RF-Sputtering applications

RF-Sputtering materials RF-Sputtering principles

Planar Waveguides

 Optical planar waveguides fabrication protocol: target geometry


 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.


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

 Photoluminescence spectra of the 4I13/24I15/2 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

 4I13/24I15/2 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.


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.

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.

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

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.

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

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

 4I13/24I15/2 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.

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.