In magnetic confinement fusion research, electron density and current density are two critical physical parameters. Electron density is not only one of the three key quantities—alongside temperature and energy confinement time—defining fusion plasma performance, but also essential for controlling and studying plasma behavior. Plasma confinement, transport phenomena, and magnetohydrodynamic stability are strongly influenced by the current density profile. The polarimeter-interferometer (POINT) system is a key diagnostic on the EAST tokamak, providing simultaneous measurements of electron density and current density profiles for both plasma control and fundamental physics research. Its operation depends on a stable, high-power far-infrared (FIR) laser source. Currently, the light sources for POINT on EAST are three SIFIR-50 optically pumped formic acid lasers from Coherent Inc. (USA), each emitting at 432 μm with a maximum output power of about 30 mW. However, after more than a decade of operation, one of these lasers has failed. This paper reports the development of a self-built, optically pumped FIR laser operating at the same 432 μm wavelength, matching the spectral line of the SIFIR-50 system. Using formic acid as the gain medium, the laser delivers a continuous-wave output power of 25 mW. Before integration into the POINT, the output beam was systematically characterized. Measurements confirm operation in the fundamental TEM00 transverse mode with a Gaussian intensity profile. By performing axial beam-profile scans and applying Gaussian beam propagation theory, the beam-waist location and radius were determined. After integration with the POINT system, the intermediate-frequency drift less than 2% over a 5 min interval, meeting the stability requirements of the interferometer. The POINT system, now employing this laser, has successfully measured line-integrated electron density, and density profiles subsequently reconstructed through inversion algorithms, demonstrating that the self-developed FIR laser can be utilized for polarimetric interferometry measurements.