RF-Sputtering applications

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Planar Waveguides

Optical planar waveguides fabrication protocol: target geometry

Fabrication protocol of flexible planar waveguides using rf-sputtering

Fabrication protocol of flexible SiO₂-HfO₂:Er³⁺ planar waveguides using rf-sputtering on PEEK, SCHOTT AS 87 eco ultra-thin aluminosilicate glass, SiO₂ and Si substrates

Refractive index n_f = 1.470±0.001 @1.548 nm
Thickness t_f = 4.0±0.1 µm
Attenuation coefficient α < 0.3 dB/cm @1.548 nm

PEEK.mp4

PEEK

SCHOTT AS 87.mp4

SCHOTT AS 87 eco ultra-thin aluminosilicate glass

SiO₂-TiO₂:Er³⁺-Yb³⁺

Photoluminescence excitation spectrum. Observed wavelength 1533 nm

Intensity at 1533 nm in the Yb³⁺ co-doped sample is more than 7 times larger than that of the sample with only Erbium spectral shape correspond to the typical Ytterbium absorption.

Effective energy transfer from Ytterbium to Erbium ions is demonstrated.

A. Chiasera, M. Montagna, C. Tosello, S. Pelli, G.C. Righini, M. Ferrari, L. Zampedri, A. Monteil, P. Lazzeri, "Enhanced spectroscopic properties at 1,5 mm in Er³⁺/Yb³⁺-activated silica-titania planar waveguides fabricated by rf-sputtering", Opt. Mat. 25 (2004) 117-122, doi: 10.1016/S0925-3467(03)00259-3.

SiO₂-HfO₂:Er³⁺-Yb³⁺

Planar waveguides SiO₂-HfO₂:Er³⁺/Yb³⁺ fabricated by rf-sputtering: optical parameter and compositional analysis

Photoluminescence spectra of the ⁴I_13/2→⁴I_15/2 transition of Er³⁺ ion for the W1 planar waveguide, obtained by exciting the TE₀ mode at 980 nm and 514.5 nm. FWHM 42 nm

⁴I_13/2→⁴I_15/2 luminescence decay profile of Er³⁺ ion in W1 samle obtained after pumping at 514.5 nm with an excitation power of 380 mW

A first step towards EDPWA. On the planar waveguide was deposited 100nm of Chromium by sputtering and the resist (cod. 1811 by Shipley) by spinning. After the develop of the resist and the removing of the Chromium the etching of the active film was carried out by a wet chemical process with a buffered HF etch.

A. Chiasera, C. Armellini, S.N.B. Bhaktha, A. Chiappini, Y. Jestin, M. Ferrari, E. Moser, A. Coppa, V. Foglietti, P.T. Huy, K. Tran Ngoc, G. Nunzi Conti, S. Pelli, G.C. Righini, G. Speranza, "Er³⁺/Yb³⁺-activated silica-hafnia planar waveguides for photonics fabricated by rf-sputtering", Journal of Non-Crystalline Solids 355 (2009), pp. 1176–1179, doi: 10.1016/j.jnoncrysol.2008.11.039.

SiO₂-GeO₂:Er³⁺-Yb³⁺

Direct writing of grating by Excimer Laser irradiation on Er³⁺/Yb³⁺-doped SiO₂-GeO₂ planar waveguides

Deflection of the guided light at 633 nm produced by a highly efficient (~100% in 1 mm) photo-induced Bragg grating on Er³⁺/Yb³⁺-doped SiO₂-GeO₂ planar waveguides, single mode at 1550 nm, deposited by radio-frequency sputtering

G. Nunzi Conti, S. Berneschi, M. Brenci, S. Pelli, S. Sebastiani, G.C. Righini, C. Tosello, A. Chiasera, M. Ferrari, "UV photoimprinting of channel waveguides on active SiO₂–GeO₂ sputtered thin films", Applied Physics Letters 89 (2006) 121102-1–121101-3, doi: 10.1063/1.2355472.S. Sebastiani, G. Nunzi Conti, S. Pelli, G.C. Righini, A. Chiasera, M. Ferrari, C. Tosello, "Characterization of a highly photorefractive RF-sputtered SiO₂-GeO₂ waveguide", Optics Express 13 (2005) 1696-1701, doi: 10.1364/OPEX.13.001696.

Direct writing of channel waveguide by Excimer Laser irradiation

Channel waveguide after irradiation with a total of 20 kJ/cm²; Single step replica of the mask pattern; WG is single mode @ 1550 nm; Propagation losses about 0.3 dB/cm - Same as in the planar waveguide.

Near field image of a photo-induced channel waveguide

GeO₂ Ultra-Transparent Glassceramics

GeO₂ transparent glass ceramic planar waveguides were fabricated by a RF-sputtering technique and then irradiated by a pulsed CO₂ laser. The effects of CO₂ laser processing on the optical and structural properties of the waveguides were evaluated by different techniques including m-line, micro-Raman spectroscopy, atomic force microscopy, and positron annihilation spectroscopy. After laser annealing, an increase of the refractive index of approximately 0.04 at 1.5 µm and a decrease of the attenuation coefficient from 0.9 to 0.5 db/cm at 1.5 µm was observed. Raman spectroscopy and microscopy results put in evidence that the system embeds GeO₂ nanocrystals and their phase varies with the irradiation time. Moreover, positron annihilation spectroscopy was used to study the depth profiling of the as prepared and laser annealed samples. The obtained results yielded information on the structural changes produced after the irradiation process inside the waveguiding films of approximately 1 µm thickness. In addition, a density value of the amorphous GeO₂ samples was evaluated.

Scheme of the nanostructural transformation of the GeO₂ films as a function of the depth measured from the surface of the sample and the irradiation time.

As shown in this scheme, besides the silica substrate (r = 2.1 g/cm³) different layers in the GeO₂ films are detected by positron spectroscopy.

From the fitting of the positron data, a density value of r = 3.15 g/cm³ for the GeO₂ was obtained

A. Chiasera, C. Macchi, S. Mariazzi, S. Valligatla, L. Lunelli, C. Pederzolli, D.N. Rao, A. Somoza, R.S. Brusa, M. Ferrari, "CO₂ Laser irradiation of GeO₂ planar waveguide fabricated by rf-sputtering", Optical Materials Express, Vol. 3, Issue 9, pp. 1561-1570 (2013), doi: 10.1364/OME.3.001561.

1-D Photonic Structures

Flexible Photonics on glass structures: 1D flexible photonic crystals

SiO2/TiO2 multilayer structure fabricated by rf-sputtering on PMMA, PEEK, SiO2 and Si substrates.

Multilayer structure on a PMMA substrate during the bending

The multilayer structure on a PMMA substrate after the bending

A. Chiasera, O. Sayginer, E. Iacob, A. Szczurek, S. Varas, J. Krzak, O.S. Bursi, D. Zonta, A. Lukowiak, G.C. Righini, M. Ferrari, "Flexible photonics: RF-sputtering fabrication of glass-based systems operating under mechanical deformation conditions", Proceedings SPIE 11357 (2020) pp. 1135705-1/11, Fiber Lasers and Glass Photonics: Materials through Applications II, doi: 10.1117/12.2551472.

Tunable Spectral Filter-based Sensor

Fabrication of Surface Functionalized Membranes

Glass multilayer structure fabricated by rf-sputtering on laser printer acetate sheets.

Membrane Filter Design

(a.) Illustration of the working principle of the sensing system.

(b.) An example reflectance spectrum response of the reflector and

(c.) an example transmittance spectrum response of the filter.

(d.) The overlapping area of two spectral features defines the spectrum of light that is finally detected by a photodiode.

Schematic of the test device

Prototype testing

O. Sayginer, A. Chiasera, S. Varas, A. Lukowiak, M. Ferrari, O.S. Bursi, "Design and fabrication of multilayer-driven optomechanical device for force and vibration sensing", Proceedings SPIE 11357 (2020) pp. 113571S-1/10, Fiber Lasers and Glass Photonics: Materials through Applications II, doi: 10.1117/12.2555347.

1-D Er³⁺-activated dielectric microcavity

SEM micrograph of the 1-D microcavity cross section. Bragg Mirror: 20 alternated quarter wave layers TiO₂ (170 nm) and SiO₂ (320 nm). Active layer: half wave (640 nm) SiO₂ activated with 0.2 mol % of Er³⁺. The dark regions corresponds to SiO₂ and the white regions corresponds to TiO₂

Transmittance spectrum of the cavity with two Bragg reflectors, each one consisting of ten pairs of SiO₂/TiO₂ layers, in the region between 1000 and 2600 nm.

The stop band range from 1490 to 1980 nm. The cavity resonance corresponds to the sharp maximum centred at 1749 nm. The incident light is unpolarized.

The line width of the resonance is 1.97 nm that correspond to a quality Q factor of 890

Schematics of the excitation and detection geometries employed for a reliable assessment of the influence of the cavity on the 1500 nm emission band of Er³⁺ ion.

Fig. (a): configuration employed for the Er³⁺-activated reference sample,

Fig. (b): configuration employed for the Er³⁺-activated 1-D microcavity

⁴I_13/2→⁴I_15/2 photoluminescence spectra of the cavity activated by Er³⁺ ion in 1-D photonic crystal and of the single Er³⁺-doped SiO₂ active layer with first Bragg mirror.

The light is recorded at 50° from the normal on the samples upon excitation at 514.5 nm

S. Valligatla, A. Chiasera, S. Varas, N. Bazzanella, D.N. Rao, G.C. Righini, M. Ferrari, “High quality factor 1-D Er³⁺-activated dielectric microcavity fabricated by RF-sputtering”, Optics Express (2012), Vol. 20 Issue 19, pp.21214-21222, doi: 10.1364/OE.20.021214.

Disordered photonic structure

Photonic structure made of alternating SiO₂ and TiO₂ with random thicknesses

Photonic structure made of alternating SiO₂ and TiO₂ with uniform thicknesses

A. Chiasera, F. Scotognella, L. Criante, S. Varas, G. Della Valle, R. Ramponi, M. Ferrari, "Disorder in Photonic Structures Induced by Random Layer Thickness", Sci. Adv. Mater. 7 (2015), pp. 1207-1212, doi: 10.1166/sam.2015.2249.

1D photonic crystal integration on SMF28 Fiber tip: direct deposition of the multilayer on the fiber tip

Sample holder geometry

Fiber position on the sample holder

Sem image of the fiber tip after the deposition

Detail of the 1D photonic crystal

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