Fabrication Of Buried Waveguides Research Articles

Laser-Induced Erasable and Re-Writable Waveguides within Silver Phosphate Glasses.

Femtosecond direct laser writing is a well-established and robust technique for the fabrication of photonic structures. Herein, we report on the fabrication of buried waveguides in AgPO3 silver metaphosphate glasses, as well as, on the erase and re-writing of those structures, by means of a single femtosecond laser source. Based on the fabrication procedure, the developed waveguides can be erased and readily re-inscribed upon further femtosecond irradiation under controlled conditions. Namely, for the initial waveguide writing the employed laser irradiation power was 2 J/cm2 with a scanning speed of 5 mm/s and a repetition rate of 200 kHz. Upon enhancing the power to 16 J/cm2 while keeping constant the scanning speed and reducing the repetition rate to 25 kHz, the so formed patterns were readily erased. Then, upon using a laser power of 2 J/cm2 with a scanning speed of 1 mm/s and a repetition rate of 200 kHz the waveguide patterns were re-written inside the glass. Scanning electron microscopy (SEM) images at the cross-section of the processed glasses, combined with spatial Raman analysis revealed that the developed write/erase/re-write cycle, does not cause any structural modification to the phosphate network, rendering the fabrication process feasible for reversible optoelectronic applications. Namely, it is proposed that this non-ablative phenomenon lies on the local relaxation of the glass network caused by the heat deposited upon pulsed laser irradiation. The resulted waveguide patterns Our findings pave the way towards new photonic applications involving infinite cycles of write/erase/re-write processes without the need of intermediate steps of typical thermal annealing treatments.

Fabrication of buried waveguides in planar silica films using a direct CW laser writing technique

A CW CO 2 laser ablation technique is used to form buried waveguides in planar silica films. It is shown that the refractive index of a silica thin film is reduced sufficiently adjacent to the laser processed region to allow the fabrication of low loss waveguides. The refractive index distribution of these structures is measured using the reflectance of a focussed spot from the surface of the films. The change in refractive index is measured to be of the order of the core cladding refractive index difference of typical single mode waveguides. The spatial resolution of the reflectance technique is 1.3 μm with a refractive index resolution of ±5 × 10 −4. Devices such as 1 × 2 and 1 × 4 multi-mode interference (MMI) splitters have also been demonstrated and shown to exhibit low transmission losses.

Fabrication of buried waveguides and nanocrystals in Er3+‐doped oxyfluoride glass

AbstractWe report on direct writing of three‐dimensional structures within the bulk of the Er3+‐doped oxyfluoride precursor glass using tightly focused femtosecond Ti‐sapphire laser pulses at 800 nm wavelength. Buried 1 µm diameter channel and spherical waveguides and three‐dimensional periodic arrays of 1 µm diameter dots have been fabricated. In the latter case, the dot could be written with a single 25 fs laser pulse. When the laser pulse energy exceeded 10 µJ/pulse/µm2, the writing resulted in nano‐ceraming of the precursor glass and creation of about 2 to 3 nm diameter Er3+‐doped fluoride nanocrystals within the written dots/waveguides, as confirmed by a characteristic change in shape of the 1.5 µm photoluminescence band of the Er3+ ions. The diameter of the buried dots/wave‐guides, and the photoinduced change of their refractive index, can be varied by changing the number of femtosecond laser pulses, the beam waist diameter, and/or laser intensity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Experimental analysis and modeling of buried waveguides fabricated by quantum-well intermixing

The fabrication of buried waveguides in InP-based quantum-well (QW) material through the use of implantation. Enhanced QW band edge blue-shifting is reported. First, the lateral selectivity of implantation-induced QW intermixing is investigated using a specially designed implantation mask and photoluminescence. The refractive index change of the intermixed material is measured near the band edge. In combination, the lateral resolution and the index difference have allowed for the fabrication of narrow buried waveguides in an InP-based laser structure. Detailed modeling of the mode excitation and beam propagation of these devices is performed, and results are compared with experimental near-field profiles. We demonstrate that the waveguides are single-mode for both TE and TM polarizations at wavelengths near the band edge. The potential applications of this waveguide structure include post-growth fabrication of buried waveguide lasers and other integrated components.