Reactive sputtering provides a scalable and robust approach to fabricate erbium doped waveguide amplifiers and can be used to integrate devices with other waveguide platforms. In this work, we present recent results on high gain (>25 dB) in Al2O3:Er3+ amplifiers fabricated via reactive sputtering, which are vertically integrated with underlying LioniX TriPleX Si3N4 circuitry.
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.
We present a novel hybrid 800 nm laser with a wide tuning range, high optical power and ultra-narrow linewidth with ⪆kHz tuning speeds and a small footprint. Tunable, narrow linewidth hybrid lasers around 800nm serve as an attractive choice for e.g. OCT, LIDAR and atomic transition locking in e.g. atomic clocks. The laser has a microring resonator based optical cavity. The laser has a tuning range of 45 nm and a maximum output power of 5 dBm. The intrinsic linewidth of the laser is measured at 22 kHz.
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.
The monolithic integration of active materials providing optical gain and optical non-linearities is instrumental to increase the functionality of integrated photonic circuits. A double layer integration scheme has been experimentally demonstrated, exhibiting transition losses between the two materials of less than 0.2 dB. Furthermore, a single layer integration scheme is proposed, which decreases the number of process steps, reducing fabrication cost, and also decreasing the sensitivity to fabrication tolerances. In this paper, we will overview our recent developments on the monolithic integration of both, Al2O3 and TiO2 onto the passive Si3N4 and Al2O3 platforms for the development of on-chip amplifiers and lasers.
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.
TiO2 is gaining interest as material for integrated photonics, due to its high refractive index, large transparency window and high non-linear refractive index. Its low phonon energy makes it attractive for the realization of active devices in the visible frequency range. In this work, we optimize different process steps of the fabrication of low loss TiO2 channel waveguides. The TiO2 layers are deposited by DC sputter deposition, using a mixed Ar/O2 plasma. Removing the hysteresis in the deposition process, results in reduced propagation losses of the TiO2 films (estimated less than 1.5 dB/cm at 632 nm wavelength). An E-beam lithography process is utilized to reduce the sidewall roughness of the waveguides. Different reactive gasses are compared to optimize the reactive ion etching recipe. BCl3 in combination with HBr shows to be most beneficial for etching TiO2 with high selectivity towards negative E-beam resist. A selectivity of 2.7 for TiO2 over the E-beam resist is obtained. The performance of a TiO2 a channel waveguide fabricated with the process before and after optimization is compared. The waveguide fabricated using the non-optimized process exhibited losses of 7.82±0.52 dB/cm at a wavelength of 632.8 nm, after applying an SiO2 cladding. After process optimization, 5.08±0.65 dB/cm were obtained, without an SiO2 cladding.
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