Structural and optical properties of rare-earth-doped Y2O3 waveguides grown by pulsed-laser deposition

Abstract

Crystalline rare-earth-doped yttrium oxide thin films were grown by pulsed-laser deposition (PLD) on SiO2/Si substrates. The structural and morphological features of these films were studied, as a function of the growth conditions (temperature from 200 to 800 °C and oxygen pressure from 10−6 to 0.5 mbar), by using Rutherford backscattering spectroscopy, x-ray diffraction, and atomic force microscopy. The related optical properties were investigated by m-lines spectroscopy at 633 nm and 1.3 μm. The optimal conditions were found to be a temperature and a pressure of 700 °C and 10−6 mbar, respectively. In that case, the Y2O3 films are stoichiometric with controlled erbium and europium rates, and present a well-crystallized, (111) textured cubic phase and a low surface roughness of about 10 Å. Moreover, the PLD films show good waveguiding properties with a high refractive index (1.92 at 633 nm), a step-index structure, and low optical losses around 1 dB/cm in the near infrared region, promising for a planar amplifier function.

Laser operation of a Tm:Y_2O_3 planar waveguide

“…The largest peaks correspond to (222) and (444) orientations of the film, as well as the (400) and (800) orientations of the underlying YAG substrate, indicating that the film is highly textured in the (222) orientation. (222)-oriented growth has been observed previously in sesquioxide deposition, both where the film and substrate were lattice matched (for example in the case of growth of yttria on sapphire, where the lattice mismatch was ∼5% [8]), and in the case of growth on amorphous substrates (where there is no lattice match, growth in the cubic phase and {111} orientation minimises the surface free energy [15]). A number of peaks at least two orders of magnitude smaller than the primary (222) orientation peak can also be observed.…”

Erbium‐doped integrated waveguide amplifiers and lasers

“…In contrast, thin film growth methods typically involve deposition on oxidized silicon wafers (the oxide layer on the silicon providing the lower cladding layer) or other substrates, thus potentially allowing for integration with other devices on the same substrate and fabrication of devices over a large area. Methods which have been utilized for depositing Er-doped waveguiding films include atomic layer deposition [129,151], dip-coating [152], flame hydrolysis [32,153], high vacuum chemical vapour deposition (HV-CVD) [154], plasma-enhanced chemical vapour deposition (PECVD) [83,127,138,[155][156][157], pulsed laser deposition (PLD) [59,126,145,[158][159][160][161][162][163], reactive cosputtering [68,84,87,128,[164][165][166], RF-sputtering [40,98,131,133,137,[167][168][169][170], the sol-gel method [134,[171][172][173][174][175]…”

Structural and optical properties of yttrium oxide thin films for planar waveguiding applications

“…27,28 Furthermore at high pressures the low kinetic energy of the evaporated material prevents the crystalline growth and leads to an amorphous films. 29 Another interesting point to note is that introduction of oxygen into the chamber reduces the growth rate by slowing the evaporated atoms within the plasma. Thin films produced under these conditions can exhibit a lower refractive index.…”