Integrated Waveguide Devices Research Articles

All-optical Bell states through a multi-poled, integrated waveguide device

In this paper, we propose the generation of all four polarization-entangled Bell states in a potassium titanyl phosphate waveguide device. This is achieved through non-degenerate spontaneous parametric downconversion and quasi-phase-matching with special non-uniform poling in different lengths. These biphoton states consist of the signal being emitted in a telecommunication wavelength. Through their joint spectral amplitude, we study the frequency correlation properties of the photon pairs. Polarization-entangled photon pairs are used as a resource of entanglement in various quantum optics experiments and there is a demand for generating all four photonic Bell states in a single waveguide-based device in quantum information applications.

Monolithic integrated waveguide device with dual functions of electro-optic modulation and optical amplification.

An organic polymer-based monolithic integrated waveguide device with dual functions of electro-optic (EO) modulation and optical amplification is demonstrated. In this Letter, the dual functions are achieved by employing EO polymer as the waveguide upper cladding and organic optical amplified material as the waveguide core layer. Based on this dual-functional waveguide structure, the waveguide amplifier and the EO switch are successfully designed and fabricated on a SiO2-Si substrate. An optical gain of 5.8 dB at the wavelength of 1535 nm is obtained in the dual-functional polymer waveguide, and the EO switch based on the dual-functional polymer waveguide also presents a high-speed response time of ∼10ns.

Erbium-doped hybrid waveguide amplifiers with net optical gain on a fully industrial 300 mm silicon nitride photonic platform.

Recently, erbium-doped integrated waveguide devices have been extensively studied as a CMOS-compatible and stable solution for optical amplification and lasing on the silicon photonic platform. However, erbium-doped waveguide technology still remains relatively immature when it comes to the production of competitive building blocks for the silicon photonics industry. Therefore, further progress is critical in this field to answer the industry's demand for infrared active materials that are not only CMOS-compatible and efficient, but also inexpensive and scalable in terms of large volume production. In this work, we present a novel and simple fabrication method to form cost-effective erbium-doped waveguide amplifiers on silicon. With a single and straightforward active layer deposition, we convert passive silicon nitride strip waveguide channels on a fully industrial 300 mm photonic platform into active waveguide amplifiers. We show net optical gain over sub-cm long waveguide channels that also include grating couplers and mode transition tapers, ultimately demonstrating tremendous progress in developing cost-effective active building blocks on the silicon photonic platform.

Grating Couplers on Silicon Photonics: Design Principles, Emerging Trends and Practical Issues.

Silicon photonics is an enabling technology that provides integrated photonic devices and systems with low-cost mass manufacturing capability. It has attracted increasing attention in both academia and industry in recent years, not only for its applications in communications, but also in sensing. One important issue of silicon photonics that comes with its high integration density is an interface between its high-performance integrated waveguide devices and optical fibers or free-space optics. Surface grating coupler is a preferred candidate that provides flexibility for circuit design and reduces effort for both fabrication and alignment. In the past decades, considerable research efforts have been made on in-plane grating couplers to address their insufficiency in coupling efficiency, wavelength sensitivity and polarization sensitivity compared with out-of-plane edge-coupling. Apart from improved performances, new functionalities are also on the horizon for grating couplers. In this paper, we review the current research progresses made on grating couplers, starting from their fundamental theories and concepts. Then, we conclude various methods to improve their performance, including coupling efficiency, polarization and wavelength sensitivity. Finally, we discuss some emerging research topics on grating couplers, as well as practical issues such as testing, packaging and promising applications.

Thermo-optical properties of binary one dimensional annular photonic crystal including temperature dependent constituents

Abstract In this research article , we present theoretical and numerical investigations concerning the effects of temperature on the transmittance properties of one dimensional annular photonic crystals. The theoretical basis of our study adopts the modified transfer matrix method applied to optical fiber waveguides. The numerical results showed many features that could be of interest. In this regard , we investigate this design to enhance the values of sensitivity based on its geometry. Our design exhibits a remarkable response to temperature changes with a sensitivity of about 0.033 nm/°C which is considered significantly high . Also, it is found that the upper edge of the photonic band gap increases considerably with temperature changes, while the lower edge is almost unchanged . The effects of the core radius and number of periods on the transmittance of our annular photonic crystals design have been also investigated. It is found that an appropriate choice for the core would give flexibility of fabrication and stability of transmission output. In addition, this study reveals that the phase shift of the reflected cylindrical waves within the core is strongly dependent on temperature. We believe our structure is potentially promising in designing and fabrication of novel high-performance temperature sensors and integrated waveguide devices such as optical switches and filters.

Highly Reliable and Repeatable Soldering Technique for Assembling Empty Substrate Integrated Waveguide Devices

In this paper, a novel mymargin soldering technique that improves the fabrication process of empty substrate integrated waveguide (ESIW) devices is presented. Up until now, in order to fabricate an ESIW device, the tin solder paste was distributed, before assembling, on the contact surface between layers, in order to ensure a good electrical contact. This process has a low degree of repeatability (random soldering thickness and distribution of tin) and reliability (a significant number of nonworking prototypes due to tin overflow). In this paper, we propose the mechanization of a set of plated vias just next to the metalized walls of the ESIW in the central layer. Next, in the top and bottom covers that close this ESIW, additional plated vias are drilled in the same position so that, when the device is assembled (using screws or rivets), metalized holes can be seen passing through the whole structure from top to bottom. These holes are then used as soldering vias that can guide the tin paste straight to the point where it is needed. When the paste is dried, soldered vias ensure a very good electrical contact between layers. In addition, the fluid tin fills any small gap that appears between layers, thus providing a very good electrical contact and mechanical union. This novel soldering technique has been validated with experimental results. Several prototypes of filters centered at 13 and 35 GHz have been fabricated, proving the repeatability and reliability of the proposed soldering technique.

Recent Progress of Imprinted Polymer Photonic Waveguide Devices and Applications.

Polymers are promising materials for fabricating photonic integrated waveguide devices. Versatile functional devices can be manufactured using a simple process, with low cost and potential mass-manufacturing. This paper reviews the recent progress of polymer photonic integrated devices fabricated using the UV imprinting technique. The passive polymer waveguide devices for wavelength filtering, power splitting, and light collecting, and the active polymer waveguide devices based on the thermal-optic tuning effect, are introduced. Then, the electro-optic (EO) modulators, by virtue of the high EO coefficient of polymers, are described. Finally, the photonic biosensors, which are based on low-cost and biocompatible polymer platforms, are presented.

Tailoring nonlinear processes for quantum optics with pulsed temporal-mode encodings

The time-frequency degree of freedom is a powerful resource for implementing high-dimensional quantum information processing. In particular, field-orthogonal pulsed temporal modes offer a flexible framework compatible with both long-distance fibre networks and integrated waveguide devices. In order for this architecture to be fully utilised, techniques to reliably generate diverse quantum states of light and accurately measure complex temporal waveforms must be developed. To this end, nonlinear processes mediated by spectrally shaped pump pulses in group-velocity engineered waveguides and crystals provide a capable toolbox. In this review, we examine how tailoring the phasematching conditions of parametric downconversion and sum-frequency generation allows for highly pure single-photon generation, flexible temporal-mode entanglement, and accurate measurement of time-frequency photon states. We provide an overview of experimental progress towards these goals, and summarise challenges that remain in the field.

Metal-cladding directly defined active integrated optical waveguide device based on erbium-containing polymer

The Er-containing polymer is synthesized by free-radical polymerization. Based on the copolymer, metal-cladding directly defined waveguide technique is proposed. The technique is advantageous to realize the multi-functional integrated circuits.

QUANTUM OPTICS. Universal linear optics.

Linear optics underpins fundamental tests of quantum mechanics and quantum technologies. We demonstrate a single reprogrammable optical circuit that is sufficient to implement all possible linear optical protocols up to the size of that circuit. Our six-mode universal system consists of a cascade of 15 Mach-Zehnder interferometers with 30 thermo-optic phase shifters integrated into a single photonic chip that is electrically and optically interfaced for arbitrary setting of all phase shifters, input of up to six photons, and their measurement with a 12-single-photon detector system. We programmed this system to implement heralded quantum logic and entangling gates, boson sampling with verification tests, and six-dimensional complex Hadamards. We implemented 100 Haar random unitaries with an average fidelity of 0.999 ± 0.001. Our system can be rapidly reprogrammed to implement these and any other linear optical protocol, pointing the way to applications across fundamental science and quantum technologies.

On-Chip Manipulation of Single Photons from a Diamond Defect

Operating reconfigurable quantum circuits with single photon sources is a key goal of photonic quantum information science and technology. We use an integrated waveguide device containing directional couplers and a reconfigurable thermal phase controller to manipulate single photons emitted from a chromium related color center in diamond. Observation of both a wavelike interference pattern and particlelike sub-Poissionian autocorrelation functions demonstrates coherent manipulation of single photons emitted from the chromium related center and verifies wave particle duality.

Graphene photo detector with integrated waveguide biochemical sensors

In this study, we demonstrate the fabrication of a graphene integrated waveguide device with graphene as the photo detector for bio-chemical sensor applications. The working principle of the sensor is based on the variation of the local evanescent wave intensity according to the variation of the analyte's refractive index. Graphene film is transferred onto the field-effect transistor device, and an overlay of polydimethylsiloxane (PDMS) is used as the waveguide. A few microliter drop of glucose is placed on the PDMS waveguide, and the change in the photocurrent through the graphene is monitored. Depending of the refractive index of the glucose (or analyte) changed, the local evanescent field changed and hence the photo current of the graphene. We believe that this sensing platform can be used for detection of various bio-analytes and for bio reactions.

Efficient Analysis of Substrate Integrated Waveguide Devices Using Hybrid Mode Matching Between Cylindrical and Guided Modes

In this paper, a new method to efficiently analyze substrate integrated waveguide (SIW) based devices with multiple accessing ports is presented. The problem is considered as a 2-D electromagnetic problem assuming no field variation normal to the dielectric substrate. The incident and scattered fields from each circular cylinder are expanded with cylindrical modes, and the fields in the waveguide ports are expanded using progressive and regressive modal summations. The addition theorems of Bessel and Hankel functions are used to analyze the full-wave behavior of the SIW device. In order to extract the circuital parameters, the hybrid mode-matching between guided and cylindrical modes is done by projecting continuity equations in a circular boundary containing the whole SIW structure over the inner modes of each region. Applying this new technique, it is possible to analyze multiple port devices by solving a set of integrals that can be easily approached analytically or by using the inverse fast Fourier transform, avoiding the use of non efficient numerical methods. It is shown that the new method runs faster than commercial software packages and other techniques recently published.

Heralding Two-Photon and Four-Photon Path Entanglement on a Chip

Generating quantum entanglement is not only an important scientific endeavor, but will be essential to realizing quantum-enhanced technologies, in particular, quantum-enhanced measurements with precision beyond classical limits. We investigate the heralded generation of multiphoton entanglement for quantum metrology using a reconfigurable integrated waveguide device in which projective measurement of auxiliary photons heralds the generation of path-entangled states. We use four and six-photon inputs, to analyze the heralding process of two- and four-photon NOON states-a superposition of N photons in two paths, capable of enabling phase supersensitive measurements at the Heisenberg limit. Realistic devices will include imperfections; as part of the heralded state preparation, we demonstrate phase superresolution within our chip with a state that is more robust to photon loss.

Multilayer dielectric cylindrical mirrors based on omnidirectional reflection from a one-dimensional photonic crystal

A multilayer dielectric cylindrical mirror (MDCM) based on the one-dimensional omnidirectional reflection of a photonic crystal is presented. In this case, the refractive indices of the two materials are 1.6 (polystyrene) and 4.6 (tellurium), and the corresponding optimized thicknesses are 0.75 a and 0.25 a. A very high reflectance over a wide frequency range is observed. In this case, a is the lattice constant of the photonic crystal. In this band, the MDCM has good reflection and focal properties. Therefore, it is feasible to use the MDCM for integrated waveguide devices. As an example, an etched diffraction grating demultiplexer based on the MDCM is also proposed. Both the operational principle and design of the device are introduced. This provides a method for designing compact integrated waveguide devices.

SWIFTS Waveguide Micro-Spectrometer Integrated on Top of a 1D-NbN SNSPD Array

The SWIFTS integrated waveguide device (Stationary Wave Integrated Transform Spectrometer) has been designed on top of a 1D parallel array of 50-nm-width single stripe Superconducting Nanowire Single Photon Detectors (SNSPD). Colored light, around 1.55-μm wavelengths, is introduced inside PE-CVD deposited and patterned Si3N4 monomode rib waveguides, in order to produce a counter-propagative stationary wave over the Nanowire array. Optical power losses are reported, mainly due to waveguide sidewall roughness scattering, end-fire fiber coupling and mode coupling mismatch. Simulations and measurements over waveguide bending, coupling and roughness quantify the loss contributions of the different factors. E-beam lithography has been re-optimized on 4-inch sapphire and NbN passivating nano-layers added for elaborating SWIFTS devices with 24 Nanowires each of 50-nm widths, capable of directly sampling the stationary wave profile. Process compatibility has been demonstrated, thanks to the MgO layer protecting NbN Nanowires before SiN deposition. Each SNSPD should operate separately at 4K in the single photon counting regime for sampling the guided standing wave, introduced by the high precision mechanical alignment of a fiber in the test set-up.

Hybrid Technique Plus Fast Frequency Sweep for the Efficient and Accurate Analysis of Substrate Integrated Waveguide Devices

In this paper, we adapt a novel mode-matching and method-of-moments hybrid technique to efficiently analyze substrate integrated waveguide (SIW) based devices. The hybrid technique is formulated in terms of a single equivalent current. This fact is used to include the emergent modal weights, i.e., the scattering parameters, as unknowns of the method-of-moments system of equations. In this case, it is relatively easy to develop fast frequency sweep schemes that can be used to highly accelerate the solution of an arbitrary device and, as a result, a very efficient technique is obtained. This technique can be applied to the analysis and design of SIW devices, and it is highly competitive when compared to other method-of-moments and mode-matching hybrid formulations or when compared to reference commercial software.

Double Tungstate Lasers: From Bulk Toward On-Chip Integrated Waveguide Devices

It has been recognized that the monoclinic double tungstates KY(WO4)2, KGd(WO4)2, and KLu(WO4)2 possess a high potential as rare-earth-ion-doped solid-state laser materials, partly due to the high absorption and emission cross sections of rare-earth ions when doped into these materials. Besides, their high refractive indexes make these materials potentially suitable for applications that require optical gain and high power in integrated optics, with rather high integration density. We review the recent advances in the field of bulk lasers in these materials and present our work toward the demonstration of waveguide lasers and their integration with other optical structures on a chip.

Terahertz all-optical modulation in a silicon–polymer hybrid system

Although gigahertz-scale free-carrier modulators have been demonstrated in silicon, intensity modulators operating at terahertz speeds have not been reported because of silicon's weak ultrafast nonlinearity. We have demonstrated intensity modulation of light with light in a silicon-polymer waveguide device, based on the all-optical Kerr effect-the ultrafast effect used in four-wave mixing. Direct measurements of time-domain intensity modulation are made at speeds of 10 GHz. We showed experimentally that the mechanism of this modulation is ultrafast through spectral measurements, and that intensity modulation at frequencies in excess of 1 THz can be obtained. By integrating optical polymers through evanescent coupling to silicon waveguides, we greatly increase the effective nonlinearity of the waveguide, allowing operation at continuous-wave power levels compatible with telecommunication systems. These devices are a first step in the development of large-scale integrated ultrafast optical logic in silicon, and are two orders of magnitude faster than previously reported silicon devices.

Compact Arrayed-Waveguide Grating with Multiple-Arrowhead Structures

A compact arrayed-waveguide grating (AWG) using multiple-arrowhead structures has been proposed. Arrowhead structures are useful for achieving low-cost and highly integrated waveguide devices because of their compactness. Therefore, the use of multiple-arrowhead structures enables us to achieve high-resolution AWGs with a channel spacing of less than 10 GHz, and we have already fabricated an 8-channel, 25-GHz-spacing AWG using a single-arrowhead structure, a 16-channel, 100-GHz-spacing AWG using a double-arrowhead structure and an 8-channel, 6.25-GHz-spacing AWG using a triple-arrowhead structure. The dimension of the third type of AWG is much smaller than a conventional AWG, with a size ratio of 1:6.4. The levels of the losses and adjacent crosstalk are mainly determined by insertion losses in the v-bend waveguides and by phase shifts due to misalignment of the mirror position, respectively.