Khu Vu

Tellurium dioxide Erbium doped planar rib waveguide amplifiers with net gain and 2.8dB/cm internal gain

We report for the first time Erbium doped Tellurium dioxide single-mode planar rib waveguide amplifiers with net fiber to fiber gain and wide bandwidth operation. Peak internal gains of up to 14 dB have been achieved in 5 cm long rib waveguides (2.8 dB/cm) fabricated by co-sputtering of Tellurium and Erbium in an oxygen ambient and reactive ion etching.

Tailoring of the Brillouin gain for on-chip widely tunable and reconfigurable broadband microwave photonic filters

An unprecedented Brillouin gain of 44 dB in a photonic chip enables the realization of broadly tunable and reconfigurable integrated microwave photonic filters. More than a decade bandwidth reconfigurability from 30 up to 440 MHz, with a passband ripple <1.9  dB is achieved by tailoring the Brillouin pump. The filter central frequency is continuously tuned up to 30 GHz with no degradation of the passband response, which is a major improvement over electronic filters. Furthermore, we demonstrate pump tailoring to realize multiple bandpass filters with different bandwidths and central frequencies, paving the way for multiple on-chip microwave filters and channelizers.

Very low loss reactively ion etched Tellurium Dioxide planar rib waveguides for linear and non-linear optics

We report on the fabrication and optical properties of the first very low loss nonlinear Tellurite planar rib waveguides ever demonstrated. A new reactive ion etch process based on Hydrogen as the active species was developed to accomplish the low propagation losses. Optical losses below approximately 0.05 dB/cm in most of the NIR spectrum and approximately 0.10 dB/cm at 1550 nm have been achieved - the lowest ever reported by more than an order of magnitude and clearly suitable for planar integrated devices. We demonstrate strong spectral broadening of 0.6 ps pulses in waveguides fabricated from pure TeO(2), in good agreement with simulations.

High Q factor chalcogenide ring resonators for cavity-enhanced MIR spectroscopic sensing

We report the characteristics of high Q factor chalcogenide ring resonators designed for sensing in the mid-infrared (MIR). The resonators consisted of an exposed Ge11.5As24Se64.5 core on a Ge11.5As24S64.5 bottom cladding and were fabricated in the racetrack coupled ring structure. Loaded Q factors at 5.2μm up to 58,000were obtained, corresponding to an intrinsic Q of 145,000 and a waveguide propagation loss of 0.84dB/cm.

Advanced Integrated Microwave Signal Processing With Giant On-Chip Brillouin Gain

Processing of microwave signals using photonics has several key advantages for applications in wireless communications. However, to bring photonic-based microwave signal processing to the mainstream requires a reduction of the form factor. Integration is a route for achieving high-performance, low-cost, and small-footprint microwave photonic devices. A high on-chip stimulated Brillouin scattering (SBS) gain is essential for synthesizing several key functionalities for advanced integrated microwave signal processing. We have optimized our on-chip SBS platform to achieve a record on-chip gain of 52 dB. In this paper, we discuss the implications of this giant gain from the viewpoint of new enabled technologies. The giant gain can be distributed over wide frequencies, which can be exploited for the realization of reconfigurable microwave bandpass, bandstop, and multiband filters. High gain also enables the demonstration of low-threshold on-chip lasers, which can be of relevance for a low-noise radio-frequency signal generation. These wide ranges of functionalities are made possible by the breakthrough on-chip gain makes Brillouin-based microwave photonic signal processing a promising approach for real-world implementation in the near future.

Compact Brillouin devices through hybrid integration on silicon

A range of unique capabilities in optical and microwave signal processing and generation have been demonstrated using stimulated Brillouin scattering (SBS). The need to harness SBS in mass-manufacturable integrated circuits has led to a focus on silicon-based material platforms. Remarkable progress in silicon-based Brillouin waveguides has been made, but results have been hindered by nonlinear losses present at telecommunications wavelengths. Here, we report on a new approach to surpass this issue through the integration of a high Brillouin gain material, As2S3, onto a silicon-based chip. We fabricated a compact spiral device within a silicon circuit, achieving an order-of-magnitude improvement in Brillouin amplification. To establish the flexibility of this approach, we fabricated a ring resonator with free spectral range precisely matched to the Brillouin shift, enabling the first demonstration, to our knowledge, of Brillouin lasing in a planar integrated circuit. Combining active photonic components with the SBS devices shown here will enable the creation of compact, mass-manufacturable optical circuits with enhanced functionalities.

Observation of Photon Echoes From Evanescently Coupled Rare-Earth Ions in a Planar Waveguide

We report the measurement of the inhomogeneous linewidth, homogeneous linewidth, and spin-state lifetime of Pr3+ ions in a novel waveguide architecture. The TeO2 slab waveguide deposited on a bulk Pr3+∶Y2SiO5 crystal allows the 3H4↔1D2 transition of Pr3+ ions to be probed by the optical evanescent field that extends into the substrate. The 2-GHz inhomogeneous linewidth, the optical coherence time of 70±5  μs, and the spin-state lifetime of 9.8±0.3  s indicate that the properties of ions interacting with the waveguide mode are consistent with those of bulk ions. This result establishes the foundation for large, integrated, and high performance rare-earth-ion quantum systems based on a waveguide platform.

Photoluminescence in Er-doped Ge-As-Se chalcogenide thin films

We report ion-implanted Er ions into Ge<inf>11.5</inf>As<inf>24</inf>Se<inf>64.5</inf> thin films with different doses, and subsequently thermal-annealed the films with different times. The characterization results indicated that the thickness, refractive index and optical bandgap of the films can be stabilized with 3 hour thermal annealing. The 1.5 μm emission arising from the ⁴I<inf>13/2</inf>→⁴I<inf>15/2</inf> transition was observed and a lifetime of 1.35 ms was obtained in films annealed at 180°C.

Reactive ion etching of tellurite and chalcogenide waveguides using hydrogen, methane, and argon

The authors report in detail on the reactive plasma etching properties of tellurium and demonstrate a high quality etching process using hydrogen, methane, and argon. Very low loss planar ridge waveguides are demonstrated. Optical losses in tellurium dioxide waveguides below 0.1 dB/cm in most of the near infrared region of the electromagnetic spectrum and at 1550 nm have been achieved—the lowest ever reported by more than an order of magnitude and clearly suitable for planar integrated devices. The etch process is also shown to be suitable for chalcogenide glasses which may be of importance in applications such as phase change memory devices and nonlinear integrated optics.

980nm pumped erbium doped tellurium oxide planar rib waveguide laser and amplifier with gain in S, C and L band

A thin film based erbium doped tellurium oxide (TeO2) waveguide amplifier producing gain from 1500nm to 1640nm when pumped at 980nm is demonstrated. At measured internal gains exceeding 14dB lasing due to end facet reflection set in producing the first tellurite waveguide laser. High gains were observed despite significant upconversion, whose impact appears to be mitigated to some extent by residual OH contamination. The device displayed no photosensitive effects from either the high pumping intensities used or the intracavity intensity at 1550nm.