Hybrid microlaser encoder

Abstract

We have developed a microlaser encoder that can detect displacements relative to an external grating scale with a resolution on the order of 10 nm. Its size is only a few tens of a percent of a conventional encoder's. A long-lasting InP laser diode with a wavelength of 1550 nm was bonded, along with several photodiode chips, within an alignment accuracy of 1 /spl mu/m onto a silicon planar lightwave circuit chip. The chip is 2.3 mm /spl times/ 1.7 mm and includes a fluorinated polyimide lightwaveguide fabricated in advance. A wide gap of more than 600 /spl mu/m was obtained between the external grating scale and the encoder despite the tiny size of the sensor. When used as a rotary encoder, the number of rotations could also be detected. Thus, this microencoder satisfies the market requirements for practical use.