Long-life micro-laser encoder

We have developed a micro-laser encoder that can detect displacements relative to an external grating scale with resolution on the order of 10 nm. Its size is only a few percent of a conventional encoder's size. A long-lasting InP laser diode with a wavelength of 1550 nm is bonded, along with several photodiode chips, within an alignment accuracy of ±1 μm onto a silicon planar lightwave circuit chip. The chip is 2.3 mm×1.7 mm and includes a fluorinated polyimide light waveguide fabricated in advance. A wide gap of more than 600 μm 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.