Single-layer active-passive Al₂O₃ photonic integration platform

Amorphous Al2O3 is an attractive platform for integrated photonics, providing active and passive functionalities. We have developed an integration procedure to create active and passive regions at the same level on one wafer. This fabrication process reduces the number of fabrication steps compared to vertical integration of two materials. The main advantage is that all structures are defined within a single photolithography and etching step and are therefore automatically aligned. As a proof of principle, we demonstrated the luminescence of an active ring resonator with passive bus waveguide

Heterogeneous integration of KY(WO4)2-on-glass : a bonding study

Rare-earth ion doped potassium yttrium double tungstate, RE: KY(WO4)(2), is a promising candidate for small, power-efficient, on-chip lasers and amplifiers. There are two major bottlenecks that complicate the realization of such devices. Firstly, the anisotropic thermal expansion coefficient of KY(WO4)(2) makes it challenging to integrate the crystal on glass substrates. Secondly, the crystal layer has to be, for example, < 1 mu m to obtain single mode, high refractive index contrast waveguides operating at 1550 nm. In this work, different adhesives and bonding techniques in combination with several types of glass substrates are investigated. An optimal bonding process will enable further processing towards the manufacturing of integrated active optical KY(WO4)(2) devices. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Modular microring laser cavity sensor

We propose and experimentally demonstrate a modular microring laser (MML) cavity for sensing applications. The proposed MML permits much more design freedom compared with a traditional simple ring cavity by decoupling the performance parameters into several regions in the cavity. Thus, the different biosensor performance parameters can be optimized semi-independently limiting the need for trade-offs on the design of the biosensing device. The first generation MML has been fabricated and tested. A fiber-to-fiber slope efficiency of up to 1.2%, a temperature coefficient of 1.35 GHz/K and a 3σ limit of detection (LOD) of 3.1 × 10−7 RIU without averaging and 6.0 × 10−8 RIU with a 60 s averaging, has been measured for the MML sensor, which is a record-low LOD in on-chip ring cavity optical sensors. Further optimization is possible, capitalizing on the key advantage of the MML concept, namely the potential for designing the laser cavity to achieve the desired optimization goals

Rare-earth ion doped Al2O3 for active integrated photonics

Aluminum oxide (Al2O3) is an emerging material in integrated photonics. It exhibits a very broad transparency window from the UV to the mid-IR, very low propagation losses and a high solubility for rare-earth ions leading to optical gain in different spectral ranges. Al2O3 can be deposited by different wafer-level deposition techniques, including atomic layer deposition and reactive magnetron sputtering, being compatible with the monolithic integration onto passive integrated photonics platforms, such as Si3N4, to which it provides optical amplification and lasing. When deposited at low temperatures, it is also compatible with integration onto CMOS chips. In this review, the state-of-the-art on the deposition, integration and device development in this photonic platform is described

A novel polishing stop for accurate integration of potassium yttrium double tungstate on a silicon dioxide

Rare-earth ion doped potassium yttrium double tungstate, RE:KY(WO4)2, is a promising candidate for the realization of on-chip lasers and amplifiers. Two major bottlenecks difficult the realization of compact, high-contrast devices. Firstly, the crystal can only be grown on a lattice matched substrate, leading to a low (<2×10-2) refractive index contrast between core and cladding. Secondly, the required thickness for the high-index contrast waveguides, ∼1 μm, makes a lapping and polishing approach very challenging. In this work we propose a novel polishing stop that will permit to accurately control the final thickness of the KY(WO4)2 waveguide within a few tens of nanometers. A 1 mm thick KY(WO4)2 substrate is flip-chip bonded with an adhesive layer onto a SiO2 substrate. Afterwards a low temperature pulsed laser deposited (PLD) Al2O3 layer-with the desired final thickness of the KY(WO4)2 waveguide core-is deposited on top of the assembly. The sample is then thinned using a multistep lapping and polishing procedure. Earlier work with a polishing stop made from SiO2, showed a decrease of the polishing speed with a factor 3-4, allowing the termination of the process within a tolerance of a few tens of nanometers

Relative oxidation state of the target as guideline for depositing optical quality RF reactive magnetron sputtered Al2O3 layers

Amorphous Al2O3 is an attractive material for integrated photonics. Its low losses from the UV till the mid-IR together with the possibility of doping with different rare-earth ions permits the realization of active and passive functionalities in the same chip at the wafer level. In this work, the influence of reactive gas flow during deposition on the optical (i.e., refractive index and propagation losses) and material (i.e., structure of the layer) characteristics of the RF reactive sputtered Al2O3 layers is investigated and a method based on the oxidation state of the sputtering target is proposed to reproducibly achieve low loss optical guiding layers despite the continuous variation of the condition of the target along its lifetime