Optical pickup device and optical read/write apparatus

An optical pickup device that is configured to write data on a track on an optical storage medium and to read the data that has been written on the track, the device comprising:

• a laser light source configured to emit a light beam;
• a diffractive element configured to diffract the light beam and split the light beam into a plurality of diffracted light beams including a zero-order diffracted light beam and ±first-order diffracted light beams;
• an objective lens configured to converge the zero-order and ±first-order diffracted light beams onto the same track on the optical storage medium;
• and
• a photodetector arranged to receive the zero-order and ±first-order diffracted light beams that have been reflected from the optical storage medium,
• wherein if a distance from a light beam spot left by the zero-order diffracted light beam on the track on the optical storage medium to light beam spots left by the ±first-order diffracted light beams on the track is d [μm], the scanning linear velocity of the optical storage medium is v [m/s], and a time it takes for a phase-change material of the optical storage medium that has once been melted by the zero-order diffracted light beam to solidify is T [μs],
• vT≦d is satisfied.