib waveguide with large cross section is investigated based on the effective index method (EIM) by using numerical computation and analytical derivation with the consideration of the polarization effects. A polarized single-mode condition for SOI rib waveguide with large cross section is presented, the results from analytical derivation are highly concordant with that from numerical computation. For the vertical single-mode condition, the deviations between HE and EH modes correlate oppositely with the total rib height of rib waveguide, and the critical rib height ratio gradually approaches but never equals to 0.5 with the increase of the total rib height. There, HE mode and EH mode are commonly known as quasi-transverse-electric (TE) mode and quasi-transverse-magnetic (TM) mode respectively. The deviation of the critical rib width between HE and EH modes for the lateral single-mode condition is relatively small, which is a function of the rib height ratio but irrelevant to the total rib height for the specified index profile. The fact that the total rib height, index profile, and polarization of modes have effects on the single-mode condition of SOI rib waveguide with large cross section was demonstrated in this work, which was not discussed in the previous works. The results in this work can give guidance to design, simulation and fabrication of SOI rib waveguide with large cross section in practical applications.

In this paper, a sub-wavelength metal grating polarizer at visible region is designed by Finite Difference Time Domain (FDTD) method. We have analyzed the effects of the period, the thickness of metal layer and the duty cycle on the performance of the metal grating polarizer. Simulation results show that in order to increase the metal grating transmissivity and extinction ratio and to reduce the angle sensitivity (±30°), the period should be less than 200 nm; Therefore, the structure with 180nm period and an 120nm Al layer is chosen, and the transmission efficiency and extinction ratio is more than 75% and 25dB respectively. Finally, a prototype of the metal grating has been fabricated by holographic-immersion lithography and ion beam etching.

With high light efficiency and long aging life, LED solid-state light source has attracted much attention in underwater application, such as optical communication and imaging. But, the large divergence angle of LED illumination has been a big challenge in practical underwater application, such as the light attenuation in water and then the decreased signal-to-noise ratio. Source-target map is a vital method in illumination optics design, and the focus is to solve numerically differential equations and then construct the freeform surface. To achieve high accuracy freeform surface, an improved method is suggested and optimized through much more advanced and accuracy Runge-Kutta method, which is different from the original design one through Euler method. The designed lens is simulated by ray trace software TracePro, and the simulation results show that the uniformity of 0.8 and the efficacy of 0.6 is obtained. While as, the method is proven to be effective, and also the accuracy of the smooth freeform surface is strengthened. One designed illumination lens is fabricated by computer numeric control (CNC) machine to demonstrate the design experimentally.

A thermally tunable half-disk resonator (HDR) with directly-integrated metallic heater is presented. The proposed resonator is based on the structure of HDR, which allows direct electrical contacts in HDR region without causing extra loss. The metallic heater is designed to be directly integrated on the silicon devices, and single-mode operation can be retained simultaneously. Metallic heater deposited on inner side of the ring, which cannot realize before because of weakened light confinement resulting in substantial leakage and loss, guides most heat power to the waveguide. This thermal localization enhances tuning efficiency. The simulation result shows a wavelength shift of 0.855 nm under ultralow driving voltage of 0.02V, corresponding to high thermal tuning efficiency of 2.831 nm/mW. The structure possesses both the advantages of high thermal tuning efficiency and low resistance, hence requiring smaller voltage and energy to drive, desirable for optical interconnects applications. Moreover, the proposed structure also eliminates the need to use doped silicon slab for electrical contacts, as widely used in conventional directly integrated heaters. Undoped strip waveguide in HDR enables higher Q-factor and improves optical performance.

The physical characteristics and optical properties of PbS nanoclusters are investigated by using density functional theory (DFT) of first-principles. Microstructure models of (PbS)n (n=1-9) nanoclusters and bulk materials are built on Materials Studio platform, and its energy band structures, highest occupied molecular orbital-lowest unoccupied molecular orbital gap (HOMO-LUMO gap), density of state (DOS), and optical properties are calculated, respectively. Compared to PbS bulk materials, PbS nanoclusters show a discrete energy gap as well as the DOS, because of the quantum confinement effect. It is interesting that the HOMO-LUMO gap of (PbS)_n (n=1-9) shows oscillates with the increasing of the n number. However, when its size is large enough, the HOMO-LUMO gap is gradually decrease with the increasing of size (>27 atoms). And, the HOMO-LUMO gap of PbS nanoclusters of different sizes is range from 2.575 to 0.58 eV, which covers the low loss communication band of optical communication. In addition, PbS nanomaterials (NMs) with small size are synthesized by using oleylamine as ligands. Sizes of PbS NMs can be accurately controlled through control of the reaction time as well as the growth temperature. The photoluminescence (PL) spectra show strong size dependence, which is large red shift with increasing size of the NMs. This trend is basically in agreement with the theoretical calculation above. Moreover, transmission electron microscopy (TEM) further reveals the morphology of PbS NMs. PbS NMs can be used in optical fiber amplifiers and fiber lasers because of its unique optical properties in optical communication bands.

The echelle gratings with the ultra-high resolution are one of the key elements in spectroscopy, optical communications and other fields. Currently, the diamond ruling and the wet etching technique are two primary methods to fabricate echelle gratings. In this paper, we have adopted a new method of the echelle gratings fabrication. Firstly, the holographic lithography is used to form a photoresist grating mask. Then, reactive ion etching is adopted to fabricate the native substrate grating mask to replace the traditional photoresist grating mask, which allows more accurate control of the profile. Finally, the tilted ion-beam etching is used to etch the native substrate grating to ensure the precise control of the blazed angle and anti-blazed angle. A prototype of the echelle gratings with a line density of 80 lp/mm has been fabricated by above method.

MFs with three zero-dispersion wavelengths are studied and designed by multi-pole method. Phase mismatch of this kind of MFs with d/Λ=0.40, Λ=1.8μm is studied when pump locates at all three zero-dispersion wavelengths and the wavelengths of some commonly used lasers. Numerical results show that broadband phase match can be achieved when the pump varies from the normal dispersion regime around the first zero-dispersion wavelength to the last zero-dispersion wavelength and two sets of phase matched wavelengths exist when the wavelengths of pump are in the anomalous dispersion regime between the first two zero-dispersion wavelengths. Then, a little air-hole is added in the fiber core and the dispersion characteristics of the new MFs are investigated for MFs with four zero-dispersion wavelengths. The phase matching topology of this kind of MFs with d/Λ=0.80, Λ=2.2μm, d₀=0.636μm is analyzed when the pump is in the anomalous dispersion regime, zero-dispersion wavelength and normal dispersion regime of the fiber. Two sets of phase matched wavelengths can also be found when the MF is pumped in the anomalous dispersion regime between two neighboring zero-dispersion wavelengths. Interestingly, when the MF is pumped in the normal dispersion regime between the second and third zero-dispersion wavelength, three phase matched wavelengths sets appear. For MFs with multiple zero-dispersion wavelengths mentioned above, in entire phase matching band, there always exists one Stokes wave whose wavelength is longer than the longest zero-dispersion wavelength of the fiber, which will provide more possibilities for frequency conversion in mid-infrared band.

II-VI semiconductors have great importance in the fabrication and application of optoelectronic devices. CdTe is one of the most promising materials among photovoltaic materials. In this research work CdS/CdTe solar cell has been prepared using screen printing and sintering technique. Various factors affecting the surface morphology of CdS window layer were also investigated. Optical Microscopy, Scanning Electron Microscopy and Electrical characterization proved that best results can be achieved by increasing the sintering duration, the Mesh number and by CdCl₂ doping. CdS/CdTe solar cell with an area of 8.8 cm² was prepared. The Fill Factor was calculated to be 0.51, with Voc = 0.56 V and I_sc = 31.5 mA. The efficiency was also measured and found to be 1.02%.

Simple polarization indirect microscopic imaging can visualize graphene layer's dimensions features, however, its limited resolution makes it impossible to analyze the other physical characteristics. Our research uses polarization parameter indirect microscopic imaging system with super-resolution to modulate the variation of far field point spread function with varying polarization status and improve wavefront aberration, sensor error, and polarization angle. This method has much higher sensitivity to graphene overlapping layers, edges, wrinkles and grain boundaries. Finally, this technique for graphene inspection that is capable of reaching super-resolution.