Displacement self-sensing align-free He–Ne laser based on hollow cube corner prism folding cavity

The displacement self-sensing laser of λ/8 resolution was previously reported, without nonlinear error on principle, and with the function of self-calibration. In this paper, we report out new result: a hollow cube corner prism (HCCP) is used for the first time to realize align-free folding-cavity He–Ne laser; using this technology, we made three important improvements below: the first one is to be an align-free laser. It can work without adjustment benefiting from the HCCP's property of retro-direction reflection and the specially designed laser structure; the second one is to increase the potential resolution up to λ/16; the last one is to enhance the robust of the laser, especially the stability of the laser power when one of the cavity mirrors of laser is moved by the object to be measured, thus, to expand the measurement range. In current demonstration, the laser has a large changeable range (approximately, 60 mm) of cavity length, i.e. a large range of measurement, and high measurement accuracy of λ/16(40 nm for He–Ne laser), at the same time, it is an align-free half intra-cavity laser, which can work without adjustment. This method has prospective benefits to be applied in displacement measurement of high resolution.