Low loss channel waveguides in polymers

The primary routes for creating polymeric channel waveguides are reviewed. Processes, materials, waveguide performance, and applications recently reported in the literature are covered. Emphasis is on an internal diffusion approach under development at Du Pont which has not been widely reported. The intent is to provide a perspective on the flexibility and versatility for fabricating polymer channel waveguides for practical integrated optic applications     

Fabrication of buried channel waveguides in fused silica usingfocused MeV proton beam irradiation

Low-loss channel waveguides have been fabricated in fused silica using a beam of MeV protons focused down to a spot size of several microns. By using a combination of beam and sample scanning, single- and multimode graded index waveguides with lateral dimensions down to approximately 5 μm×5 μm have been fabricated using ion doses in the range (3×10¹⁴)-(6×10¹⁶) ions/cm ². Typical beam currents in the range 100 pA-10 nA were used. Optical mode profiles have been measured at 670 nm and propagation losses of the order of 3 dB/cm measured in unannealed samples. Annealing the substrate for 1 h at 500°C reduced these losses to below 0.5 dB/cm     

Low-insertion-loss channel waveguides in LiNbO3 fabricated by proton exchange

We describe single-mode proton exchange waveguides in Z-cut LiNbO3 at the 1.32 ?m wavelength having low fibre/waveguide/fibre insertion loss.     

Optical waveguides in fluoride lead silicate glasses fabricated by carbon ion implantation

The carbon ion implantation with energy of 4.0 MeV and a dose of 4.0×1014 ions/cm2 is employed for fabricating the optical waveguide in fluoride lead silicate glasses. The optical modes as well as the effective refractive indices are measured by the prism coupling method. The refractive index distribution in the fluoride lead silicate glass waveguide is simulated by the reflectivity calculation method (RCM). The light intensity profile and the energy losses are calculated by the ?nite-difference beam propagation method (FD-BPM) and the program of stopping and range of ions in matter (SRIM), respectively. The propagation properties indicate that the C2+ ion-implanted fluoride lead silicate glass waveguide is a candidate for fabricating optical devices.     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

Low loss GaAs optical waveguides

To realize an optical integrated circuit, various losses in the semiconductor waveguide such as absorption loss, waveguide loss, bending loss, and coupling loss, have to be minimized. Theoretical and experimental considerations for the reduction of these losses have been presented. A propagation loss of less than 0.5 dB/cm has been observed for a well-designed GaAs ridge waveguide. Moreover its coupling loss with a polarization-maintaining optical fiber decreased below 1.5 dB.     

用飞秒激光在石英玻璃体内写入光波导和光栅的研究

用飞秒激光在石英玻璃写入了光波导和光栅等结构。飞秒激光辐射照形成波导效应时的折射率改变量为0.001至0.008。折射率的改变量依赖于飞秒激光脉冲辐照的剂量和功率密度。通过Raman光谱和AFM图像,研究了波导区的物质结构变化,并对飞秒激光写入过程的物理机制进行了探讨。     

Low radiation loss branching/combining of optical circuits using high-silica channel waveguides

A new branching/combining optical circuit structure using high-silica channel waveguides was proposed to reduce radiation loss where branching occurs. In this structure, an additional low-refractive-index layer was formed at the junction surface between the main and branching channels. The loss in a conventional circuit could be successfully reduced by over 0.4 dB in the through channel and 0.1 dB in the reflecting channel. The allowable conditions for a low-refractive-index layer were obtained through experimental and theoretical studies.     

Low loss fused D fibre couplers

Low loss fused D fibre couplers are fabricated by a technique simpler than any previously reported. No pre-treatment of the D fibre is required and because of the simplicity of the coupler structure, heat treatment such as core diffusion and tapering, which increase coupling, and annealed twists, which decrease coupling, can be applied without compromising the coupler's excess loss.<>     

Total reflection mirrors fabricated on silica waveguides with focused ion beam

Efficient total reflection mirrors are fabricated on silica-based waveguides by direct milling with a focused ion beam. To reduce the excess losses of the mirrors, a two-step milling technique is employed that reduces the roughness of the mirror surface while maintaining a high milling rate. A focused ion beam is used to fabricate low-loss mirrors with small excess losses of about 1.0 dB.     

Near-infrared channel waveguides formed by electron-beamirradiation of silica layers on silicon substrates

Results are presented for channel guides formed by electron beam irradiation of silica layers formed on Si substrates by plasma-enhanced chemical vapor deposition. Electroplating is shown to be a simple method of fabricating the required surface mask. Optical insertion loss measurements performed at 1.525 μm wavelength show a strong dependence on the irradiation mask width, charge dose, and electron energy, and parameters for low propagation and coupling loss are identified. Optimum propagation losses are 0.4 dB/cm (TE), 0.75 dB/cm (TM). Spectral loss measurements are also presented for as-deposited and thermally annealed material, and it is shown that beneficial results are obtained by annealing before irradiation. The stability of irradiation-induced changes is also described     

Low loss mirrors for InP/InGaAsP waveguides

The loss associated with a mirror in an InP-based waveguide has been investigated. Mirror roughness and non-verticality were both significant sources of loss. Mirrors with only 1 dB loss have been produced through novel fabrication techniques.<>     

Polymer channel waveguides with low loss at 1.3 mu m

Highly transparent polymers in the 0.6-1.3 mu m wavelength region have been synthesised from deuterated or halogenated methacrylate monomers. Low loss waveguides of less than 0.1 dB/cm at a wavelength of 1.3 mu m have been fabricated using the polymers.<>     

Lithium niobate ridge waveguides fabricated by wet etching

The authors report a novel method for fabricating proton exchanged LiNbO₃ ridge waveguides by the wet etching of proton-exchanged LiNbO₃. To demonstrate a simple and easy application of the LiNbO₃ ridge waveguide, a Mach-Zehnder interferometric modulator with selfaligned electrode was fabricated     

Low loss, heat-resistant optical waveguides using new fluorinated polyimides

Two types of polymer ridge optical waveguide are prepared using new fluorinated polyimides with excellent transparency and refractive index controllability. One has a polyimide core with a refractive index n of 1.573 and an SiO/sub 2/ undercladding layer. The other has a polyimide core (n=1.521) and a polyimide undercladding layer (n=1.520). These waveguides exhibit a low loss of 0.3 dB/cm at 1.3 mu m. In addition, they have high thermal stability because of high temperature curing (above 350 degrees C).<>     

Optical waveguides fabricated by electric-field controlled ion exchange in glass

Electric-field assisted silver-sodium ion exchange fabrication of low-loss waveguides in glass has been demonstrated. The process can be very fast and the index distribution controllable.     

Optical gain in Er-Yb doped waveguides fabricated by femtosecondlaser pulses

Er-Yb doped waveguides at 1.5 μm fabricated by femtosecond laser pulses are reported. Demonstrated is a Gaussian mode-profile, low propagation loss and internal gain in a 25 mm-long waveguide used as the active element in a standard waveguide-amplifier setup     

Optical waveguides fabricated on polymer substrate by electron beam

In the field of optical telecommunication, polymers are an interesting class of materials for the fabrication of passive optical devices. Electron beam (EB) irradiation appears as a promising method to achieve structures presenting a layer with a modified index of refraction, and therefore to generate optical waveguiding. The poly(diethylene glycol bis(allyl carbonate)) studied here fulfils the requirements of high transparency and is consequently widely used by the optical industry. A scanning electron microscope delivers the EB with a highest energy of 30 keV. The electrons induce an increase of the substrate refractive index (≥8×10⁻³ for an electronic fluence ≥5×10¹⁴ e/cm²) on a thickness corresponding to the penetration depth of the electrons in the material (≤10 μm for a 25 keV EB). Some optical characteristics are presented such as, the surface refractive index, the effective indices and, therefore, the index profile of the waveguides.     

Loss measurements in stress-induced optical waveguides fabricated by an embossing process

Stress-induced light guides have been fabricated by an embossing process. The results of detailed loss measurements show that these waveguides can exhibit low optical attenuation.     

Scattering loss reduction in polymer waveguides by reflowing

A polymer channel waveguide was fabricated by reactive ion etching. Loss measurements were performed on this waveguide before and after reflowing. The waveguide loss decreases from 3 to 1 dB/cm by heating the sample slightly above the glass transition temperature of the core material. This result in channel loss is very close to the measured film losses of 0.8 dB/cm.