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KY(WO4)2 crystal has a lot of potential as an on-chip waveguide material for lanthanide ion-doped, Raman active lasers and on-chip amplifiers. One method of fabricating these waveguides is by using swift carbon ion irradiation, which produces a step-like, damage-induced refractive index contrast of up to Δ n ≈ 0.2. The irradiation is followed by an annealing step to reduce color centers that cause high optical absorption, leading to an optical slab waveguide with optical transmission losses as low as 1.5 dB/cm at 1550 nm. In this article, we report an upper limit of ∼ 450 ° C to the annealing temperature, above which stresses and recrystallization induce additional scattering detrimental to waveguide performance. The effects are characterized using transmission electron microscopy and Raman microscopy. [ABSTRACT FROM AUTHOR]

Planar waveguides formed in the Raman-active crystal KGd[(W[O.sub.4]).sub.2] is characterized by using swift carbon, fluorine and oxygen ion irradiation. Raman spectroscopy measurements have shown the details of the Raman properties of the crystal in the waveguiding region in relation to the rest of the sample for the different ion irradiations and both these measurements are important for use of KGd[(W[O.sub.4]).sub.2] in integrated Raman-active devices.

On chip waveguide optical amplifiers have been extensively studied over the last years, with a wide variety of materials tested and proposed for different applications. Among the most prominent solutions for on-chip amplification, erbium doped waveguide amplifiers (EDWAs) are able to offer attractive performance metrics that can exceed SOA-based amplification solutions in traditional single and multi-channel systems. In this letter, we experimentally demonstrate a record high $8\times 40$ Gbps non return to zero (NRZ) wavelength division multiplexing (WDM) data amplification through a 5.9 cm long on-chip amplifier consisting of an erbium-doped aluminum oxide spiral waveguide monolithically integrated on the Si3N4 platform. Experimental results show more than 12.7 dB amplification per channel for low saturation total input power of −2.75 dBm, and clear eye diagrams and bit-error rate values below the KR4-FEC limit of $2\times 10 ^{-5}$ for all eight channels without any digital signal processing (DSP) applied to the signal to the receiver or transmitter side. The high losses from the fiber to chip interfaces, however, prevented achieving device net gain. [ABSTRACT FROM AUTHOR]

In this letter, a direct measurement of a refractive index change in potassium gadolinium tungstate (KGW) created by a low-dose ion implantation of 1 MeV hydrogen ions is reported. The characterization was performed using both microreflectivity and Raman spectroscopy measurements. The microreflectivity results show both negative and positive changes in refractive index in the damage region when measuring refractive index along different polarization axes. Micro-Raman spectroscopy analysis shows preservation of the Raman characteristics of KGW in the nondamaged crystal regions. These results show that ion implantation in KGW has a great potential for fabricating waveguide structures in Raman-based photonic devices. [ABSTRACT FROM AUTHOR]