To overcome the increased absorption of commercially available waveguide platforms for UV wavelengths, Al2O3 has been suggested due to its low losses below 450 nm. In this work, we demonstrate Al2O3 waveguides fabricated via reactive sputtering, electron beam lithography and dry etching with losses as low as 2.3 dB/cm at 369 nm. A variety of building blocks required for typical photonic devices are realized using the process which shows promise as a waveguide platform for applications that require UV wavelengths.
Hybrid integrated diode lasers offer a robust and small-sized solution for applications in telecommunications, quantum optics and metrology due to their wide tunability and ultra-narrow linewidth. Here, we present the fabrication, packaging and successful operation of the first fully integrated, aluminum oxide (Al2O3) based, hybrid diode laser operating at 405 nm. Low-loss, high-confinement waveguides are fabricated with a measured propagation loss of only 2.8 ± 0.3 dB/cm. The hybrid laser consists of a GaN SLED butt-coupled to an Al2O3 feedback circuit comprising of two microring resonators that form a frequency selective Vernier filter. The chip assembly is packaged in a hermetically sealed, butterfly housing for optimal performance and durability. The laser shows a maximum output power of 0.74 mW and is tunable over the entire gain bandwidth of 4.4 nm.
We present a low propagation loss aluminium oxide integrated photonics platform enabling applications with operation down to the UV wavelength range (i.e., <250 nm). Single mode fully etched waveguides were fabricated with losses below 2 dB/cm at 405 nm. The influence of waveguide dimensions on the propagation losses are presented, indicating that losses are sidewall roughness limited. Lower losses can be achieved by further optimization of the cross-section of the waveguides. In this presentation, the aluminium oxide platform will be introduced together with the characterization of the waveguides at near-UV wavelengths.
Photonic integrated circuits (PICs) have experienced an exponential growth in a number of applications, including telecom/datacom, LiDAR, optical sensing/metrology and quantum technology. Most materials and platforms commonly used in integrated photonics, such as silicon-on-insulator (SOI), silicon nitride (Si3N4) and indium phosphide (InP) do not show transmission below ~400 nm, hindering the development of PICs operating in the ultraviolet wavelength range. Furthermore, devices in this wavelength range also require fast modulation and switching in order to enable complex emerging applications. Aluminum nitride (AlN) is a material with a band gap of 6.2 eV, exhibiting a wide transparency window, from the ultraviolet to the mid-infrared. AlN has the capacity to achieve high electro-optic[1], non-linear[2] and piezo-electric[3,4] coefficients, which makes AlN an interesting material for PICs with operation down to the ultraviolet wavelength range. However, high losses have prevented PICs from benefiting from its excellent optical properties. In this work, we present our work on the sputter deposition of low-loss AlN slab waveguides. The optical performance of AlN sputtered slab waveguides after annealing at different temperatures and their relation with the film morphology will be discussed. Preliminary slab propagation losses as low as 1.5 dB/cm at 633 nm of wavelength have been demonstrated.
Compact laser sources are crucial for the next generation of photonic integrated circuits, where bulky mechanical components and other optical bench top systems can be realized on a single tiny chip. Similarly, biological sensing, environmental real-time monitoring and telecommunications all benefit from the advances seen in on-chip photonic components, in particular, active devices such as the amplifier and laser which have significant challenges in being implemented on a silicon substrate. The study of Erbium doped Aluminium Oxide (Al2O3:Er3+) has attracted significant interest from the research community due to its high solubility for rare-earth ions, wide optical transparency, and capability to be integrated as a hybrid coating or patterned into waveguides on a Si substrate using conventional fabrication techniques. Results point towards amorphous Al2O3 as an ideal candidate for further research into the discovery of amplifiers and lasers for photonic integrated circuits (PIC). Here, we report on the spectroscopic parameters as well as prospects for Al2O3:Er3+ doped films and their integration onto an existing low-loss waveguide platform for the realization of amplifiers and lasers. A review of past results will be given with pathways towards optimized films and improved laser performance in the future.
TiO2 is a very promising material for integrated photonics due to its high refractive index (~2.3 at 633 nm), wide transparency window from the visible to the mid-infrared and high non-linear refractive index. However, to date, high propagation losses hinder its utilization in real-life applications. In this work, we carry out a systematic study of the different fabrication processes involved in the realization of TiO2 channel waveguides, including RF sputter deposition, electron-beam lithography and thermal annealing, showing film losses below 1 dB/cm for wavelengths above 633 nm and channel losses of 1-1.5 dB/cm at 1550 nm.
Luminescence quenching due to ion cluster formation in erbium ion doped amorphous aluminium oxide, limits the maximum doping concentration that can be incorporated into the material and, consequently, the maximum achievable optical gain. By controlling the reactive sputtering deposition parameters, layers with different morphologies can be deposited. In this work, we investigate low propagation loss poly-crystalline aluminium oxide thin films and the effect of erbium doping on the crystallinity. We have developed a reactive sputter process to reproducibly obtain high refractive index (n~1.72 at 633 nm) poly-crystalline thin films with very low slab waveguide losses from the near-UV to the midinfrared wavelength range. Slab waveguide losses as low as 1.8 dB/cm at 407 nm and less than 0.1 dB/cm at 1550 nm of wavelength have been experimentally characterized. Both the undoped and erbium doped layers were deposited by reactive sputter coating with, a set substrate temperature of 700 °C. Preliminary TEM analyses show no discernible change in the crystallinity of the doped layers with respect to their undoped counterparts. The high optical quality of this material, in combination with a potentially increased rare-earth ion doping concentration, could pave the way towards high-gain on-chip amplifiers in different wavelength ranges and efficient on-chip lasers.
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