Measurement of the modal birefringence of single-mode K(+) ion-exchanged planar waveguides with polarimetric interferometry.
The polarimetric interference pattern on the surface of single-mode planar waveguides made by potassium ion exchange in soda-lime glass substrates can be observed through a 45 degrees analyzer, which allows for the high-precision measurement of the modal birefringence of samples in a wide range of 0 to 5 x 10(-4). Using this method, believed to be new, we investigated the effects of exchange temperature and time on the modal birefringence of single-mode potassium ion-exchanged waveguides. The modal birefringence profile was achieved by measurement of the variation of the phase difference between the TE(0) and the TM(0) modes with hydrofluoric-acid-etching depth of the sample.
A disposable ozone sensor based on a grating-coupled glass waveguide coated with a tapered film of copper tetra-t-butylphthalocyanine
Abstract An integrated optical sensor specifically sensitive to ozone has been developed by vacuum evaporating a tapered thin film of copper tetra-t-butylphthalocyanine (CuPct) through a mask onto a slab waveguide made by K+–Na+ ion-exchange in glass. A pair of photoresist gratings fabricated on the waveguide offer the sensor a good long-term stability in optical coupling. The evaporated dye film composed of CuPct H-aggregates has a large absorption at 633 nm and a high-index of refraction relative to that of glass substrates. Therefore, the waveguiding mode excited with a 633 nm laser beam in the CuPct film-coved waveguide is highly attenuated. The CuPct film is very stable in air but ozone exposure at room temperature can result in a rapid and irreversible decoloration of the film. In the presence of a given concentration of ozone in the ambient air about the senor, the output light intensity was detected to linearly increase with time. It has been demonstrated that the sensor containing a 15 mm long and tens-of-nanometers thick dye film can detect 33 ppb ozone in air at room temperature.
Coherent pulsed injection seeding of two gain-switched semiconductor lasers
High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 AA wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated.<<ETX>>