In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.

Integrated optics

Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures

The interest in organic-inorganic hybrids as materials for optics and photonics started more than 25 years ago and since then has known a continuous and strong growth. The high versatility of sol-gel processing offers a wide range of possibilities to design tailor-made materials in terms of structure, texture, functionality, properties and shape modelling. From the first hybrid material with optical functional properties that has been obtained by incorporation of an organic dye in a silica matrix, the research in the field has quickly evolved towards more sophisticated systems, such as multifunctional and/or multicomponent materials, nanoscale and self-assembled hybrids and devices for integrated optics. In the present critical review, we have focused our attention on three main research areas: passive and active optical hybrid sol-gel materials, and integrated optics. This is far from exhaustive but enough to give an overview of the huge potential of these materials in photonics and optics (254 references).

Hybrid materials for optics and photonics.

Recently, the desired very high throughput of 5G wireless networks drives millimeter-wave (mm-wave) communication into practical applications. A phased array technique is required to increase the effective antenna aperture at mm-wave frequency. Integrated solutions of beamforming/beam steering are extremely attractive for practical implementations. After a discussion on the basic principles of radio beam steering, we review and explore the recent advanced integration techniques of silicon-based electronic integrated circuits (EICs), photonic integrated circuits (PICs), and antenna-on-chip (AoC). For EIC, the latest advanced designs of on-chip true time delay (TTD) are explored. Even with such advances, the fundamental loss of a silicon-based EIC still exists, which can be solved by advanced PIC solutions with ultra-broad bandwidth and low loss. Advanced PIC designs for mm-wave beam steering are then reviewed with emphasis on an optical TTD. Different from the mature silicon-based EIC, the photonic integration technology for PIC is still under development. In this paper, we review and explore the potential photonic integration platforms and discuss how a monolithic integration based on photonic membranes fits the photonic mm-wave beam steering application, especially for the ease of EIC and PIC integration on a single chip. To combine EIC, for its accurate and mature fabrication techniques, with PIC, for its ultra-broad bandwidth and low loss, a hierarchical mm-wave beam steering chip with large-array delays realized in PIC and sub-array delays realized in EIC can be a future-proof solution. Moreover, the antenna units can be further integrated on such a chip using AoC techniques. Among the mentioned techniques, the integration trends on device and system levels are discussed extensively.

Advanced Integration Techniques on Broadband Millimeter-Wave Beam Steering for 5G Wireless Networks and Beyond

The 2 x 2 MMI-MZI polymer thermo-optic switch in a high refractive index contrast (0.102) with a new structure design is realized. The fabrication was done using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of dB has been achieved. Meanwhile, the extinction ratio of 28.6 dB has been achieved in this device. The polarization-dependent loss of 0.3 dB was measured at 1550 nm wavelength. In terms of wavelength dependency, the device shows a good performance within C-band wavelength with vacillation of the insertion loss value around 0.88 dB. The power consumption of 1.85 mW was measured to change the state of the switch from the cross to bar state. The measured switching time was 0.7 ms.

MMI-MZI Polymer Thermo-Optic Switch With a High Refractive Index Contrast

Response-time improvement of a 2×2 thermo-optic switch with polymer/silica hybrid waveguide

Low switching power 2 × 2 thermo-optic switch using direct ultraviolet photolithography process

New types of UV curable polymeric ultra-long array waveguide true-time-delay (TTD) lines for wideband phased array antennas (PAA) are designed and fabricated using direct UV photolithography process. The unique feature of the approach consists of different 1 × N waveguide splitters, low-loss S-bend cosine waveguide connectors, and 180° array bend waveguides with a constant spacing difference ?R between adjacent waveguides. The delay time increments are measured from 1.4 ns to 6.6 ps. 1 × 2, 1 × 4, 1 × 8 polymeric star coupler devices are also successfully prepared. The bend loss of different curved waveguides is calculated and analyzed by the 3-D semivectorial beam propagation method (BPM). The optimized structural properties of the UV curable polymeric waveguides and fabrication procedures are demonstrated. The near-infrared field guided-mode patterns of the devices are obtained. The new technique can be well suited for realizing absence of "beam squint" in the antenna pattern as its frequency is switched from L(1-2.6 GHz) to X(8-12 GHz) band.

Ultra-Long Compact Optical Polymeric Array Waveguide True-Time-Delay Line Devices

Enhanced ferro- and piezoelectric properties of a sol–gel derived BiFe0.95Mn0.05O3 thin film on Bi2O3-buffered Pt/Ti/SiO2/Si substrate

Response speed and power consumption are improved for a Mach–Zehnder interferometer (MZI) thermo-optic (TO) switch, by using a hybrid silica/polymer waveguide structure and optimizing both the thickness of the silica under cladding and that of the PMMA-GMA upper cladding. Fabrication techniques, including chemical vapor deposition (CVD), spin-coating and wet-etching, are adopted to develop the switch sample. Under 1550 nm wavelength, the driving powers under ON and OFF states are measured to be 0 and 13 mW, respectively, indicating a switching power of 13 mW. The fiber-to-fiber insertion loss under the ON state is 15 dB, the extinction ratio between the ON state and the OFF state is 18.3 dB, and the rise time and fall time are 73.5 and 96.5 µs, respectively. Compared with the TO switches based on Si/SiO2 or all-polymer waveguide structure, the proposed device possesses both low power consumption and fast response speed, by virtue of the large TO coefficient of the polymer core, thin upper/under claddings ...

Yunfei Yan

Papers

Response-time improvement of a 2×2 thermo-optic switch with polymer/silica hybrid waveguide

Low switching power 2 × 2 thermo-optic switch using direct ultraviolet photolithography process

Ultra-Long Compact Optical Polymeric Array Waveguide True-Time-Delay Line Devices

Enhanced ferro- and piezoelectric properties of a sol–gel derived BiFe0.95Mn0.05O3 thin film on Bi2O3-buffered Pt/Ti/SiO2/Si substrate

Low-power and high-speed thermo-optic switch using hybrid silica/polymer waveguide structure: design, fabrication and measurement