The linear and nonlinear properties of laser-drawn silicon core fibers (SCFs) are characterized in the telecom band for the first time. We show that the SCFs produced with micrometer-sized core diameters exhibit low optical losses ( ∼ 1 dB/cm) straight from the drawing tower, indicating a high-quality of the crystalline core materials. Moreover, by using an adapted fiber tapering method, the core diameter of these fibers can be precisely tailored to obtain longitudinal profiles optimized for low loss coupling, with uniform waist regions over lengths up to ∼ 7 cm and a further reduction in the linear losses to ∼ 0.2 dB/cm. Characterization of the nonlinear parameters reveals values in good agreement with previous measurements of single-crystal silicon. By exploiting the long lengths and low losses, an on-off Raman gain up to 9 dB was obtained when pumping with a continuous wave power of only < 0.1 W. The high Raman gain achieved in this work highlights the potential of using these fibers for compact nonlinear signal amplification or laser systems.

Raman scattering is a nonlinear process that can be used to generate or amplify optical signals in wavelength regions where traditional light sources are limited or unavailable. Thus, when constructed from high-power lasers coupled to waveguides with broad transmission windows, Raman scattering can be used to extend the wavelength coverage of existing laser systems [1]. In this regard, silicon core fibres (SCFs) are a promising platform for Raman shifting processes due to their high damage threshold, strong Raman response and extended infrared transmission (1.1 ~ 7 µm). Moreover, as they are clad in silica, the SCFs are stable, and compatible with other glass fibre components, such as the pump laser, opening a route for the development of robust all-fibre systems [2].

The mid-infrared spectral region is of great interest for many applications in areas such as environmental sensing, free space communications, and medical diagnostics. However, accessing tuneable sources in the mid-infrared can be difficult due to the limited gain media in this region. An alternative approach is to make use of existing high power telecoms band pump lasers and couple them with highly nonlinear waveguides that offer efficient wavelength conversion via processes such as four-wave mixing (FWM) [1]. An advantage of this approach is that the signals can also be converted back to the telecom band where there are excellent diagnostic tools. In this regard, silicon core fibres (SCFs) have recently emerged as a promising platform for FWM processes due to their high damage threshold, strong nonlinear refractive index and extended infrared transmission (1.1 ~ 7 µm) [2]. Moreover, as they are clad in silica, the SCFs are directly compatible with the fiberized pump sources, opening a route for the development of robust all-fibre systems [3].

Femtosecond laser irradiation followed by chemical etching (FLICE) is a powerful and enabling technology for microstructuring glass substrates in 3D. The irradiated focal volume expresses increased etching selectivity with respect to the pristine material, enabling the fabrication of optical components with micrometric resolution, but with critical residual roughness (about 400 nm rms). Here we compare the surface quality of microlenses processed with different methods as CO2 laser annealing, thermal annealing in oven and polishing by direct dielectric barrier discharge inert gas plasma at atmospheric pressure. The optimized optical elements will be integrated on more complex devices for optical investigations of biological specimens.

We report, to the best of our knowledge, the first demonstration of a telecom photon-pair source based on a silicon core fiber, published by Rizzotti, et al., APL photonics 9 (2024). The 58 mm long fiber works at room temperature and shows brightness and coincidence-to-accidental ratio comparable to state-of-the-art.

Femtosecond laser micromachining (FLM) has emerged as a powerful technique for the precise fabrication of optical components, enabling high-resolution structuring in transparent materials such as fused silica and borosilicate glass. The nonlinear absorption mechanisms involved allow for localized modifications at the microscale with minimal thermal effects. In this work, we demonstrate the application of FLM for the fabrication of integrated optical beam splitters and microlenses. By carefully controlling laser parameters and subsequent post-processing steps, we achieve structures with high optical quality and functional performance. The results demonstrate the potential of femtosecond laser technology in integrating complex optical components, opening new possibilities for the development of lab-on-chip systems.

The nonlinear properties of CO laser-drawn silicon core fibres are characterised for the first time. By employing a tapering process to optimise the coupling into fibres with micrometre-sized core diameters, we show that the nonlinear parameters are in good agreement with single-crystal silicon.

Rapid manufacturing of high purity fused silica glass micro-optics using a filament-based glass 3D printer has been demonstrated. A multilayer 5 x 5 microlens array was printed and subsequently characterized, showing fully dense lenses with uniform focal lengths and good imaging performance. A surface roughness on the order of R-a = 0.12 nm was achieved. Printing time for each lens was <10 s. Creating arrays with multifocal imaging capabilities was possible by individually varying the number of printed layers and radius for each lens, effectively changing the lens height and curvature. Glass 3D printing is shown in this study to be a versatile approach for fabricating silica micro-optics suitable for rapid prototyping or manufacturing.

Integrated quantum sources are proving to be the most effective technology of sources for scalable quantum applications. A platform that satisfies all the requirements has not prevailed yet. In this framework, we report, to the best of our knowledge, the first demonstration of a photon pair source in a silicon core fiber. The fiber, only 58 mm long, works at room temperature and shows an intrinsic brightness of 570 kHz/nm/mW(2) and a coincidence-to-accidental ratio of 133 +/- 2 at around 1.55 mu m wavelength. The low propagation losses of the platform, similar to 0.3 dB/cm in our source, pave the way for effective fiber-based quantum sources in the telecom band. A comparison with state-of-the-art further confirms the potential of this platform for future applications, especially in the field of quantum communication.

Silica fibers are highly desired due to their robustness and easy integration with existing infrastructure. Although fabrication of silica gain fibers can be performed using well-established methods e.g., Modified Chemical Vapor Deposition (MCVD), each production cycle can be time-consuming and expensive. Additive manufacturing (AM) on the other hand is an attractive way of fabrication, where reduced waste and short cycles are widely recognized. Today, AM is commonly used to make functional components and prototypes.