  Tilt-to-length (TTL) coupling, caused by the jitter of test masses or
satellites, is a significant noise source in space-based gravitational wave
detection. Calibrating and suppressing TTL coupling noise at the sub-nanometer
level is essential. One main challenge in current ground-based TTL coupling
testing is the residual translational movement of the tilt actuator. This paper
introduces the development of an advanced pure tilt actuator (APTA)
specifically designed for testing TTL coupling. The APTA provides precise tilt
motion and is monitored by a four-beam interferometer, which measures the
displacement of attached array pyramids. We present a detailed theoretical
model and experimental setup. Experimental results demonstrate that this
optical test bed, equipped with the APTA, can achieve subnanometer-level TTL
coupling calibration. In addition, a typical heterodyne interferometer was
tested using the APTA test bed. Comparative testing demonstrated that the
imaging system is capable of effectively suppressing TTL coupling errors. The
TTL coupling coefficients were reduced from over plus-minus 30 micrometers per
radian to within plus-minus 5 micrometers per radian across a range of
plus-minus 200 microradians, meeting the preliminary requirements for the
TianQin mission. This APTA test platform has the potential to be widely
utilized for ground-based TTL coupling inspection.
