Magane Aoki

Focusing waveguide mirror with a tapered edge

We propose a focusing waveguide mirror with a shallow tapered edge in a slab waveguide and demonstrate it by planar processes and wet etching. A light beam 2 mm wide is focused to 6.5 µm full width at half-maximum at a wavelength of 0.6328 µm. A reflectivity of higher than 90% at the tapered edge is obtained. The inclination ratio of the tapered mirror edge is 1:90. Fairly good correspondence between measured and calculated focused spot sizes is obtained.

Integrated optical pickup with highly sensitive servo signal detection

We proposed a novel structure for an integrated optical pickup based on monolithic integration of waveguide mirrors and photodetectors in a waveguide on a Si substrate. The detection characteristics of focusing and tracking error signals have been demonstrated to be sufficient for practical applications.

Integrated waveguide device for magneto-optical disk signal detection and its fabrication techniques

We propose an integrated optical polarization detection device for magneto-optical disk pickups. The device has a prism coupler and a TE/TM mode splitter which is monolithically integrated on a silicon substrate with p-i-n photodiodes and two optical waveguides with different effective indices of refraction. These two waveguides are connected at two tapered transition regions. This paper describes the device fabrication techniques and the performance of each element integrated in the device. The optical waveguide TE/TM mode splitter is shown to have wide tolerance for wavelength change, fabrication error, or deviation from designed incident angle.

TE/TM mode splitter with waveguide photodetectors

We propose a novel TE/TM mode splitter for an integrated optical detection device for magneto-optical disk pickup. The new mode splitter is monolithically integrated on a Si substrate with pin-photodiodes. This device is composed of optical waveguides A and B with effective indices of refraction NA and NB, where NA > NB. These two waveguides are connected by a tapered transition region. The light wave guided in waveguide A is incident on the tapered transition region at an angle of incidence greater than the critical angle for the TE0 mode and smaller than the critical angle for the TM0 mode. The TE0 mode is totally reflected and the TM0 mode is totally transmitted at that region so that this device works as a TE/TM mode splitter. We fabricated the mode splitters tapered transition region using a novel wet etching process, then examined the TE/TM mode splitting operation using a GaAlAs laser diode ((lambda) equals 0.788 micrometers ). When both TE0 and TM0 modes were exited in waveguide A, the extinction ratios of the TE0 and TM0 modes were measured with the integrated photodiodes. The extinction ratios were -25.4 dB for the TE0 mode and -23.3 dB for the TM0 mode. These values are sufficient for practical application. Furthermore, the polarization detection function was experimentally confirmed using a Faraday rotator.