Locally erasable couplers for optical device testing in silicon on insulator

Wafer scale testing is critical to reducing production costs and increasing production yield. Here we report a method that allows testing of individual optical components within a complex optical integrated circuit. The method is based on diffractive grating couplers, fabricated using lattice damage induced by ion implantation of germanium. These gratings can be erased via localised laser annealing, which is shown to reduce the outcoupling efficiency by over 20 dB after the device testing is completed. Laser annealing was achieved by employing a CW laser, operating at visible wavelengths thus reducing equipment costs and allowing annealing through thick oxide claddings. The process used also retains CMOS compatibility

The effects of varied deposition conditions, including the use of argon, on thin-film silicon solar cells prepared using PECVD

This paper reports the effects of varied deposition conditions on the resultant energy conversion efficiencies of thin-film silicon solar cells. Cells were deposited using an Oxford Instruments PlasmaLab System 100 on to Pilkington TEC-8 TCO glass, and thoroughly investigated using electrical methods. Thin film devices were fabricated using the decomposition of silane gas within a reaction chamber of 13.56 MHz plasma discharge. The deposition conditions, including substrate temperature, gas flow rates, RF power, chamber pressure, and film thickness are all explored to determine the optimum cell performance. A view toward high-efficiency solar structures, including hetero-junction with intrinsic thin layer (HIT) and micro-morph cell designs using the same conditions is presented

Reflectance properties of silicon moth-eyes in response to variations in angle of incidence, polarisation and azimuth orientation

We report a study of the optical properties of silicon moth-eye structures using a custom-made fully automated broadband spectroscopic reflectometry system (goniometer). This measurement system is able to measure specular reflectance as a function of wavelength, polar incidence angle and azimuth orientation angle, from normal to near-parallel polar incidence angle. The system uses a linear polarized broadband super-continuum laser light source. It is shown that a moth-eye structure composed of a regular array of protruding silicon rods, with finite sidewall angle reduces reflectance and sensitivity to incident wavelength in comparison to truly cylindrical rods with perpendicular sidewalls. It is also shown that moth-eye structures have omnidirectional reflectance properties in response to azimuth orientation of the sample. The importance of applying the reflectometer setup to study the optical properties of solar cell antireflective structures is highlighted

Erasable diffractive grating couplers in silicon on insulator for wafer scale testing

Unlike electronic integrated circuits, robust systems are not widely available for effectively testing optical integrated circuits at intermediate points on a waveguide, without introducing substantial losses into the devices. This makes quality control difficult, only the output of the entire optical circuit can be observed; providing complete system information, rather than localising a problem. A benefit of the Silicon on Insulator platform is its low cost; however processed silicon quickly becomes expensive. Each processing step costs money, testing is critical to reducing costs and increasing production yield. Here we report a method for more complete testing of optical circuits

L'élaboration du rendement du cotonnier et de la qualité du coton-graine

We demonstrate an erasable grating coupler which allows optical device testing throughout the fabrication process without impairing final circuit performance. Refractive index variation is introduced using ion implantation and can be subsequently removed using laser annealing